DIY Foam Roof Insulation

Attach air baffles, stapling each baffle to the underside of the decking prior to installing the foam insulation. Air baffles are attached to roof decking to protect against water condensation and to help moderate temperature.

Purchase good-quality foam insulation. It should be labeled with the measurement of depth that should be used as a guide for the installation. Properly following this measurement and other product instructions should ensure the foam insulation is used safely and effectively on the roof.

Look for gaps between the rafters where air can circulate outside the baffles. Fill these gaps with insulation batts and be sure they are appropriately-sized. It will pay off to make sure these gaps are properly insulated, because they are a common cause of insulation defects that result in costly and time-consuming fixes and increased heating bills.

Position foam insulation, flattening each panel of foam in the same manner it would if installed between wall studs. Be sure that insulation batts do not overlap or compress any air baffles. With caution, use a utility knife to trim off any insulation that does not fit; however, make sure not to cut off too much and create additional air gaps.

Insulate headers. Roof framing commonly includes headers designed to bridge window and door openings. The plywood core can be replaced with a layer of half-inch thick foam insulation; however, make sure that local codes allow this.