8.3   Compliance Process

Any certified computer program may be used to comply with the Standards using the performance method. The following steps are a general outline of the typical computer program procedure:

1.   Collect all necessary data on each component. For the building envelope the area of each fenestration, wall, door, roof, ceiling and floor needs to be available. For each component the applicable energy characteristics needs to be defined including U-factor, solar heat gain coefficients, solar reflectance, and thermal mass values. The type and efficiency of space conditioning equipment. For hydronic space heating, the specific water heater model. For fan-forced conditioning systems, the location and amount of insulation of the duct system.

2.   For domestic hot water systems, if the system is either not a "standard" system, or if credit is to be taken for a specific system design, the following will be required:

      Water heater model(s)

      Quantity of water heaters

      Location served by each water heater

      Distribution system design

      Additional information will be required for "built-up" systems.

Other efficiency measures and options exist that can be used to improve building efficiency. To review the complete list of options refer to your compliance software user’s guide.

3.   Start by entering the building envelope basic data such as square footage, number of stories, occupancy type and climate zone. Define each opaque surface with its orientation, area and thermal performance properties. Add the fenestrations that are associated with each opaque surface, including any fixed shading such as overhangs and side-fins. Enter the data on the equipment and distribution systems for the space conditioning and water heating systems. Input values and assumptions must correctly correspond to the information on the final approved plan set; and inputs must be equal to or more energy efficient than required mandatory measures.

4.   Launch a computer run to automatically calculate the TDV energy of the standard design and the proposed design.

The building energy efficiency complies if all the mandatory measures are met and the total TDV energy use of the proposed design is the same as or less than the standard design TDV energy budget.

When creating a computer input file, use the space provided for the project title information to concisely and uniquely describe the building being modeled. User-designated names should be clear and internally consistent with other orientations and/or buildings being analyzed. Title names and explanatory comments should assist individuals involved in both the compliance and enforcement process.

8.3.1    Defining the Standard Design

Each approved computer program must automatically calculate the TDV energy use of the standard design. The standard design is created based upon data entered for the proposed design using all the correct fixed and restricted inputs.

The computer program defines the standard design by modifying the geometry of the proposed design and inserting the building features of prescriptive Package A. This process is built into each approved computer program and the user cannot access it. Key details on how the standard design is created and calculated by the computer programs, including the listing of fixed and restricted input assumptions are documented in the 2013 Residential ACM 'Manual.

The standard design assumes the same total conditioned floor area, conditioned slab floor area, and volume as the proposed design, and the same gross exterior wall area as the proposed design, except that the wall area in each of the four cardinal orientations is equal. The standard design uses the same roof/ceiling area, raised floor area, slab-on-grade area and perimeter as the proposed design, assuming the standard insulation R-values required in the prescriptive packages.

Total fenestration area in the standard design is equal to the proposed design if the fenestration area in the proposed design is less than or equal to 20 percent of the floor area, otherwise, the fenestration area of the standard design is equal to 20 percent of the floor area. Fenestration area in the standard design is evenly distributed between the four cardinal orientations. SHGC and U-factors are those listed in Package A, and no fixed shading devices such as overhangs are assumed for the standard design.

The standard design includes minimum efficiency heating and cooling equipment, as well as the minimum duct R-value with ducts in a vented attic if the proposed design has an attic. Ducts are assumed to be sealed as required by §150.0(m). The standard design also has correct refrigerant charge as required by §150.1(c)7A

For water heating systems that serve individual dwelling units, the standard design is a 50 gallon gas storage water heater with an Energy Factor equal to the federal minimum standard. The standard design has a trunk and branch distribution system, that includes the assumption that all mandatory measures are met (i.e., the first 5 ft of hot and cold water piping from heating source) and that all piping ¾ of an inch or larger is insulated and the entire length of piping to kitchen fixtures are insulated as specified in §150.0(j)2A or §150.0(j)2B.

For multiple dwelling unit buildings, either a central distribution system may be used or individual water heaters may be installed in each unit. The standard design system type is based on what the proposed design uses. However, the standard design does not have pumped recirculation or no recirculation.

Standard Reports

For consistency and ease of enforcement, the manner in which building features are reported by Compliance Software programs is standardized. Energy Commission-approved Compliance Software programs must automatically produce compliance reports in this standard format. The principal report is the Certificate of Compliance (CF-1R).

The CF-1R has two highly visible sections, one for special features and modeling assumptions, and a second for features requiring field verification and/or diagnostic testing by approved HERS raters. These two sections serve as a punch list for special consideration during compliance verification by the local enforcement agency and the HERS rater. Items listed in the Special Features and Modeling Assumptions section indicate that unusual features or assumptions are used for compliance, and they call for special care by the local enforcement agency. Items listed in the HERS Required Verification section are for features that rely on diagnostic testing and independent verification by approved HERS providers/raters to ensure proper field installation. Diagnostic testing and verification by HERS providers/raters is in 'addition to local enforcement agency inspections.

8.3.2    Professional Judgment

Some modeling techniques and compliance assumptions applied to the proposed design are fixed or restricted. There is little or no freedom to choose input values for energy compliance modeling purposes. However, other aspects of energy modeling remain for which some professional judgment may be acceptable or necessary. In those instances, the Compliance Software user must exercise proper judgment in evaluating whether a given input is appropriate.

Enforcement agencies have discretion to reject a particular input if the permit applicant cannot substantiate the value with supporting documentation or cannot demonstrate that appropriate professional judgment has been applied.

Two questions may be asked in order to resolve whether professional judgment has been applied correctly in any particular case:

1.   Is a simplified input or assumption appropriate for a specific case? If simplification reduces the predicted energy use of the proposed building or reduces the compliance margin when compared to a more explicit and detailed modeling assumption, the simplification is not acceptable. That is, simplification must reflect the same or higher energy use than a more detailed model, and reflect the same or lower compliance margin when comparing the Standard and Proposed TDV energy.

2.   Is the approach or assumption used in modeling the proposed design consistent with the approach or assumption used by the Compliance Software when generating the Standard Design energy budget?

One must always model the proposed design using the same assumption and/or technique used by the Compliance Software Manager when calculating the energy budget unless drawings and specifications indicate specific differences that warrant energy compliance credits or penalties.

Any unusual modeling approach, assumption or input value should be documented with published data and should conform to standard engineering practice.

For assistance in evaluating the appropriateness of particular input assumptions, call the Energy Hotline or call the vendor of the Compliance Software program.


Example 8-1


Three different sized windows in the same wall of a new home are designed without exterior shading, and they have the exact same NFRC-rated U-factors and SHGC values. Is it acceptable professional judgment to simplify the computer model by adding the areas of the three windows together and inputting them as a single fenestration area?


Yes. The Compliance Software will produce the same results whether or not the windows are modeled individually or together as one area because the orientation, fenestration U-factors and SHGC values of the windows are identical. However, if overhangs and side-fins are modeled, the correct geometry of fixed shades must be modeled for each window.