Spraying closed cell spray foam directly to fiberglass batts?
Working on a house in Chattanooga TN (zone 4) that needs weatherization badly. Already decided on cc SPF to seal some “crawlspace walls” and exposed floor system from below that are outside the “crawlspace”. There are many angles, transitions and irregularities that would make rigid foam or air barrier protecting batts very difficult hence the reason for going with SPF.
The plan is to remove the batts and spray 2-2.5″ to the subfloor and cover the joists (including bottom edge) with around 1″. Iam tempted to skip the batt removal as much of it is installed decently and there would be plenty of framing for the foam to bond with. Is it a terrible idea to directly spray to the bottom of the batts and joists?
I realize the correct way is to remove them and reinstall them under the spf but detailing an air barrier to protect them would be extremely difficult, expensive and labor intensive. I dont think the homeowner would want to add the appropriate amount of insulation (under the spf) given the mild climate, and long payback (and I sure dont want to work with FG batts). Why not maintain all that R, protect it with the cc spf and it would even make it easier to remove the foam in the future if needed.
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