For the TAG/TAB/Cirrus- The R-value of the cut insulation we place between the rafters is rated as a 3.6. We use a foiled double bubble, which lays on top. Unlike traditional insulation this product is not rated by an R-value. Bubble insulation is rated by it's reflectivity and emissivity. R-values are based on thermal resistance (how long heat takes to pass through the product), the thicker it is the higher the R-value. Bubble insulation is very thin, 1/8", but has a high reflectivity, 96%, and a low emissivity, 4%. Only 4% of radiant heat passes through the insulation, we are not trying to slow the way heat passes through the insulation but trying to slow the way heat passes through the insulation but trying to eliminate heat from passing through it. The R-value of the Azdel and block insulation combination is rated as a 4.5.