Frequently Asked Questions (FAQs)

The COMcheck trade-off alternative used for enforcing the IECC is permitted under a clause in Section 101 (referencing 2012 IECC). That clause is a fairly common code element that gives the jurisdiction and, more explicitly, the building official the latitude to allow any compliance approach that "makes sense" with respect to accomplishing the code's objectives. This kind of clause is often referred to as a "deemed to comply" approach. Through legislative and/or legal procedures, jurisdictions agree and accept to adopt this provision when adopting the IECC editions and in many cases amend the adopted code to explicitly include language that expressly permits use of the COMcheck software.

Specifically, Section 101 allows a building official to approve compliance tools that are deemed to meet "the intent of [the] code." The intent of the IECC commercial code is explicitly defined here: "C101.3 Intent. This code shall regulate the design and construction of buildings for the effective use and conservation of energy over the useful life of each building. This code is intended to provide flexibility to permit the use of innovative approaches and techniques to achieve this objective." The various compliance paths of the code are alternative "recipes" designed to achieve that intent, but Section 101 implies that other recipes are permitted if they accomplish the same overall objective.

The trade-off methodology used by COMcheck is consistent with the "Normative Appendix C: Methodology for Building Envelope Trade-Off Option" found in the referenced ASHRAE 90.1 code. However, to determine compliance with an IECC edition, all IECC requirements are applied to and enforced within that trade-off methodology including Section C402.3.1 "maximum fenestration and skylight area" (COMcheck restricts users from using the trade-off approach when the C402.3.1 provisions are not met, redirecting them to use of the referenced 90.1 as allowed by C401.2).

The IECC explicitly references what version of ASHRAE 90.1 corresponds with IECC sections on page C-78 of the 2012 IECC.

Codes: 2009 and 2012 IECC, ASHRAE Standard 90.1-13/2015 IECC

The 2009/2012 editions of the IECC (commercial provisions) do not include language explicitly describing a defined envelope trade-off compliance method. Only a set of prescriptive envelope requirements are provided. However, Section 101 of the IECC has a clause that has been widely interpreted and understood to give a building code official or jurisdiction the latitude to allow any compliance approach that "makes sense" with respect to accomplishing the code's objectives. This kind of clause is often referred to as a "deemed to comply" approach. Through legislative and/or legal procedures, jurisdictions agree and accept to adopt this provision when adopting the IECC codes.

Specifically, Section 101 allows a building official to approve compliance tools that are deemed to meet "the intent of [the] code." The intent of the IECC commercial code is explicitly defined here: "C101.3 Intent. This code shall regulate the design and construction of buildings for the effective use and conservation of energy over the useful life of each building. This code is intended to provide flexibility to permit the use of innovative approaches and techniques to achieve this objective." The various compliance paths of the code are alternative "recipes" designed to achieve that intent, but Section 101 implies that other recipes are permitted if they accomplish the same overall objective.

Excepting COMcheck support for 90.1-2013 and 2015 IECC, the envelope trade-off methodology used by COMcheck is the "Normative Appendix C: Methodology for Building Envelope Trade-Off Option" found in the referenced ASHRAE 90.1 code. The ASHRAE Appendix C trade-off method does include a limited number of “embedded” references to ASHRAE 90.1 based “prescriptive” requirements that must be enforced. Obviously, these prescriptive requirements are specific to ASHRAE 90.1 section numbers and thus relevant to the IECC codes. For this reason, and that it is only the “trade-off method” that is being “borrowed” for use with the IECC requirements, these Appendix C embedded requirements are not considered when this method is applied to the IECC codes in COMcheck. When applied to the IECC energy codes, all IECC code requirements are applied and enforced within that trade-off methodology when a clear and obvious reference can be established. More specifically, this applies to the table references to individual envelope assemblies U-factor requirements. 

The “embedded” Appendix C requirements discussed in the previous paragraph pertain to maximum window (WWR) and skylight (SRR) areas and minimum skylight area. When determining compliance to one of the ASHRAE 90.1 energy codes, COMcheck will enforce the WWR and SRR per guidance from Appendix C. However, the minimum skylight area requirement as described in Appendix C is worded and interpreted in such a way as to be deemed not applicable therefore is not enforced in COMcheck for either 90.1 or IECC energy codes. When determining compliance to one of the IECC codes the minimum skylight requirement will be enforced through the envelope report inspection checklist and the WWR and SRR requirements will be enforced prescriptively. That is, when complying with IECC and the WWR and SRR values are found to be noncompliant the user will be directed to use the equivalent ASHRAE 90.1 energy code.

To summarize, when the Appendix C trade-off method is applied to IECC codes, the IECC requirements will be applied to the method when and where that method provides guidelines for doing so. When guidelines are not provided by the trade-off method language or refers to nonexistent section numbers, the IECC requirement will be enforced prescriptively. As noted above, ASHRAE 90.1-2013 and 2015 IECC energy codes are exceptions to all of this discussion. ASHRAE 90.1-2013 Appendix C supports a trade-off method that is based on building performance simulations using EnergyPlus completely differently than earlier versions of the 90.1 code family. Only 90.1-2013 uses this method currently although 2015 IECC does allow a project to apply 90.1-2013 in its entirety as an alternative. 2015 IECC Component Performance Alternative is used for 2015 IECC and state codes based upon this code. This new compliance method replaces the use of ASHRAE 90.1 Appendix C and is based generally speaking on a “Total UA” approach.

When entering your fenestration in COMcheck the pop up window has three options to enter your fenestration.  Choose the second option called Product Performance in accordance with NFRC.  If you do not have a pending product number, enter NA and enter your proposed values.  Note, test results should be submitted with the COMcheck report to verify the values entered.

 If the product has not been tested or accredited, choose option 3.  The code defaults come directly from the tables within the code.  Code defaults use worst case scenario for fenestration values and most defaults do not meet the prescriptive requirements dependent upon climate zone. Best recommendation is to choose fenestration products that are tested and NFRC labeled that have better U-factor and SHGC ratings.  

COMcheck computes an envelope index that is a reflection of the difference between a 'design' building energy performance factor (EPF) and a 'code' or budget building EPF.  The total building load (made up of cooling, heating, lighting, and miscellaneous plug load) is determined by the location you are in, the specific assembly and building types you specify, and internal gains from lighting and miscellaneous plug loads, and of course the thermal properties and orientation of the envelope assemblies. The methodology used to determine EPF is provided in ASHRAE 90.1 Normative Appendix C: Methodology for Building Envelope Trade-off Option.

A commercial building is defined as all other buildings that are not considered a residential building.

COMcheck determines compliance for additions in the same manner as new construction. When entering an addition, only the new portions of the building need to be shown in the software. COMcheck will perform trade-offs between envelope assemblies when determining compliance.

COMcheck determines compliance for alterations on a component-by-component basis. Each component is checked to verify it meets or exceeds the minimum prescriptive requirements of the selected code. No trade-offs are available for alterations and no compliance percentage will be generated–the software shows a pass/fail for compliance.

Exemptions and allowances for lighting are an option that must be activated in COMcheck. To activate the exemptions and allowances, take the following steps:

• Select either the Interior Lighting or Exterior Lighting Tab
• Go to the Options menu and select Interior Lighting Exemptions and Allowances for Interior Lighting or Exterior Lighting Exemptions for Exterior Lighting.

Note that activation of the exemptions and allowances will add an extra column to the applicable worksheet–it may be necessary to enlarge the window in order to see the new column.

If multiple users are putting information into COMcheck, each may fill out the appropriate section independently. However, all sections of the building must show compliance to the same code or standard (e.g., cannot show envelope compliance to IECC and lighting compliance to ASHRAE Standard 90.1). COMcheck does not require that all sections be completed to perform compliance checks.

The IECC addresses mixed occupancies by stating that commercial occupancies must comply with the commercial portion of the code and residential occupancies must comply with the residential portion of the code.  

ASHRAE Standard 90.1 addresses high-rise residential and all other commercial buildings.  Residential spaces are those used primarily for living and sleeping and include dwelling units, hotel/motel guest rooms, dormitories, nursing homes, patient rooms in hospitals, lodging houses, fraternity/sorority houses, hostels, prisons, and fire stations.

REScheck determines compliance for additions in the same manner as new construction. When entering an addition, only the new portions of the building need to be shown in the software. REScheck will perform trade-offs between envelope assemblies when determining compliance.

REScheck determines compliance for alterations in a similar manner as additions and new construction, however, each component that is being altered will need to be identified as either meeting an “exemption” from the drop down list of exemption choices or choose “no exemptions” apply and the proposed insulation and/or fenestration values must be entered.  REScheck will perform trade-offs between envelope assemblies that have been identified as “no exemptions” apply to the assembly when determining overall compliance for alterations for a specific project.

Code adoption takes place at the state, and in some cases municipal, level. To determine the code in a particular state, visit the Status of State Energy Code Adoption page.

The 2009 IECC requires that a minimum of 50% of the lamps in permanently installed lighting fixtures be high-efficacy lamps (2009 IECC, Section 404.1). The 2012 IECC has increased the minimum percentage from 50% to 75%, along with an exception for low-voltage lighting (2012 IECC, Section R404.1).

REScheck currently does not have a lighting input function; therefore, the lighting requirement should be confirmed under the Requirements Tab in the program.

Walls that do not fit into any of the preset categories in REScheck (preset categories come directly from the applicable code currently selected in the Code menu) may be entered under the "Other" wall type. When "Other" is chosen as the wall type, the software requires an overall U-factor for the assembly. The assembly U-factor is calculated from the spacing of any framing and its R-value, the R-value of installed insulation, and the R-value of the balance of assembly (items such as OSB sheathing, drywall, interior and exterior air films, etc.). Details of how to perform a U-factor calculation can be found in any basic heat transfer text book or handbook.

Fenestration is considered anything that transmits light, however, COMcheck cannot calculate fenestration without having a wall associated with it. In this case the wall is entirely fenestration therefore, the square footage would be the same for both the wall and window area and the software will calculate the wall area as net zero since the fenestration is the entire wall.

For the spandrel glass or translucent wall systems the way to enter that into COMcheck would be to first define a wall by choosing wall as "other" from the drop down list of wall assembly types, enter the square footage of the wall system (e.g. 100 sq. ft), enter the U-factor for the wall system (e.g. 0.23) and also you will need to enter the heat capacity of the wall. For information on heat capacity and how to calculate it, in COMcheck, go to the help menu, help topics and wall software inputs.

After defining the wall, define the window area by choosing window as "other" from the drop down list of window assembly types, enter the square footage of the wall system (e.g. 100 sq. ft.) and choose option two under Fenestration details "Product performance tested in accordance with NFRC", if you do not have a product ID, enter "NA", then enter your U-factor and SHGC values from the product manufacture specifications.

After selecting a basement wall type, a basement wall illustration will appear with input boxes for the basement wall height, depth below grade, and depth of insulation. The illustration helps identify the dimensions being requested. You may enter basement wall dimensions directly into this illustration and select the OK button to have them transferred to the corresponding row in the table on the Envelope screen. If you prefer to enter the dimensions directly into the table on the Envelope screen, you can select Cancel to remove the illustration without entering dimensions. To view the basement wall illustration and inputs at a later time, click the right-mouse button anywhere on the basement row and select Edit Basement Inputs from the popup menu. 

Both the 2009 and 2012 IECC require duct tightness to be verified. Verification can take place via either a post-construction test or a rough-in test.

For the post-construction test, leakage measurement must be made across the entire system, including the manufacturer’s air handler enclosure, with all register boots taped or sealed at a test pressure of 0.1 inches w.g. (25 Pa). The 2009 IECC limits the leakage to outdoors to less than or equal to 8 cfm per 100 ft² of conditioned floor area or total leakage less than or equal to 12 cfm per 100 ft² of conditioned floor area. The 2012 IECC only contains a requirement for total leakage of less than or equal to 4 cfm per 100 ft² of conditioned floor area.

For the rough-in test, leakage measurement is made across the system, with the manufacturer’s air handler enclosure if it is installed. The test is conducted at 0.1 inches w.g. (25 Pa) with all registers taped or sealed. The 2009 IECC limits leakage to less than or equal to 6 cfm per 100 ft² of conditioned floor area when the air handler is installed and 4 cfm when it is not installed. The 2012 IECC limits the leakage to 4 cfm per 100 ft² of conditioned floor area when the air handler is installed and 3 cfm when it is not installed.

• Copies of the International Energy Conservation Code (IECC) can be purchased from the International Code Council website.
• Copies of ASHRAE standards can be purchased from the ASHRAE website.
• For codes specific to a state or municipality, contact the authority having jurisdiction.