4.9 Additions and Alterations

4.9.1    Overview    

This section addresses how the Standards apply to mechanical systems for additions and alterations to existing buildings.

A.   Application of the Standards to existing buildings is often more difficult than for new buildings because of the wide variety of conditions that can be experienced in the field. In understanding the requirements, two general principles apply:

1.   Existing systems or equipment are not required to meet the Standards.

2.   New systems and equipment are required to meet both the mandatory measures and the prescriptive requirements or the performance requirements as modeled in conjunction with the envelope and lighting design.

When heating, cooling or service water heating are provided for an alteration or addition by expanding an existing system, in general, that existing system need not comply with the mandatory measures or prescriptive requirements. However, any altered component must meet all applicable mandatory measures and prescriptive.

B.   Relocation of Equipment

When existing heating, cooling, or service water heating systems or components are moved within a building, the existing systems or components need not comply with mandatory measures nor with the prescriptive or performance compliance requirements.

Performance approach may also be used to demonstrate compliance for alterations. Refer to Chapter 11, Performance Approach, for more details.

4.9.2    Mandatory Measures – Additions and Alterations

New mechanical equipment or systems in additions and/or alterations must comply with the mandatory measures as 'listed below. Additional information on these requirements is provided in earlier sections of this Chapter.


Mandatory Measure

Application to Additions and Alterations

§110.1 – Mandatory Requirements for Appliances (see Section 4.2)

The California Appliance Efficiency Regulations apply to small to medium sized heating equipment, cooling equipment and water heaters. These requirements are enforced for all equipment sold in California and therefore apply to all equipment used in additions or alterations.

§110.2 – Mandatory Requirements for Space-Conditioning Equipment (see Section 4.2)

This section sets minimum efficiency requirements for equipment not covered by §110.1. Any equipment used in additions or alterations must meet these efficiency requirements.

§110.3 – Mandatory Requirements for Service Water-Heating Systems and Equipment (see Section 4.2)

This section sets minimum efficiency and control requirements for water heating equipment. It also sets requirements for recirculating hot water distribution systems. All new equipment installed in additions and/or alterations shall meet the requirements. The recirculation loop requirements of §110.3(c)5 apply when water heating equipment and/or plumbing is changed.

§110.4 – Mandatory Requirements for Pool and Spa Heating Systems and Equipment (see Section 110.4).

The pool requirements of §110.4 do not apply for maintenance or repairs of existing pool heating or filtration systems.

§110.5 – Natural Gas Central Furnaces, Cooking Equipment, and Pool and Spa Heaters: Pilot Lights Prohibited (see Section 4.2)

Any new gas appliances installed in additions or alterations shall not have a standing pilot light, unless one of the exceptions in §110.5 is satisfied.

§120.1 – Requirements for Ventilation (see Section 4.3)

Systems dedicated to additions or alterations shall meet the outside air ventilation requirements, and in this case, no modifications are needed for the existing system, even if it does not comply.

When existing systems are extending to serve additions or when occupancy changes in an existing building (such as the conversion of office space to a large conference room), the outside air settings at the existing air handler may need to be modified and in some cases, new controls may be necessary.

§120.2 – Required Controls for Space-Conditioning Systems (see Section 4.5)

§120.2(a) requires a thermostat for any new zones in additions or new zones created in an alteration.

§120.2(b) requires that new thermostats required by §120.2(a) meet the minimum requirements.

§120.2(c) applies to hotel/motel guest rooms only when the system level controls are replaced; replacement of individual thermostats are considered a repair. However, §120.2(c) applies to all new thermostats in high rise residential, including replacements.

§120.2(d) requires that new heat pumps used in either alterations or additions have controls to limit the use of electric resistance heat, per §110.2(b). This applies to any new heat pump installed in conjunction with an addition and/or alteration.

§120.2(e) requires that new systems in alterations and additions have scheduling and setback controls.

§120.2(f) requires that outside air dampers automatically close when the fan is not operating. This applies when a new system or air handling unit is replaced in conjunction with an addition or alteration.

§120.2(g) requires that areas served by large systems be divided into isolation areas so that heating, cooling and/or the supply of air can be provided to just the isolation areas that need it and other isolation areas can be shut off. This applies to additions larger than 25,000 ft² and to the replacement of existing systems when the total area served is greater than 25,000 ft².

§120.2(h) requires that direct digital controls (DDC) that operate at the zone level be programmed to enable non-critical loads to be shed during electricity emergencies. This requirement applies to additions and/or alterations anytime DDC are installed that operate at the zone level.

§120.2(i) requires a Fault Detection and Diagnostic System (FDD) for all new air-cooled unitary direct expansion units (including packaged, split system, heat pumps, and variable refrigerant flow (VRF) where the VRF capacity is defined by that of the condensing unit) used in either additions or alterations equipped with an economizer and mechanical cooling capacity at AHRI conditions equal to or greater than 54,000 Btu/hr in accordance with subsections 120.2(i)2. through 120.2(i)9.


§120.3 – Requirements for Pipe Insulation (see Section 4.4)

The pipe insulation requirements apply to any new piping installed in additions or alterations.

§120.4 – Requirements for Air Distribution System Ducts and Plenums

The duct insulation, construction and sealing requirements apply to any new ductwork installed in additions or alterations.

§120.5 – Required Nonresidential Mechanical System Acceptance

Acceptance requirements are triggered for systems or equipment installed in additions and alterations they same way they are for new buildings or systems.

4.9.3    Requirements for Additions     

A.   Prescriptive Approach

All new additions must comply with the following prescriptive requirements:

1.   §140.4 – Prescriptive Requirements for Space Conditioning Systems

2.   §140.5 – Prescriptive Requirements for Service Water-Heating Systems

For more detailed information about the prescriptive requirements, refer to following sections of this chapter:

1.   4.5.2 HVAC Controls

2.   4.6.2 HVAC System Requirements

B.   Performance Approach

The performance approach may also be used to demonstrate compliance for new additions. When using the performance approach for additions §141.0(a)2B defines the characteristics of the standard design building.  

Refer to Chapter 11, Performance Approach, for more details.

C.   Acceptance Tests

Acceptance tests must be conducted on the new equipment or systems when installed in new additions.

For more detail, see Chapter 12, Acceptance Requirements

4.9.4    Requirements for Alterations    

A.   Prescriptive Requirements – New or Replacement Equipment

New space conditioning systems or components other than space conditioning ducts must meet applicable prescriptive requirements of §140.4.

Minor equipment maintenance such as replacement of filters or belts does not trigger the prescriptive requirements. Equipment replacement such as the installation of a new air handler or cooling tower would be subject to the prescriptive requirements of §140.4. Another example is if an existing VAV system is expanded to serve additional zones, the new VAV boxes are subject to zone controls of §140.4(d). Details on prescriptive requirements may be found in other sections of this chapter.

Replacements of electric resistance space heaters for high rise residential apartments are also exempt from §140.4 requirements. Replacements of electric heat or electric resistance space heaters are allowed where natural gas is not available.

For alterations there are special rules for

1.   New or Replacement Space Conditioning Systems or Components in §141.0(b)2C, and

2.   Altered Duct Systems in §141.0(b)2D

3.   Altered Space –Conditioning Systems in §141.0(b)2E

4.   Service water heating has to meet all of §140.5 with the exception of the solar water heating requirements (§141.0(b)2L)

B.   Prescriptive Requirements – Air Distribution Ducts (§141.0(b)2D)    

When new or replacement space-conditioning ducts are installed to serve an existing building, the new ducts shall meet the requirements of §120.4 (insulation levels, sealing materials and methods, etc.). Details on duct requirements of §120.4 can be found in Section 4.4 of this 'manual.

If the ducts are part of a single zone constant volume system serving less than 5,000 ft² and more than 25 percent of the ducts are outdoors or in unconditioned area including attic spaces and above insulated ceilings the criteria of §140.4(l)1, 2, and 3, the duct system shall be sealed and tested for air leakage by the contractor. In most nonresidential buildings this requirement will not apply because the roof is insulated so that almost all of the duct length is running through directly or indirectly conditioned space.

If the ducts are in unconditioned space and have to be sealed, they must also be tested to leak no greater than 6 percent if the entire duct system is new or less than 15 percent if the duct system is added to a pre-existing duct system. The description of the test method can be found in Section of Reference Nonresidential Appendix NA2. The air distribution acceptance test associated with this can be found in Reference Nonresidential Appendix NA7. This and all acceptance tests are described in Chapter 12 of this manual.

If the new ducts form an entirely new duct system directly connected to an existing or new air handler, the measured duct leakage shall be less than 6 percent of fan flow; or

If the new ducts are an extension of an existing duct system, the combined new and existing duct system shall meet one of the following requirements:

1.   The measured duct leakage shall be less than 15 percent of fan flow; or

2.   If it is not possible to meet the duct sealing requirements of  §141.0(b)2Dii, all accessible leaks shall be sealed and verified through a visual inspection and smoke test performed by a certified HERS rater utilizing the methods specified in Reference Nonresidential Appendix NA

Exception to §141.0(b)2Dii: Existing duct systems that are extended, which are constructed, insulated or sealed with asbestos are exempt from the requirements of §141.0(b)2Dii.

Once the ducts have been sealed and tested to leak less than the above amounts, a HERS rater will be contacted by the contractor to validate the accuracy of the duct sealing measurement on a sample of the systems repaired as described in Reference Nonresidential Appendix NA1.

C.   Prescriptive Requirements – Space-Conditioning Systems Alterations (§141.0(b)2E)    

Similar requirements apply to ducts upon replacement of small (serving less than 5,000 ft²) constant volume HVAC units or their components (including replacement of the air handler, outdoor condensing unit of a split system air conditioner or heat pump, or cooling or heating coil). Again the duct sealing requirements are for those systems where over 25 percent of the duct area is outdoors or in unconditioned areas including attic spaces and above insulated ceilings.

One can avoid sealing the ducts by insulating the roof and sealing the attic vents as part of a larger remodel, thereby creating a conditioned space within which the ducts are located, and no longer meets the criteria of §140.4(l).

When a space conditioning system is altered by the installation or replacement of space conditioning equipment (including replacement of the air handler, outdoor condensing unit of a split system air conditioner or heat pump, or cooling or heating coil), the duct system that is connected to the new or replaced space conditioning equipment, if the duct system meets the criteria of §140.4(l)1, 2, and 3, shall be sealed, as confirmed through field verification and diagnostic testing in accordance with procedures for duct sealing of existing duct systems as specified in the Reference Nonresidential Appendix NA1, to one of the requirements of §141.0(b)2D; and the system shall include a setback thermostat that meets requirements of Reference Joint Appendix JA5.

Exception 1 to 141.0(b)2E: Buildings altered so that the duct system no longer meets the criteria of §140.4(l)1, 2, and 3.

Ducts would no longer have to be sealed if the roof deck was insulated and attic ventilation openings sealed.

Exception 2 to §141.0(b)2E: Duct systems that are documented to have been previously sealed as confirmed through field verification and diagnostic testing in accordance with procedures in Reference Nonresidential Appendix NA2.

Exception 3 to §141.0(b)2E: Existing duct systems constructed, insulated or sealed with asbestos.

Per §141.0(b)2Ei,  for all altered unitary single zone, air conditioners, heat pumps, and furnaces where the existing thermostat does not comply with Reference Joint Appendix JA5, the existing thermostat must be replaced with a thermostat that complies with Reference Joint Appendix JA5. All newly installed space-conditioning systems requiring a thermostat shall be equipped with a thermostat that complies with Reference Joint Appendix JA5.  A JA5 compliant is also known as the Occupant Controlled Smart Thermostat (OSCT), which is capable of responding to demand response signals in the event of grid congestion and shortages during high electrical demand periods.

D.   Performance Approach    

When using the performance approach for alterations, see §141.0(b)3.

E.   Acceptance Tests

Acceptance tests must be conducted on the new equipment or systems when installed in new additions:

For more detail, see Chapter 12, Acceptance Requirements.

Example 4-50


A maintenance contractor comes twice a year to change the filters and check out the rooftop packaged equipment that serves our office. Do the Standards apply to this type of work?


In general, the Standards do not apply to general maintenance such as replacing filters, belts or other components; however if the rooftop unit wears out and needs to be replaced, then the new unit would have to meet the equipment efficiency requirements of §110.2 as well as the mandatory requirements of §120.1 §120.4 and the prescriptive requirements of §140.4.


Example 4-51


Our building is being renovated and the old heating system is being entirely removed and replaced with a new system that provides both heating and cooling. How do the Standards apply?


All of the requirements of the Standards apply in the same way they would if the system were in a new building.

Example 4-52


A 10,000 ft² addition is being added to a 25,000 ft² building. The addition has its own rooftop HVAC system. The system serving the existing building is not being modified. How do the Standards apply?


The addition is treated as a separate building and all the requirements of the Standards apply to the addition. None of the requirements apply to the existing system or existing building since it is not being modified.

Example 4-53


A 3,000 ft² addition is being added to a 50,000 ft² office. The existing packaged variable air volume (PVAV) system has unused capacity and will be used to serve the addition as well as the existing building. This system has direct digital controls at the zone level and an air side economizer.

Ductwork will be extended from an existing trunk line and two additional VAV boxes will be installed with hot water reheat. Piping for reheat will be extended from existing branch lines. How do the Standards apply?


The general rule is that the Standards apply to new construction and not to existing systems that are not being modified. In this case, the Standards would not apply to the existing PVAV. However, the ductwork serving the addition would have to be sealed and insulated according to the requirements of §120.4, the hot water piping would have to be insulated according to the requirements of §120.3, The new thermostats would have to meet the requirements of 120.2 (a), (b), and (h), ventilation would have to be provided per §120.1, fractional fan motors in the new space would have to comply with §140.4(c)4, and the new VAV boxes would have to meet the requirements of 140.4(d).

Example 4-54


In the previous example (3,000 ft² addition is added to a 50,000 ft² office), how do the outside air ventilation requirements of §120.1 apply?


The outside air ventilation rates specified in §120.1 apply at the air handler. When existing air handlers are extended to serve additional space, it is necessary to reconfigure the air handler to assure that the outside air requirements of §120.1 are satisfied for all the spaces served. 'In addition, the acceptance requirements for outside air ventilation are also triggered (see Chapter 12). It would be necessary to evaluate the occupancies both in the addition and the existing building to determine the minimum outside air needed to meet the requirements of §120.1. The existing air handler would have to be controlled to assure that the minimum outside air is delivered to the spaces served by the air handler for all positions of the VAV boxes. (See Section 4.3 of this Manual for details on how this is achieved. Additional controls may need to be installed at the air handler to meet this requirement.)

Example 4-55


In the previous example, the 3,000 ft² addition contains a large 400 ft² conference room. What additional requirements are triggered in this instance?


In this case, the demand control requirements of §140.4(c) would apply to the conference room, since it has an occupant density greater than 25 persons per 1,000 ft² and the PVAV system serving the building has an air side economizer and direct digital controls (DDC) at the zone level. If the existing system did not have an outside air economizer or if it did not have DDC controls at the zone level, then the demand control requirements would not apply. A separate sensor would need to be provided in the conference room to meet this requirement.  The programming on the OSA damper would have to be modified to increase OSA if the zone ventilation wasn't satisfied.

Example 4-56


An existing building has floor-by-floor VAV systems with no air side economizers. The VAV boxes also have electric reheat. Outside air is ducted to the air handlers on each floor which is adequate to meet the ventilation requirements of §120.1, but not large enough to bring in 100 percent outside air which would be needed for economizer operation. A tenant space encompassing the whole floor is being renovated and new ductwork and new VAV boxes are being installed. Does the economizer requirement of §140.4(e) apply? Does the restriction on electric resistance heat of §140.4(g) apply?


Since the air handler is not being replaced, the economizer requirement of §140.4(e) does not apply. If in the future the air handler were to be replaced, the economizer requirement would need to be satisfied; however for systems such as this a water side economizer is often installed instead of an air side economizer. The electric resistance restriction of §140.4(g) does however apply, unless the Exception 2 to §149(a) applies. This exception permits electric resistance to be used for the additional VAV boxes as long as the total capacity of the electric resistance system does not increase by more than 150 percent.

Example 4-57


In the previous example, the building owner has decided to replace the air handler on the floor where the tenant space is being renovated because the new tenant has electronic equipment that creates more heat than can be removed by the existing system. In this case, does the economizer requirement of §140.4(e) apply?


In this case, the economizer requirement does apply. The designer would have a choice of using an air-side economizer or a water-side economizer. The air side economizer option would likely require additional or new ductwork to bring in the necessary volume of outside air. The feasibility of a water economizer will depend on the configuration of the building. Often a cooling tower is on the roof and chillers are in the basement with chilled water and condenser water lines running in a common shaft. In this case, it may be possible to tap into the condenser water lines and install a water economizer, however, pressure controls would need to be installed at the take offs at each floor and at the chiller.

Example 4-58


400 tons of capacity is being added to an existing 800 ton chilled water plant. The existing plant is air cooled (two 400 ton air cooled chillers). Can the new chillers also be air cooled?




No. The requirements of §140.4(j) apply in this case and a maximum of 300 tons of air-cooled chillers has been reached (and exceeded) at this plant. The remainder has to be water cooled.  They would not have to retrofit the plant to replace either of the existing air-cooled chillers with water cooled.  If one of the existing air-cooled chillers failed in the future they would have to replace it with a water-cooled chiller.  If both air-cooled chillers failed they could only provide 300 tons of air cooled capacity.