Yet another insulation question
I’m done framing my house (2×6) and we’re working on the mechanicals. Soooooo, I’m about to decide on insulation.
So far I decided that I wouldn’t use batts unless it was over an inch of sprayed foam. Then I started looking into dense pack cellulose. The contractor I talked to says 5 1/2″ of dense pack has R 20. Another guy I talked to says he sprays BIB fiberglass and that “it’s way better” R 23.
Now I realize that an additional R 3 isn’t gonna make much difference if the wall containing it isn’t as infiltration proof.
I’m getting a little confused again. (OK, so maybe I’m typically confused…)
I was quoted $.78 per sqr ft for dense pack. $.52 for BIB. And considerably more for foam with batts stuffed over it.
I’m leaning toward the dense pack, but I’d appreciate any good reasons to do, or not, any of these approaches.
Something is what it does.
Replies
Hasbeen, what were you quoted for an inch of closed cell polyurethane?
The guys I deal with believe the best wall (2x6) for the cost has 2" closed cell with fg 3 1/2 batt behind it. Strengthens the wall, seals it very well, and with sheathing and sheetrock, provides r-30. In a really hard climate, either from extreme heat or cold, I like a layer of covered foam board over the sheathing to provide a thermal break to the studs.
If that is too much to do, I would fall back to 1 inch of poly foam sprayed in and sprayed cells or (third place) fg batt behind the foam.
Bottom line, I would definitely have an inch of closed cell foam in the walls, and probably 1/2" in the attic to seal the ceiling , partitions, joints, wires etc. with a little extra at the perimeter area due to depth limitations of the backup insulation.
In a multistory house, I would hit the band board with a couple of inches of foam.
Look for some serious energy price hikes thanks to OPEC in the near future. I think you are lucky to have the walls open at this time.
Paul
How 'bout the Mooney wall?
I figure (based on the ft² quote by the dense pack guy) that your cell cost would be about $1.00/ft², and the 2x3 strapping would be about $.13/ft².
Section R value of 22, compared to the actual R of 17.5 with 2x6 and dp cells.
So for an extra $.35/ft² you kill the thermal bridge, give yourself some nice blocking to hang trim/cabs to, and Tim then gets the royalties!
Jon Blakemore
I have been in the "how much we use game", but it worked out to the original estimate pretty well. They also did some extra, like sprayed the underside of a large hot tub, and hit the band boards both between floors and basement sill/board cavity with two inches, and foam filled some block walls prior to house framing. The owner of the company then had the house pressure tested at his expense, because he had seen the care we put into it, and he wanted to know the end result. Believe it was .19 ACH., and we could not control all of the building work.(production builder, his design and shortcuts)
I had heard the blowing agent is changing again, but not that it cost 20% more. You could call NCFI in North Carolina, and ask their tech people what the increase might be, but local guy still has final say to you.
Hope it works out for you, I really believe in the stuff, and how well it makes the rest of the wall perform. Mooney wall is good to get depth, kill the thermal bridge, super sheetrock support etc, but you already have enough depth to keep all your Btus. Any way best of luck to you./ Paul
Double check that comparison again on the cells and the BIBsystem. my understanding is that the fibreglas gets slightly less R value than cells but that it does depennd on whether loose fill or denspack so just be sure you are comparing apples to apples there.
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