Interior walls should be insulated not only for optimal energy efficiency but for soundproofing as well.
All exterior walls need sufficient insulation, as they are one of the biggest sources of heat loss in a home.
Insulation should be installed in both ventilated and unventilated crawl spaces. Insulation here can help prevent moisture damage.
Ductwork in unconditioned spaces should be insulated (as well as sealed). Radiant barrier insulation is particularly effective in attics with air ducts.
A properly insulated foundation helps improve the comfort of below-grade rooms and also helps prevent moisture problems and insect infestation. Ideal insulation materials and placement differ climate to climate.
Insulation is needed for floors throughout any home. This includes floors built directly on the ground as well as flooring above unconditioned spaces, like unheated garages.
In unconditioned attics, insulation should be installed in the access door as well as between and over floor joists. In finished attics, insulation should be installed between knee wall studs.
