11.5   Building Space Conditioning System Requirements

This section addresses the requirements for space conditioning systems in multifamily buildings. Requirements related to ventilation and indoor air quality are discussed in Chapter 11.4.

Requirements for a space conditioning system that serves one or more dwelling units are described in Chapters 11.6.3 and 11.6.4. Requirements for a space conditioning system that serves common use areas of the building—including community rooms, corridors, fitness areas, common laundry rooms, and parking garages—are described in Chapter 11.6.5. Space conditioning systems that serve both dwelling units and common use areas must meet both sets of requirements.

Systems serving nonresidential occupancies in a mixed occupancy building must comply with nonresidential requirements in §120.0 through §141.1. See Chapter 4 for information on those systems.

Chapter 11.6.7 covers the heating and cooling requirements for additions to existing dwellings and for alterations to existing heating and cooling systems.

Table 11-26: Overview of Space Conditioning System Requirements in the Energy Code and Compliance Manual Organization-

Source: California Energy Commission

11.5.1      What’s New for the 2022 Energy Code

The following is an overview of the new HVAC requirements for the 2022 Building Energy Efficiency Standards (Energy Code).

•    The mandatory testing requirements that applied to multifamily buildings up to three habitable stories under the 2019 Energy Code (duct leakage, airflow rate, and fan efficacy) now apply to all multifamily buildings with HVAC systems serving individual dwelling units with some exceptions. The HERS Rater field verification and HERS Provider data registry requirements of Reference Residential Appendix RA2 and RA3 are not required for multifamily dwelling units in buildings with four or more habitable stories. In these cases, the installer must certify on the Certificate of Installation that diagnostic testing was performed in accordance with the applicable procedures.

•    For dwelling units in multifamily buildings with up to three habitable stories, the prescriptive approach requires the space conditioning system to be a heat pump in Climate Zones 1-15. For Climate Zone 16, the space conditioning system must be an air conditioner with a gas-fired furnace. In addition, in Climate Zones 4-10, if the ventilation system is a balanced system without heat or energy recovery, the fan efficacy must be 0.4 W/CFM or less.

•    For dwelling units in multifamily buildings with four or more habitable stories prescriptive approach requires the space conditioning system to be a heat pump in Climate Zones 2-15. For Climate Zones 1 and 16, the space conditioning system should be a dual-fuel heat pump.

•    The prescriptive refrigerant charge testing requirements that applied to multifamily buildings up to three habitable stories the 2019 Energy Code now apply to all multifamily buildings with HVAC systems serving individual dwelling units. The HERS Rater field verification and HERS Provider data registry requirements of Reference Residential Appendix RA2 and RA3 are not required for multifamily dwelling units in buildings with four or more habitable stories. In these cases, the installer must certify on the certificate of installation that diagnostic testing was performed in accordance with the applicable procedures.

•    Ducts in conditioned space can be uninsulated if specific conditions are met, as explained in Chapter 11.6.4

•    New requirements for space conditioning system that serve common use areas of the building are described in Chapter 4.1.

•    Filter racks or grilles must use a gasket, sealing or other means to prevent air from bypassing the filter

•    Variable Capacity Heat Pump Compliance Option that was approved in November 2019 is incorporated into the Energy Code

For alterations and additions, the following changes are included:

•    For altered duct systems the prescriptive duct insulation R-Value is R-8 in Climate Zones 1-2, 4, and 8 through 16.

•    The 40-foot trigger for prescriptive duct sealing and insulation has been reduced to 25 ft. for altered systems. The minimum length requirement for additions has been eliminated, and duct sealing is required whenever an existing duct system is extended to serve an addition.

A new prescriptive requirement for insulation and sealing in vented attics was added, which is triggered by the installation of an entirely new or complete replacement duct system is in a vented attic. Requirements apply in all climate zones, except 5 and 7, and various exceptions are allowed. See Chapter 11.6.7.2 of the compliance manual for additional details.

11.5.2      California Appliance Standards and Equipment Certification

Most heating and cooling equipment installed in California multifamily buildings is regulated by the National Appliance Efficiency Conservation Act (NAECA) and/or the California Appliance Efficiency Regulations (Title 20). Both the federal and state appliance standards apply to the manufacturing and sale of new equipment, whether for installation or replacement in newly constructed buildings, additions, or alterations. The Appliance Efficiency Regulations are enforced at the point of sale (except central split-system air conditioners and central single package air conditioners, see Table 11-27), while the Energy Code explained in this compliance manual is enforced by local enforcement agencies.

The equipment listed below is covered by the Appliance Efficiency Regulations. The manufacturer must certify that the equipment complies with the current Appliance Efficiency Regulations at the time of manufacture. The energy efficiency of other equipment, usually larger equipment, is regulated by the Energy Code §110.2(a)|topic=(a) Efficiency..

Appliances covered by the Appliance Efficiency Regulations include:

•    Room air-conditioners

•    Room air-conditioning heat pumps

•    Central air conditioners with a cooling capacity of less than 135,000 British thermal units per hour (Btu/hr.)

•    Central air conditioning heat pumps

•    Gas-fired central furnaces

•    Gas-fired boilers

•    Gas-fired furnaces

•    Gas-fired floor furnaces

•    Gas-fired room heaters

•    Gas-fired duct furnaces

•    Gas-fired unit heaters

The Appliance Efficiency Regulations do not require certification for:

•    Electric resistance space heaters.

•    Oil-fired wall furnaces, floor furnaces, and room heaters. (Some are voluntarily listed with certified gas-fired furnaces.)

Equipment that does not meet the federal appliance efficiency standards may not be sold in California. Any equipment covered by the Appliance Efficiency Regulations and sold in California must have the date of manufacture permanently displayed in an accessible place on that equipment. This date is frequently included as part of the serial number.

Generally, equipment manufactured before the effective date of a new standard may be sold and installed in California indefinitely as long as the performance approach demonstrates energy compliance of the building using the lower efficiency of the relevant appliances. An exception is central split-system air conditioners and central single package air conditioners installed in California. The U.S. Department of Energy (DOE) requires compliance with the minimum efficiencies specified in Table 11-27 at the time of installation.

The compliance and enforcement processes should ensure that all installed HVAC equipment regulated by the Appliance Efficiency Regulations is certified by the California Energy Commission.

11.5.3      Dwelling Unit Space Conditioning Equipment Requirements

Dwelling unit space conditioning systems must meet the following mandatory Energy Code requirements:

•    Space Conditioning Equipment Certification and Equipment Efficiency: §110.1|topic=SECTION 110.1 – MANDATORY REQUIREMENTS FOR APPLIANCES, §110.2

•    Restrictions on Pilot Lights for Natural Gas Appliances and Equipment: §110.5|topic=SECTION 110.5 – NATURAL GAS CENTRAL FURNACES\, COOKING EQUIPMENT\, POOL AND SPA HEATERS\, AND FIREPLACES\: PILOT LIGHTS PROHIBITED

•    Space Conditioning System Controls: §160.3(a)1 Dwelling Unit Thermostats

•    Dwelling Unit Space Conditioning and Air Distribution Systems: §160.3(b)

•    Fluid Distribution Systems – Pipe Insulation: §160.3(b)6, §160.3(c)1|topic=1. Pipe Insulation..

Prescriptive requirements include:

Prescriptive requirements for Space Conditioning Systems are in §170.2(c)3.

The requirements for the performance approach are in §170.1.

11.5.3.1    Mandatory Requirements

This section addresses the mandatory requirements for heating and cooling equipment, including furnaces, boilers, heat pumps, air conditioners, and electric resistance equipment, serving multifamily dwelling units. Residential equipment used in common use areas must meet these mandatory requirements. Commercial equipment used in common use areas must meet the mandatory requirements described in Chapter 11.6.5.1.

11.5.3.2    Equipment Efficiency

The efficiency of most dwelling unit heating and cooling equipment is regulated by the National Appliance Energy Conservation Act of 1987 (NAECA, the federal appliance standard) and California’s Appliance Efficiency Regulations. These regulations are not contained in the Energy Code but are published separately. These regulations are referenced in §110.1. The energy efficiency of larger equipment is regulated by §110.2(a)|topic=(a) Efficiency.. The Appliance Efficiency Regulations include definitions for all types of equipment and are regularly updated.

Note: The Appliance Efficiency Regulations that are in effect when the building permit is applied for will determine the minimum efficiency of the appliances identified in the compliance documentation.

L.     Central, Single-Phase Air Conditioners and Air Source Heat Pumps

Central, single-phase air conditioners and air source heat pumps  commonly installed in multifamily dwelling units have a capacity less than 65,000 Btu/hr.

Air conditioner efficiencies are determined according to federal test procedures. The efficiencies are reported in terms of SEER and EER. The Appliance Efficiency Regulations for this equipment require minimum SEER. The SEER of all new central, single-phase air conditioners and air source heat pumps with an output less than 65,000 Btu/h must be certified to the Energy Commission to have values no less than the values listed in Table 11-27.

Table 11-27: Minimum Cooling Efficiencies for Central Air Conditioners and Heat Pumps
(Cooling Capacity Less Than 65,000 Btu/h)

See 10 CFR section 430.32(c) for less stringent federal standards applicable to these units that are manufactured on or after January 1, 2015, and installed in states other than Arizona, California, Nevada, or New Mexico.

Source: California Appliance Efficiency Regulations, Title 20, Table C-3, and Federal Appliance Standards (NAECA)

M.   Heat Pumps and Electric Heating

Efficiency requirements for package terminal air conditioners, package terminal heat pumps, single-package vertical air conditioners, and single-package vertical heat pumps are listed in Table 110.2-E of the Energy Code.

Heat pumps must be certified to have a HSPF or coefficient of performance (COP) equal to or better than those listed in Table 11-28.

There are no minimum appliance efficiency standards for electric-resistance or electric-radiant heating systems.

Table 11-28: Minimum Heating Efficiency for Heat Pumps

Source: California Appliance Efficiency Regulation Title 20

N. Other Air Conditioners and Heat Pumps

The Appliance Efficiency Regulations contain minimum efficiency requirements for three-phase models, larger-capacity central air conditioners and heat pumps, and all room air conditioners and room air conditioner heat pumps. The efficiency for these types of equipment must be certified to the Energy Commission by the manufacturer. Table 11-29 and Table 11-30 include efficiency requirements for equipment with a cooling capacity less than 65,000 Btu/hour. Efficiency requirements for larger equipment requirements are covered in Chapter 4.

Table 11-29 Minimum Cooling Efficiency for Three-Phase Models and Central Air Conditioners and Heat Pumps

* Three-phase models only

1 Applies to equipment that has electric resistance heat or no heating.

2 Applies to equipment with all other heating-system types that are integrated into the unitary equipment.

3. Deduct 0.2 from the required EER for units with heating sections other than electric resistance heat.

Source : California Appliance Efficiency Regulations Table C-4, C-5

Table 11-31: Minimum Efficiency for Gas- and Oil-Fired Central Furnaces

Source: California Appliance Efficiency Regulations Title-20 - Table E-6

Noncentral gas furnaces and space heaters must be certified to have AFUE values greater than or equal to those listed in Table 11-32.

Table 11-30: Minimum Cooling Efficiency for Noncentral Space-Cooling Equipment

Cap. = Cooling Capacity (Btu/hr)

Note: Including room air conditioners and room air conditioner heat pumps,

Source: California Appliance Efficiency Regulations Title 20, Table B-3, the Energy Code Table 110.2-E

O.    Gas and Oil-Fired Furnaces

The Appliance Efficiency Regulations require gas- and oil-fired central furnaces with outputs less than 225,000 Btu/hr to be rated according to the associated annual fuel utilization efficiency (AFUE). Gas- and oil-fired central furnaces with outputs greater than or equal to 225,000 Btu/hr are rated according to the respective thermal (or steady-state) efficiency.

Equipment with outputs less than 225,000 Btu/hr is listed in Table E-6 of the Appliance Efficiency Regulations and incorporated in Table 11-31. Efficiency for equipment with outputs greater than or equal to 225,000 Btu/hr is listed in Table E-6 of the Appliance Efficiency Regulations and included in Appendix B.

Table 11-32: Minimum Heating Efficiency for Nonducted, Noncentral, Gas-Fired Heating Equipment

Source: California Appliance Efficiency Regulations Title 20 - Table E-2

P.    Gas- and Oil-Fired Central Boilers and Electric Boilers

Gas- and oil-fired central boilers must be certified to have and AFUE or combustion efficiency equal to or better than those listed in the Energy Code Table 110.2-J.

11.5.3.3    Dwelling Unit Controls

§110.2 (b) & (c), §160.3(a)1

The Energy Code includes a mandatory requirement for thermostat controls. Unless controlled by a central energy management control system the thermostat must have setback capabilities. An exception is allowed only if the system is one of the following non-central types:

•    Non-central electric heaters such as mini-split heat pumps

•    Room air conditioners

•    Room air conditioner heat pumps

•    Gravity gas wall heaters

•    Gravity floor heaters

•    Gravity room heaters

•    Wood stoves

•    Fireplace or decorative gas appliances

When it is required, the setback thermostat must have a clock or other mechanism that allows the resident to schedule the heating and/or cooling set points for at least four periods over 24 hours.

If more than one piece of heating or cooling equipment is installed in a dwelling unit, the setback requirement may be met by controlling all heating or cooling units by one thermostat or by controlling each unit with a separate thermostat. Separate heating or cooling units may be provided with a separate on/off control capable of overriding the thermostat.

Thermostats for heat pumps equipped with supplementary electric resistance heat must be thermostats that minimize the use of supplementary electric resistance heating during startup and recovery from setback, as discussed in Heat Pump System Controls Example 11-27

11.5.3.4    Heat Pump System Controls

Heat pump systems must be controlled by a central energy management control system (EMCS) or by a setback thermostat as described under Dwelling Units Controls. Any heat pump with supplementary electric resistance heating requires controls with capabilities to limit the electric resistance heating. The first required capability is to set the cut-on and cut-off temperatures for the heat pump and supplementary electric resistance heating at different levels.

For example, if the heat pump begins heating when the inside temperature reaches 68°F, the electric resistance heating may be set to come on if the temperature goes below 65°F if the heat pump alone could not maintain the set point of 68°F. Also, there must be an OFF mode that automatically shuts off the electric resistance when the inside temperature reaches 68°F.   

The second control capability must prevent the supplementary electric resistance heater from operating if the heat pump alone can meet the heating load, except during defrost. There is a limited exception to this second function for “smart thermostats” that provide intelligent recovery, staging, ramping, or another control mechanism that prevents the unnecessary operation of supplementary electric resistance heating when the heat pump alone can meet the heating load.

To meet the thermostat requirements, a thermostat for a heat pump with supplementary electric resistance heating must be a thermostat that minimizes the use of supplementary heating during startup and recovery from setbacks.

Note: Room air conditioner heat pumps are not required to comply with the thermostat requirements.

11.5.3.5    Equipment Sizing

The Energy Code does not set limits on the sizing of heating and cooling equipment, but does require that heating and cooling loads be calculated for new HVAC systems. Oversized equipment typically operates less efficiently and can create comfort problems due to excessive cycling and improper airflow. Ducts must be sized correctly, otherwise the system airflow rate may be restricted, adversely affecting the efficiency of the system and preventing the system from meeting the mandatory minimum airflow rate requirements.

Acceptable load calculation procedures include methods described in the following publications:

•    The ASHRAE Handbook – Equipment

•    The ASHRAE Handbook – Applications

•    The ASHRAE Handbook – Fundamentals

•    The SMACNA Residential Comfort System Installation Standards Manual

•    ACCA Manual J

The Energy Code requires that the outdoor design conditions for heating load calculations be selected from JA2 and that the indoor design temperature for heating load calculations be 68°F. The outdoor design temperature must be no lower than the “heating winter median of extremes,” as listed in JA2. The outdoor design conditions for cooling load calculations must be selected from JA2, Table 2-3, using values no greater than the “1.0 percent cooling dry bulb” and “mean coincident wet bulb” values listed. The indoor design temperature for cooling load calculations must be 75°F.

If the actual city location for a project is not included in JA2, or if the data given for a particular city do not match the conditions at the actual site as well as that given for another nearby city, consult the local building department for guidance.

The load calculations must be submitted with the compliance documentation when requested by the building department.

The load calculations may be prepared by 1) a mechanical engineer, 2) the mechanical contractor who is installing the equipment or 3) someone who is qualified to do so in the State of California according to Division 3 of the Business and Professions Code.

The Business and Professions Code does not prohibit an unlicensed person from preparing plans, drawings, or specifications for certain buildings containing no more than four dwelling units of wood-frame construction and not more than two stories and basement in height.

11.5.3.6    Standby Losses and Pilot Lights

§110.5|topic=SECTION 110.5 – NATURAL GAS CENTRAL FURNACES\, COOKING EQUIPMENT\, POOL AND SPA HEATERS\, AND FIREPLACES\: PILOT LIGHTS PROHIBITED and §110.2(d)

Fan-type central furnaces may not have a continuously burning pilot light. This requirement does not apply to wall furnaces, floor furnaces, or any gravity-type furnace. Household cooking appliances also must not have a continuously burning pilot light, except for those without an electrical supply voltage connection and in which each pilot consumes less than 150 Btu/h.

Larger gas-fired and oil-fired forced air furnaces with input ratings equal to or greater than 225,000 Btu/h (which is bigger than a typical residential furnace) must also have an intermittent ignition device and either power venting or a flue damper.

A vent damper is an acceptable alternative to a flue damper for furnaces where combustion air is drawn from the conditioned space. All furnaces with input ratings equal to or greater than 225,000 Btu/h, including electric furnaces, that are not within the conditioned space must have jacket losses not exceeding 0.75 percent of the input rating.

11.5.3.7    Pipe Insulation

Specific insulation requirements for heating and cooling system piping in dwelling units are the same as requirements in common use areas. These requirements are detailed in Chapter 11.1.18.1, Chapter 4.5, and Tables 4-15a through 4.15f.

For air conditioners and heat pumps, two refrigerant lines connect the indoor and outdoor units of split-system air conditioners and heat pumps: the liquid line (the smaller diameter line) and the suction line (the larger diameter line). If the liquid line is at an elevated temperature relative to outdoor and indoor temperatures, it should not be insulated. In those areas, heat escaping from it is helpful.

The suction line carries refrigerant vapor that is cooler than ambient in the summer and (with heat pumps) warmer than ambient in the winter. This line must be insulated to the required thickness (in inches).

Insulation used for refrigerant suction lines located outside of conditioned space must include a Class I or Class II vapor retarder. The vapor retarder and insulation must be protected from physical damage, UV deterioration, and moisture with a covering that can be removed for equipment maintenance without destroying the insulation. Insulation is typically protected by aluminum, sheet metal jacket, painted canvas, or plastic cover. Adhesive tape should not be used as insulation protection because removal of the tape will damage the integrity of the original insulation during preventive maintenance. See Figure 11-34 for example of refrigerant line insulation.

Figure 11-34: Refrigerant Line Insulation

Source: Airex Manufacturing Inc.

11.5.3.8    Outdoor Condensing Units

Any obstruction of the airflow through the outdoor unit of an air conditioner or heat pump lowers efficiency. Dryer vents are prime sources for substances that clog outdoor coils and sometimes discharge substances that can cause corrosion. Therefore, condensing units must not be placed within five ft. of a dryer vent. This requirement is applicable to new installations and to replacements. Regardless of location, condenser coils should be cleaned regularly. The manufacturer installation instructions may include requirements for minimum horizontal and vertical distance to surrounding objects that should be met if greater than the minimum distance required by the Energy Code. Figure 11-35 shows an example when a condensing unit installed location does not meet the clearance requirement.

Figure 11-35: Noncompliant Condensing Unit Clearance from Dryer Vents

Source: California Energy Commission

Liquid line filter driers are components of split system air-conditioners and split system heat pumps that are installed in the refrigerant line to remove moisture and particles from the refrigerant stream. These contaminants may be introduced in the refrigerant as a result of improper flushing, evacuation, and charging procedures, causing the efficiency and capacity of the air conditioner to be impaired or damaging components. If required by manufacturer’s instructions, liquid line filter dryers must be installed. Sometimes, liquid line filter dryers are preinstalled by manufacturers within condensing units. Some manufacturers install liquid line filter dryers outside condensers, so they can be easily serviced by technicians and more easily verified by HERS Raters.

The quality of the filter dryer installation impacts the effectiveness of the liquid line filter dryer, as some liquid line filter dryers can be installed without regard to the direction of refrigerant flow. Heat pumps, for example, allow refrigerant flow in both directions. However, in other air conditioners where refrigerant flow occurs in only one direction, correct orientation of the liquid line filter dryer is important.

11.5.3.9    Dwelling Unit Prescriptive Requirements

Prescriptive compliance requires the installation of a heat pump for dwelling units in buildings up to three habitable stories in Climate Zones 1-15. For Climate Zone 16, the installation of an air conditioner with gas-fired furnace is prescriptively required. For buildings with four or more habitable stories, prescriptive compliance requires installation of a heat pump for Climate Zones 2-15. For Climate Zone 1 and 16, prescriptive compliance requires the installation of a dual-fuel heat pump that uses gas as supplemental heat.

In addition, for buildings with three habitable stories in Climate Zones 4-10, see Chapter 11.4.2.2 for ventilation fan power requirements. 

When using the prescriptive compliance approach, the installed heat pump or gas heating system gets no additional credit for higher efficiency equipment.

Prescriptive requirements for air-cooled air conditioners and air-source heat pumps installed in Climate Zones 2 and 8 through 15 necessitate the installation of a measurement access hole (MAH), refrigerant charge verification (RCV), and minimum system airflow verification. The minimum system airflow installation and RCV must be performed by the installer and/or HERS Rater or ATT. The MAH provides a nonintrusive means of measuring return air temperature, which is an important parameter to the RCV process. The alternative to RCV by a HERS Rater is the installation of a refrigerant FID. When installing an FID, the installer must still perform RCV.

11.5.3.10  Dual-fuel Heat Pump System

For Climate Zones 1 and 16, the prescriptive requirement includes the use of a dual-fuel heat pump for buildings four habitable stores or greater. This system pairs an electric heat pump with a gas-fired furnace and alternates between the two fuel sources for heating. Heat pumps face a challenge in colder climates where their capacity for providing heat and the efficiency of the equipment reduces as the outdoor temperature drops. This is especially true for the type of minimal efficiency heat pumps that are the basis for the federal appliance standards for heat pumps. To address these challenges, gas-fired furnace can be used for space heating when outdoor air temperature is below a certain threshold, normally between 35-45°F.

The dual-fuel heat pump system can be controlled similarly to a heat pump with electric resistance required by §110.2(b). The control should have the capability to set the cut-on and cut-off temperatures for the heat pump and supplementary gas-fired heating at different levels. For example, if the heat pump begins heating when the inside temperature reaches 68°F, the gas-fired furnace heating may be set to come on if the temperature goes below 65°F, if the heat pump alone could not maintain the set point of 68°F. Also, there must be an OFF mode that automatically shuts off the gas-fired heating when the inside temperature reaches 68°F. The system may also have a control capability that prevents the supplemental gas-fired furnace from operating if the outdoor air temperature is above a pre-set threshold.

11.5.3.11  Supplemental Heating System

Supplemental heating systems are allowed prescriptively, and the designer may elect to provide supplemental heating to a space such as a bathroom. In this instance, the supplemental heating system must be installed in a space that is served by the primary heating system and must have a thermal capacity of less than 2 kilowatts (kW) or 7,000 Btu/h while being controlled by a time-limiting device not exceeding 30 minutes. Electric resistance and electric radiant heating installation are not allowed as the primary heating system when using the prescriptive compliance method.

11.5.3.12  Measurement Access Hole

The MAH provides a nonintrusive means for refrigerant charge verification by HERS Raters or ATT and other third-party inspectors. They eliminate the need for raters/inspectors to drill holes into the installed air conditioning equipment enclosures to place the temperature sensors that are required by the refrigerant charge verification test procedures described in the Reference Residential Appendix RA3.2.

Installation of MAH must be performed by the installer of the air conditioner or heat pump equipment according to the specifications given in Reference Residential Appendix RA3.2.

The MAH feature consists of one 5/8-inch (16 millimeters [mm]) diameter hole in the return plenum, upstream from the evaporator coil. (See Figure RA3.2-1 in Reference Residential Appendix RA3.2.)

11.5.3.13  Refrigerant Charge Verification

The prescriptive standards for Climate Zones 2 and 8-15 require all cooling systems— including ducted air-cooled air conditioners, ducted air-source heat pumps, small-duct high-velocity systems, and mini-split systems — to have the correct refrigerant charge verified. Verification of refrigerant charge must be conducted by a HERS Rater for multifamily buildings with up to three habitable stories. For multifamily buildings with four or more stories, testing only needs to be conducted and certified by the installing contractor, and neither a HERS Rater nor registration with a HERS Provider is required. The RCV procedures are documented in Reference Residential Appendix RA1.2, RA2.4.4, and RA3.2.

Refrigerant charge refers to the actual amount of refrigerant present in the system. Excessive refrigerant charge (overcharge) reduces system efficiency and can lead to premature compressor failure. Insufficient refrigerant charge (undercharge) also reduces system efficiency and can cause compressors to overheat. Ensuring correct refrigerant charge can significantly improve the performance of air-conditioning equipment. Refrigerants are the working fluids in air-conditioning and heat-pump systems that absorb heat energy from one area (through the evaporator), transfer, and reject it to another (through the condenser).

Verification of proper refrigerant charge must occur after the HVAC contractor has installed and charged the system in accordance with the manufacturer’s specifications. The procedure requires properly calibrated digital refrigerant gauges, thermocouples, and digital thermometers. When multiple systems in the same dwelling unit require testing, test each system.

In a typical cooling system, there are two important performance criteria that are relatively easy to verify that there is neither too much nor too little refrigerant in the system. In systems with a fixed-orifice device in the evaporator coil, the number to check is called the superheat. In a system with a variable-metering device, the number to check is called the subcooling.

Superheat refers to the number of degrees the refrigerant is raised after it evaporates into a gas. This occurs inside the evaporator coil (or indoor coil). The correct superheat for a system will vary depending on certain operating conditions. The target superheat for a system must be obtained from a table provided in the RA3.2 protocols or the manufacturer’s superheat table. There is an allowed range of several degrees between the measured superheat and the target superheat for a system to pass.

Subcooling refers to the number of degrees the refrigerant is lowered after it condenses into a liquid. This occurs inside the condenser coil (or outdoor coil). The manufacturer specifies the correct subcooling for a system. It may vary depending on operating conditions. Like superheat, there is an allowed range of several degrees between the measured subcooling and the target subcooling for a system to pass.

The temperature at which a refrigerant condenses or evaporates is called the saturation temperature. Above the saturation temperature, a refrigerant is always a gas. Below the saturation temperature, a refrigerant is always a liquid.

Saturation is when a refrigerant exists as both a liquid and a gas. It always occurs at the same temperature, depending on what the pressure of the refrigerant happens to be. At higher pressures, the saturation temperature goes up and vice versa. This convenient property is what makes refrigeration work.

The saturation temperature can be determined by simply measuring the pressure of a refrigerant and referring to a table, known as a pressure-temperature (PT) table, for that specific refrigerant. Saturation temperatures are well-documented for all common refrigerants.

Because variable refrigerant metering devices are prone to failure and even more so to improper installation, it is important that the operation of these devices be checked. A metering device maintains a relatively constant superheat over a wide range of operating conditions; therefore, checking the superheat, in addition to the other tests performed, will indicate if the metering device is operating correctly.

Unfortunately, checking superheat and subcooling can be done only under certain indoor and outdoor conditions. This verification procedure, called the Standard Charge Verification Method, is very weather-dependent.

There is another way to verify proper refrigerant charge that is not weather–dependent, and that is by weighing the refrigerant. Called the Weigh-in Charge Verification Method, this approach can be performed only by the installer. It can be verified by the HERS Rater either by simultaneous observation or by using the standard method when conditions permit.

11.5.3.14  Minimum System Airflow Verification for Refrigerant Charge Verification

To have a valid charge test, the system airflow must be verified to be at least 300 CFM/ton for altered systems and 350 CFM/ton for new systems. The procedures for measuring total system airflow are found in RA3.3. They include plenum pressure matching using a fan flow meter, a flow grid, a powered flow hood, and the traditional (nonpowered) flow hood. The airflow verification procedures for refrigerant charge verification no longer include the temperature split method.

If an altered system does not meet the minimum airflow requirements, remedial steps are required to increase system airflow. More airflow is generally better for systems with air conditioning. Not only does this allow proper refrigerant charge to be verified, but it improves the overall performance of the system. When able to be performed on a system, regardless of the refrigerant charge verification procedure, minimum system airflow must always be verified.

In some alterations, improving airflow may be cost-prohibitive, and there is a process for documenting this (RA3.3.3.1.5). When this option is used, verification by sample groups is not allowed. Minimum airflow is critical to proper air-conditioner operation. Reducing airflow reduces cooling capacity and efficiency. Many systems in California have oversized equipment and undersized ducts. In newly installed duct systems, the minimum airflow requirement is higher because the opportunity exists to design and install a better system. In altered systems, the installer may be required to modify the ducts system to meet the minimum airflow. The minimums of 300 and 350 CFM/ton are lower than the desired airflow for most systems, which is usually 400 CFM/ton and higher.

11.5.3.15  Standard Charge Verification Procedure (RA3.2.2)

The first step is to turn on the air-conditioning system and let it run for at least 15 minutes to stabilize temperatures and pressures. While the system is stabilizing, the HERS Rater or the installer may attach the instruments needed to take the measurements.

Figure 11-39: Measurements for Refrigerant Charge and Airflow Tests

Source: California Energy Commission

The following measurements must be taken by the technician or HERS Rater, when applicable.

1.  The return air wet bulb and dry bulb temperatures are measured in the return plenum before the blower at the location labeled "Title 24 – Return Plenum Measurement Access Hole." This hole must be provided by the installer, not the rater (See Points 1 and 2 in Figure 11-39). See Figure RA 3.2-1 for more information on the placement of the measurement access hole (MAH).

2.  Moreover, the outdoor air dry bulb temperature is measured at the point where the air enters the outdoor condensing coil. (See Point 3 in Figure 11-39). It is important that this outdoor temperature sensor be shaded from direct sun during the verification procedure.

In addition to the air temperature measurements, four refrigerant properties need to be measured. Two of these measurements are taken near the suction line service valve before the line enters the outdoor unit and are used to check the superheat.

1.  The first measurement is the temperature of the refrigerant in the suction line, which is taken by a clamp-on thermocouple or other suitable device insulated from the outdoor air. (See Point 4 in Figure 11-39.)

2.  The second measurement determines the saturation temperature of the refrigerant in the evaporator coil. (See Point 5 in Figure 11-39.) The saturation temperature can be determined from the low-side (suction line) pressure and a saturation temperature table for the applicable refrigerant.

To check the subcooling, two more refrigerant properties are required and may be measured near the liquid line service valve at the point where the line exits the outdoor unit.:

1.  The liquid refrigerant temperature in the liquid line is measured by a clamp-on thermocouple insulated from the outdoor air. (See Point 6 in Figure 11-39.)

2.  The condenser saturation temperature can be determined from the liquid line pressure and a saturation temperature table for the applicable refrigerant. (See Point 7 in Figure 11-39.)

Determination of the condenser saturation temperature and the liquid line temperature is used only for the subcooling verification method on systems with TXV or EXV metering devices.

11.5.3.16  Superheat Charge Verification Method (RA3.2.2.6.1)

The Superheat Charge Verification Method is used on units with a fixed-orifice refrigerant metering device (not a TXV or EXV).

Airflow verification must be confirmed before starting the Superheat Verification Method.

The Superheat Verification Method compares the actual (measured) superheat temperature to a target value from a table. The actual superheat temperature is the measured suction line temperature (T_{Suction, db}) minus the evaporator saturation temperature (T_{Evaporator, Saturation}). The target superheat value is read from a table (Table RA3.2-2 or the manufacturer’s superheat table).

Only an EPA-certified technician may add or remove refrigerant. Under no circumstances may HERS Raters add or remove refrigerant on systems that they are verifying.

11.5.3.17  Subcooling Verification Method (RA3.2.2.6.2)

The Subcooling Verification Method is used on units with a variable refrigerant metering device (a TXV or EXV).

Airflow verification must be confirmed before starting the Subcooling Verification Method.

The Subcooling Verification Method compares the actual subcooling temperature to the target value supplied by the manufacturer. The actual subcooling is the condenser saturation temperature (T_{Condenser, Saturation}) minus the liquid line temperature (T_Liquid).

11.5.3.18  Weigh-In Charging Procedure (RA3.2.3)

The weigh-in charging procedure charges the system by determining the appropriate weight of refrigerant based on the size of the equipment and refrigerant lines rather than by measuring steady-state performance of the system. Systems using the weigh-in procedure to meet the refrigerant charge verification requirement may not use group sampling procedures for HERS verification compliance.

The weigh-in procedure does not relieve the installer of the responsibility to comply with the required minimum system airflow.

There are two installer options for completing the weigh-in procedure. One involves adjusting the amount of refrigerant supplied by the manufacturer in a new system, as specified by the manufacturer (weigh-in charge adjustment). The other involves evacuating the entire system and recharging it with the correct total amount of refrigerant, by weight (weigh-in total charge).

The weigh-in charge adjustment procedure may be used only when a new factory-charged outdoor unit is being installed and the manufacturer provides adjustment specifications based on evaporator coil size and refrigerant line size and length.

The weigh-in total charge may be used for any weigh-in procedure but still requires manufacturer’s adjustment specifications. Only the installer/technician may perform any kind of weigh-in procedure.

11.5.3.19  Equipment Limitations

The Energy Code specifically requires verification of refrigerant charge only for air-cooled air conditioners and air-source heat pumps. All other types of systems are not expressly exempt from the refrigerant charge requirements. Certain portions of the requirements may still apply, such as the minimum system airflow requirement. The installer would have to confirm with the manufacturer and the CEC. The installer must adhere strictly to the manufacturer’s specifications.

Variable refrigerant flow systems and systems such as some mini-split systems that cannot be verified using the standard charge verification procedure in RA3.2.2 must demonstrate compliance using the weigh-in method. Verification by the HERS Rater can be accomplished only by simultaneous observation of the installer’s weigh-in as specified by RA3.2.3.2, and only if use of HERS Rater observation procedure is specified by the Energy Code.

11.5.3.20  HERS Verification Procedures

When required by the CF1R, HERS Raters must perform field verification and diagnostic testing of the refrigerant charge, including verification of minimum system airflow and verification of installation of the measurement access hole.

The verification procedures are essentially identical for the rater and the installer except that the tolerances for passing the superheat and subcooling tests are less stringent for the rater’s test. This is to allow for some variations in measurements due to instrumentation or test conditions (for example, weather).

The following conditions prohibit verification using sample groups:

1.  When the weigh-in method is used

2.  When the minimum airflow cannot be met despite reasonable remediation attempts. (See RA3.3.3.1.5).

As always, to be eligible for sampling, the installer must first verify and pass the system. If sampling is not being used, the rater will perform the verification only after the installer has charged the system according to manufacturer’s specifications.

11.5.3.21  Winter Setup Procedures

Reference Appendix RA1 provides for the approval of special case refrigerant charge verification procedures. These protocols may be used only if the manufacturer has approved use of the procedure for their equipment.

One such procedure is found in RA1.2 Winter Setup for the standard charge verification procedure (winter charge setup). It provides for a modification to the standard charge procedure when temperature conditions do not allow use of the RA3.2.2 standard charge verification procedure.

The winter charge setup allows both installers and HERS Raters to verify the charge when outdoor temperatures are below the manufacturer's allowed temperature, or the outdoor temperature is less than 55°F. The Weigh-in Charging Procedure specified in RA3.2.3 may also be used when the outdoor temperatures are below the manufacturer's allowed temperature or below 55°F but may be used only by the installer.

The winter charge setup procedure allows the system to operate in the same range of pressure differences between the low-side pressure and the high-side pressure as occurs during warm outdoor temperatures, by restricting the airflow at the condenser fan outlet. The winter charge setup is used only for units equipped with variable metering devices, which include thermostatic expansion valves (TXV) and electronic expansion valves (EXV) for which the manufacturer specifies subcooling as the means for determining the proper charge for the unit, including units equipped with microchannel heat exchangers. Once this pressure differential is achieved, the variable metering device calculations are conducted in the same way as the variable metering device procedures described in RA3.2.2.6.2. All other applicable requirements in RA3.2.2 remain the same and must be completed when using the winter charge setup.

Though not specifically mentioned in the FID protocols in Residential Appendix RA3.4.2, the RA1.2 winter setup method may be used if applicable. Thus, for FID verification, the winter setup method may be used in place of the subcooling method.

11.5.3.22  Using Weigh-In Charging Procedure at Low Outdoor Temperatures

When a new HVAC system is installed, the HVAC installer must check the refrigerant charge, and a HERS Rater must verify the correct charge; however, an exception to §150.1(c)7A provides for an alternative third-party HERS verification if the weigh-in method is used when the outdoor temperature is less than 55 degrees F.

Typically, when the weigh-in method is used by the installing contractor, a HERS Rater must perform a charge verification in accordance with the RA3.2. standard charge procedure. However, because the RA3.2.2 procedures cannot be used when the outdoor temperatures are less than 55 degrees, the Energy Code provides the installer with two choices:

1.    Use the RA3.2.3.1 Installer Weigh-In Charging Procedure to demonstrate compliance and install an occupant-controlled smart thermostat (OCST).

2.    Wait for warmer temperatures then perform the standard charge verification procedure. In this case, the installer must agree to return to correct refrigerant charge if a HERS Rater determines later, when the outside temperature is 55 degrees F or above, that correction is necessary as described in Residential Appendix RA2.4.4. The installer must also provide written notice to the owner and enforcement agency that the charge has not yet been verified. An example owner’s notification is shown in Figure 11-40 .

Figure 11-40: Example of Notification to Owners of Delayed Charged Verification

Source: California Energy Commission

11.5.3.23  Minimum System Airflow

Ducted forced-air cooling systems must comply with the minimum system airflow rate of greater than or equal to 350 CFM/ton, or 250 CFM/ton for small duct, high velocity systems, when performing the refrigerant charge verification. The airflow is important when performing the refrigerant charge verification to validate the measured values for pressure and temperature. The correct airflow will also improve the performance of the air-conditioning equipment.

The airflow verification procedure is documented in Reference Residential Appendix RA3.3.

11.5.3.24  Fault Indicator Display (FID)

The installation of an FID may be used as an alternative to the prescriptive requirement for HERS diagnostic testing of the refrigerant charge in air conditioners and heat pumps. The installation of an FID does not preclude the HVAC installer from having to properly charge the system with refrigerant. The FID provides real-time information to the building occupant or operator about the status of the system refrigerant charge, metering device, and system airflow. The FID will monitor and determine the operating performance of air conditioners and heat pumps and provide visual indication to the system owner or operator if the refrigerant charge, airflow, or metering device performance of the system does not conform to approved target parameters for minimally efficient operation. Thus, if the FID signals the owner/occupant that the system requires service or repair, the occupant or operator can immediately call for a service technician to make the necessary adjustments or repairs. An FID can provide significant benefit by alerting the owner/occupant to the presence of inefficient operation that could result in excessive energy use/costs over an extended period. An FID can also indicate system performance faults that could result in system component damage or failure if not corrected, thus helping the owner/occupant avoid unnecessary repair costs.

Fault indicator display technologies are expected to be installed at the factory; otherwise, they may be installed in the field according to manufacturer's specifications. Reference Joint Appendix JA6 contains more information about FID technologies.

The presence of an FID on a system must be field-verified by a HERS Rater or ATT. See Reference Residential Appendix RA3.4.2 for the HERS verification procedure, which consists of a visual verification of the presence of the installed FID technology. The Rater must inspect to see that the visual indication display component of the installed FID technology is mounted adjacent to the thermostat of the split system. When the outdoor temperature is greater than 55°F, the Rater must also observe that the system reports no system faults when the system is operated continuously for at least 15 minutes when the indoor air temperature returning to the air conditioner is at or above 70°F. When the outdoor temperature is below 55°F, the Rater must observe that the FID performs a self-diagnosis and indicates that the sensors and internal processes are operating properly.

11.5.3.25  Dwelling Unit Performance Approach

There are several options for compliance credit related to the dwelling unit heating and cooling system through the performance approach.

11.5.3.26  High-Efficiency Heating

Heating system efficiencies are explained in Chapter 11.6.3.1 0. The minimum efficiency is required for prescriptive compliance. When the performance approach is used, additional compliance credit may be available from higher efficiency heating equipment.

When a heat pump is providing space heating, if the efficiency used for compliance is higher than the minimum required HSPF, the system efficiency must be verified by a HERS Rater. Moreover, because the capacity of the heat pump affects the amount of back-up electric resistance heating required to attain and maintain comfort conditions, if the capacity proposed for compliance is different than the default capacity used in the compliance software, the Air Conditioning, Heating, and Refrigeration Institute (AHRI) ratings for heating capacity of the installed heat pump must be verified by a HERS Rater to confirm the heating capacities at 47°F and 17°F are equal or greater than the heating capacities given on the certificate of compliance. See RA3.4.4.2 for more information about this HERS verification

11.5.3.27  High-Efficiency Air Conditioner

Savings can be achieved by choosing an air conditioner that exceeds the minimum efficiency, SEER and (or) EER, requirements.

The EER is the full-load efficiency at specific operating conditions. It is possible that two units with the same SEER can have different EERs. In cooling climate zones of California, for two units with a given SEER, the unit with the higher EER is more effective in saving energy. Using the performance approach, credit is available for specifying an air conditioner with an EER greater than the minimums identified in Chapter 11.5.3. When credit is taken for a high EER and/or SEER, field verification by a HERS Rater or ATT is required. (See Reference Residential Appendix RA3.4.4).

11.5.3.28  Central Fan Ventilation Cooling

Central fan ventilation cooling performs a function similar to a WHF using the central space-conditioning ducts to distribute outside air. There is no performance credit for central fan ventilation cooling because the compliance software does not include it as an option.

11.5.3.29  Zonal Control

A credit is provided for zoned heating systems, which save energy by providing selective conditioning for only the occupied areas of a dwelling unit. A dwelling unit having at least two zones (living and sleeping) may qualify for this compliance credit. The equipment may consist of one heating system for the living areas and another system for sleeping areas or a single system with zoning capabilities, set to turn off the sleeping areas in the daytime and the living area unit at night. This compliance credit is not commonly applied in multifamily buildings.

There are unique eligibility and installation requirements for zonal control to qualify under the Energy Code. The following steps must be taken for the building to show compliance with the Energy Code under this exceptional method:

1.      Temperature Sensors. Each thermal zone, including a living zone and a sleeping zone, must have air temperature sensors that provide accurate temperature readings of the typical condition in that zone.

2.      Habitable Rooms. For systems using central forced-air or hydronic heating, each habitable room in each zone must have a source of space heating, such as forced-air supply registers, radiant tubing, or a radiator. For systems using a combination of a central system and a gas-vented fireplace or other conditioning units, the zone served by the individual conditioning unit can be limited to a single room. Bathrooms, laundry, halls and/or dressing rooms are not habitable rooms.

3.      Noncloseable Openings. The total noncloseable opening area (W) between adjacent living and sleeping thermal zones (such as halls, stairwells, and other openings) must be less than or equal to 40 ft². All remaining zonal boundary areas must be separated by permanent floor-to-ceiling walls and/or fully solid, operable doors capable of restricting free air movement when closed.

4.      Thermostats. Each zone must be controlled by a central automatic dual-setback thermostat that can control the conditioning equipment and maintain preset temperatures for varying periods in each zone independent of the other. Thermostats controlling vented gas fireplace heaters that are not permanently mounted to a wall are acceptable as long as they have the dual-setback capabilities.

Other requirements specific to forced-air-ducted systems include the following:

1.  Each zone must be served by a return air register located entirely within the zone. Return air dampers are not required.

2.  Supply air dampers must be manufactured and installed so that when they are closed, there is no measurable airflow at the registers.

3.  The system must be designed to operate within the equipment manufacturer's specifications.

4.  Air is to positively flow into, though, and out of a zone only when the zone is being conditioned. No measurable amount of supply air is to be discharged into unconditioned or unoccupied space to maintain proper airflow in the system.

Although multiple thermally distinct living and/or sleeping zones may exist in a residence, the correct way to model zonal control for credit requires only two zones: a living zone and a sleeping zone. All separate living zone components must be modeled as one living zone; the same must be done for sleeping zones.

11.5.3.30  Alternative Systems

Alternative system types can comply through the performance approach. Chapter 11.6.6 describes some common alternative systems used in dwelling units and the associated code requirements.

11.5.4      Dwelling Unit Air Distribution System Ducts, Plenums, Fans, and Filters

Air distribution system performance impacts overall HVAC system efficiency. Therefore, air distribution systems are required to meet several mandatory and prescriptive requirements as discussed below.

The Energy Code requires that air distribution ducts to be sealed and tested in all climate zones. There are also several compliance credits available related to duct system design.

Duct efficiency is affected by the following parameters:

•    Duct location (attic, crawlspace, basement, inside conditioned space, or other)

•    Specific conditions in the unconditioned space, for example, presence of a radiant barrier

•    Duct insulation characteristics

•    Duct surface area

•    Air leakage of the duct system

In performance calculations, duct efficiency can be calculated in one of two ways:

• Default input assumptions

• Diagnostic measurement values

The compliance software uses default assumptions for the proposed design when the user does not include improvements in duct efficiency.

11.5.4.1    Dwelling Unit Mandatory Requirements

Unless otherwise noted, the enforcement of these minimum standards is normally the responsibility of the building official. HERS Raters or ATTs may also verify compliance with these requirements in conjunction with mandatory testing.

11.5.4.2    Duct Installation Standards

Duct construction must comply with the California Mechanical Code Sections 601, 602, 603, 604, 605, and the applicable requirements of the Energy Code. Some highlights of these requirements are listed in this section, along with some guidance for recommended quality construction practice.

Q.    Minimum Insulation

Portions of supply-air and return-air ducts and plenums that are not installed entirely in conditioned space must have an R-value of R-6. Ducts installed in conditioned space do not require insulation if the following conditions are met and verified by visual inspection by the building department:

•    The non-insulated portion of the duct system is located entirely inside conditioned space within the building’s thermal envelope.

•    At all locations where non-insulated portions of the duct system penetrate unconditioned space, the penetration must be draft stopped compliant with California Fire Code (CFC) sections 703.1 and 704.1 and air-sealed with materials complaint with CMC section E502.4.2. All connections in unconditioned space must be insulated to at least R-6.0.

CFC Sections 703.1 and 704.1 require that materials and firestop systems used through penetrations in fire-resistance-rated construction, construction installed to resist the passage of smoke, and materials and systems used to protect joints and voids in the following locations must be maintained.

•    Joints in or between fire-resistance-rated walls, floors or floor/ceiling assemblies and roof or roof/ceiling assemblies.

•    Joints in smoke barriers.

•    Voids at the intersection of a horizontal floor assembly and an exterior curtain wall.

•    Voids at the intersection of a horizontal smoke barrier and an exterior curtain wall.

•    Voids at the intersection of a nonfire-resistance-rated floor assembly and an exterior curtain wall.

•    Voids at the intersection of a vertical fire barrier and an exterior curtain wall.

•    Voids at the intersection of a vertical fire barrier and a nonfire-resistance-rated roof assembly.

The materials and systems must be securely attached to or bonded to the construction being penetrated or the adjacent construction, with no openings visible through or into the cavity of the construction.

CMC E502.4.2 requires that all joints, seams, and penetrations of must be made airtight by means of mastics, gasketing, or other means.

Alternatively, ducts may be uninsulated if the entire duct system is verified to be entirely in conditioned space as defined in §100.1 by visual inspection and by using the protocols of RA3.1.4.3.8. For buildings with four or more habitable stories, testing may be conducted by the installing contractor and verified by the enforcement agency field inspector. For buildings with up to three habitable stories, the testing and visual inspection must be conducted by a HERS Rater.

RA3.1.4.3.8 describes the duct leakage to outside test that determines whether the ducts are within the pressure boundary of the space being served by the duct system. A basic visual inspection of the ducts ensures that no portion of the duct system is obviously outside the apparent pressure/thermal boundary.

Leakage to outside means conditioned air leaking from the ducts to anywhere outside the pressure boundary of the dwelling unit conditioned space served by the duct system, which includes leakage to outside the building and leakage to adjacent dwelling units or other interior building spaces.

Exception to §160.3(b)5A: Ducts and fans integral to a wood heater or fireplace are exempt from §160.3(b)5A.

For determining the installed R-value of duct insulation based on thickness, when not an integral part of a manufacturer-labeled, insulated duct product such as vinyl flex duct, the following must be used:

•    For duct wrap, the installed thickness of insulation must be assumed to be 75 percent of the nominal thickness due to compression.

•    For duct board, duct liner, and factory-made rigid ducts not normally subjected to compression, the nominal insulation thickness must be used.

R.  Joints

All joints must be sealed to be airtight with either mastic, tape, aerosol sealant, or other duct-closure system that meets the applicable requirements of UL 181, UL 181A, UL 181B, or UL 723. Duct systems must not use cloth-backed, rubber-adhesive duct tape regardless of UL designation, unless it is installed in combination with mastic and clamps. The CEC has approved three cloth-backed duct tapes with special butyl synthetic adhesives rather than rubber adhesive to seal flex duct to fittings. These tapes are:

1.  Polyken 558CA, manufactured by Berry Plastics Tapes and Coatings Division.

2.  Nashua 558CA, manufactured by Berry Plastics Tapes and Coatings Division.

3.  Shurtape PC 858CA, manufactured by Shurtape Technologies, Inc.

These tapes passed Lawrence Berkeley Laboratory tests comparable to those that cloth-backed, rubber-adhesive duct tapes failed. (The LBNL test procedure has been adopted by the American Society of Testing and Materials as ASTM E2342.) These tapes are allowed to be used to seal flex duct to fittings without being in combination with mastic. These tapes cannot be used to seal other duct system joints, such as the attachment of fittings to plenums and junction boxes. These tapes have on the backing a drawing of a fitting to plenum joint in a red circle with a slash through it (the international symbol of prohibition) to illustrate where they are not allowed to be used, installation instructions in the packing boxes that explain how to install them on duct core to fittings, and a statement that the tapes cannot be used to seal fitting to plenum and junction box joints.

Mastic and mesh should be used where round or oval ducts join flat or round plenums. (See Figure 11-36.)

Figure 11-36: Sealing Metallic Ducts with Mastic and Mesh

Source: Richard Heath & Associates/Pacific Gas and Electric Company

All ducts must be adequately supported. Rigid ducts and flex ducts may be supported on rigid building materials between ceiling joists or on ceiling joists.

For rigid round metal ducts that are suspended from above, hangers must occur 12 ft. apart or less (See Figure 11-37).

Figure 11-37: Options for Suspending Rigid Round Metal Ducts

Source: Richard Heath & Associates/Pacific Gas and Electric Company

For rectangular metal ducts that are suspended from above, hangers must occur at a minimum of 4 ft. to 10 ft., depending on the size of the ducts (refer to Figure 11-38).

Figure 11-38: Options for Suspending Rectangular Metal Ducts

Source: Richard Heath & Associates/Pacific Gas and Electric Company

For flex ducts that are suspended from above, hangers must occur at 4 ft. apart or less, and all fittings and accessories must be supported separately by hangers (See Figure 11-39).

Figure 11-39: Minimum Spacing for Suspended Flex Ducts

Source: Richard Heath & Associates/Pacific Gas and Electric Company

For vertical runs of flex duct, support must occur at 6 ft. intervals or less (See Figure 11-40).

Figure 11-40: Minimum Spacing for Supporting Vertical Flex Ducts

Source: Richard Heath & Associates/Pacific Gas and Electric Company

The routing and length of all duct systems can have significant effects on system performance, due to possible increased airflow resistance. The CEC recommends using the minimum length of duct to make connections and the minimum possible number of turns.

For flexible ducts, the CEC recommends fully extending the duct by pulling the duct tightly, cutting off any excess duct, avoiding bending ducts across sharp corners or compressing them to fit between framing members (See Figure 11-41) and avoiding incidental contact with metal fixtures, pipes, or conduits or installation of the duct near hot equipment such as furnaces, boilers, or steam pipes that are above the recommended flexible duct use temperature.

Figure 11-41: Minimizing Radius for Flex Duct Bends

Source: Richard Heath & Associates/Pacific Gas and Electric Company

All joints between two sections of duct must be mechanically fastened and substantially airtight. For a flex duct, this must consist of a metal sleeve no less than four inches between the two sections of flex duct.

All joints must be properly insulated. For flex ducts, installers must pull the insulation and jacket back over the joint and use a clamp or two wraps of tape. Aerosol sealant injection systems are an alternative that typically combines duct testing and duct sealing in one process.

Figure 11-42 shows the computer-controlled injection fan temporarily connected to the supply duct. The plenum is blocked off by sheet metal to prevent the sealant from entering the furnace. Supply air registers are also blocked temporarily to keep the sealant out of the house. Ducts must still be mechanically fastened even if an aerosol sealant system is used.

Figure 11-42: Computer-Controlled Aerosol Injection System

Source: Richard Heath & Associates/Pacific Gas and Electric Company

All joints must be mechanically fastened. For residential round metal ducts, installers must overlap the joint by at least 1½ inches and use three sheet metal screws equally spaced around the joint (See Figure 11-43).

Figure 11-43: Connecting Round Metallic Ducts

Source: Richard Heath & Associates/Pacific Gas and Electric Company

For round, nonmetallic flex ducts, installers must insert the core over the metal collar or fitting by at least one inch. This connection may be completed with either mesh, mastic and a clamp, or two wraps of tape and a clamp.

For a mesh and mastic connection, the installer must first tighten the clamp over the overlapping section of the core, apply a coat of mastic covering both the metal collar and the core by at least one inch, and then firmly press the fiber mesh into the mastic and cover with a second coat of mastic over the fiber mesh (See Figure 11-44).

Figure 11-44: Connecting Flex Ducts Using Mastic and Mesh

Source: Richard Heath & Associates/Pacific Gas and Electric Company

For the tape connection, first apply at least two wraps of approved tape covering both the core and the metal collar by at least one inch, then tighten the clamp over the overlapping section of the core (See Figure 11-45).

Figure 11-45: Connecting Flex Ducts Using Tape and Clamps

Source: Richard Heath & Associates/Pacific Gas and Electric Company

S.     Factory-Fabricated Duct Systems

Factory-fabricated duct systems must comply with the following requirements:

•    All factory-fabricated duct systems must comply with UL 181 for ducts and closure systems, including collars, connections, and splices, and be labeled as complying with UL 181.

•    All pressure-sensitive tapes, heat-activated tapes, and mastics used in the manufacture of rigid fiberglass ducts must comply with UL 181 and UL 181A.

•    All pressure-sensitive tapes and mastics used with flexible ducts must comply with UL 181 and UL 181B.

•    Joints and seams of duct systems and related components cannot be sealed with cloth-backed rubber adhesive duct tapes unless such tape is used in combination with mastic and draw bands.

•    The tape has on the backing the phrase "CEC approved," a drawing of a fitting to plenum joint in a red circle with a slash through it (the international symbol of prohibition), and a statement that it cannot be used to seal fittings to plenums and junction box joints.

T.     Field-Fabricated Duct Systems

Field-fabricated duct systems must comply with the following requirements:

•    Factory-made rigid fiberglass and flexible ducts for field-fabricated duct systems must comply with UL 181. All pressure-sensitive tapes, mastics, aerosol sealants, or other closure systems used for installing field-fabricated duct systems must meet the applicable requirements of UL 181, UL 181A, and UL 181B.

•    Mastic sealants and mesh:

o  Sealants must comply with the applicable requirements of UL 181, UL 181A, and/or UL 181B and be nontoxic and water-resistant.

o  Sealants for interior applications must be tested in accordance with ASTM C731 and D2202.

o  Sealants for exterior applications must be tested in accordance with ASTM C731, C732, and D 2202.

o  Sealants and meshes must be rated for exterior use.

•    Pressure-sensitive tapes must comply with the applicable requirements of UL 181, UL 181A, and UL 181B.

•    Joints and seams of duct systems and their components must not be sealed with cloth-backed rubber adhesive duct tapes unless such tape is used in combination with mastic and draw bands.

•    The tape has on the backing the phrase "CEC approved," a drawing of a fitting to plenum joint in a red circle with a slash through it (the international symbol of prohibition), and a statement that it cannot be used to seal fittings to plenums or junction box joints.

U.    Flexible Duct Draw Bands

•    Draw bands must be either stainless-steel worm-drive hose clamps or UV-resistant nylon duct ties.

•    Draw bands must have a minimum tensile strength rating of 150 pounds.

•    Draw bands must be tightened as recommended by the manufacturer with an adjustable tensioning tool.

V.    Aerosol-Sealant Closures

•    Aerosol sealants must meet the requirements of UL 723 and be applied according to manufacturer specifications.

•    Tapes or mastics used in combination with aerosol sealing must meet the requirements of this section.

If mastic or tape is used to seal openings greater than 1/4 inch, the combination of mastic and either mesh or tape must be used.

Building spaces such as cavities between walls, support platforms for air handlers, and plenums defined or constructed with materials other than sealed sheet metal, duct board, or flexible duct must not be used for conveying conditioned air, including return air and supply air. Using drywall materials as the interior surface of a return plenum is not allowed. Building cavities and support platforms may contain ducts. Ducts installed in cavities and support platforms must not be compressed to cause reductions in the cross-sectional area of the ducts. Although a HERS Rater or acceptance test technician may examine this as a part of his or her responsibilities when involved in a project, the enforcement of these minimum standards for ducts is the responsibility of the building official.

W.  Product Markings

All factory-fabricated duct systems must meet UL 181 for ducts and closure systems and be labeled as complying with UL 181. Collars, connections, and splices are factory-fabricated duct systems and must meet the same requirement.

Insulated flexible duct products installed to meet this requirement must include labels, in maximum intervals of three ft., showing the R-value for the duct insulation (excluding air films, vapor barriers, or other duct components), based on the tests and thickness specified in §160.3(b)5D and §160.3(b)5Eiii.

X.    Dampers to Prevent Air Leakage

Fan systems that exhaust air from the building to the outside must be provided with back draft or automatic dampers.

Gravity ventilating systems must have an automatic or readily accessible, manually operated damper in all openings to the outside, except combustion inlet, outlet air openings, and elevator shaft vents. This includes clothes dryer exhaust vents when installed in conditioned space.

Y.     Protection of Insulation

Insulation must be protected from damage, including damage from sunlight, moisture, equipment maintenance, and wind, but not limited to the following:

•    Insulation exposed to weather must be suitable for outdoor service, for example, protected by aluminum, sheet metal, painted canvas, or plastic cover.

•    Cellular foam insulation must be protected as above or painted with a coating that is water-retardant and shields from solar radiation that can degrade the material.

Z.     Porous Inner Core Flex Duct

Over time, the outer vapor barrier of flex duct can degrade and be easily damaged. Therefore, porous inner core flex duct must have a non-porous layer or air barrier between the inner core and the outer vapor barrier.

11.5.4.3    Duct System Sealing and Leakage Testing

Duct system sealing and leakage testing is mandatory in all climate zones. Duct systems in newly constructed multifamily dwellings are required to comply with the requirements regardless of the duct system location, except for buildings with four or more habitable stories in Climate Zone 1, 3, 5, and 7, which are exempt from the testing requirements. When the air-handling unit is installed and the ducts connected directly to the air handler, the total leakage of the duct system must not exceed 12% of the nominal system air handler airflow or the duct system leakage to outside must not exceed 6% of the nominal system air handler airflow.

The duct system leakage must be determined according to the applicable procedures outlined in RA3.1.4.3. Verification of duct leakage must be conducted by a HERS Rater for multifamily buildings with up to three habitable stories. For other multifamily buildings in Climate Zones 2, 4, 6, and 8-16, testing only needs to be conducted and certified by the installing contractor and neither a HERS Rater nor registration with a HERS Provider is required. Entirely new or complete replacement duct systems as part of an addition or alteration in all climate zones are required to comply with these mandatory maximum leakage criteria. A duct system in an existing building is considered entirely new when:

•    At least 75% of the duct material is new.

•    All remaining components from the previous system are accessible and can be sealed.

11.5.4.4    Air Filtration

Air filtration is used in forced air systems to protect the equipment from dust accumulation that could reduce the capacity or efficiency of the system. Preventing dust buildup may also prevent the system from becoming a host to biological contaminants such as mold, especially if dust is deposited on cooling coils that become wet from water condensation during comfort cooling operation. Air filter efficiencies of Minimum Efficiency Reporting Value (MERV) 6 to MERV 8 are sufficient for protection from these large airborne dust particles. Air filter efficiencies of at least MERV 13 are needed to protect occupants from exposure to the smaller airborne particles that are known to adversely affect respiratory health. These smaller particles are often referred to as PM 2.5, which refers to particulate matter of 2.5 microns or smaller. PM2.5 is produced from several sources including combustion from cooking and from exhaust from motor vehicles that enters a dwelling through ventilation openings and infiltration.

AA. Air Filter Pressure Drop

Standards §160.2(b)1D requires all systems to be designed to accommodate the clean-filter pressure drop imposed by the system air filter device(s). This applies to space-conditioning systems and to the ventilation system types described in the Air Filter Particle Removal Efficiency Requirements – MERV 13 section. The design airflow rate and maximum allowable clean-filter pressure drop at the design airflow rate applicable to each air filter device must be determined and posted on a sticker or label by the installer inside the filter grille or near the filter rack, according to Air Filter Particle Removal Efficiency Requirements – MERV 13 section below.

Designers of space-conditioning systems must determine the total system external static pressure losses from filters, coils, ducts, and grilles, such that the sum is not greater than the available static pressure of the air handling unit at the design airflow rate. Therefore, air filters should be sized to minimize static pressure drop across the filter during system operation. The air filter pressure drop can be reduced by increasing the amount of air filter media surface area available to the system airflow. Increased media surface area can be accomplished by adjusting one, two, or all three of the following factors:

a.    Adjust the number of pleats of media per inch inside the air filter frame. The number of pleats per inch inside the filter frame is determined by the manufacturer’s filter model design and is held constant for all filter sizes of the same manufacturer’s model. For example, all 3M Filtrete 1900 filters will have the same media type, the same MERV rating, and the same number of pleats of media per inch inside the filter frame regardless of whether the nominal filter size is 20” X 30” or 24” X 24”, and so forth. Generally, as the number of pleats per inch is increased, the pressure drop is reduced if all other factors remain constant. The pressure drop characteristics of air filters vary widely between air filter manufacturers and between air filter models, largely because of the number of pleats per inch in the manufacturer’s air filter model design. System designers and system owners cannot change the manufacturer's filter model characteristics, but they can select a superior air filter model from a manufacturer that provides greater airflow at a lower pressure drop by comparing the filter pressure drop performance shown on the air filter manufacturer's product label (see example label in Table 11).

b.    Adjust the face area of the air filter and filter grille. Face area is the nominal cross-sectional area of the air filter, perpendicular to the direction of the airflow through the filter. Face area is also the area of the filter grille opening in the ceiling or wall. The face area is determined by multiplying the length times width of the filter face (or filter grille opening). The nominal face area for a filter corresponds to the nominal face area of the filter grille in which the filter is installed. For example, a nominal 20” X 30” filter has a face area of 600 in² and would be installed in a nominal 20” X 30” filter grille. Generally, as the total system air filter face area increases, the pressure drop is reduced if all other factors remain constant. Total system air filter face area can be increased by specifying a larger area filter/grille or by using additional/multiple return filters/grilles, summing the face areas. The filter face area is specified by the system designer or installer.

c.     Adjust the depth of the filter and filter grille. Air filter depth is the nominal filter dimension parallel to the direction of the airflow through the filter. Nominal filter depths readily available for purchase include one, two, four, and six inches. Generally, as the system air filter depth increases, the pressure drop is reduced if all other factors remain constant. For example, increasing filter depth from one inch to two inch nominally doubles the filter media surface area without increasing the filter face area. The filter depth is specified by the system designer or installer.

BB.    Air Filter Particle Removal Efficiency Requirements – MERV 13

An air filter with a particle removal efficiency equal to or greater than MERV 13 or a particle size efficiency rating equal to or greater than 50 percent in the 0.30-1.0 μm range, and it is and equal to or greater than 85 percent in the 1.0-3.0 μm range is required for the following systems:

•    Mechanical space conditioning (heating or cooling) systems with a total of more than 10 ft. of duct. The total is determined by summing the lengths of all the supply and return ducts for the forced-air system.

•    Mechanical supply-only ventilation systems that provide outside air to an occupiable space.

•    The supply side of mechanical balanced ventilation systems, including heat recovery ventilation systems and energy recovery ventilation systems that provide outside air to an occupiable space.

Evaporative coolers are exempt from the air filtration requirements.

CC.    Air Filter Requirements for Space-Conditioning Systems:

•    Space conditioning systems may use any of the three following compliance approaches:

•    Install a filter grille or accessible filter rack that accommodates a minimum 2-inch depth filter and install the appropriate filter.

•    Install a filter grille or accessible filter rack that accommodates a minimum 1” depth filter and install the appropriate filter. The filter/grille must be sized for a velocity of ≤ 150 ft per minute. The installed filter must be labeled to indicate the pressure drop across the filter at the design airflow rate for that return is ≤ 0.1 inch water column (w.c. [25 PA]).

Use the following method to calculate the 1" depth filter face area required. Divide the design airflow rate (ft³/min) for the filter grille/rack by the maximum allowed face velocity 150 ft/min. This yields a value for the face area in ft². Since air filters are sold using nominal sizes in terms of inches, convert the face area to in² by multiplying the face area (ft²) by a conversion factor of 144 in²/ft². Summarizing:

Filter Nominal Face Area (in²) = airflow (CFM) ÷ 150 x 144

•    Comply with Standards Tables 160.3-A and B, which prescribe the minimum total system nominal filter face area and return duct size(s). The installed filter must be labeled to indicate the pressure drop across the filter at the design airflow rate for that return is ≤ 0.1 inch w.c. (25 PA). This option is an alternative to the §160.3(b)5L requirement for HERS-verified fan efficacy and airflow rate, but it requires instead a HERS verification of the return duct design.

DD.   Air Filter Requirements for Ventilation Systems

§ Filters with a depth of 1” or greater are allowed.

§ The design airflow rate, and maximum allowable clean-filter pressure drop at the design airflow rate applicable to each air filter device, must be determined by the system designer or installer and that information must be posted on a sticker by the installer inside or near the filter grille/rack according to Chapter 11.6.4.10FF.

§ Ventilation systems must deliver the volume of air specified by §160.2(b)2 with filters in place.

EE.  Filter Access and Filter Grille Sticker: Design Airflow and Pressure Drop

All filters used in all system types must be accessible to facilitate replacement.

•    Air filter grille sticker. The design airflow rate and maximum allowable clean-filter pressure drop at the design airflow rate applicable to each air filter grille/rack must be determined by the designer/installer and posted on a sticker placed by the installer inside or near the filter grille/rack. The design airflow and initial resistance posted on this sticker should correspond to the conditions used in the system design calculations. This requirement applies to space conditioning systems and also to the ventilation system types described in Air Filter Particle Removal Efficiency Requirements – MERV 13 section above.

An example of an air filter grille sticker showing the design airflow and pressure drop for the filter grille/rack is shown in Table 11-33.

•    Air filter manufacturer label. Space-conditioning system filters are required to be labeled by the manufacturer to indicate the pressure drop across the filter at several airflow rates. For the system to comply, and to ensure adequate airflow for efficient heating and cooling equipment operation, the manufacturer's air filter label must display information that indicates the filter can meet the design airflow rate for that return grille/rack at a pressure drop ≤ the value shown on the installer's filter grille sticker. This requirement does not apply to the ventilation system types described in Air Filter Particle Removal Efficiency Requirements – MERV 13 section above.

Table 11-33: Example of Installer's Filter Grille Sticker

Source: California Energy Commission

Figure 11-46: Example Manufacturer's Filter Label

Source: California Energy Commission

FF.   Air Filter Selection

For a filter to meet the system specifications for airflow and pressure drop, it must be rated by the manufacturer to provide more than the specified airflow at less than the specified pressure drop. It is unlikely that a filter will be available that is rated to have the exact airflow and pressure drop ratings specified, so filters should be selected that are rated to have less than the specified pressure drop at the specified airflow rate. Otherwise, select filters that are rated to have greater than the specified airflow rate at the specified pressure drop. See Table 11-34 for an example of an installer's filter grille sticker that provides an air filter rating specification for minimum airflow of 750 CFM at maximum pressure drop 0.1 inch w.c.

Manufacturers of air filters may make supplementary product information available to consumers that will assist with selecting the proper replacement filters. This product information may provide more detailed information about the filter model airflow and pressure drop performance – details such as airflow and pressure drop values that are intermediate values that lie between the values shown on their product label. The information may be published in tables, graphs, or presented in software applications available on the internet or at the point of sale.

Figure 11-47 below shows a graphical representation of the initial resistance (pressure drop) and airflow rate ordered pairs given on the example air filter manufacturer's label shown in Figure 11-49 above. The graph in Figure 11-47 makes it possible to visually determine the airflow at 0.1 inch w.c. pressure drop for which the values are not shown on the manufacturer's filter label.

If there is no supplementary manufacturer information available, and it is necessary to determine the performance of a filter model at an airflow rate or pressure drop between two values shown on a manufacturer's label, linear interpolation may be used. Linear interpolation apps are readily available on the internet, and formulas for linear interpolation are shown below.

The linear interpolation method may be used to determine an unknown pressure drop corresponding to a known airflow rate by use of Equation 11-2a, or it may also be used to determine an unknown airflow rate corresponding to a known pressure drop by use of Equation 11-2b.

Equation 11-2a

p = p₁ + [(f-f₁) ÷ (f₂-f₁)] x (p₂ – p₁)

where:

f = a known flow value between f₁ and f₂

p = the unknown pressure drop value corresponding to f.

p₁ and p₂ = known values that are less than and greater than p respectively.

f₁ and f₂ are the known values corresponding to p₁ and p₂.

Equation 11-2b

f = f₁ + [(p-p₁) ÷ (p₂-p₁)] x (f₂ – f₁)

where:

p = a known pressure drop value between p₁ and p₂

f = the unknown flow value corresponding to p.

f₁ and f₂ = known values that are less than and greater than f respectively.

p₁ and p₂ are the known values corresponding to f₁ and f₂.

See Example 11-31 for sample calculations that determine the rated airflow of the filter corresponding to a known pressure drop specification (0.1 inch w.c.).

Figure 11-47: Plot of Pressure drop vs. Airflow for a 20" X 30" X 1" Depth Air Filter

From Manufacturer Label Information

H. Preventing Bypass

Any gaps around an air filter allows air to bypass the filter. The Energy Code requires that filter racks and grilles use gaskets, sealing, or other means to close gaps around inserted filters and prevent air from bypassing the filter. Filter racks and grilles include any device that houses the air filter used to satisfy the air filtration requirements. 

11.5.4.5    Forced-Air System Duct Sizing, Airflow Rate, and Fan Efficacy

Adequate airflow is critical for cooling equipment efficiency. Further, it is important to maintain adequate airflow without expending excessive fan power. §160.3(b)5L establishes mandatory requirements that are intended to ensure adequate cooling airflow through properly sized ducts and efficient fan motors.

There are two options allowed to ensure adequate air flow. The first option is to design and install the systems using standard design criteria and then have the airflow and fan efficacy of the system tested in the field. The second option is to size the return ducts according to Table 11-34 and Table 11-35 (as specified by EXCEPTION 1 to §160.3(b)5Lii and iv).

Both options require verification. Verification must be conducted by a HERS Rater for multifamily buildings with up to three habitable stories. For other multifamily buildings in Climate Zones 2-16, verification only needs to be conducted and certified by the installing contractor and neither a HERS Rater nor registration with a HERS Provider is required. Buildings with four or more habitable stories in Climate Zone 1 are exempt from these mandatory requirements.

A.    Airflow and Watt Draw Measurement and Determination of Fan Efficacy

When using the airflow (CFM/ton) and fan efficacy (watt/CFM) method, the following criteria must be met:

•      Provide airflow through the return grilles that is equal to or greater than:

o  350 CFM per ton of nominal cooling capacity for systems that are not small-duct high-velocity systems.

o  250 CFM per ton for small duct for high velocity systems.

Nominal cooling capacity: To determine the required airflow for compliance in CFM/ton, the nominal cooling capacity of the system in tons must be known. The nominal cooling capacity system may be obtained from the manufacturer's product literature or from listings of certified product ratings from organizations such as AHRI, but the nominal capacity is usually shown in the unit model number on the manufacturers nameplate attached to the outdoor condensing unit. A two- or three-digit section of the manufacturer's model number typically indicates the nominal capacity in thousands of BTU/hour. Given that there are 12,000 BTU/hour per ton of cooling capacity, the nameplate will display something similar to one of the following number groupings:  "018" which represents 1.5 tons; "024," which represents 2 tons; "030," which represents 2.5 tons; "036," which represents 3 tons; "042," which represents 3.5 tons; "048," which represents 4 tons; or “060,” which represents 5 tons.

•    At the same time, the fan watt draw must be less than or equal to

o  0.45 watts per CFM for gas furnaces, or

o  0.58 watts per CFM for air handling units that are not gas furnaces.

o  0.62 watts per CFM for small duct, high velocity systems.

See Table 11-36 for a summary of the requirements.

The methods for measuring the air-handling unit watt draw are described in Reference Residential Appendix RA3.3. Three acceptable apparatuses are:

•    A portable watt meter.

•    An analog utility revenue meter.

•    A digital utility revenue meter.

Note that when measuring fan watt draw in package air conditioners or heat pumps, it is recommended to use a portable true power clamp-on meter to provide flexibility for isolating the correct fan wires. These meters may need to be high-voltage-capable.

Ducted mini-split heat pumps and air conditioners are typically exempt from the requirement to measure fan watt draw because of the difficulties with isolating the fan power and accurately measuring it. They are not exempt from the airflow measurement requirement.

There are three acceptable methods for determining compliance with the system airflow requirement. They are described in Reference Residential Appendix RA3.3 and use one of the following:

•    An active or passive flow capture hood to measure the total airflow through the return grill(s)

•    Flow grid device(s) at the return grill(s) or other location where all the central fan airflow passes through the flow grid

•    Fan flow meter device (also known as a duct blaster) to perform the plenum pressure matching procedure

The flow grid and the fan flow meter methods both require access to static pressure measurements of the airflow exiting the cooling coil, which require use of a HSPP or PSPP (RA3.3.1.1).

The contractor must install either a hole for the placement of a static pressure probe (HSPP) or provide a permanently installed static pressure probe (PSPP) stated in Reference Residential Appendix RA3.3.

The HSPP or PSPP simplifies cooling coil airflow measurement when using devices or procedures that depend on supply plenum pressure measurements.

The California Green Code (CALGreen or Title 24, Part 11) and the California Mechanical Code require that residential duct systems be designed according to ACCA Manual D, or equivalent. If reasonable care and judgment are used while designing the duct system (both return and supply ducts), and the system is designed to reasonable parameters for airflow per ton, static pressure across the fan, and friction rate, these systems should have no problem passing the diagnostic tests.

The following design guidelines will increase the chances of the system passing the airflow and fan efficacy testing:

•    Right-size the HVAC system. If a two-ton unit is enough to satisfy the cooling load, do not install a three-ton unit just to be safe. Oversizing equipment can cause comfort problems in addition to excessive energy use.

•    The HVAC designer must coordinate closely with the architect and structural engineer to make sure that the ducts will fit into the dwelling unit as designed.

•    Prepare a detailed mechanical plan that can be followed in the field. If deviations must occur in the field, make sure that they are coordinated with the designer and that the design is adjusted as needed.

•    Follow Manual D for duct sizing:

o  Make sure that the correct duct type is used (vinyl flex, sheet metal, rigid fiberglass, or other).

o  Make sure that all equivalent lengths and pressure drops are correctly accounted for (bends, plenum start collars, t-wyes, filters, grilles, registers, and so forth.

o  Select an air handler that will provide at least 400 CFM/ton at the desired static pressure of 125 to 150 Pa (0.5 to 0.6 inches w.c.).

o  Design the duct system to a static pressure across the fan of no more than 150 Pa (0.6 inches w.c.).

o  Consider upsizing the evaporator coil relative to the condenser to reduce the static pressure drop. This upsizing results in better airflow and slightly better capacity and efficiency. Manufacturers commonly provide performance data for such condenser coil combinations.

o  Consider specifying an air handler with a high efficiency (brushless permanent magnet) fan motor.

•      Install a large grill area and use a proper filter for the system.

•      Locate registers and equipment to make duct runs as short as possible.

•      Make all short-radius 90° bends out of rigid ducting.

•      Install flex duct properly by stretching all flex duct tight and cutting off excess ducting. Ensure the duct is not kinked or compressed and is properly supported every four ft. or less using one inch strapping. Flex duct should have less than two inches of sag between supports.

•      Consider using better quality supply and filter grilles. Bar-type registers have considerably better airflow performance than standard stamped-face registers. Refer to the manufacturer’s specifications and select accordingly.

B.    Return Duct System Design Method

This method allows the designer to specify, and the contractor to install, a system that does not have to be tested for airflow and fan efficacy. This method can be used for systems with either one or two return grilles. Each return must not exceed 30 ft. as measured from the return plenum to the filter grille. When bends are needed, sheet metal elbows are desirable. Each return can have up to 180 degrees of bend, and flex duct can have no more than 90° of bend. To use this method, the designer and installer must provide return system sizing that meets the appropriate criteria in Energy Code Table 160.3-A and B, also shown in Table 11-34 or Table 11-35 below.

Energy Code Tables 160.3-A and B (Table 11-34 or Table 11-35) allow for only one or two returns. There may be times where three returns are necessary on a single system. Furthermore, Table 160.3-B does not allow for deviation from the two sizes specified. For example, the table requires two 14-inch return ducts for a 2.5-ton system, but specific airflow requirements and architectural constraints may dictate an 18-inch and a 12-inch. In this situation, airflow and fan efficacy diagnostic testing are required.

Historically, duct systems have been sized to fit into the dwelling unit at the expense of proper airflow. The performance of these systems, in terms of efficiency and capacity, has suffered greatly because of this practice. The dwelling unit should be designed to accommodate properly sized ducts. This requires improved coordination among the architect, structural engineer, and mechanical designer early in the process.

Tables 160.3-A and B require the use of return grilles that are sized to achieve an optimal face velocity and static pressure drop. Tables 160.3-A and B also require the return grille devices to be labeled in accordance with the requirements in §160.2(b)1A to disclose the design airflow rate of the grille and the maximum allowable clean-filter pressure drop for the air filter media, as determined by the system design or applicable standards requirements. The nominal size of the air filter grille or air filter media should be used to calculate the return filter grille gross area for determining compliance with Tables 160.3-A and B. The nominal size of the filter grille is expected to be the same as the nominal size of the air filter media that is used in the grille and is most often the information used to identify these items for purchases. For example, a nominal 20-inch x 30-inch filter grille will use nominal 20-inch x 30-inch air filter media.

Table 11-34: Return Duct Sizing for Single Return Duct Systems

Source: From Table 160.3-A of the Energy Code

Table 11-35: Return Duct Sizing for Multiple Return Duct Systems

Source: From Table 160.3-B of the Energy Code

C.    Zonally Controlled Central Forced-Air Cooling Systems

The primary purpose of zoning ducted air conditioners, heat pumps, and furnaces is to improve comfort. Increased comfort is attained by having the capacity of the HVAC system (cooling or heating delivered) follow the shift in load as it changes across the dwelling unit.

Since the most common dwelling unit is single-zoned and has only one thermostat placed near the center of the unit, temperatures in the rooms distant from that thermostat will vary, sometimes significantly. If zoning is added, the more distant rooms may be conditioned to a more comfortable temperature. This increased conditioning requires more energy. When designed correctly, zoning allows only the zones that need conditioning to be conditioned, thus potentially saving energy.

It is common for single-speed zonally controlled central forced-air cooling systems to produce lower total system airflow through the returns when fewer than all zones are calling for conditioning. The reduced airflow lowers the sensible efficiency of single-stage heating or cooling equipment. Two primary causes of lower airflow in multiple zone dampered systems are:

1.      Restriction of some system supply ducts by closing zoning dampers in zones that do not need additional cooling, while other zones do need cooling.

2.      Recirculation of already-cooled air from the supply plenum directly back to the return plenum without first delivering the cooled air to the conditioned space by use of a bypass duct.

To prevent the lower efficiency that results from reduced system airflow or from recirculated bypass duct airflow, single-speed compressor zonally controlled central cooling systems must demonstrate they simultaneously meet mandatory fan efficacy and airflow requirements in all zonal control modes, which is possible with a duct system design that does not restrict the system total airflow when fewer than all zones are calling for conditioning and does not use a bypass duct. §170.2(c)3v prohibits use of bypass ducts prescriptively, but bypass ducts may be used if the efficiency penalty due to the reduced airflow through the return grille is modeled as described later in this section.

Zonally controlled cooling systems with or without bypass dampers (multiple zones served by a single air handler with motorized zone dampers) usually do not meet the airflow and fan efficacy requirements when fewer than all zones are calling. The energy penalty that results from this is greater than the benefit of having zonal control; therefore, zonal control is not always a better-than-minimum condition.

Zonal control accomplished by using multiple single-zone systems is not subject to the requirements specified in §160.3(b)5Liii.

Two-speed and variable-speed compressors are considered multi-speed. Multispeed compressors allow the system capacity to vary to match reduced cooling loads more closely when fewer than all zones call for cooling. Therefore, an exception to §160.3(b)5Liii gives multispeed compressor systems special consideration when used in zoned systems, and these systems are not required to verify performance in all zonal control modes. Instead, the airflow and fan efficacy testing are required to be performed only at the highest speed when all zones call for cooling.

An exception to §160.3(b)5Liiiallows single-speed compressor systems to comply with the mandatory airflow and fan efficacy requirements only at the highest fan speed and when all zones call for cooling, rather than in every zonal control mode. This is allowed if:

•    The performance approach is used.

•    Airflow is tested in all zonal control modes when fewer than all zones call for cooling to be no less than that specified by the software user and reported on the compliance report.

•    Fan efficacy is tested in all zonal control modes to be no greater than that specified by the software user and reported on the compliance report.

In the compliance software, if the system is modeled as a zoned system with a single-speed compressor, the minimum allowable airflow drops to 150 CFM/ton. The compliance software calculates a penalty for the reduced airflow (specified by the user) during operation when fewer than all zones call for cooling. Other energy features for the building must offset this penalty. A value between 150 CMF/ton and 350 CFM/ton can lessen the penalty resulting from the minimum allowed value of 150 CFM/ton.

The energy consultant should model airflow and fan efficacy values that are reasonable and can be verified. If not, the compliance calculations will have to be revised to match the actual verified value. Energy consultants should coordinate with the HVAC designer before registering the certificate of compliance.

See Table 11-36 for a summary of the requirements.

Bypass dampers may be installed only if the certificate of compliance specifically states that the system was modeled as having a bypass damper.

Table 11-36: Central Forced-Air Cooling Systems Airflow & Fan Efficacy Requirements

¹Exception: Airflow and fan efficacy testing not required if return system meets Tables 160.3-A or B. However, verification that return duct installation meets Tables 160.3-A or B is required

² For the prescriptive approach use of a bypass duct is not allowed. For the performance approach use of a bypass duct may be specified in the compliance software input for the zoned system type.

D.    Hole for Static Pressure Probe (HSPP) or Permanently Installed Static Pressure Probe (PSPP)

Space-conditioning systems that use forced air ducts to cool occupiable space must have a HSPP or PSPP installed downstream from the evaporator coil. The HSPP or PSPP must be installed in the required location, in accordance with the specifications detailed in Reference Residential Appendix RA3.3. The HSPP or PSPP are required to promote system airflow measurement when using devices/procedures that depend on supply plenum pressure measurements. The HSPP or PSPP allows HERS Raters to perform the required diagnostic airflow testing in a nonintrusive manner by eliminating the necessity for the raters to drill holes in the supply plenum for placement of pressure measurement probes.

The size and placement of the HSPP/PSPP must be in accordance with RA3.3.1.1 and must be verified by a HERS Rater. If the HSPP/PSPP cannot be installed as shown in Figure RA3.3-1 because of the configuration of the system or that the location is not accessible, an alternative location may be provided that can accurately measure the average static pressure in the supply plenum. If an alternative location cannot be provided, then the HSPP/PSPP is not required to be installed. The HERS Rater will verify this for multifamily buildings up to three stories. Not installing an HSPP/PSPP will limit the airflow measurement method to either a powered flow hood or passive (traditional) flow hood.

The HSPP/PSPP requirement also applies when the plenum pressure matching method or the flow grid method of airflow measurement is used by either the installer or the rater to verify airflow in an altered system. The HSPP/PSPP must be installed by the installer, not the rater.

See Chapter 11.6.4 for discussion regarding mandatory sizing/airflow requirements for ducted systems with cooling.

11.5.4.6    Dwelling Unit Prescriptive Requirements

The Energy Code is designed to offer flexibility to multifamily newly constructed building designers and builders to achieve code compliance as shown in Figure 11-48.

Figure 11-48: Duct Prescriptive Compliance Choices

Source: California Energy Commission

11.5.4.7    Duct Location

Standard multifamily construction practice in California is to place ducts and associated air handling equipment in conditioned space. Ducts are typically in a dropped soffit or in-between floors, and equipment may also be in the ceiling or an interior mechanical closet. When meeting the prescriptive requirements for the Energy Code, there are two options for where ducts and equipment can be located:

•    Ducts in conditioned space (DCS) with the duct system and air handler(s) within the thermal envelope and air barrier of the building. This DCS option requires field verification to meet the prescriptive requirement. This option applies to both attic roofs and non-attic roofs.

•    For buildings with attic roofs, ducts may be installed in a vented attic if Option B in Table 170.2-A is met. Option B requires a high-performance attic (HPA) design in climate zones 4 and 8-16. A HPA implements requirements that minimize temperature differences between the attic space and the conditioned air being transported through ductwork in the attic. The package consists of insulation below the roof in addition to insulation at the ceiling. These requirements and approaches to meet the requirements are explained in Chapter of this manual.

For the DCS prescriptive approach, additional requirements apply:

•    Air handlers containing a combustion component should be direct-vent (sealed combustion chambers) and must not use air from any conditioned or unconditioned space as combustion air. Other types of combustion heating systems are possible if the system installer adheres to the combustion air requirements found in Chapter 7 of the California Mechanical Code.

•    Duct location needs to be verified through a visual inspection per Reference Residential Appendix RA3.1.4.1.3. This must be conducted by a HERS Rater for multifamily buildings up to three habitable stories. Otherwise, the installing contractor can certify the results.

•    Duct leakage to outside needs to be confirmed by field verification and diagnostic testing in accordance with Reference Residential Appendix RA3.1.4.3.8. This must be conducted by a HERS Rater for multifamily buildings up to three habitable stories. Otherwise, the installing contractor can certify the results.

For the vented attic with HPA prescriptive approach, additional requirements apply. Refer to Chapter 3.5 of the Single-Family Compliance Manual for more information on this option.

•    Ducts are insulated to a level required in Table 170.2-K.

•    Ceiling and below roof deck insulation must meet the levels required in Table 170.2-A Option B. Roof deck insulation must be installed with an air space present between the roofing and the roof deck, such as is typical with standard installation of concrete or clay tile.

•    Roofing products must meet the reflectance and emittance values in Table 170.2-A Option B.

•    A radiant barrier is required is Climate Zones 2, 3, and 5-7 per Table 170.2-A Option B.

If a building is not able to meet all the requirements listed above, it must use the performance approach. The prescriptive options apply to dwelling units individually. Multifamily buildings with vented attics may have ductwork in the attic above the top floor units with lower floor unit ductwork in conditioned space. To comply prescriptively, the top floor units need to meet the requirement for ducts in a vented attic, which may include HPA depending on climate zone. The lower floor units need to meet all the requirements for DCS.

There are several methods of achieving the goal of DCS. For additional information, the basic information of the strategies, related benefits, challenges, and potential solutions to those challenges are described in the Single-Family Compliance Manual Chapter 4.4.2.

11.5.4.8    Duct Insulation

Projects meeting the prescriptive requirements for DCS need to only meet the mandatory insulation requirements of R-6. All ducts in a ventilated attic space must be insulated to a minimum installed level as specified by Table 170.2-K, which requires either R-6 or R-8 depending on the climate zone. Prescriptively, the attic must also meet the insulation requirements per Table 170.2-A Option B. Since R-6 is the mandatory minimum for ducts in unconditioned space, where R-8 is prescriptively required, this can be traded off against other features using the performance approach.

11.5.4.9    Central Fan-Integrated (CFI) Ventilation

CFI ventilation uses a central forced air heating and/or cooling system that operates regularly to pull outside air into the air distribution system and distribute air around the dwelling unit. There is a prescriptive requirement that CFI systems meet the same mandatory fan efficacy requirements for other forced air cooling systems. This requires no greater than 0.45 W/CFM for gas furnaces and 0.58 W/CFM for all other air handler including heat pumps. This can be traded-off using the performance approach. Verification must be conducted by a HERS Rater for multifamily buildings with up to three habitable stories. For other multifamily buildings, verification only needs to be conducted and certified by the installing contractor, and neither a HERS Rater nor registration with a HERS Provider is required.

11.5.4.10  Dwelling Unit Performance Approach

The Energy Code provide credit for several compliance options related to duct design and construction.

11.5.4.11  System Airflow and Fan Efficacy

Performance compliance credits are available for demonstrating the installation of a high-efficiency system with a lower fan wattage and/or higher airflow than the mandatory requirements. Compliance with these credits can be achieved by installing a well-designed duct system and can be assisted by a high-efficiency fan. There are two possible performance compliance credits:

•    The performance approach allows the user’s proposed fan efficacy to be entered and credit earned if it is lower than the default mandatory values. To obtain this credit for a system with cooling, the system airflow must meet the mandatory requirement of at least 350 CFM/ton of nominal cooling capacity.

•    The performance approach allows the user’s proposed system airflow to be entered and credit earned if it is higher than the default of 350 CFM/ton of nominal cooling capacity. To obtain this credit, the fan efficacy must meet the mandatory requirements listed above.

The performance approach allows the user’s proposed airflow and fan efficacy to be entered into the program, and credit will be earned if the airflow is greater than the minimum required, and fan efficacy is lower than the default. After installation, the contractor must test the actual airflow and fan efficacy of each system using the procedure in Reference Residential Appendix RA3.3 and show that it is equal or less than what was proposed in the compliance software analysis.

For multifamily buildings up to three habitable stories the fan efficacy and airflow must be verified by a HERS Rater.

11.5.4.12  Duct Location

For multifamily buildings up to three habitable stories, there are three ways to achieve credit for favorable duct location when using the performance approach and the building has an attic.

•    Credit is available if no more than 12 linear ft. of duct are outside the conditioned space. This total must include the air handler and plenum lengths. This credit results in a reduction of duct surface area in the computer software. This option requires certification by the installer and field verification by a HERS Rater.

•    The second alternative applies when 100% of the ducts are in conditioned space. This credit results in eliminating the conduction losses associated with the return and supply ducts; however, leakage rates still apply. This option requires field verification of the duct system by means of a visual inspection by a HERS Rater.

•    Additional credit is available when ducts are in conditioned space and a HERS Rater verifies that duct leakage to outside does not exceed 25 CFM.

There may also be compliance credit for the distribution system for choosing a ductless heating or cooling system. However, many of these systems do not perform as well as the baseline system, which can result in an overall penalty.

For buildings with no attic, the standard design assumes ducts inside the conditioned space with duct leakage verified to not exceed 25 CFM. No additional credit is available within the software for duct location.

There is no duct location compliance credit for multifamily buildings four or more habitable stories, because the software does not evaluate distribution systems.

11.5.4.13  Duct Insulation

For multifamily buildings up to three habitable stories, performance credit is available for ducts in unconditioned space if all the ducts are insulated to a level higher than required by the prescriptive package. If ducts with multiple R-values are installed, the lowest duct R-value must be used for the entire duct system. However, the air handler, plenum, connectors, and boots must be insulated to the mandatory minimum R-value.

As an alternative when there is a mix of duct insulation R-values, credit is available through the method described in the next section.

There is no duct insulation compliance credit for multifamily buildings four or more stories, because the software does not evaluate distribution systems.

11.5.4.14  Verified Duct Design: Duct Location, Surface Area, and R-value

For multifamily buildings up to three habitable stories when all or a portion of ducts are in unconditioned space, this compliance option allows the designer to take credit for a high-efficiency duct design that incorporates duct system features that may not meet the criteria for the duct location and/or insulation compliance options described above. This method requires that the designer enter the design characteristics of all ducts that are not within the conditioned space. The information required for the input to the compliance software includes the length, diameter, insulation R-value, and location of all ducts. This method will result in a credit if the proposed duct system is better than the standard design.

To claim this credit, the duct system design must be documented on plans that are submitted to the enforcement agency and posted at the construction site for use by the installers, the enforcement agency field inspector, and the HERS Rater. The duct system must be installed in accordance with the approved duct system plans, and the duct system installation must be certified by the installer on the certificate of installation form and verified by a HERS Rater on the certificate of verification form. Details of this compliance option are described in the Nonresidential ACM Reference Manual, and verification procedures are described in RA3.1 of the Reference Residential Appendix.

11.5.4.15  Buried and Deeply Buried Ducts

For multifamily buildings up to three habitable stories, this compliance option allows credit for the special case of ducts that are buried by blown attic insulation. For ducts that are within 3.5 inches of the ceiling, the effective R-value is calculated based on the duct size and R-value, depth of ceiling insulation, and type of blown insulation (fiberglass or cellulose) as shown in Tables 16, 17, and 18 in the Residential ACM Reference Manual. The user-entered duct system can be any combination of unburied, buried, and deeply buried duct runs. The software will determine the overall duct system effective R-value by weight averaging the user entered duct system.

Ducts must have a minimum insulation level prior to burial, R-6 for new ducts and R-4.2 for existing. Deeply buried ducts meet the requirements for buried ducts on the Ceiling and ducts are completely covered by at least 3.5 inches of attic insulation. Deeply buried ducts must be enclosed in a lowered portion of the ceiling or buried by use of a durable containment system (e.g., gypsum board, plywood, etc.), or buried under a uniform level of insulation that achieves the 3.5-inch burial level.

Figure 11-49: Buried Ducts on Ceiling and Deeply Buried Ducts

Source: California Energy Commission

Deeply buried containment systems must be installed such that the walls of the system are at least 7 inches wider than the duct diameter (3.5-inch clearance on each side of duct) extend at least 3.5 inches above the duct outer jacket, and the containment area surrounding the duct must be completely filled with blown insulation.

In addition to the above requirements, the attic area containing the buried or deeply buried ducts must have insulation with uniform depth (not mounded over the duct), level ceiling, and at least six inches of space between the duct outer jacket and the roof sheathing. Insulation raised by a containment system is an exception to the uniform depth requirement.

To take credit for buried ducts, the system must meet the verified duct system design criteria described above and meet the requirements for QII described in Reference Appendices RA3.5.

11.5.5      Common Use Area Space Conditioning Systems Requirements

This section provides an overview of the Energy Code requirements for space conditioning systems serving common use areas of the building, such as community rooms, corridors, fitness areas, and common laundry rooms. Since there are similar requirements for space conditioning systems serving common use area and systems serving nonresidential occupancies, more detailed discussion of the applicable requirements can be found in Chapter 4.

Requirements for systems serving nonresidential occupancies in mixed occupancy buildings are in §120, §130, §140 and §141 of the Energy Code.

11.5.5.1    Common Use Area Mandatory Requirements

Applicable mandatory requirements for common use area space conditioning systems, as described in Chapter 4 include:

•    Space conditioning equipment certification and equipment efficiency

•    Restrictions on pilot lights for natural gas appliances and equipment

•    Space conditioning system air filtration

•    Space conditioning system controls

•    Fluid distribution system: Pipe insulation

•    Fluid distribution systems - Requirements for Air Distribution System, Ducts, and Plenum

•    Mechanical acceptance testing

Residential equipment used in common use areas needs to meet requirements outlined in Chapter 11.6.3.1.

11.5.5.2    Common Use Area Prescriptive Requirements

Applicable Prescriptive requirements for common use area space conditioning systems are covered in Chapter 4 and include:

•    Space conditioning system sizing and equipment selection

•    Space conditioning system calculations

•    Space conditioning system requirement

11.5.5.3    Common Use Area Performance Approach

Refer to Chapter 4.9 for applicable performance approach requirements for common use area space conditioning systems.

11.5.6      Alternative Systems

Alternative system types can comply through the performance approach. This section describes some common alternative systems used in dwelling units and the associated code requirements. See Chapter 4 for more about systems serving common use areas and central systems.

11.5.6.1    Variable Capacity Heat Pumps

Several manufacturers offer mini-split or multi-split heat pump equipment that may or may not use air distribution ducts to heat or cool spaces. These systems provide advanced controls and multispeed compressors for optimizing performance through a wide range of conditioning loads.

These systems are generally required to be modeled as minimally efficient systems. A variable capacity heat pump (VCHP) compliance option is available to provide credit for systems meeting the eligibility requirements published in the Residential Appendices RA3.4.4.3. The credit can be applied through a CEC-approved modeling software by selecting the VCHP compliance option for the HVAC system type. The certificate of compliance will indicate when a space conditioning system requires verification of the VCHP compliance option eligibility requirements. A system that does not meet the eligibility requirements upon verification will not be eligible to claim the VCHP performance compliance credit for the specified space conditioning system.

Compliance with the mandatory duct system sealing and leakage and fan airflow rate and fan efficacy testing are not required for systems that use this VCHP performance compliance option. However, there are requirements to verify that VCHP system indoor unit ducts are located entirely in conditioned space that are specified as eligibility requirements for this compliance option. There are also requirements for verification of minimum airflow rates for VCHP system indoor units that are specified as eligibility requirements for this compliance option.

Additional verification requirements apply depending on the system type and credit taken, including:

•    Low-static certification for ducted systems

•    Non-continuous indoor unit fan operation

•    Refrigerant charge verification

•    Ducts located entirely in conditioned space

•    Indoor units located entirely in conditioned space

•    Supply to all habitable spaces

•    Wall-mounted thermostat

•    Space-conditioning system airflow

•    Air filter sizing

•    Air filter pressure drop rating

11.5.6.2    Hydronic Heating Systems

Hydronic heating is the use of hot water to distribute heat. A hydronic heating system consists of a heat source, which may be a gas boiler, gas or heat pump water heater, and a distribution system. There are three main types of hydronic distribution systems, and they may be used individually or in combination: baseboard convectors or radiators, air handlers, and radiant panel systems. Radiant panel surfaces can include floors, walls, and/or ceilings. Air handlers and radiant panels may be used for heating and cooling. Hot water air handlers may also be equipped with DX coils for cooling. The three distribution options are illustrated in Figure 11-50. Ducting is used only with air handlers.

If the hydronic system serves both dwelling units and common use areas or nonresidential spaces, applicable requirements for nonresidential space conditioning system must be met too.

11.5.6.3    Hydronic Heating Systems Mandatory Requirements

For hydronic heating systems without ducts, the mandatory requirements cover pipe insulation, tank insulation, and boiler efficiency. For fan coils with ducted air distribution, the mandatory air distribution requirements also apply. For combined hydronic systems, as described below, mandatory water heating requirements also apply to the water heating portion of the system.

E.     Pipe and Tank Insulation

The typical residential hydronic heating system operating between 105° and 140° F must have at least 1 inch (25 mm) of insulation on pipes less than 1 inch in diameter and 1.5 inch (38 mm) of insulation on pipes 1 inch or more in diameter. Systems operating between 141° and 200° F must have at least 1.5 inches of insulation on pipes less than 1.5 inches in diameter. For other temperatures and pipe insulation characteristics, see . There are a few exceptions where insulation is not required:

•    Sections of pipes where they penetrate framing members

•    Pipes that provide the heat exchange surface for radiant heating and/or cooling

•    Piping in the attic that is covered by at least 4 inches (100 mm) of blown insulation on top

•    Piping installed within walls if all the requirements for QII are met (see Chapter 3 Building Envelope Requirements).

If the system includes an unfired hot water storage tank, then the tank must be either wrapped with R-12 insulation or insulated internally to at least R-16.

Piping used to deliver chilled water to panels or air handlers should be continuously insulated with closed-cell foam to prevent condensation damage.

Figure 11-50: Hydronic Heating System Components

Source: Richard Heath & Associates/Pacific Gas and Electric Company

Figure 11-51: Combined Hydronic System with Water Heater as Heat Source

Source: Richard Heath & Associates/Pacific Gas and Electric Company

For pipes in hydronic heating systems that operate at pressure greater than 15 psi, the requirements of §160.3(c)1 apply. These are the same requirements that apply to nonresidential piping systems per §120.3.

F.     Equipment Efficiency

Equipment for residential space heating must meet the minimum efficiency set by the Energy Code. Electric resistance water heaters are not allowed for use in dedicated space heating systems. Therefore, some water heaters may be used for space heating only if used as part of a combined hydronic system, as described below. In that case, the mandatory water heater requirements apply.

There are no minimum efficiency requirements for heat pumps that produce hot or chilled water, but compliance calculations must use ratings listed in the CEC’s Title 20 appliance database under the category “Central Heat Pumps” and appliance type “Heat Pump Water Heating Packages.”

https:/cacertappliances.energy.ca.gov/Pages/ApplianceSearch.aspx

Thermostat requirements also apply to hydronic systems, as described in Chapter 4.5.1.

F.     Hydronic Heating Systems Prescriptive Requirements

There are no specific prescriptive requirements that apply to hydronic systems. However, if the system has a fan coil with ducted air distribution, the relevant prescriptive requirements apply, including duct insulation and duct sealing.

G.   Hydronic Heating Systems Performance Approach

Credit for choosing a hydronic heating system is possible using the performance approach. The standard design is assumed to use air distribution system. Therefore, hydronic systems without ducts can take credit for avoiding duct leakage penalties. In addition, minimizing the amount of pipe outside conditioned space will provide some savings. Hydronic heating and cooling compliance calculations are described in the Residential ACM Manual.

If the proposed hydronic system includes ducted air distribution, then the associated compliance options described earlier in this chapter may apply, such as improved airflow (if there is air conditioning) and supply duct location.

A combined hydronic system is a compliance option using the performance method. Combined hydronic heating refers to the use of a single water heating device as the heat source for space and domestic hot water heating.

Combined hydronic systems may use either a boiler (as in the figure below) or a water heater as a heat source. The boiler heats domestic water by circulating hot water through a heat exchanger in an indirect-fired water heater. The water heater provides domestic hot water as usual.

Figure 11-52: Combined Hydronic System with Boiler and Indirect Fired Water Heater

Source: Richard Heath & Associates/Pacific Gas and Electric Company

Space heating is accomplished by circulating water from the boiler or water heater through the space heating delivery system. Sometimes a heat exchanger is used to isolate potable water from the water circulated through the delivery system. Some water heaters have built-in heat exchangers for this purpose.

For compliance calculations, the water heating function of a combined hydronic system is analyzed for water heating performance as if the space heating function were separate. For the space heating function, an effective AFUE or HSPF rating is calculated. These calculations are performed automatically by the compliance software.

11.5.6.4    Air-to-Water Heat Pumps

Air-to-water heat pumps (AWHPs) provide space heating and cooling by conditioning water at the outdoor unit and circulating it to indoor delivery systems (e.g., fan coils, radiant floors, radiant ceiling panels). Some AWHPs can also provide domestic water heating capability. Title 20 requires AWHPs to be listed, but there are currently no minimum efficiency requirements. The compliance software treats fixed compressor speed AWHPs as equivalent to the prescriptive standard air source heat pump and provides a 2% heating and 8% cooling energy reduction for variable speed AWHPs, relative to the prescriptive standard air source heat pump. Current Title 20 listings for AWHPs can be found at the following link with Category “Central Heat Pumps” and Appliance “Heat Pump Water Heating Packages” selected.

www.cacertappliances.energy.ca.gov/Pages/Search/AdvancedSearch.aspx

11.5.6.5    Radiant System

Radiant slab-on-grade floor systems, using either hydronic tubing or electric cable, must meet mandatory insulation requirements. Radiant floors may take one of several forms. Tubing or electric elements for radiant floor systems may be:

•    Embedded in a concrete floor slab.

•    Installed over the top of a wood subfloor and covered with a concrete topping.

•    Installed over the top of a wood subfloor in between wood furring strips.

•    Installed on the underside surface of a wood subfloor

In the latter two types of installations, aluminum fins are typically installed to spread the heat evenly over the floor surface and reduce the temperature of the water as required. All hydronic systems use one or more pumps to circulate hot water. Pumps are controlled directly or indirectly by thermostats or by special outdoor reset controls.

When concrete slab-on-grade is heated by radiant tubing or cables, one of the insulation methods listed in the Energy Code Table 110.8-A must be complied with to prevent excessive heat loss from the slab edge. Chapter 3.2.8.1 provides more details about the heated slab floor insulation requirements.

11.5.6.6    Evaporatively Cooled Condensers

Evaporatively cooled condenser air conditioners are a type of air-conditioning system that can provide significant space-cooling savings, especially in hot, dry climates. The equipment minimal efficiencies are determined according to federal test procedures. The efficiencies of these air conditioners are reported in terms of energy efficiency rating (EER).

If credit is taken for a high EER, field verification by a HERS Rater is required. Other HERS verifications are also required, including duct sealing, airflow, fan efficacy, and refrigerant charge or FID.

Besides the HERS verification, there are additional special requirements for evaporatively cooled condensing air conditioners. These include that the manufacturer provide certification that water use is limited to no more than 0.15 gallon per minute per ton of capacity and that the supply line be no larger than ¼-inch in diameter. For a listing of all the requirements for evaporatively cooled condensing air conditioners, see the certificate of installation form.

11.5.7      Additions and Alterations

New or altered mechanical systems serving alterations or additions for dwelling units or common use areas must meet all applicable mandatory requirements and comply with either the prescriptive or performance approach. If a building does not meet all applicable prescriptive requirements, then the performance method using an approved compliance software is the alternative.

All HVAC systems serving additions generally are required to meet the newly constructed building prescriptive requirements, with few exceptions. Table 11-37 summarizes the requirements.

Table 11-37: HVAC Requirements for Prescriptive Additions

Source: California Energy Commission

If the heating and cooling system is unchanged as part of an addition or alteration, compliance for the HVAC system is not necessary. However, changing, altering, or replacing any component of a system triggers prescriptive requirements for that component. If the extended ducts are serving dwelling units, the combined new and existing duct system must meet the requirement to seal the ducts and verify that duct leakage is no greater than 15% of system airflow. If 15% leakage or lower cannot be attained, there are alternatives, including sealing all accessible leaks and confirming by a visual inspection.

When the HVAC system is entirely new or a complete replacement, then additional mandatory and prescriptive requirements apply.

The Energy Code make a distinction between two HVAC changeout situations:

•    Entirely new or complete replacement space conditioning systems.

•    Altered space conditioning systems.

11.5.7.1    Entirely New or Complete Replacement Space Conditioning Systems Serving Dwelling Units

An entirely new or complete replacement must meet all applicable mandatory and prescriptive requirements as described below.

•    §160.2(b)1: Air filtration requirements.

•    §160.3(a)1: Setback thermostats or controlled by EMCS.

•    §160.3(b)1-2: Cooling and heating load calculations.

•    §160.3(b)3: Outdoor condensing unit requirements.

•    §160.3(b)4: Heating furnace temperature rise requirements.

•    §160.3(b)5A-J: Duct insulation, labeling, & damper requirements.

•    §160.3(b)5L: Static pressure probe, airflow, and fan efficacy requirements (or alternative return duct sizing as per Table 160.3-A and B). Multifamily buildings in Climate Zone 1 with four or more habitable stories are exempt from this requirement.

•    §160.3(b)6: Pipe insulation.

•    §170.2(c)3A: Prescriptive heating system type: the new or complete replacement space-conditioning system may be a heat pump or gas heating system.

•    §170.2(c)3Bi: Prescriptive refrigerant charge verification.

•    §170.2(c)3Biii: Prescriptive central fan integrated ventilation system airflow and fan efficacy.

•    Table 180.2-C: Prescriptive duct insulation.

A system installed in an existing dwelling unit as part of an alteration must be considered entirely new when both of the following conditions are met:

•    The air handler and all the system heating/cooling equipment (e.g., outdoor condensing unit and indoor cooling or heating coil for split systems; or complete replacement of a package unit), are new.

•    The duct system is entirely new (including systems with less than 40 ft. in length).

An entirely new duct system may be part of an entirely new space conditioning system, or it may be connected to an existing space conditioning system. Duct systems are classified as entirely new when:

•    At least 75% of the duct material is new. Up to 25% may be composed of reused parts from the existing duct system.

•    All remaining components from the previous system are accessible and can be sealed.

Completely new or replacement duct systems in dwelling units must meet the 12% (total leakage protocol) or 6% (leakage to outside protocol) criteria used for newly constructed systems. A new duct system may be connected to an existing air handler, which typically leaks substantially more than new equipment. If the 12% leakage rate criteria cannot be met, a smoke test should be performed to verify that excess leakage is not from other accessible portions of the duct system. The protocol for the smoke test for accessible-duct sealing is given in RA3.1.4.3.7.

Verification of duct leakage must be conducted by a HERS Rater for multifamily buildings with up to three habitable stories. For other multifamily buildings, testing only needs to be conducted and certified by the installing contractor and neither a HERS Rater nor registration with a HERS Provider is required.

In addition, entirely new ducts systems must meet the following mandatory requirements:

•    §160.2(b)1: Air filtration requirements.

•    §160.3(b)5L: Static pressure probe, airflow, and fan efficacy requirements (or alternative return duct sizing as per Table 160.3-A and B). Multifamily buildings in Climate Zone 1 with four or more habitable stories are exempt from this requirement.

When an entirely new duct system and the furnace or air handler it is connected to are in a vented attic the following prescriptive requirements also must be met.

•    §180.2(b)1Bi: Attic insulation and air sealing requirements.

Altered duct systems that are not entirely new or complete replacements are treated as an extension of an existing system.

11.5.7.2    Altered Space Conditioning Systems Serving Dwelling Units

11.5.7.3    New and Altered Duct System – Insulation

When more than 25 linear ft. of new ducts are installed in an unconditioned space, the new ducts must be insulated to a minimum R-value as described in Table 11-38. When 25 ft. or less of ducts are installed in an unconditioned space, they must be insulated to the minimum mandatory insulation level of R-6 in all climate zones.

Table 11-38: Duct Minimum R-Value

Source: California Energy Commission

When new ducts are installed in conditioned space, the ducts must be insulated to the minimum mandatory insulation level of R-6 unless an exception or alternative mandatory minimum applies. For multifamily buildings four habitable or more stories, this can be confirmed by visual verification of the enforcement agency. For multifamily buildings up to three habitable stories, the entire duct system must be tested and confirmed to be in conditioned space by a HERS Rater per RA3.1.4.3.8.

H.   Altered System Duct Sealing

In all climate zones altered existing duct systems must be sealed and tested. An existing duct system is considered altered under any of the following conditions:

•    An outdoor condensing unit of a split system air conditioner or heat pump is installed or replaced.

•    A packaged system is completely replaced.

•    A cooling or heating coil is installed or replaced.

•    An air handler is installed or replaced.

•    More than 25 ft. of new or replacement ducts are installed.

•    The ducts are extended to serve an addition, regardless of the length of duct.

If a dwelling unit has more than one duct system, only the altered ducts or ducts connected to the altered equipment need to be sealed and verified.

There are three options for showing compliance for altered existing duct systems listed below. Compliance must at least be attempted with one of the first two options (15% total leakage or 10% leakage to outside); then the third option (sealing all accessible leaks) any of the other options can be used.

•    Total leakage is less than 15% of nominal system fan airflow (RA3.1.4.3.1).

•    Leakage to the outside is less than 10% of system fan airflow (RA3.1.4.3.4).

•    If the first two option leakage targets cannot be met, then compliance can be achieved by sealing all accessible leaks and conducting a smoke test (RA3.1.4.3.7).

For multifamily buildings with up to three habitable stories, HERS verification is required for all options listed above. For Options 1, and 2, verification can be accomplished through sampling. For Option 3, sampling is not allowed; a certified HERS Rater must do the visual inspection and the smoke test on every house. For other multifamily buildings, testing only needs to be conducted and certified by the installing contractor, and neither a HERS Rater nor registration with a HERS Provider is required.

Some judgment is required in determining if ducts are accessible. The local code enforcement agency will have the final say when it is not immediately obvious.

There are a few cases where duct sealing and duct leakage verification are not required. These exceptions include:

•    Ducts that have already been sealed, tested, and certified by a HERS Rater. This does not apply if the sealing requirements are triggered by the installation or new or replacement ducts (duct extension).

•    Duct systems with less than 40 ft. of duct. This does not apply if the sealing requirements are triggered by the installation or new or replacement ducts (duct extension).

•    Duct systems that are insulated or sealed with asbestos.

11.5.7.4    Altered System Refrigerant Charge Verification and Airflow

In Climate Zones 2 and 8 through 15, when a refrigerant-containing component of an air conditioner or heat pump is replaced or installed in an existing building, any system that does not have an FID installed must have refrigerant charge field tested in accordance with all applicable procedures specified in RA3.2.2 or RA1.

When refrigerant charge verification is required for compliance, the system must also comply with the minimum airflow of 300 CFM/ton according to the procedures specified in RA3.3.

Entirely new or complete replacement space-conditioning systems must meet the minimum 350 CFM/ton airflow rate compliance criterion or the duct design alternative along with the other prescriptive and mandatory requirements described above.

Verification of refrigerant charge and airflow must be conducted by a HERS Rater for multifamily buildings with up to three habitable stories. For other multifamily buildings, testing only needs to be conducted and certified by the installing contractor and neither a HERS Rater nor registration with a HERS Provider is required.

G.    Thermostats

When an existing system has a refrigerant containing component added or replaced, the thermostat must be upgraded to a setback type that meets §110.2(c)

11.5.7.5    Heating System Replacements

Prescriptive compliance requires new heating systems be limited to a heat pump or a gas or propane system. Altered systems must not use electric resistance as the primary heat source unless the existing space heating system is electric resistance and one of the following conditions are met:

•    Non-ducted electric resistance systems.

•    Ducted electric resistance systems only when a ducted space cooling system is not being replaced or installed as part of the alteration.

•    Any electric resistance systems in Climate Zones 6, 7, 8 or 15.

11.5.7.6    Entirely New or Complete Replacement Space Conditioning Systems Serving Common Use Area

An entirely new or complete replacement must meet all applicable mandatory and prescriptive requirements as described below.

•    §170.2(c)1: Space conditioning system sizing and equipment selection

•    §170.2(c)2: Space conditioning system calculations

•    §170.2(c)4: Space conditioning system requirement

Each new or replacement fan system must meet the fan power budget requirement specified in Table 180.2-D.

11.5.7.7    Altered Air Duct Systems Serving Common Use Area

Since there are similar requirements for altered air distribution systems serving common use area and systems serving nonresidential occupancies, more detailed discussion of the applicable requirements can be found in Chapter 4.9.1.1.1.10.

11.5.7.8    Altered Space Conditioning Systems Serving Common Use Area

Since there are similar requirements for altered space conditioning systems serving common use area and systems serving nonresidential occupancies, more detailed discussion of the applicable requirements can be found in Chapter 4.9.1.1.1.11.

11.5.8      Compliance and Enforcement

This section describes compliance documentation and field verification requirements related to heating and cooling systems.

11.5.8.1    Design-Phase Documentation

The following are heating and cooling system features that will be listed on the certificate of compliance if they exist in the proposed design:

•    Information summarizing requirements for field verification and diagnostic testing is presented in Table RA2-1 of the Reference Residential Appendix RA2. The field verification and diagnostic testing protocols that must be followed to qualify for compliance credit are described in RA3 of the Reference Residential Appendix.

Registration of the certificate of compliance with an approved HERS Provider is required for buildings up to three stories. The building owner or the person responsible for the design must submit the Certificate of Compliance to the HERS Provider Data Registry for retention according to the procedures described in §10-103 and  Reference Residential Appendix RA2. Registration ensures that the project follows the appropriate verification process, provides tracking, and provides electronic access to the documentation.

11.5.8.2    Construction-Phase Documentation

During construction, the general contractor or specialty subcontractors must complete all applicable certificate of installation documents for the building design special features specified on the certificate of compliance.

Like the certificate of compliance, registration of the certificate of installation is required except for multifamily buildings four or more stories. For all other buildings, the licensed contractor responsible for the installation must submit the certificate of installation information that applies to the installation to a HERS Provider Data registry using procedures described in §10-103 and Reference Residential Appendix RA2. Certificate of installation documents corresponding to the list of special features requiring HERS Rater verification in Chapter Error! No bookmark name given. above are required. For buildings four or more stories, the licensed contractor responsible for the installation must complete and submit the certificate of installation to the building department or authority having jurisdiction.

11.5.8.3    Field Verification and Diagnostic Testing

For buildings for which the certificate of compliance requires HERS or ATT field verification for compliance with the Energy Code, a HERS Rater or ATT must visit the site to perform field verification and diagnostic testing to complete the applicable heating and cooling system certificates of verification. Certificate of verification documents corresponding to the list of special features requiring HERS Rater or ATT verification in Chapter Error! No bookmark name given. above are required.

Field verification for nonmandatory features is necessary only when performance credit is taken for the feature. Some field verifications are mandatory requirements and will occur in all dwelling units unless they are exempt from the requirement.

Like the certificate of compliance and certificate of installation, registration of the certificate of verification is required. The HERS Rater or ATT must submit the field verification and diagnostic testing information to the HERS Provider Data Registry as described in Chapter 2. For additional details describing HERS verification and the registration procedure, refer to Reference Residential Appendix RA2.

Requirements for HERS Field Verification and Diagnostic Testing

Special features requiring HERS Rater verification for multifamily buildings with up to three habitable stories:

Duct sealing

Verified duct design: for reduced duct surface area or buried ducts

Low-leakage ducts in conditioned space

Low-leakage air handlers

Verification of return duct design

Verification of bypass duct prohibition

Refrigerant charge verification

Installation of an FID

Verified system airflow

Air handler fan watt draw

High energy efficiency ratio

High SEER

High heating seasonal performance factor

Heat pump - rated heating capacity

The requirements in Table 11-39: require additional verification. For all multifamily buildings, testing must be conducted and certified by the installing contractor. For multifamily buildings up to three habitable stories, the contractor results must be verified by a HERS Rater and all applicable certificates of compliance, installation, and verification must be registered with an approved HERS Provider. For multifamily buildings four or more habitable stories neither a HERS Rater nor registration with a HERS Provider is required. Verification, testing, and sampling procedures should follow Chapter 2.2.

Table 11-39: Air Distribution System Verification Requirements

Source: California Energy Commission

11.5.9      Code in Practice

11.5.9.1    Garden Style Multifamily Case Study

The Garden Style Multifamily Case Study considers a new two-story garden style multifamily building in Burbank, California (Climate Zone [CZ] 9). This is a sample project created for training purposes, and it consists of 7,216 ft² of conditioned floor area with eight dwelling units and no common use areas. The case study tables in this chapter compare the proposed building mechanical system features to Mandatory and Prescriptive Energy Code requirements and evaluate possible compliance options.

Figure 53 Garden Style Multifamily Case Study: North (Rear) Elevation Showing Outdoor Condensers

Table 11-40: Garden Style Multifamily Mechanical Schedule

Source: California Energy Commission

Table 11-41: Garden Style Multifamily Case Study Compared to Mandatory and Prescriptive Mechanical System Requirements (Climate Zone 9)

Table 11.42: Distribution, Ventilation and Verifications

Source: California Energy Commission

The proposed mechanical system meets all applicable mandatory requirements plus some of the relevant prescriptive requirements.

The split heat pump space heating and cooling equipment complies with the prescriptive heat pump requirement and meets the Federal mandatory minimum SEER and HSPF efficiency requirements. Note that the applicable heat pump heating and cooling efficiency requirements are listed in Title 20 Section 1605.1 Table C-3 for heat pumps under 65,000 Btuh, rather than in Table 110.2-B in Title 24, Part 6 which covers larger capacity heat pumps. Mandatory minimum whole dwelling unit ventilation for indoor air quality is calculated per Energy Code equation 160.2-B:

Q_tot = (0.03 x A_floor) + (7.5 x (N_br + 1))

Q_tot = Total required ventilation rate in CFM
A_floor = Dwelling unit floor area in ft²
N_br = Number of bedrooms (must be one or more)

1-bedroom units: ( 0.03 CFM/ft² x 750 ft²) + (7.5 CFM x (1 + 1)= 37.5 CFM

2-bedroom units: (0.03 CFM/ft² x 1080 ft²) + (7.5 CFM x (2 +1) = 54.9 CFM

HERS-verified continuous exhaust fan ventilation combined with HERS-verified limits to building envelope leakage, plus HERS-verified kitchen range hoods meet Mandatory ventilation requirements. Note that the kitchen hoods must be AHAM/HVI certified as meeting airflow rate or capture efficiency, and sound rating.

By contrast, the duct locations for the proposed systems as shown do not comply prescriptively. The building plans show the heat pump air handling units in the mechanical closets for each dwelling. On the first level the closets only open to the outside, so they are unconditioned space. R-8 ducts run from the air handlers up through the ceiling framing between levels to serve the conditioned spaces below. On the second level, the mechanical closets only open into the conditioned space of the dwelling units, so they are indirectly conditioned spaces. R-8 ducts run up from the air handlers into the vented attic which only has ceiling insulation but no roof insulation. These designs meet all mandatory requirements, but the Prescriptive path only allows two duct location options:

1.    Ducts and air handling units both in conditioned space

2.    R-8 ducts in a high performance attic designed to Prescriptive Option B with both ceiling and roof insulation

The Prescriptive Approach requires that a building meets all Prescriptive requirements. Unless the design team and owner are willing to change this particular building envelope to accommodate ducts and air handlers in conditioned space for the first floor, and either ducts in conditioned space or in a high performance attic for the second floor, the building will need to show compliance using the Performance Approach.

The Performance method allows trade-offs between different building features to offset components that do not comply prescriptively. There are also HVAC Performance compliance credit options available, such as:

•    Higher efficiency equipment

•    Variable capacity heat pump (VCHP)

•    Low leakage air-handling unit (AHU)

•    Pre-cooling

•    ERV/HRV

•    Whole house fan

•    Central fan ventilation cooling system

Figure 54: Garden Style Multifamily: Bathroom Exhaust and Kitchen Hood Ducts

11.5.9.2    Mid-Rise Multifamily Case Study

The Mid-Rise Multifamily Case Study covers a new five-story multifamily building in Sacramento, California (Climate Zone [CZ] 12). This is a sample project created for training purposes, and it includes 112,044 ft² of conditioned floor area with 88 dwelling units, shared residential corridors, laundry rooms, fitness center and lounge, plus ground floor retail. The case study tables in this chapter compare the proposed building mechanical system features to Mandatory and Prescriptive Energy Code requirements and evaluate possible compliance options.

Figure 55: Mid-Rise Multifamily Case Study: Mechanical and Central DHW Roof Plan

Figure 56: Mid-Rise Multifamily Case Study: 5th Floor Apartment Air Handler and Condenser

Table 11-43: Mid-Rise Multifamily Case Study Compared to Mandatory and Prescriptive Mechanical System Requirements (Climate Zone 12)

Source: California Energy Commission

Figure 57: Section 100.0(f) Exception 1 for Mixed Occupancy

Table 11-44: Fuel Type, Equipment Type and Efficiency

Source: California Energy Commission

Table 11-45: Distribution, Air Handlers and Fan Systems

Table 11-46: Ventilation and Verifications

Source: California Energy Commission

Table 11-47: Mid-Rise Multifamily Mechanical Schedule: Dwelling Units

Notes on System:

• ERV Systems: Providing dwelling unit ventilation

• Balanced Energy Recovery Ventilation (ERV):  Studios and 1-Bedroom units: 40 CFM, 0.032 bhp. 2-Bedroom units: 60 CFM, 0.048 bhp; 3-Bedroom units: 75 CFM, 0.060 bhp

• Kitchen hood:  Installed over induction electric cooktops in each dwelling unit

• Bathroom exhaust fans: 70 CFM each, 0.055 bhp

• HVAC Controls: Programmable setback thermostats

Source: California Energy Commission

Table 11-48: Mid-Rise Multifamily Mechanical Schedule: Multifamily Common Use and Retail

Source: California Energy Commission

VRF systems: Separate multi-split VRF heat pump systems serving retail and multifamily common use areas

Dedicated Outdoor Air Systems (DOAS): MERV 13 Filters, Demand Control Ventilation

Retail ERV: Outdoor Air Volume: 4,100 CFM, Supply Fan: 2 hp, Exhaust Air Volume: 4,100 CFM, Exhaust Fan: 2 hp

HVAC Controls: Programmable setback thermostats for each zone, occupant sensor shut-off controls in corridors and stairwells with partial OFF lighting controls, automatic time switch shut-off controls in other zones

MF CU ERV: Outdoor Air Volume: 3,100 CFM, Supply Fan: 1.5 hp, Exhaust Air Volume: 3,100 CFM, Exhaust Fan: 1.5 hp

This mid-rise multifamily case study has different types of mechanical systems for the dwelling units versus the multifamily common use areas and retail zones.

The dwelling unit split heat pump space heating and cooling equipment complies with the Prescriptive heat pump requirement and meets the Federal Mandatory minimum SEER and HSPF efficiency requirements. Note that the applicable heat pump heating and cooling efficiency requirements are listed in Title 20 Section 1605.1 Table C-3 for heat pumps under 65,000 Btuh. Each system consists of a heat pump air handler located in a dwelling unit and a separate condenser located on the roof. Since there are 88 total dwelling units with split heat pumps, there are 88 condensers located on the roof. In this case study, those condensers are placed around the roof perimeter next to the parapets to leave room for the required solar photovoltaic (PV) panels.

The multifamily common use areas and the retail spaces are served by VRF heat pump equipment with central condensing units on the roof and VRF heat pump fan coil units in each zone. The selected equipment meets the Federal Mandatory minimum heating and cooling efficiency requirements found in Energy Code Table 110.2-H for VRF air cooled systems. There are different cooling efficiency requirements for VRF systems with different cooling capacities ranging from less than 65,000 Btuh to greater than or equal to 240,000 Btuh. There are also different heating efficiency requirements based on cooling, not heating, capacities ranging from less than 65,000 Btuh to 135,000 Btuh or more. Note that while the VRF fan coil units all have cooling capacities less than 65,000 Btuh, the two different VRF condensers for retail and common use areas are both over 240,000 Btuh. The efficiencies in Table 110.2-H are based on the condenser cooling capacity, not that for the fan coil units. Knowing that, Table 110.2-H shows that these particular VRF systems must meet or exceed a cooling efficiency of 9.5 EER and a heating efficiency of 3.2 COP.

Supplying mandatory ventilation outside air is handled differently for the residences compared to the common use areas and retail zones. The dwelling unit ventilation system includes three main components within each residence:

•    The primary air handler in each unit connected to ducts in conditioned space that deliver heated and cooled air throughout the residence

•    A balanced energy recovery ventilator or ERV that supplies outdoor air and exhausts indoor air

•    The kitchen hood installed over the electric induction cooktop that exhausts cooking fumes directly to the outside

By contrast, the multifamily common use areas and retail spaces have the following ventilation components:

•    Central ERV dedicated outside air systems (DOAS) – one that delivers outside air to all the retail spaces and another that delivers outside air to all the multifamily common use areas. Since these systems are ERVs, they also exhaust the same amount of indoor air from the zones they serve.

•    VRF heat pump fan coil units in each zone that deliver heated and cooled air within the space. The retail fan coil units are ductless, so they deliver conditioned air from one central location within each store. The common use fan coil units deliver air through ducting throughout each space.

Overall, the proposed mechanical systems meet all applicable mandatory requirements and prescriptive requirements, so the proposed systems comply prescriptively as designed.

Figure 58: Mid-Rise Multifamily: 5th Floor Apartment HVAC Supply, ERV and Kitchen Hood Layout with Ducts