Notes that many existing dwellings are inadequately insulated and in need of caulking and weatherstripping. Gives criteria for the selection of retrofit materials which are eligible for the Department of Energy Weatherization Assistance Program. Materials discussed are insulation, storm windows and doors, caulks and sealants, weatherstripping, vapour barriers, clock thermostats and replacement windows. Discusses the literature on retrofitting. Describes the different caulks and sealants available. Outlines precautions to be taken when applying different retrofit materials.