A fillet application at the joint a one inch application across the whole cavity as might be used in a flash and batt application and a three inch application filling the bay.
Spray foam underside of roof deck.
No interior class i vapor retarders e g plastic sheeting are installed on the ceiling side attic floor of the.
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.
Lstiburek takes blame for bad language.
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.
In our neck of the woods closed cell foam costs about 56 more than open cell.
Unlike solid insulation products that require careful measurement cutting and fitting spray foam can cover even the most uneven surface instantly.
University of florida researchers tested three levels of spray foam roof underside retrofit.
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.
It s not coming from above the roof and it s not some new moisture source resulting from the spray foam.
Where wood shingles or shakes.
Most unvented attics incorporate spray polyurethane foam spf on the underside of the roof deck and attic walls.