SOPRA-CELLULOSE VENT is a pre-folded rigid cardboard piece perforated along folding lines used to prevent the overflow of SOPRA-CELLULOSE cellulosic fibre on the roof overhang during and after installation. It also maximizes the R-value at the edges of the building and allows good ventilation in the attic. SOPRA-CELLULOSE VENT must be installed with SOPRA-CELLULOSE insulation in ventilated roofs. SOPRA-CELLULOSE VENT XL is longer than the standard version to meet the new attic insulation requirements of provincial and national regulations (up to R-61 or RSI-10.8).