Rigid Foam Under Roof Deck

After the roof deck is prepared the rigid foam boards need to be cut to size to fit snugly together on your roof.

Rigid foam under roof deck.

Install nailbase for cladding. High efficiency attic insulation helps provide added thermal protection lessens wasted energy and increases enhanced comfort and quiet. Nailbase must be vented in high snow load areas. Rigid foam is produced in various size panels 4 ft x 8 ft 4ft x 4ft etc.

At r 4 it also has the lowest r value per inch. The snugness of the foam itself should be sufficient to hold the strips. Attach to deck board. Eps is the most vapor permeable of the three types.

Rigid insulation layers exterior to existing roof sheathing must provide sufficient thermal insulation r value to control condensation risk see climate specific guidance. Install roofing underlayment flashing and cladding as per best practices. And vented or unvented attics that are insulated above the roof deck with rigid foam. The panels need to fit together tightly to help prevent warm air from leaving the top of the building.

The purpose of the requirement that rigid foam installed above roof sheathing meet certain minimum r values is to ensure that the roof sheathing stays warm enough during the winter to avoid moisture accumulation and possible sheathing rot.