2.10 Additions/Alterations

Addition and alteration compliance is based on standards Section 150.2. 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, as “existing+addition+alteration,” or the entire building may be modeled as an entirely new building (whole building, Section 150.2[c]).

Additions that are 1,000 ft² or less are exempt from dwelling unit ventilation requirements of Section 150.0(o)1C, 150.0(o)1E, or 150.0(o)1F. 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.

2.10.1  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 or less energy than the standard design.

2.10.2  Alteration-Alone Approach

The proposed alteration alone floor area is modeled. The alteration requirements of Section 150.2(b) are applied to any features that do not exist.

2.10.3  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 compliance approach (Section 2.10.4), are given to the addition alone approach. (See Standards Section 150.2[a]2.B.) The addition complies if the proposed design uses equal or less space heating, space cooling, and water heating TDV energy 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.

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 proposed design shall assume the same efficiency for the HVAC equipment as the standard design. (See Sections 2.4.1 and Section 2.4.5)

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.

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

A.   When roofing requirements are included in Table 150.1-A or 150.1-B, they are included in the standard design if the added conditioned floor area is greater than 300 ft².

B.   When ventilation cooling (whole-house fan) is required by Table 150.1-A or 150.1-B, it is included in the standard design when the added conditioned floor area is greater than 1,000 ft². The capacity shall be based on 1.5 CFM/ft² of conditioned floor area for the entire dwelling unit conditioned floor area.

C.   When compliance with indoor air quality requirements of Section 150.0(o) 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 indoor air quality requirements apply.

D.   PV requirements are not included.

2.10.4  Existing + Addition + Alteration Approach

Standards Section 150.2(a)2 contains the provisions for additions and Section (b)2 for alterations when the existing building is included in the calculations. These provisions are the “Existing + Addition + Alteration” (or “E+A+A”) performance approach.

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 E+A+A standard design using the rules in the standards 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 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.

•      Verified Altered: the surface or system is altered in the proposed design, and the original condition is verified by a HERS rater (an optional selection).

•      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.

Section 150.2(b), Table 150.2-C specifies the details of the standard design for altered components based on whether verification of existing conditions is selected or not:

Altered with no third-party verification of existing conditions (the default selection). This compliance path does not require an on-site inspection of existing conditions prior to the start of construction. The attributes of the existing condition is undefined, with the standard design for altered components based on Section 150.2, Table 150.2-B, and the climate zone. Energy compliance credit or penalty is a function of the difference between the value for that specific feature allowed in Table 150.2-B and the modeled/installed efficiency of the feature.

Verified Altered existing conditions. This compliance path requires that a HERS rater perform an on-site inspection of prealteration conditions prior to construction. If an altered component or system meets or exceeds the prescriptive alteration requirements, the compliance software uses the user-defined and verified existing condition as the standard design value. Energy compliance credit is then based on the difference between the verified existing condition for that altered feature and the modeled/installed efficiency of the proposed design.

2.10.4.1      QII

The standard design includes QII for additions greater than 700 square feet in any low-rise single-family building in Climate Zones 1-16 and in any low-rise multifamily building in Climate Zones 1-6 and 8-16 (Section 150.2(a)1Bv).

The provisions of Section 150.2(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.

2.10.4.2      PV

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

2.10.4.3      Roof/Ceilings

The standard design roof/ceiling construction assembly is based on the proposed design assembly type as shown in Table 26. For additions less than or equal to 700 square feet, radiant barrier requirements follow Option C (Section 150.1[c]9B). The standard design for unaltered ceilings and roofs is the existing condition.

Table 26: Addition Standard Design for Roofs/Ceilings

Source: California Energy Commission

2.10.4.4      Exterior Walls and Doors

The 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 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.

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 Section 150.0[c]1 and Section 150.2(a)1).

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.

If the proposed wall area is framed, the gross exterior wall area (excluding knee walls) is equally divided among the four building orientations: front, left, back and right. The gross exterior wall area of any unframed walls is also equally divided among the four orientations in the standard design.

The standard design exterior wall construction assembly is based on the proposed design assembly type as shown in Table 27. Framed walls 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 0.02 U-factor. Fire-rated doors (from the house to garage) use the proposed design door U-factor as the standard design U-factor.

Table 27: Addition Standard Design for Walls and Doors

Source: California Energy Commission

2.10.4.5      Fenestration

Table 28: Addition Standard Design for Fenestration (in Walls and Roofs)

Source: California Energy Commission

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 Section 150.2(b)1.B 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 proposed design fenestration as shown in Table 28 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 28:

•      Proposed design < allowed % 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 the addition, new fenestration is divided equally among the four project compass points similar to new gross wall areas in the addition described above.

•      Proposed design > allowed % 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.

2.10.4.6      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 29 Exterior shading (limited to bug screens) is treated differently than fixed overhangs and sidefins, as explained in Section 2.5.6.9.

Table 29 : Addition Standard Design for Overhangs, Sidefins, and Other Exterior Shading

Source: California Energy Commission

2.10.4.7      Window Film

Proposed Design

A window film must have at least a 10-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.

2.10.4.8      Floors

Standard Design

Table 150.2-C requires that the standard design be based on the mandatory requirements from Section 150.0(d). The standard design for floors is shown in Table 30.

Table 30: Addition Standard Design for Raised Floor, Slab-on-Grade, and Raised Slab

Source: California Energy Commission

2.10.4.9      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 Section 2.5.4.1.

2.10.4.10     Air Leakage and Infiltration

Standard design air leakage and infiltration is shown in Table 31.

Table 31: Addition Standard Design for Air Leakage and Infiltration

Source: California Energy Commission

2.10.4.11     Space Conditioning System

Standard Design

The standard design for space-conditioning systems is shown in Table 32.

When cooling ventilation (whole-house fan) is required by Sections 150.1 and 150.2, the capacity is 1.5 CFM/ft² of conditioned floor area for the entire dwelling unit.

When compliance with indoor air quality requirements of Section 150.0(o) 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 indoor air quality requirements shall apply.

Table 32: Addition Standard Design for Space Conditioning Systems

Source: California Energy Commission

2.10.4.12     Duct System

Standard Design

Table 33: Addition Standard Design for Duct Systems

Based on Table 150.2-A

Note 1: Refer to Section 150.2(b)1Diia a for definition of an “Entirely New or Complete Replacement Duct System.”

Source: California Energy Commission

2.10.4.13     Water Heating System

Standard Design

Table 34: Addition Standard Design for Water Heater Systems

Source: California Energy Commission