Most roofing professionals understand a building's roof assembly serves an important role in controlling a building's
overall energy efficiency and building owners' heating and cooling costs. However, some may not realize that codes
mandate minimum thermal insulation requirements for the energy efficiency of most buildings.
Energy conservation codes usually are adopted by individual states and are applicable to all buildings within that
state. Most states have adopted one of several editions of the International Energy Code (IECC), published by the
International Code Council (ICC), to serve as the technical basis of their energy codes. In some instances, individual
states modify the IECC to address specific regional or local issues.
To assist roofing professionals, NRCA compiled a database of states' current energy code adoption. This information was
obtained either from individual states' Web sites or the Department of Energy's "Energy Code's Program's" website,
https://www.energycodes.gov/adoption/states. Users are encouraged to contact
the government agency having jurisdiction to verify the specific energy code(s) applicable to their projects.
IECC provides two methods of determining commercial buildings' minimum insulation requirements: the use of specific
tables within the Code or compliance with American Society for Heating, Refrigerating and Air-Conditioning Engineers
Inc. (ASHRAE) Standard 90.1 (ASHRAE 90.1), “Energy Standard for Buildings Except Low-Rise Residential
Buildings,” building envelope provisions.
If you want to determine minimum R-value requirements per ASHRAE 90.1, you should consider using EnergyWise Roof
NRCA, in partnership with The Roofing Industry Alliance for Progress developed EnergyWise Roof Calculator Online,
developed this free, Web-based application based in part on the Prescriptive Building Envelope Option contained in
ASHRAE Standard 90.1, versions 1999(2001), 2004 and 2007.
EnergyWise Roof Calculator Online also provides a graphical method of constructing roof assemblies to evaluate thermal
performance and estimated energy costs under normal operating conditions. This application is intended to be a
simplified guide. For complex energy evaluation calculations, consult the ASHRAE Fundamentals Handbook or an
experienced mechanical engineer.
If you want to become more familiar with roofing-related energy code requirements, you are encouraged to read
"Conserving energy" by Mark Graham, NRCA's Associate Executive Director of Technical Services. This article provides an
overview of energy codes' minimum requirements and how these requirements apply to existing buildings when
In addition, NRCA offers Guidelines for Complying With Energy Code Requirements for Roof Assemblies: International
Energy Conservation Code, 2009 and 2012 Editions for sale in the NRCA Bookstore. This publication provides a
step-by-step guide for complying with the requirements of the International Energy Conservation Code's (IECC's) 2009
and 2012 editions and ASHRAE 90.1, "Energy Standard for Buildings Except Low-Rise Residential Buildings," 2007 and 2010
editions, which are referenced in IECC's 2009 and 2012 editions, respectively.