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The IECC - 2009, 2012 and 2015: A Cross-Code Comparison

Posted by Laureen Blissard

Jun 24, 2015 10:29:00 AM

The Green Builder Coalition analyzes the residential energy efficiency sections of the 2015 IECC

THE INTERNATIONAL CODE COUNCIL (ICC) continues to develop the International Energy Conservation Code (IECC) on a three-year cycle which has culminated in the latest version, the 2015 IECC. However, not every state is inclined to follow the same cycle when it comes to adoption of the IECC. Reasons for non-adoption vary, from perceived cost implications to lack of enforcement resources to complexity of changes. We will take on this last item, complexity of changes, in a multipart study. This first part, presented here, includes a general analysis of Sections R401 through R402 of the 2009, 2012, and 2015 IECC.


The International Code Council (ICC) was founded in 1994 as a nonprofit member-focused association with the express purpose of developing a single set of national model construction codes. Founding members came from the Building Officials and Code Administrators International, Inc. (BOCA), the International Conference of Building Officials (IBCO), and the Southern Building Code Congress International, Inc. (SBCCI). The efforts of the three organizations culminated in the International Codes, or I-Codes starting in 2000 with a three-year cycle for revisions and updates.

2015 IECC


This is a very general overview of the differences between the IECC 2009, 2012 and 2015 Residential Energy Efficiency Sections R401 through R402. Section R401 focuses on the scope of the regulations (residential buildings), compliance paths and requirements of the displayed certificate. Section R402 focuses on fenestration and insulation requirements. For further clarification, please consult the following links:

IECC 2015 Fact Sheet: http://bit.ly/1K6W6Ld


Section R401.2 (2009 and 2012) are essentially the same with regard to compliance paths. 2015 adds the energy rating index (ERI) as a third option for compliance that will be found under a brand-new section for 2015: Section R406. Section R401.2.1 is an entirely new section introduced for 2015 as a prescriptive path of compliance for homes built in tropical zones.

R402.1: General Criteria Section

R402.1 (2009 and 2012) have essentially the same text pertaining to the sections for thermal envelope compliance; however, 2015 allows for the separation of low-energy buildings.

Sections R402.1.1 through R402.1.5 have been renumbered; there is also a new section and some new text.

Section R402.1.1 (2009 and 2012) have essentially the same reference to complying with the thermal envelope requirements of Table 402.1 .1. This section is replaced in 2015 with new text addressing vapor retarders via Section R702.7 of the International Residential Code or Section 1405.3 of the International Building Code, if applicable. The original text for Section R402.1.1 found in 2009 and 2012 has been shifted to Section R402.1.2 in the 2015.

Table 402.1.1 “Insulation and Fenestration Requirements by Component” appears in all versions, except that in 2015 it is now labeled Table R402.1.2. The R-value and U-factor requirements have changed between versions, but are not being analyzed as a part of this study.

Section 402.2: Specific Insulation Requirements

Section R402.2 is just a heading in 2009, but in 2012 and 2015 this section addresses specific sections for insulation requirements.

R402.2.1: 2009, 2012 and 2015 all include text that addresses exceptions for uncompressed insulation that allows for a reduction in R-value. However, 2015 incorporates a caveat based on a percentage of ceiling area requiring insulation and still allows for a reduction from R-49 insulation level requirements to R-38 if the full height of uncompressed insulation extends over the wall top plate at the eaves. This reduction still does not apply to the U-factor alternative approach.

Section R402.2.3 (2009) has the same text as Section R402.2.4 in 2012 and 2015 and addresses access hatches and doors from conditioned spaces to unconditioned spaces. For 2015, there is an exception for vertical doors to meet fenestration requirements.

Section R402.2.3 2012 and 2015 addresses air permeable insulation. This concept is completely missing from the 2009.

Section R402.2.4 2009 addresses mass walls much in the same way Section R402.2.5 does for 2012 and 2015. 2015 does add the flexibility of any other wall types that have a specific heating capacity.

R402.2.5 (2009) and Section R402.2.6 (2012 and 2015) all have similar text regarding steel-framed walls. The label for Table R402.1.3 (U-factor requirements) in 2012 changes to Table R402.1.4 in 2015.

Section R402.2.6 (2009), Section R402.2.7 (2012) and Section R402.2.8 (2015) are essentially the same text; they pertain to floor insulation being installed to maintain permanent contact with the underside of subfloor decking. However, the 2015 provides an exception depending on assembly.

Section R402.2.7 (2009) addresses basement wall insulation requirements and is connected to Section R402.2.8 (2012) and Section R402.2.9 (2015).

For 2015, Section R402.2.7 is new text that addresses continuous insulation and exterior walls.

Section R402.2.8 (2009) addresses slab-on-grade floor insulation requirements and is connected to Section R402.2.9 (2012) and Section R402.2.10 (2015).

Section R402.2.9 (2009) addresses crawlspace insulation and sealing. It shifts to Section R402.2.10 (2012) and then to Section R402.2.11 (2015).

Section R402.2.10 (2009) provides an exception for a solution of the horizontal portion of the foundation that supports masonry veneer. This corresponds to Section R402.2 .11 (2012) and Section R402.2 .12 (2015).

Section R402.2.11 (2009) pertains to ceiling and wall insulation for thermally-isolated sunrooms. Section R402.2.12 (2012) and Section R402.2.13 (2015) have exceptions that were introduced in the 2012 version.

Section R402.3: Fenestration

Section R402.3 is just a heading in 2009, but in 2012 and 2015 new text has been added to list specific fenestration requirements and sections of the code.

The following sections are the same across the board unless noted otherwise:

Section R402.3.1 (U-factor weighted average allowance)

Section R402.3.2 (Glazed fenestration SHGC): 2009 and 2012 have the same text; for 2015, dynamic glazing is now included as part of the section.

Section R402.3.3 (Glazed fenestration exemption)

Section R402.3.4 (Opaque door exemption)

Section R402.3.5 (Thermally isolated sunroom U-factor): All three versions address sunrooms, but with subtle differences across the board.

Section R402.3.6 (Replacement fenestration)

Section R402.4: Air Leakage

This section is just a heading in 2009, but in 2012 and 2015 new text has been added to list specific code sections that address air leakage reduction requirements. 2009 does not have sections labeled 402.4.1.1 or 402.4.1.2.

Section number 402.4.1.1 (2012 and 2015) pertains to visual inspection of air sealing, air barriers and insulation contact in a table corresponds to Section R402.4.2.2 (2009).

Section 402.4.1.2 (2012 and 2015) pertains to envelope testing. There is a subtle difference between 2012 and 2015 in that 2015 specifically states that testing should be conducted in accordance with ASTM E.

The major differences between Section 402.4.2.1 (2009) and Section 402.4.1.2 (2012 and 2015) are the decreases in ACH50 from a base of 7ACH50 for all climate zones in 2009 to 5ACH50 for zones 1 and 2 and 3ACH50 for zones 3–8 in 2012. 2015 is the same as 2012.

Section R402.4.2 (2009) is just a heading that outlines compliance to either Section 402.4.2.1 (2009) or 402.4.2.2 (2009), which then are shifted to new sections in 2012.

Section R402.4.3 (2009) addresses wood-burning fireplaces, as does Section 402.4.2 (2012 and 2015); however, gasketed doors are required in 2009 where they are not mentioned in 2012. Fireplace doors reappear in 2015 as an option.

Section R402.4.4 (2009), which addresses fenestration air leakage, corresponds to Section R402.4.3 (2012 and 2015).

Section R402.4.5 (2009), which addresses air leakage at recessed lighting installed in the building thermal envelope, corresponds to Section R402.4.4 (2012) and Section R402.4.5 (2015), although some text (“air movement from the conditioned space to the ceiling cavity”) was removed from 2009 to 2012.

A Controversial New Section?

Section R402.4.4 in the 2015 is an old 2012 section number that is being used as an entirely new mandatory compliance strategy. The new Section R402.4.4 in the 2015 addresses open combustion fuel-burning appliances. Some have called this an atmospheric room or a combustion closet; ether way, it appears as if this section was specifically written to address atmospherically-vented combustion appliances. The exception to this rule includes direct-vent appliances with both their intake and exhaust installed directly to the outside, as well as fireplaces and stoves that comply with Section R402.4.2 and Section R1006 of the International Residential Code.

There are some options to avoid having to build this “closet” besides using direct-vent appliances. One option is to not have any combustion appliances at all. This essentially means building a home that does not directly use fossil fuels. The other option is to locate your combustion appliances outside the home’s thermal envelope.

The Market Effect and Relevance

Under the American Recovery and Reinvestment Act of 2009, the U.S. Department of Energy agreed to provide funds to states that adopted the 2009 International Energy Conservation Code (IECC) or an equivalent for residential construction, contingent upon at least 90 percent compliance by 2017. So far, we continue to see a mixed bag of IECC adoption across the country. Vermont and Maryland have already adopted the 2015. Ten states have adopted the 2012 and 24 states are still using the 2009. Finally, there are 14 states that are either using an IECC older than 2009 or that do not have a statewide energy code.

We will continue to provide our analysis of the IECC 2009, 2012, and 2015 in future installments of CodeWatch.



International Code Council http://www.iccsafe.org/

2015 IECC Fact Sheet http://bit.ly/1FBlPKE

2009 IECC Requirements of Most Immediate Concern to Manufacturers http://bit.ly/1LDeImn

Status of State Energy Code Adoption http://1.usa.gov/1SktOCx

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