by Rebecca Walker — January 15, 2010—Changes to assembly descriptions and U-Factors regarding metal building assemblies are being considered for the 2010 version of Standard 90.1, expected to be published in the fall.
ANSI/ASHRAE/IESNA Standard 90.1-2007, Energy Standard for Buildings Except Low-Rise Residential Buildings, provides minimum requirements for the energy-efficient design of buildings except low-rise residential buildings.
The changes regarding metal buildings are among many being proposed for the 2010 standard. Some 43 addenda already have been approved, impacting the standard in a variety of ways from energy recovery to controls to daylighting.
The proposed changes are in Standard 90.1 Appendix A “Rated R-Value of Insulation and Assembly U-Factor, C-Factor and F-Factor Determinations.” The revised Appendix A resulted from a Metal Building Task Group investigation of existing metal building stock that revealed that typical installation practices of the single and double-layer assemblies described in Appendix A compress insulation and thereby negatively affects the thermal performance of the assembly. The previously published R-Values/U-Factors did not reflect the thermal performance from such installation methods, which typically yield lower R-Values and higher U-Factors. The proposed Appendix A adds revised modeling equations to estimate the performance of compressed insulation in metal building assemblies based on these less energy-efficient installation practices, as well as incorporates the modified R-Values/U-Factors for metal building assemblies that reflect these new modeling equations.
For more information, see the ASHRAE Web site.
