Is fiberglass batt insulation an acceptable material to close off eaves of a cathedral ceiling to stop closed cell foam? If so, if the fibe

Asked by Cjr
New York, NY

I had closed cell foam installed in a cathedral ceiling. Fiberglass was used to stop the foam along the exterior walls. The fiberglass penetrated the interior space and the closed cell didn't create a full barrier onto the exterior plate. I had moisture build up in this area. Was the foam installed incorrectly? What can be done to rectify this?


Sean Lintow Sr

Answered by Sean Lintow Sr

Naperville, IL

SLS Construction & Building Solutions

April 23, 2014

In short they should have used solid blocking & ensured the foam made full contact with all the framing & sheathing members. Could this be the source of moisture or could it be from the cathedral area - that is hard to know as many of the needed specs are missing here. Was the cathedral area fully filled or just X amount of inches added, what is the R-Value, How many penetrations are there entering into this space (recessed lights, etc...), do you run humidifiers, vent your bath & kitchen exhaust, etc... The fix, well you would need someone in there to look over all the factors to start. Might it be as simple as fixing the eave area - possibly. Might it involve you controlling the moisture levels in the house, probably so. Might it require more insulation for the whole assembly, that could also be a possibility. For More: (Scroll down to condensation section)

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