The biggest weak point in my opinion is that if there is a roof leak you won t find out until the wood is rotted.
Spray foam under roof deck.
Spf is not a greater risk under a roof deck than the risk associated with commercial compact flat roofs with multiple layers of insulation sandwiched between roof membranes and metal and wood structural decks.
It is not the end of the world.
Open cell spray polyurethane foam ocspf and closed cell spray polyurethane foam ccspf insulation sprayed to the underside of roof sheathing is a popular strategy for increasing roof insulation levels in all climate zones.
Just make sure you overdo your roof when the roof is installed.
No interior class i vapor retarders e g plastic sheeting are installed on the ceiling side attic floor of the.
Spf is not a greater risk under a roof deck than the risk associated with sips.
Yeah you probably still breathed some of it but not as much as you will now with spray foam on the roof deck.
By encapsulating the attic and leaving the old insulation up there that filth is in your conditioned space.
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.
Unlike solid insulation products that require careful measurement cutting and fitting spray foam can cover even the most uneven surface instantly.
Most unvented attics incorporate spray polyurethane foam spf on the underside of the roof deck and attic walls.
Your indoor air quality may get worse.
Lstiburek takes blame for bad language.
Where wood shingles or shakes.
I ve done a lot of work in energy efficient building and design.
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.
Ready for something else.
The spray foam definitely has its merits.
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.
It s not coming from above the roof and it s not some new moisture source resulting from the spray foam.