Spray Foam Directly On Roof

Polyurethane or polystyrene spray foams can provide thorough coverage to roof rafters and attic walls in much less time than is needed for other materials.

Spray foam directly on roof.

An open cell foam about 0 5 pound density is the most cost effective way to insulate but any opening over 1 16 could cause the foam to expand out onto the roof. The primary risks are rainwater leaks condensation from diffusion air leakage and built in construction moisture. Matt p posted in general questions on february 9 2016 12 54pm i have a conditioned attic currently insulated with r19 fiberbatts between the rafters. Despite the advantages of using spray foam under the roof deck there are some potential risks.

Murmurs and hearsay about open cell spray foam insulation have been gaining traction for a while. Spray foam roofing cons. This is not an issue specific to spray foam as much as it is a characteristic of peel and stick membranes. Wood has an r value of about one per inch of thickness.

The term hot roof comes in because the spray foam insulation is being affixed directly to the roof sheathing which removes the need for ventilation. It rots roofs people have told me. Attics typically have an insulated floor and have ventilation. It would be better to use a closed cell 2 pound density foam because it doesn t expand as much as open cell and is more likely to fill voids but not go through them.

Unlike solid insulation products that require careful measurement cutting and fitting spray foam can cover even the most uneven surface instantly. If spray foam is used a vent space may still be needed directly under the roof deck. No airsealing hence i want to remove the fiberbatts and spray 3 inches of closed cell spray foam in before putting the fiberbatts back in place. How hot roofs differ from traditional roofs.

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. Here are some negatives to spray foam roofing that might make you want to consider a different option. Spf roofs are installed by spraying a liquid on the existing roof and allowing it to expand into a foam. After cleaning the existing roof the spf roof can be applied directly over asphalt shingles concrete metal and wood.

Reducing the thickness to a few inches and allowing to dry will reduce the amount of moisture directly against the metal roofing but more importantly it will reduce the amount of heat generated on the panel during the application. If you continue with the option to spray the foam insulation you will want to limit the thickness on the first pass. Spray on roofs can be expensive to get installed but this can easily pay for itself and more in the long run when you factor in how long it lasts as well as the amount you should save on energy costs.