Spray Foam Directly On Roof

How hot roofs differ from traditional roofs.

Spray foam directly on roof.

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. 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. Unlike solid insulation products that require careful measurement cutting and fitting spray foam can cover even the most uneven surface instantly. It rots roofs people have told me.

The primary risks are rainwater leaks condensation from diffusion air leakage and built in construction moisture. 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. Attics typically have an insulated floor and have ventilation. After cleaning the existing roof the spf roof can be applied directly over asphalt shingles concrete metal and wood.

The spray foam can also serve as the thermal and vapor control layers in both new and retrofit construction. 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. 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 spray foam is used a vent space may still be needed directly under the roof deck.

If you continue with the option to spray the foam insulation you will want to limit the thickness on the first pass. Spf roofs are installed by spraying a liquid on the existing roof and allowing it to expand into a foam. 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. This process means that the foam can conform to all roof shapes and types even irregularly shaped roofs.

Murmurs and hearsay about open cell spray foam insulation have been gaining traction for a while. Spray foam roofing cons. 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 underside of roof.

Wood has an r value of about one per inch of thickness. Here are some negatives to spray foam roofing that might make you want to consider a different option. 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.