Continuous exterior insulation is a newer, popular way to support optimal thermal and moisture protection for new builds, additions, and some renovation projects. Model ReModel 2022’s builder Symbi Homes will follow the same high performance building method for their net zero in-law suite addition.
Symbi installed a continuous layer of R-5 rigid polystyrene foam on top of a Tyvek water resistant barrier across all exterior walls. When added to their R-21 Greenfiber spray-applied cellulose on the interior, the unit now boasts a super-efficient R-26 wall assembly.
So what makes exterior insulation so special?
Because rigid exterior insulation is outside the framing members, it can wrap continuously around a building (with the exception of window and door openings) unimpeded by wall studs. Traditional lumber is notoriously low in R-value (about R-1 per inch), and therefore diminishes the thermal protection in a typical wall assembly.
Second, exterior insulation adds another layer of protection around the entire shell of the home. In warm climates, a foil-faced exterior foam can prevent solar heat gain from entering the building. In cold climates, a rigid polystyrene foam can help insulate the exterior sheathing of the house, preventing condensation on the inside.