Helpful? 0

Flash and Batt foam thickness

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??

Asked by Michael Margulies
Posted Fri, 01/25/2013 - 10:33
Edited Fri, 01/25/2013 - 10:35

Tags:

1 Answer

Select your preferred way to display the comments and click "Save settings" to activate your changes.
1.
Helpful? 1

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.")

Answered by Martin Holladay, GBA Advisor
Posted Fri, 01/25/2013 - 10:40

Other Questions in Energy efficiency and durability

Rigid polyiso in side attics?

In Green building techniques | Asked by Ryan Griffin | Nov 22, 14

Polyiso on interior

In GBA Pro help | Asked by William Lucrisia | Nov 21, 14

Super insulating and soundproofing

In Green building techniques | Asked by Ryan Griffin | Nov 22, 14

Detail for stone veneer

In Green building techniques | Asked by Robert Holland | Nov 16, 14

Mid Roof Edge Vents / Ice Dams

In Energy efficiency and durability | Asked by Robert Eaton | Nov 23, 14
Register for a free account and join the conversation


Get a free account and join the conversation!
Become a GBA PRO!