Open Cell Spray Foam—Bubble Repair
I’m building a new 1 1/2 story home in a HH climate (2B). Insulation is ocspf—6″ in walls and roof (i.e. semi-conditioned attic).
The insulation is complete, but there are just a few small areas that aren’t well done. There are some areas (corners mostly) that have fist-sized holes in the insulation. It appears that there is enough foam to seal to the outside, but not full thickness because of a bubble. The contractor and the manufacturer both advised that I should just fill these up with canned window foam.
SO HERE’S THE QUESTIONS—-
1) Window foam is closed cell. If I spray this in the holes, I am concerned about creating a vapor barrier where I don’t want one. Would I create a condensing surface in the wall? Is a small area like this a problem, or would any condensate just sort of dry around the repair ball of foam? The walls are wood frame, plywood sheathing, and tar paper WB. The first floor is brick facade with air gap; second floor is fiber-cement siding with no gap. Roof is metal with polymer under-layment and plywood deck. So the roof must dry to the inside and the walls can dry from both sides.
2) I have some scrap chunks of the foam. Since the bubble areas appear to be sealed to the plywood sheathing, why couldn’t I just put a chunk of insulation into the bubble? The manufacturer didn’t like this option–something about the edges of the repair chunk wouldn’t be sealed. So what?
3) There are some areas (gaps) that were too narrow to spray with a foam rig. Such as the gap (1/4″ or so) between a roof rafter and the adjacent plywood sheathing in a dormer-type room. Would this be best sealed with window foam or should I just caulk the gap? Either one is vapor impermeable.
4) The manufacturer mentioned a 2-part ocspf kit (like propane bottle size) available from the big box stores, but not from him. But he said it was difficult to use. Any thoughts on this. I do have one larger spot on the roof I just discovered that I’ll have to either fix with this, or get the contractor back with his rig.
I would appreciate any comments on this.
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