Spray Foam Insulation On Roof Decking

Gaco is a best in class provider of silicone roof coating systems waterproofing and insulation solutions for commercial and residential buildings.

Spray foam insulation on roof decking.

Murmurs and hearsay about open cell spray foam insulation have been gaining traction for a while. 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 is a great question. 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.

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. 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. I have not heard of any evidence to support your theory. This should not be a concern when applying foam to the underside of a roof deck.

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. The insulation extends down the roofline to the rim joists and soffit areas as well as on gable wall ends. A number of factors should be taken into consideration when choosing between these two especially the climate zone that you re building in. Radiant barrier sheathing is inexpensive and reflects thermal radiation to keep attic spaces cool.

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. Spray foam is a material that is essentially manufactured when applied at the building site. Moving the air control layer and thermal control layer to the underside of the roof deck has significant advantages in cases where the hvac system is located in the attic. The code allows for insulation directly to the underside of the structural roof sheathing providing the unvented attic is contained completely within the.

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.