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Insulating a Maine Roof with Dense-Pack Cellulose

comments (1) November 8th, 2011 in Blogs

Scott Gibson, contributing writer

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In Portland, Maine, Dean Manoogian is pondering how to insulate the roof of his Cape Cod-style home. It's been constructed without gable, soffit or ridge vents, and Manoogian's plan of attack is to attach 2 in.-thick sheets of rigid foam to the bottoms of the rafters and fill rafter bays with dense-pack cellulose.

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Vented or Unvented Attic?

As he explains in a Q&A post at GreenBuildingAdvisor, the rub is what becomes of water vapor that migrates through the insulation in winter. Without a means of venting the moisture to the outside, the roof may be a victim of condensation, mold and decay. To forestall the possibility, Manoogian wonders whether a peel-and-stick membrane should be applied to the roof sheathing and rafters before the rest of the insulation is installed.

The vapor-impermable membrane would presumably keep moisture away from sheathing and rafters. The city has already approved his plans, but is he on the right track?

That's the subject of this week's Q&A Spotlight.

Read the whole article at Green Building Advisor

posted in: Blogs, energy efficiency, insulation

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Comments (1)

midmobuilder writes: I am curious about moisture in a similar situation. I have a client with a 27 year old 3/12 modular with a single 2 x 6 rafter that is drywalled, packed with rock wool (I think) and sheathed with 1/2" plywood. After removing the drywall and insulation, we discovered much black staining on the underside of the plywood, along with considerable plywood degradation near the ridge (some had been replaced 9 years ago when the house was reroofed). I am unsure how to put the roof back together after it is reroofed. Closed cell foam to black vapor and insulate well and no insulation? Insulation baffles and a ridge vent (don't know what the ridge is like, it is a modular). Grace Corp says to vent if we cover with ice and water shield (I thought about covering the whole roof with their product since it is a 3/12 and is leaking after only 9 years on these shingles). Any ideas?
Posted: 9:32 pm on November 14th

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