DrAg93 said:
makes sense. Thanks for the reply. I am doing new home construction and I've been debating insulation options.
It all depends.
1. The home is a system. A new construction home properly prepared with equivalent roofing, windows, fresh air systems, mechanical systems and so on and foam is great. A remodel is much more challenging to get right. Everything works together.
2. Open cell foam is open. Vapor and moisture travel through it. Again, it's about proper install and controlling other conditions. We've been foaming homes for decades and haven't had a single issue with moisture retention except for 1 remodel where an existing gutter was failing and letting water come into the sub floor. There was closed cell below and water wasn't able to exit so it just rotted out the subfloor. It was an old home and we advised against foam but the architect and client wanted it.
3. Iirc, open cell is like 4.5R/in and closed is like 6R/in. Somewhere in that range
4. Open cell foam is living in the 4-5 $/sqft range. For a small job, I'm sure there is a minimum.
5. Its a good idea to dehumidify or condition the attic space to help reduce the chance of condensation on duct work.
6. If you're retroing- the mechanical system has to work. The attic must be able to be properly sealed
7. No matter what you go with, proper install is the key.
8. If I were doing my own house from scratch, I'd insulate outside the walls and create a sealed envelope. If I couldn't do that, I'd go with rock wool.