When the Shoup household’s leaking and un-insulated roof demanded a fix, the family chose spraying polyurethane foam (SPF) as a relatively green and cost-effective fix. They chose SPF for several reasons, the first of which being that SPF can provide insulation for a roof from the outside without needing any work done inside the house. SPF also has an R-value of 6.5 per inch and works particularly well because their flat roof (necessary for SPF) had parapets to define the foam’s edge. Additionally, four inches of spray-foam counts as a Class II water retarder, which solves the issue of the leaking roof handily.
Read the full article here: Spraying Polyurethane Foam Over an Existing Roof