Spray Foam Insulation On Roof Decking

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Spray foam insulation on roof decking.

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. The insulation extends down the roofline to the rim joists and soffit areas as well as on gable wall ends. In the northwest where foam has been sprayed directly to the underside of roof decks for over a decade the building officials interpret the code to require removal of existing insulation. This should not be a concern when applying foam to the underside of a roof deck.

Take measurements before the installation of the air impermeable insulation to help ensure that the roof deck is dry enough to be covered with spray foam insulation. It rots roofs people have told me. This illustration shows a sloped roof with cavity spray foam insulation sprayed on the underside of the roof deck and covered with sprayed on thermal or ignition barrier coating. Murmurs and hearsay about open cell spray foam insulation have been gaining traction for a while.

Both open cell and closed cell spray foam insulation adhears extremely well to the underside of roof decks and the rafters surrounding them when installed correctly. Only spray polyurethane foam can be used for this application as batt insulation will end up sagging and blown insulation simply can t adhere to the roof decking. Radiant barrier sheathing is inexpensive and reflects thermal radiation to keep attic spaces cool. This is a great question.

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. The code allows for insulation directly to the underside of the structural roof sheathing providing the unvented attic is contained completely within the. 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. I have not heard of any evidence to support your theory.

When installing attic insulation a case can be made for both radiant barrier sheathing with typical types of insulation as well as spray foam insulation.