![]() ![]() 2010ĭuring the investigation on existing buildings, representatives from various companies and organizations in the metal building industry objected to any revisions of these U-Factors, claiming that the U-Factors were correct but that the products were not being installed properly. For multilayer installations, the last rated R-value of insulation is for unfaced insulation draped over purlins and then compressed when the metal roof panels are attached. Uncompressed, unfaced insulation rests on top of the membrane between the purlins. Liner System (Ls): “ A continuous membrane is installed below the purlins and uninterrupted by framing members. Although, liner systems have been on the market for more than 25 years, ASHRAE and now the IECC have finally recognized and incorporated these systems in the energy code. In addition to the revised values, the news release also included a 'new' metal building roof insulation assembly called a Liner System. ![]() Published performance values were overstated up to 42%. ![]() The revised ASHRAE 90.1 Appendix A resulted from a 90.1 Envelope Subcommittee 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. These representations are found in 90.1 Appendix A. The news release includes revised thermal performance representations that reflect typical installation practices that were proposed for inclusion in the 90.1-2010 Standard. On January 12, 2010, the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) published a news release acknowledging that the thermal performance representations in the 90.1-1999 through 90.1-2010 Standards for typical over-the-purlin, over-the-girt and sag-and-bag methods of insulating pre-engineered metal building roofs and walls do not reflect the performance of these assemblies as they are typically installed. ASHRAE Acknowledges Metal Building U-Factors in 90.1 Standard do not reflect typical installations. ![]()
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