New spray foam contractor is getting conflicted information. I want to do the right thing.
Good Evening. I joined GBA to ask this specific question but I’ll stick around as I believe it’s a good resource.
Climate zone: 6B
TLDR: 3 bidders + myself (last bidder). Owner wants to fully insulate 40x50x18 shop envelope with SPF.
2 installers want to put 3″ closed cell SPF on the underside of a 5/12 pitch roof while 1 wants to put 2″. 2/3 are reputable contractors in our area and say that’s sufficient. – Is it truly?
My background: EIFS and plaster/stucco 8 years with my Pop who is a hard a$$, making me a 5th generation plasterer. I want to do my Pop proud since he loves this trade (mostly to avoid getting lecture of why I’m wrong) so I try hard to retain most of what I pick up. Most of the construction knowledge I have is specific to my trade, so outside of that, I’m am generally inexperienced. Though I am gaining traction on SPF.
My Pop and I have started a new business in the SPF industry (to feed us during the stucco off season) and we found out that a friend of ours was preparing to insulate his 40x50x18 (LxWxH) isolated shop.
Half of that he’s converting into an apartment. Shop on left side, and renting out the apartment which is above its own garage on right.
Before we came along he obtained 3 bids to SPF the envelope.
The focus here is adequate insulation in the roof.
2 bidders say 3″ of CCSPF (r-21 ya?) is enough R factor in the 5/12 pitch rafter bays while 1 bidder says 2″ is enough. That’s it, nothing else for the lid.
My own battle is this:
My accumulated knowledge, plus the manufacturers of our SPF say 7″ of CCSPF = r49. Our regions building codes say all envelope hats must be r49.
My Pops says that 3 other bidders who say 2-3″ is fine, can’t be wrong. (our friend shared the estimates with us to help us out)
These estimators either are just going with what the shop owner wants (he’s got money but also a cheap skate, think Ebenezer Scrooge.) , or seem to have the homeowner convinced he only needs 2-3″ of foam up there. 3 bidders can’t be wrong, right?
I want to give the shop owner what he wants, but I also want to give him what he NEEDS.
Can someone tell me how 2-3″ of CCSPF = R49 or equivalent?
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