Complete gut remodel – need foam insulation advice
My buddy’s got a house, completely gutted. Location is Kansas City, Missouri, so we have hot, humid summers and cold, dry winters.
3-wythe solid brick wall construction up to the eave/soffit. All of the exterior-wall plaster is down (brick face exposed at interior) and there is no insulation anywhere. Please advise approaches to insulating:
Our plan right now is to build interior walls with 2×4 furring, blow on foam insulation, then drywall. His first insulation bid was for open-cell foam, but I think he needs to go with closed-cell for the WRB properties. If open cell gives R-3.5 per inch, he’d have R-12.5 walls versus R-21 for closed cell. I suppose it might even be OK to go with 2×3 furred out walls with closed cell.
I assume with closed-cell, we wouldn’t have to worry about vapor barrier and we could spray the insulation directly onto the inside face of brick (no venting). I also assume with open-cell we’d have to add a poly WRB barrier somewhere, but the question is “where”?
The ceiling rafters (2×6) would also have blown on foam and then drywall. My gut is to go with a “hot roof” for ease of construction, but can anyone with more up-to-date knowledge advise if this is still a good idea or not? Everything’s wide open right now and easy to work on, so we could cut in ridge vents, add soffit vents when we redo the soffits and then install vent chutes on all the sloped portions of roof, but that’s a lot of work (and expense) if the cost of not doing that is to lose some durability with the roof.
Roof would be asphalt shingles on felt paper on 1×12 wood sheathing. He’s having new HVAC installed with ERV and all that, so he wants the house to be as “tight” as possible.
Replies
Closed cell
The last couple of additions I have used closed cell (Corbond).
I have used open cell (Icylene), and while it is less expensive, I like the closed cell better.
I was involved with one house as a subcontractor where after the drywall was hung on the ceiling the Icylene installer sprayed about 6 " in the attic. Made for an airtight lid. My thoughts were to spray a couple of inches against the backside of the ceiling for air sealing, then blow cellulose over the top.
My problem is I'd like an installer that does both closed cell and open. The local inspectors will not allow closed cell sprayed in the bond area without drywall covering it (concerned about smoke and flame spread), but I still want closed cell in the wall cavities
Terry
Also, what needs to happen at the basement? The foundation is either brick or stone, parged, and very dry. I assume foam the cavities around the rim joist, but for a total envelope, what is the best practice for dealing with the basement?