Damage investigations of spray foam insulation wood roof decks have found instances where deterioration of a wood deck has occurred due to water intrusion.
Spray foam insulation on roof deck.
Unlike solid insulation products that require careful measurement cutting and fitting spray foam can cover even the most uneven surface instantly.
It s not coming from above the roof and it s not some new moisture source resulting from the spray foam.
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Where wood shingles or shakes.
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.
Spray foam insulation can create a barrier that reduces the drying rates of wood roof decks which may result in an unfavorable buildup of moisture in the wood.
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.
Moisture generated indoors or that infiltrates into the home is responsible for the bulk of the moisture in an attic insulated with spray foam on the underside of the roof sheathing.
No interior class i vapor retarders e g plastic sheeting are installed on the ceiling side attic floor of the.
This construction approach was first used in the 1970s and it has been implemented much more widely since it was first included in the international code council s icc model building code in 2007 irc section 806 4.
The installation steps are as follows.
Insulate an attic in an existing home by installing spray foam open cell or closed cell on the underside of the roof deck.
The code allows for insulation directly to the underside of the structural roof sheathing providing the unvented attic is contained completely within the building thermal envelope.
How spray foam should be installed on the underside of the roof decking the unvented attic space is completely within the building s thermal envelope.
If you ve never heard the phrase hot roof i m sure you ve heard of an unvented attic.
This measure will convert a vented attic to a nonvented attic.