Isover Spacesaver is a glass mineral wool roll which is pre-perforated to fit between common joist spacing at ceiling level. It is supplied in longer-length rolls to increase efficiency by reducing the number of rolls required to be delivered, stored and opened during installation. Ease of Install - The benefit to the installer with our Spacesaver products is that they are pre-perforated rolls to fit common joist spacing, significantly aiding installation. In contrast, other insulation materials—such as insulation boards—typically require manual cutting to fit joist spacing, increasing installation time and effort. Coverage:8.15m2