Spray Foam Roof Deck

The concern here is with an unvented attic where insulation is installed directly under the roof deck the shingles may degrade rapidly due to the increased heat caused by the insulation.

Spray foam roof deck.

I m assuming that you are installing the spray polyurethane foam to the underside of the roof deck. The spray foam can also serve as the thermal and vapor control layers in both new and retrofit construction. Foam lok is spray applied to the roof s surface making it possible to vary the thickness of foam and ensure proper drainage. Proper drainage prevents ponding water deck deflection and protects the roof from leaks and premature failures.

Even small gaps can allow the passage of. This concern is over exaggerated. The movement of air into indirect conditioning of an unvented attic is a slow gradual process that will not be noticeable by occupants and typically will not put any strain on the hvac system. Skimping on roof deck preparation can reduce spf s adherence factor and reduce the useful life of the roof.

The primary risks are rainwater leaks condensation from diffusion air leakage and built in construction moisture. Not long ago someone even told me that in florida roofing companies won t let their workers go up on roofs with open cell spray foam because the roofs are so spongy the guys fall right through. This results in extended life span. Spray foam roofing has become a particularly popular solution in the commercial roofing industry but that doesn t mean it can t be right for your residential roof.

If you use open cell spray foam on your roof rafters you should cover the finished application with a paint or sealant that retards water vapor. While spf offers decent r value when precisely applied its thermal resistance is only as good as the worker controlling the spray foam mix. It rots roofs people have told me. But spray foam insulation used at the underside of the roof deck would need to be covered by a thermal barrier and intumescent coatings are commonly used.

Sloped roof with cavity spray foam insulation sprayed on underside of roof deck and covered with a sprayed on thermal or ignition barrier coating over the spray polyurethane foam insulation if necessary based on the material properties of the spray polyurethane foam or as required by code source. Despite the advantages of using spray foam under the roof deck there are some potential risks.