Flash and Batt foam thickness
MMargulies
| Posted in Energy Efficiency and Durability on
I’m in NJ climate zone 5 and have a project with an installed falsh and batt with 1″ closed cell foam and Roxul batt in wood framing. I usually spec 2″+ but would like to avoid ripping everything apart and spraying more foam. Is there a chart/rule-of-thumb anywhere showing wtih of foam based on climate zone averages or any specific data to justify thickness besides doing a calc? This seems like a case where it would probably be ok but with a small chance for a big problem??
GBA Detail Library
A collection of one thousand construction details organized by climate and house part
Search and download construction details
Replies
Michael,
Relax -- your walls should be fine.
The guidelines you are looking for can be found in either of these two articles:
Calculating the Minimum Thickness of Rigid Foam Sheathing (Look for the paragraph with the headline, "What about flash-and-batt jobs?")
Why Flash and Batt Makes Sense ("According to building scientist Joseph Lstiburek, flash-and-batt installations require at least 1 inch of spray foam in climate zone 5, 1 1⁄2 inch in zone 6, and 2 inches in zone 7.")