9.5   Additions

For a definition of an addition in the Standards, and several useful examples of additions, see the Introduction, Section 9.1 of this chapter. 

For a summary of compliance alternatives for additions, see Compliance Approaches, Section 9.2 of this chapter.

Beyond the outline provided in Section 9.2, this section provides more specific information, descriptions and guidelines on how to meet the Standards using each of the available compliance paths. Copies of compliance forms referenced here are included in the Compliance Forms Summary, Appendix A of this 'manual.

9.5.1    Prescriptive Requirements

In general, the prescriptive requirements apply to additions in the same way they apply to entirely new buildings and must be documented on the CF1R-ADD Form. However, there are a few exceptions as noted below and summarized in Table 9-3A.

There are three prescriptive paths available for additions based on the total conditioned floor area (CFA) of the addition.  The total CFA of the addition may include floor areas representing several physically separate additions to the building under the same permit.

Table 9-3A summarizes the key features of the prescriptive envelope requirements for the three prescriptive addition options in §150.2(a)1 of the Standards.  Envelope requirements unique to that type of prescriptive addition are shown in bold face on white background. Table 9-3B shows that all prescriptive additions have the same mechanical system and water heating system requirements as the Package A prescriptive measures for new construction 'listed in §150.1(c) and explained in Chapters 4 and 5.

A.   Additions ≤ 400 ft²

All prescriptive Package A requirements must be met except:

1.   Total glazing area may be up to 75 ft² or 30% of conditioned floor area, whichever is greater;

2.   West-facing glazing area may be up to 60 ft²;

3.   Required exterior wall insulation:

a.   In 2x4 wood frame walls, insulation shall be R-13 or an overall construction assembly U-factor < 0.102, for wood or metal frame walls;

b.   In 2x6 or greater wood frame walls, insulation shall be R-19 or an overall construction assembly U-factor < 0.074, for wood or metal frame walls;

4.   No requirement for a whole house fan (WHF) to provide ventilation cooling;

5.   For additions ≤ 300 ft² cool roof compliance is not required.

B.   Additions > 400 ft² and ≤ 700 ft²:

All prescriptive Package A requirements must be met except:

1.   Total glazing area may be up to 120 ft² or 25% of conditioned floor area, whichever is greater;

2.   West-facing glazing area may be up to 60 ft²;

3.   Required exterior wall insulation:

a.   In 2x4 wood frame walls, insulation shall be R-13 or an overall construction assembly U-factor < 0.102, for wood or metal frame walls;

b.   In 2x6 or greater wood frame walls, insulation shall be R-19 or an overall construction assembly U-factor < 0.074, for wood or metal frame walls;

4.   No requirement for a whole house fan (WHF) to provide ventilation cooling.

C.   Additions > 700 ft²

All prescriptive Package A requirements must be met except:

1.   Total glazing area may be up to 175 ft² or 20% of conditioned floor area, whichever is greater;

2.   West-facing glazing area may be up to 70 ft² or 5% of conditioned floor area, whichever is greater;

3.   If the addition is < 1,000 ft², there is no requirement for a whole house fan (WHF) to provide ventilation cooling;

4.   Additions > 1,000 ft² must include provide ventilation cooling with a WHF as indicated in §150.1(c)12;

5.   If the Total Proposed fenestration area exceeds the Standard Maximum Glazing Area of 20% then the performance compliance approach must be used. Likewise, if the Proposed West-Facing fenestration area in climate zones 2, 4, and 6-16 exceeds 5% of the conditioned floor area, then the performance compliance approach must be used;

6.   If the addition has a floor area >700 ft² and < 1,000 ft², all requirements of Package A apply except the West-Facing Glazing Area may be up to 70 ft² for additions up to 1,400 ft² (since 70 ft² is 5% of 1,400 ft²). See §150.2(a)1A.

Figure 9-2 – Prescriptive Addition Envelope Requirements

Compliance Forms for Prescriptive Additions

The permit applicant must submit a completed version of the Certificate of Compliance, CF1R-ADD form, for prescriptive additions when less than 100 ft² .

Important note:  All projects which require third party diagnostic testing and/or field verification by a HERS rater must also have the CF1R-ADD form uploaded and registered online with a HERS provider (see Chapter 2).

Use the CF1R-ADD form to document fenestration by orientation. The total percentage of fenestration should be no greater than the amount summarized above and in Table 9-3A. West facing area includes skylights tilted to the west or tilted in any direction when the pitch is less than 1:12 (9.5 degrees from the horizontal), and must not exceed 5 percent of the conditioned floor area (CFA) in climate zones 2, 4, and 6-16.

Note: Plan checkers will verify on the CF1R-ADD form that the Total Proposed Glazing Area is less than or equal to the Standard Maximum Glazing Area; and that the Proposed West-Facing Glazing Area is less than or equal to the Standard West-Facing Glazing Area.

9.5.2    Fenestration Exceptions

New fenestration in prescriptive additions must meet the area-weighted average U-factor and SHGC requirements in §150.1(c)3A with the following exceptions particularly relevant to additions:

1.   EXCEPTION 1:  For each dwelling unit, up to 3 ft² of new glazing in doors and up to 3 ft² of tubular skylights with dual pane diffusers are exempt;

2.   EXCEPTION 2:  For each dwelling unit, up to 16 ft² of skylights with a maximum U-factor of 0.55 and a maximum SHGC of 0.30 is exempt.

See Section 3.5 for further information on fenestration which meets or is exempt from §150.1(c)3A in new construction.

Other Prescriptive Addition Envelope Measures

For further information on prescriptive envelope measures which are not specific to additions and not highlighted above, see Chapter 3.

Prescriptive Mechanical Measures

For a summary and discussion of prescriptive mechanical requirements when installing new or replacement space conditioning equipment and/or ducts, see Section 9.6.1.

Table 9-3A:  Envelope Roof/Ceiling Requirements for Prescriptive Additions

Table 9-3B:  Envelope Glazing Requirements for Prescriptive Additions

Table 9-3C:  Envelope Insulation Requirements for Prescriptive Additions

Table 9-3D  HVAC and Water Heating Requirements for Prescriptive Additions

9.5.3    Prescriptive Water Heating System

If an addition increases the number of water heaters serving a dwelling unit, then the addition can comply prescriptively if any one of the following conditions contained in §150.2(a)1D.i, ii and iii:

The additional water heater is a 50 gallon or less, gas storage or gas instantaneous, non-recirculating water heater with an EF (Energy Factor) equal to or greater than the federal minimum standards as defined in Section 5.4; or

The building does not have natural gas or propane available; and the additional water heater is a 50 gallon or less electric storage tank water heater, or electric instantaneous with an EF equal to or greater than the federal minimum standards;  or

A water-heating system determined by the Executive Director of the Energy Commission to use no more energy than the one specified in item 1 above; or if no natural gas is connected to the building, a water-heating system determined by the Executive Director to use no more energy than the one specified in item 2 above.

If none of these conditions can be met when adding a water heater to an existing dwelling unit, then the prescriptive addition compliance path cannot be used.  In that case, the Existing + Addition + Alterations compliance approach must be used to demonstrate overall compliance with whatever combination of existing and new water heaters serve the dwelling unit.  This is summarized in §150.2(a)1D.iv and discussed as part of the overall performance method in Section 9.5.2. 

For other alterations to the water heating system that occur as part of an addition, see Section 9.6.

9.5.4    Performance Method: Addition Alone and Existing + Addition + Alterations Approach

Additions may comply using the performance approach with one of the following compliance paths summarized in Section 9.2, Table 9-1:

1.   Addition Alone;

2.   E + A + A Without Third Party Verification;

3.   E + A + A With Third Party Verification;

4.   E + A + A as New Construction.

Energy Commission-approved compliance software is used to model the building as explained in Chapter 8. Whichever compliance path is selected, the Certificate of Compliance (CF1R) generated by the compliance software must be submitted for permit.   If the CF1R includes energy measures that require HERS testing or verification, the CF1R must also be registered online with a HERS provider. See Section 2.2.2.

To learn more about what kinds of alterations are assigned energy credit using the Existing + Addition + Alterations performance approach, see Section 9.5.2.

A.   Addition Alone

In this compliance scenario, the addition alone is modeled using the compliance software and the existing building is not modeled at all.  This approach may work well when the existing building is not undergoing alterations, and the permitted work scope covers only the addition. 

1.   Advantages: Data for the existing building is not needed except for the total existing conditioned floor area which is used to calculate the fractional “number of dwelling units” for the addition. The existing building is not modeled and not analyzed for altered components or systems. This typically saves a large amount of time performing the analysis.

2.   Disadvantages: If the addition includes a large area of glazing or is otherwise deficient in comparison with the prescriptive requirements, it may be difficult to demonstrate compliance under this approach.  Alterations to the existing conditions which improve the energy performance of the existing building cannot be used in this approach as “trade-offs” with the addition.

B.   Existing + Addition + Alterations Without Third Party Verification

The existing building with all alterations is modeled together with the addition; and existing conditions are not verified by a third party HERS Rater.  The Standard Design that sets the energy budget for this approach is automatically based only on the type of each altered component and not on the existing conditions. Under this performance path the building is modeled as follows:

1.   Addition: All new components at the addition and all new systems serving the addition are modeled including roof/ceilings and skylights, exterior walls and glazing (fenestration), raised floors and slab floors, HVAC equipment, ducts and water heating. All these elements are tagged within the compliance software as “New”; or

2.   Existing Components to Remain Unchanged:  Existing components and systems to remain as is (untouched) are modeled and tagged within the compliance software as “Existing”; or

3.   Existing Components to be Altered or Replaced, "Altered”:  Each altered component (i.e. a new component which replaces an existing component) is modeled and tagged within the performance compliance program as "altered".  Each component or system which remains is modeled and tagged within the compliance software as “Altered” such as, a new water heater that replaces an existing water heater would be labeled "altered”;  a new water heater that is added to supplement an existing water heater would be labeled "new". Also, new mechanical equipment that does not replace existing mechanical equipment would be tagged as "new". No verification of existing conditions is required in this compliance path; therefore, no “Existing” (pre-alteration) conditions are specified.

Note:  Portions of new fenestration including skylights that will occur in the existing opening of fenestration to be replaced are tagged "altered".  Portions of new fenestration that will occur where there is no existing fenestration opening are labeled as "new".

C.   Existing to be Removed:

Existing roof/ceilings to be removed as part of the permitted work, plus any skylights within those removed roof/ceilings, are excluded from the model (i.e., they are completely omitted from the calculations); exterior walls to be removed, and all fenestration areas in those removed walls, are not modeled; and raised floors and slab-on-grade floors to be removed are also omitted. 

Note: This is an important change in the E+A+A modeling rules from the 2008 Standards as discussed in Section 9.6.

Advantages: Energy improvements to the existing building that go beyond the Standard Design levels are an energy credit that can be effectively “traded” against features of the addition that are less energy efficient than required by the prescriptive levels that set the Standard Design for the addition alone.  For example, an addition with a large glazing area may comply by replacing the existing HVAC system with high-efficiency equipment. 

Disadvantages:  Detailed plans and other information on the existing building may be difficult to document and obtain.  The E+A+A analysis may be relatively complex and time-consuming.

Refer to Table 9-4 for a summary of E+A+A modeling rules.

D.   Existing + Addition + Alterations With Third Party Verification

The existing building with alterations is modeled together with the addition(s); and existing conditions of the components being altered must be verified by a third party HERS Rater before any construction work begins.  The Standard Design that sets the energy budget may, depending on the energy efficiency of the altered component or system, be based on the pre-altered existing conditions.  In those instances, energy credit is calculated as a function of the difference between pre-altered existing conditions and post-alteration energy measures. Under this approach the building is modeled as follows:

1.   Addition: All new components for the addition and all new systems serving the addition are modeled including roof/ceilings and skylights, exterior walls and glazing (fenestration), raised floors and slab floors, HVAC equipment, ducts and water heating. All these elements are tagged within the compliance software as “New”; or

2.   Existing Components to Remain Unchanged:  Existing components and systems to remain as is (untouched) are modeled and tagged within the compliance software as “Existing”; or

3.   Existing Components to be Altered or Replaced: "Existing to be Altered:  Each altered component (i.e. a new component which replaces an existing component) is modeled and tagged within the performance compliance program as "altered".  Each component or system which remains is modeled and tagged within the compliance software as “Altered” such as, a new water heater that replaces an existing water heater would be labeled "altered”;  a new water heater that is added to supplement an existing water heater would be labeled "new". Also, new mechanical equipment that does not replace existing mechanical equipment would be tagged as "new". No verification of existing conditions is required in this compliance path; therefore, the “Existing” (pre-alteration) conditions must be specified.

Note: Removing an area of fenestration in an existing wall or roof, and re-inserting up to the same total area of glazing in different openings, is considered replacement or “altered” fenestration as defined in §150.2(b)1B. Any net glazing area added to the total existing fenestration in an existing wall or existing roof is considered “new” fenestration.

4.   Removed Surfaces:  Existing roof/ceilings to be removed as part of the permitted work, plus any skylights within those removed roof/ceilings, are excluded from the model (i.e., they are completely omitted from the calculations). Exterior walls to be removed, and all fenestration areas to be removed in those walls, are not modeled; and raised floors and slab-on-grade floors to be removed are also omitted. 

Note: This is an important change in the E+A+A modeling rules from the 2008 Standards summarized in Section 9.6.

5.   Advantages: Energy improvements meeting certain threshold values are credited based on the difference between existing conditions and the altered component or system.  These energy credits can be effectively “traded” against features of the addition that are less energy efficient than required by the prescriptive levels that set the Standard Design for the addition alone.  For example, an addition with a large glazing area may comply by upgrading insulation levels in the existing house. 

6.   Disadvantages:  Detailed plans and other information on the existing building may be difficult to document and obtain.  The E+A+A analysis may be relatively complex and time-consuming. And a third party verification must be conducted of all existing conditions prior to construction, and that verification must be registered online with a HERS provider prior to permit submittal.

Refer to Table 9-4 for a summary of E+A+A modeling rules.

E.   Existing + Addition + Alterations as New Construction

A compliance approach rarely used, but available within the Standards, is to model Existing + Addition + Alterations as all “New” components and systems and the compliance software sets the energy budget as if the project were an entirely new building.

1.   Advantages: Modeling the existing building with alterations and additions as all new makes the performance analysis relatively simple and less time-consuming.  This method will provide the owner and designer with an energy efficiency compliance relative to requirements for new construction.  Any owner who wants to bring their building up to new construction energy efficiency levels should have their project modeled as “new”.

2.   Disadvantages:  The energy budget with this approach is very stringent.  Unless a building is going through a complete retrofit of all its envelope components, as well as replacing all mechanical and water heating systems, it is unlikely that the building will meet the Standards with this approach.

F.   Summary of Modeling Rules

Table 9-4 summarizes the basic rules for compliance software users analyzing a residential addition or alteration using the Existing + Addition + Alterations approach. For further information, see the specific compliance software user's 'manual for details on how to input data correctly.

Table 9-4: Modeling Rules for Existing + Addition + Alterations