The Standards Council of the American Iron and Steel Institute has formed a new group that will be primarily responsible for the ongoing development of AISI S250, North American Standard for Thermal Transmittance of Building Envelopes with Cold-Formed Steel Framing. The new Committee on Energy Standards falls under the administrative oversight of the AISI Standards Council, which also oversees the Committee on Specifications and the Committee on Framing Standards.

The new group is recognized as a consensus body by the American National Standards Institute. It is comprised of AISI staff and experts from the steel construction industry and will develop and maintain methods for determining heat transfer through building envelopes for assemblies containing cold‐formed steel and other materials; develop prescriptive and performance solutions for code compliance, construction details and installation quality standards; and address other similar issues that impact cold‐formed steel in the energy codes and standards arena. The first meeting of the committee was held virtually on March 7.

“Thermal performance is increasingly influencing material selection in building design and construction,” said AISI Vice President of Construction Robert J. Wills, P.E. “The work of this committee will ensure that cold-formed steel is a viable option for those targeting advanced or net-zero buildings by 2030.”

AISI S250-21 is a single source for calculating the thermal transmittance (U-factors) of walls and ceiling/roof envelope assemblies that contain cold-formed steel framing. The advantages of AISI S250-21 over all previous calculation methods include the ability to analyze wall assemblies that have framing members spaced from 6 inches to 24 inches on center, framing member steel thicknesses from 33 mils (0.0329 inches) to 68 mils (0.0677 inches) and wall assemblies with insulation in the cavity, partially in the cavity or no cavity insulation.

The standard is intended for adoption and use in the United States, Canada and Mexico and is available for free download at www.aisistandards.org.

A spreadsheet is available at no cost from AISI that performs the mathematical calculations based on AISI S250-21. It substantially reduces the time needed to calculate various envelope assemblies based on the standard. The spreadsheet is accessible from a link in the Preface of AISI S250-21.