Its raining in my attic!!

Not enough insulation depth to stop condensation from forming on the surface of this spray foam roof line. The BER does not recommend installing a flash and batt attic roof installation unless you install enough spray foam to ensure that the surface temperature of the insulation does not drop below the dewpoint temperature of the warm, humid inside air. Also, the surface texture of the insulation will not allow the batt insulation to maintain complete contact with the spray foam, rendering the batt insulation an R-value of close to zero. Not to mention that gravity will eventually pull the insulation down and away from the roof deck in any case. It only takes a small air space to completely devalue the batt insulation. We recommend either spraying the full IECC code required R-value depth in the roof deck, or a flash and net/spray in place fiber or cellulose insulation that is fully supported with rigid backing so it does not sag and separate from the spray foam surface. In any case, the spray foam should be at a sufficient depth to ensure no condensation will form on its own, regardless of what additional insulation you install beneath it.

Comment

You need to be a member of Home Energy Pros to add comments!

Join Home Energy Pros

Home Energy Pros

Home Energy Pros was founded by the developers of Home Energy Saver Pro (sponsored by the U.S. Department of Energy,) and brought to you in partnership with Home Energy magazine.

Latest Activity

Diane Chojnowski replied to Jennifer Luitwieler's discussion Google+//Will it SAVE THE WORLD? in the group Social Media and Energy Efficiency
"How to delete extra google+ pages. "
4 hours ago
Joshua Moore replied to Jennifer Luitwieler's discussion Google+//Will it SAVE THE WORLD? in the group Social Media and Energy Efficiency
"Good to hear we're not alone. I think it was such a headache for us that we shelved dealing…"
8 hours ago
Everblue replied to Jennifer Luitwieler's discussion Google+//Will it SAVE THE WORLD? in the group Social Media and Energy Efficiency
"Hey Joshua, we've had the same problem with YouTube and Google+. It is infuriating! In fact,…"
8 hours ago
ichko Ichko Rachev is now a member of Home Energy Pros
9 hours ago
Marie Fuentes posted events
10 hours ago
Bud Poll replied to Chad Mcaulife's discussion BPI QCI Cert.
"I can't think of any test I've ever taken where I wasn't able to determine what I…"
yesterday
jerry gentile replied to Chad Mcaulife's discussion BPI QCI Cert.
"you are spot on my friend-- during the exam I said this is ridiculous--- I have bpi certs for…"
yesterday
Eric Kjelshus commented on Jeremy Begley's blog post The Home Envelope : Does it Really Matter in a Heat Loss Caculation
"IT all matters,  I lot of sealing,  A lot of air barrier.  A lot of "R" A…"
yesterday

© 2014   Created by Lawrence Berkeley National Laboratory.

Badges  |  Report an Issue  |  Terms of Service