Guide describing how to add spray foam insulation to the underside of the existing roof deck as part of the conversion of a vented attic to an unvented, insulated attic.
Vapor retarders can be a crucial part of the building envelope and can help manage moisture issues to keep the home dry. However, before installing a vapor retarder, installers must be aware that in some instances vapor retarders can increase the likelihood of condensation issues.
Vapor retarder plastic should not be installed over fibrous insulation on basement or crawlspace walls unless rigid foam or spray foam is installed directly against the concrete, behind the blanket insulation.