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Community and Q&A

Insulating a sloped ceiling

Frank Mengler | Posted in Energy Efficiency and Durability on

I have a 1.5 story home built in 1900 in southern NH. Minimal insulation on attic floor and some stuffed into the sloped ceiling from the attic. The insulation contractors that have looked at it want to dense pack the bays on the sloped part with cellulose. One said he could flash it with spray foam to seal it first, then dense pack. I have read that insulating with no venting is a bad idea. I understand without ripping the drywall down, it would be very difficult to insulate properly and add vent chutes. The roof is probably 7 or 8 years old, with board decking that should that have been replaced in several spots. Not sure what I will find when I pull out the insulation on the sloped ceiling. I was thinking of attaching rigid foam, 1 or 2 inches, on the sloped parts then sheet rock over that. No ridge vent, or soffets, just two gable vents in the attic. This winter being mild it wasn’t an issue, but 6 years ago when I got the house, it snowed and there was ice damming. Worse, on the roof where the sloped ceiling is. Also, there is no knee wall to get behind as they go out to the overhang. Not sure what to do.

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  1. GBA Editor
    Martin Holladay | | #1

    There is no simple or inexpensive solution. The best solution is to install one or more layers of rigid foam on the exterior side of your roof sheathing, followed by a second layer of OSB or plywood sheathing and new roofing.

    These three articles should tell you everything you need to know:

    How to Build an Insulated Cathedral Ceiling

    Insulating a Cape Cod House

    How to Install Rigid Foam On Top of Roof Sheathing

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