Is there code language that allows the use of COMcheck?

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.