Increased thermal performance of metal building roof and wall assemblies can be achieved by using double layers of fiberglass batt insulation. Determination of the installed double layer assembly U-factor is more complex than that of a single layer assembly when each layer has different material properties. Experimental data on the compression of typical fiberglass batt insulation samples are presented along with the derivation of the double layer U-factor equations. Finally, an example is presented to illustrate the application of the Ufactor equations. These equations comprise the basis for the revised double layer U-factors for ASHRAE Standard 90.1- 2010.

Units: Dual