The American Iron and Steel Institute (AISI) has published a new cold-formed steel framing research report, “AISI RP20-2: Development of a U-Factor Calculation Procedure for Cold-Formed Steel C-Shaped Clear Wall Assemblies.” The report is available for free download.
The research was undertaken to support a new energy standard being developed by AISI’s Committee on Framing Standards. In addition to its work in research and development, AISI is an American National Standards Institute (ANSI)-accredited developer of American National Standards.
The new standard, AISI S-250, North American Standard for Thermal Performance of Building Envelopes with Cold-Formed Steel, is being prepared for public review as part of the consensus process.
AISI RP20-2 delivers a simplified calculation procedure that can be easily used by architects, engineers and building owners to evaluate building envelope designs that demonstrate compliance with energy codes such as ASHRAE Standard 90.1, the International Energy Conservation Code, and state/local adopted energy codes. The results address five key constructions:
- Nominal stud dimensions (2×4, 2×6, 2×8, 2×10 and 2×12)
- Stud spacings (6 in. oc, 12 in. oc, 16 in. oc and 24 in. oc)
- Designation thicknesses (33, 43, 54 and 68 mils)
- Cavity insulation (R-0 to R-38)
- Insulated sheathings (R-0 to R-20)
Previously, the procedures were cumbersome and included:
- A series path procedure to correct for parallel path thermal bridging which had limited lookup.
- The modified zone method which was restricted in scope.
- Sophisticated two- and three-dimensional computer simulation programs which required technical expertise to use.
“The findings from AISI RP20-2 are significant because they will help equip users with the tools to make more accurate evaluations of cold-formed steel framing for clear wall assemblies that meet energy code analysis and compliance,” said Jay Larson, P.E., F.ASCE, managing director of AISI’s Construction Technical Program. “We are developing a roadmap for additional research needed to make steel more competitive in this area.”