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2021 International Energy Conservation Code

Insulated Siding as Home Insulation (ISHI): A Guide for Users and Energy Raters

Insulated siding is vinyl cladding with a substantial thickness of rigid foam plastic insulation that is permanently attached. Various national building energy performance programs recognize insulated siding as an energy-efficient exterior cladding.

Insulated Siding as Home Insulation

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This Guide instructs specifiers and energy specialists on how insulated siding can be applied to meet the energy efficiency requirements, including but not limited to:

International Energy Conservation Code (IECC)

The major regulatory tool for energy-efficiency residential construction is the IECC. Insulated siding is listed in both the 2012 and 2015 energy code among materials that can be used outside of the building to provide the required total wall R-value in the coldest climate zones. Generally speaking, builders and remodeling contractors are able to use insulated siding to meet the R-value/U-factor requirements. This Guide will help you identify sections applicable within the code.

Insulated siding also meets the requirements of the 2015 International Residential Code through third-party certification based on ASTM D7793 Standard Specification for Insulated Vinyl Siding. ASTM D7793 includes the requirements for both the vinyl siding component and the foam plastic component, as well as performance requirements for the product as a whole.

ENERGY STAR® Qualified Homes

In order to earn the ENERGY STAR label, a new home must meet EPA’s guidelines for energy efficiency. Insulated siding has been added to the checklist of building products or methodologies that can help qualify homes under ENERGY STAR Qualified Homes version 3 because of its ability to reduce thermal bridging. This Guide will help builders who want to earn the ENERGY STAR label for homes use insulated siding to comply with thermal bridging requirements.

R-value Testing

FTC regulations govern home insulation marketing claims and the means by which the R-value of home insulation is determined. The claimed or rated R-value must be based on actual testing conducted in accordance with one of the test methods specified in the regulations. This Guide discusses the Standard Test Method for Thermal Performance of Building Materials and Envelope Assemblies by Means of a Hot Box Apparatus (ASTM C1363). ASTM D7793 specifies sample configurations and installation details used in the ASTM C1363 tests to produce accurate and consistent R-value for insulated siding. Chapter 6 of this Guide provides detailed information on how tested R-values can be used to calculate a wall assembly’s U-factor.