6.12   Additions/Alterations

Addition and alteration compliance is based on Energy Code, §180.0, §180.1, §180.2, and §180.3. The energy budget for additions and alterations is based on TDV energy. Alterations must model the entire dwelling unit. Additions may be modeled as addition alone, alteration alone or ExistingAdditionAndAlteration

Additions that are 1,000 ft² or less and junior accessory dwelling units are not required to comply with whole-dwelling unit ventilation airflow specified in §160.2(b)2Aiv or §160.2(b)2Av. When an addition to any building creates a new dwelling unit, this exception does not apply.

The standard design does not include:

•   Cool roof when an addition is 300 ft2 or less.

•   Ventilation cooling for additions that are 1,000 ft2 or less.

•   Solar generation/PV requirements.

6.12.1         Whole Building

The entire proposed building, including all additions or alterations or both, is modeled the same as a newly constructed building. The building complies if the proposed design uses equal to or less energy than the standard design.

6.12.2         Alteration-Alone Approach

The proposed alteration alone floor area is modeled. The alteration requirements of §180.2 are applied to any new features.

6.12.3         Addition-Alone Approach

The proposed addition alone is modeled the same as a newly constructed building except that the internal gains are prorated based on the size of the dwelling. None of the exceptions included for prescriptive additions, which are implemented in the existing plus addition plus alteration compliance approach (Chapter 6.13.4 Existing+ Addition Alteration Approach), are given to the addition alone approach. (See Energy Code, §180.1[b]2.) The addition complies if the proposed design source and TDV energy budget is less than the standard design.

The addition-alone approach shall not be used when alterations to the existing building are proposed. Modifications to any surfaces between the existing building and the addition are part of the addition and are not considered alterations.

Proposed Design

The user shall indicate that an addition alone is being modeled and enter the conditioned floor area of the addition. Any surfaces that are between the existing building and the addition are not modeled or are treated as adiabatic surfaces. All other features of the addition shall be modeled the same as a newly constructed building.

When an existing HVAC system is extended to serve the addition, the standard design shall assume the same efficiency for the HVAC equipment as the proposed design. (See Chapter 6.8.1 Heating Subsystems and Chapter 6.8.2 Cooling Subsystems.)

When a dual-glazed greenhouse or garden window is installed in an addition or alteration, the proposed design U-factor can be assumed to be 0.30.

Standard Design

The addition alone is modeled the same as a newly constructed building, with the following exceptions:

Ø When roofing requirements are included in Table 170.2-A, they are included in the standard design if the added conditioned floor area is greater than 300 ft2.

Ø When compliance with IAQ requirements of §160.2 apply to an addition with greater than 1,000 ft2 added, the conditioned floor area of the entire dwelling unit shall be used to determine the required ventilation airflow. For additions with 1,000 ft2 or less of added conditioned floor area, no IAQ requirements apply.

Ø PV requirements are not included.

Ø For multifamily buildings with three habitable stories or less in Climate Zones 1-15 the space conditioning system is a heat pump. For multifamily buildings with three habitable stories or less in Climate Zone 16 the space conditioning system is an air conditioner with furnace. For multifamily buildings with more than three habitable stories in Climate Zones 2-15 the space conditioning system is a heat pump. For multifamily buildings with more than three habitable stories in Climate Zones 1 and 16 the space conditioning system is a dual-fuel heat pump. See Chapter 6.9.1 Heating Subsystems for equipment efficiencies and operating details for each type of system. The cooling system for the standard design building is a nonzonal control system, split-system ducted cooling system, meeting the minimum requirements of the Appliance Efficiency Regulations. See Chapter 6.9.2 Cooling Subsystems for equipment efficiencies and operating details for each type of system.

Ø For dwelling units with water heaters serving individual dwelling units, the standard design DHW system is a heat pump water heater with a 2.0 UEF. In climate zone 3, 4, 13 and 14, if the proposed design is gas, the standard design DHW system is a natural gas tankless (or propane if natural gas is not available) water heating system. See Chapter 6.11.2 Individual Dwelling Units for equipment efficiencies and operating details for each type of water heater.

6.12.4         ExistingAdditionAndAlteration Approach

Energy Code §180.1 contains the provisions for additions and §180.2 for alterations when the existing building is included in the calculations. These provisions are the ExistingAdditionAndAlteration performance approach. The proposed existing + addition + alteration design complies if the TDV energy budget is less than the standard design

Proposed Design

The proposed design is modeled by identifying each energy feature as part of the existing building (as existing, altered, or new), or as part of the addition. The compliance software uses this information to create an ExistingAdditionAndAlteration standard design using the rules in the Energy Code that take into account whether altered components meet or exceed the threshold at which they receive a compliance credit and whether any related measures are triggered by altering a given component.

For building surfaces and systems designated below, all compliance software must provide an input field with labels for the proposed design, which define how the standard design requirements are established based on the option selected by the compliance software user:

•   Existing: The surface or system remains unchanged within the proposed design. (Both standard design and proposed design have the same features and characteristics.)

•   Altered: the surface or system is altered in the proposed design. No verification of existing conditions is assumed with this designation.

•   New: a new surface or system is added in the proposed design (may be in the existing building or the addition).

Deleted features are not included in the proposed design.

§180.2, Table 180.2-B specifies the details of the standard design for altered components.

QII

Standard Design

For multifamily building up to three habitable stories, the standard design includes QII for additions greater than 700 ft² in multifamily building in Climate Zones 1-6 and 8-16(§180.1[a]1Bv).

The provisions of §180.1[a]1Aiv, as applied to converting an existing unconditioned space to conditioned space, are accommodations made by the HERS rater in the field. No adjustments to the energy budget are made.

PV

Standard Design

The standard design does not include PV for additions and alterations.

Roof/Ceilings

Standard Design

The standard design roof/ceiling construction assembly is based on the proposed design assembly type as shown in Table 3i. For additions equal to or less than 700 ft², radiant barrier requirements follow Option C (§170.2[a]1Bii). The standard design for unaltered ceilings and roofs is the existing condition.

Table 43: Standard Design for Roofs/Ceilings

Source: California Energy Commission

Exterior Walls and Doors

The compliance software allows the user to indicate whether a new wall in an addition is an extension of an existing wood-framed wall and, if so, the dimensions of the existing wall. The standard design exterior wall construction assembly is based on a wood-framed wall with R-15 cavity insulation for existing 2x4 walls or R-21 cavity insulation for existing 2x6 walls.

The compliance software allows the user to indicate if a wall is existing, where siding is not removed or replaced. The user also identifies if the walls have 2x4 or 2x6 framing. The standard design exterior wall construction assembly is based on a wood-framed wall with R-15 cavity insulation for existing 2x4 walls or R-21 cavity insulation for existing 2x6 walls.

Proposed Design

Existing structures with insulated wood-framed walls that are being converted to conditioned space using an E+A+A approach are allowed to show compliance using the existing wall framing, without having to upgrade to current prescriptive continuous insulation requirements. The walls are modeled as an assembly with the existing framing and either R-15 (in 2x4 framing) or R-21 (in 2x6 framing) insulation (Exception to §160.1[b] and §180.1[a]1).

Standard Design

The areas, orientation, and tilt of existing, new, and altered net exterior wall areas (with windows and doors subtracted) are the same in the existing and addition portions of standard design as in the proposed design.

The gross exterior wall areas (wall area without subtracting window area and orientations of the standard design match the proposed design.

The standard design exterior wall construction assembly is based on the proposed design assembly type as shown in Table 44: Addition Standard Design for Walls and Doors are modeled as 16-in. on center wood framing. The standard design for unaltered walls is the existing condition.

The standard design for exterior opaque or swinging doors is 0.20 U-factor. Fire-rated doors (from the house to garage) use the proposed design door U-factor as the standard design U-factor.

Table 44: Addition Standard Design for Walls and Doors

Source: California Energy Commission

Fenestration

Proposed Design

Fenestration areas are modeled in the addition as new. In an existing building, they may be existing, altered, or new. Altered (replacement) fenestration is defined in §180.2(b)1C as “existing fenestration area in an existing wall or roof [which is] replaced with a new manufactured fenestration product... Up to the total fenestration area removed in the existing wall or roof....“ Altered also includes fenestration installed in the same existing wall, even if in a different location on that wall. Added fenestration area in an existing wall or roof is fenestration that did not previously exist and is modeled as new.

Standard Design

Standard design fenestration U-factor and SHGC are based on the values shown in Table 45: Standard Design for Fenestration (in Walls and Roofs). Vertical glazing includes all fenestration in exterior walls such as windows, clerestories, and glazed doors. Skylights include all glazed openings in roofs and ceilings.

New fenestration in an alteration is modeled with the same U-factor and SHGC as required for an addition.

West-facing limitations are combined with the maximum fenestration allowed and are not an additional allowance.

The standard design is set for fenestration areas and orientations as shown in Table 45: Standard Design for Fenestration (in Walls and Roofs)

•   Proposed design < allowed percentage of total fenestration area:

In the existing building, the standard design uses the same area and orientation of each existing or altered fenestration area (in the respective existing or altered wall or roof.)

In an addition, the standard design uses the same area and orientation of up to the allowed fenestration.

•   Proposed design > allowed percentage of total fenestration area:

The standard design first calculates the allowed total fenestration area as the total existing and altered fenestration area in existing or altered walls and roofs. Added to this is the percent of fenestration allowed in the addition, based on the conditioned floor area of the addition.

Table 45: Standard Design for Fenestration (in Walls and Roofs)

Source: California Energy Commission

Overhangs, Sidefins and Other Exterior Shading

Standard Design

The standard design for a proposed building with overhangs, sidefins, and exterior shades is shown in Table 46: Standard Design for Overhangs, Sidefins, and Other Exterior Shading Exterior shading (limited to bug screens) is treated differently than fixed overhangs and sidefins, as explained in Chapter 6.9.6.9 Exterior Shading.

Table 46: Standard Design for Overhangs, Sidefins, and Other Exterior Shading

Source: California Energy Commission

Window Film

Proposed Design

A window film must have at least a 15-year warranty and is treated as a window replacement. The values modeled are either the default values from Tables 110.6-A and 110.6-B or the NFRC Window Film Energy Performance Label.

Floors

Standard Design

The standard design for floors is shown in Table 47: Standard Design for Floors.

Table 47: Standard Design for Floors

Source: California Energy Commission

Thermal Mass

Standard Design

The standard design for thermal mass in existing plus addition plus alteration calculations is the same as for all newly constructed buildings as explained in Chapter 6.9.4.1 Internal Thermal Mass.

Air Leakage and Infiltration

Standard Design

Standard design air leakage and infiltration is shown in Table 48: Standard Design for Air Leakage and Infiltration.

Table 48: Standard Design for Air Leakage and Infiltration

Source: California Energy Commission

Space Conditioning System

Standard Design

The standard design for space-conditioning systems is shown in Table 49: Standard Design for Space Conditioning Systems

When compliance with IAQ requirements of §160.2 apply to an addition with greater than 1,000 ft² added, the conditioned floor area of the entire dwelling unit is used to determine the required ventilation airflow. For additions with 1,000 ft² or less of added conditioned floor area, no IAQ requirements shall apply.

Table 49: Standard Design for Space Conditioning Systems

Source: California Energy Commission

Duct System

Proposed Design

Duct insulation shall be based on the new or replacement R-value input by the user. Duct leakage shall be based on the tested duct leakage rate entered by the user or a default rate of 30 percent.

Standard Design

Table 50: Standard Design for Duct Systems

Based on Table 180.2-C

Note 1: Refer to §180.2(b)2Aii for definition of an “Entirely New or Complete Replacement Duct System.”

Source: California Energy Commission

Water Heating System

Standard Design

Table 51: Standard Design for Water Heater Systems

Source: California Energy Commission