Q&A: A Forum for Green Building Experts and Beginners

I'm considering using rigid foam on the exterior of my roof. Cost is of course a big concern with this approach. I'm found sites online that sell recycled rigid foam. Apparently, it is often recovered from commercial buildings and shipping containers.

I read one post on the site that caution against using foam that had been degrade during freeze/thaw cycles. Are there any other issues to look out for? Have anyone tried the "recycled" approach? Is there a reputable source for material? Any lessons learned you folks could share would be greatly appreciated.

I'm getting quotes from contractors right now to insulate a small cottage with an unvented cathedral ceiling using 2x10s. I'm in zone 3C.

One contractor has suggested spraying 5.5" of open-cell foam between the rafters and calling it a day. I asked if we could just fill the entire 9.5" cavity and he said, "You achieve maximum efficiency @5.5. Any more is overkill. It will expand a couple more inches as we will not cut it but leave the excess."

Code requires R-30 for ceilings around here.

I may be wrong but doesn't more insulation mean higher R-value?

I'm trying to decide which product to use for my interior air barrier. I'm constructing a double stud wall system and intend on placing my interior air barrier on the outside of my inside stud wall. My choices are..

- Certainteed's Membrain
- Siga Majpell 5
- ProClima Intello +
- ProClima DB+

Everything was going well in our green home planning process until a short conference call with our mechanical contractor today.

His assertions:

1. our home will be too dry (we are omitting a humidifier)
2. our bathrooms still need exhaust fans (we are installing an HRV) in order to pass inspection and meet code
3. an HRV should never pull exhaust air from the laundry room as it will create negative pressure