Radiant Or Spray Foam Roof

Another alternative to radiant barrier foil are the various types of foam insulation.

Radiant or spray foam roof.

What is foam insulation. Foam insulation rigid boards are 4 x8 sheets usually cast of closed cell polystyrene designed to fit directly inside walls against the interior or exterior of plywood sheathing as. Spray foam insulation doesn t protect attic spaces from radiant heat but does protect them from convection and conduction. All manufacturers of radiant barrier sheathing say not to spray against their product it will render it useless.

Bill delamar i have wondered if spray foam installed directly on the sheathing will shorten the life of the roof covering if no baffling is provided. The challenge with a spray foam enclosed attic roof is that you cannot typically have a radiant barrier because of the lack of a proper air gap. A foil manufacturer suggested the foil on the inside of the truss leaving an air gap between the foam and the foil. In the summer radiant heat is the biggest contributor to heated attic spaces so spray foam insulation may not be as effective in keeping attics cool.

These issues may go unnoticed for years until it s too late. Some heat will still flow by conduction through the roof foam assembly. Spray foam applied to the underside of the roof deck has the potential to trap moisture caused by roof leaks potentially leading to rot and decay of the roof framing. The shingles are connected to the roof deck and the deck is connected to foam.

I typically spray enough foam 5 lb open cell to achieve r 38 in our roofs. Spray foam insulation radiant barrier sheathing radiant barrier sheathing can reflect back up to 95 of the heat absorbed and can consequently reduce attic temperatures by up to 20 degrees f.