Replies

1. 
   derekr | Jan 19, 2023 10:19pm | #1

   Almost sounds like what I’m doing, I would go with rockwool batts over the fiberglass if you don’t do spray foam

1. 
   ramand | Jan 20, 2023 01:32pm | #5

   Thanks much. I heard about formaldehyde issues with rockwool. What is out cost difference compared to fiberglass?

1. 
   derekr | Jan 20, 2023 06:19pm | #6

   I haven’t heard anything about formaldehyde in rockwool, I haven’t compared the prices recently because I bought mine a year ago, at the time I bought though it was only going to be 2k-3k more than fiberglass, it might be more now

   Worth it for the fireproofing, sound proofing, and moisture resistance

2. Expert Member
   BILL WICHERS | Jan 20, 2023 09:07am | #2

   Skip the spray foam. Run a bead of sealing around the perimeter of the framing before you put the plywood sheathing up, then tape the seams. That will get you a good exterior side air barrier. Use canned foam to seal any penetrations in the top and bottom plates in the wall. I would install the interior drywall airtight too for some extra insurance. You now have a very well air sealed wall assembly, there is no need for the spray foam for air sealing. Use batts in the walls (I would use mineral wool) and you're good to go.

   Flat roofs can be more of an issue here. I would probably go with closed cell spray foam in the unvented roof assembly, and I'd use that for all of the R value, skipping batts to save on labor.

   Bill

1. 
   ramand | Jan 20, 2023 01:30pm | #4

   Thanks Bill Appreciate it. My ply is already up. I guess I have to do a better job on air sealing at my dry wall.
   I like the idea of using closed cell. In this case drying will happen to the exterior. Does using the peel and stick on the ply and ALX west coat system hinder any dryness?
   Or is it better to use peel and stick with TPO or torch down?

3. 
   Deleted | Jan 20, 2023 01:30pm | #3

   Deleted