Applications for thick insulation foam sheets include use as exterior insulation, either installed before backfilling a structure's foundation or over a structure's exterior sheathing, as well as an interior installation in finished basements. Typically, building codes require that interior insulation foam sheets are protected with an approved fire-resistant material.
When installing thick insulation foam sheets against metal framing studs, use cap-headed screws of at least 1 inch in length. Cap-headed screws are less likely to accidentally drive through the panel due to the circular disc located near the screw's head. When installing thick insulation foam sheets against wooden studs, use either cap-headed screws or cap-headed nails. Make sure to space the fasteners apart at a distance of about 12 inches. When installing thick insulation foam sheets directly on concrete foundations, apply a suitable construction adhesive to the back of the panel and tape the seams between panels for the best insulation.
The more dense a foam insulation sheet is, the better it is at stopping the infiltration of air. Sunlight and moisture tend to break down the foam material that these panels are made out of, so be sure to install them in ways that protect them from exposure.
There are different types of foam insulation sheets, such as molded polystyrene board and extruded polystyrene board. Extruded polystyrene is denser and offers increased insulation then molded polystyrene.