Building Science Corporation
April 11, 2013
Very Cold Cold


Polyisocyanurate insulation is a common commercial and residential roof and wall insulation.  It has one of the highest R-values per inch of thickness among common insulations. However, labeled R-value differs from in-service R-value for many insulations.  Building Science Corporation (BSC), and others have been examining this difference. BSC has found significant thermal performance differences between different manufacturers of insulation products and significant differences based on in-service temperature. The following discussion relates to BSC’s work to date with polyisocyanurate roof insulation.