Insulating An Inaccessible Unvened Attic Space
Most of my home has a 2′ roof overhang, except my kitchen is cantilevered over the foundation eliminating the roof overhang. This length of roof is unvented and my kitchen ceiling has a soffit. This area of roof is always the first to melt snow and does not develop frost on frosty mornings which obviously means one thing, the soffit, including the pinch point, is not insulated well. I know it has some fiberglass batts inside, likely settled and not doing its job well. My question is, how to better insulate this area? Is is essentially inaccessible from the main attic. My mind is telling me to cut holes in the soffit from the kitchen, remove the fiberglass batts, then fill the soffit with dense pack cellulose, dense pack fiberglass, or spray foam.
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If it's unvented, spray foam is probably your best option here. With closed cell spray foam, you can spray right up under the sheathing and not worry about moisture problems.
I would also check for air leaks. I have battled air dams on my home too (mostly fixed now), and a lot of the time, the issue could be traced back to air leaks, not just insulation being a bit light on R value in the trouble spot. Air sealing, and sometimes installing an air barrier, often makes more difference than just beefing up the insulation. My first thought with your specific issue is: does that soffit have any recessed can lights in it? If you have some recessed cans in that soffit, they are probably leaking warm air up into that soffit area and causing the snow melt problem you're seeing. Fix that issue first. If that's the issue, check for signs of mold and rot in that unvented roof section while you're up there.
Bill
Thanks Bill. There are no recessed lights or penetrations of any kind in the soffit. I'm assuming it's just not insulated well. I'm debating between closed cell spray foam and dense pack cellulose. Foam seals and insulates better but apparently cellulose has hygroscopic properties that can handle very small amounts of moisture. I'm leaning towards opening up the bottom of the soffit, pulling out the old fiberglass, and spraying foam into the pinch point and on the underside of the roof sheathing.
Does the soffit need to be completely filled with foam or is a void below the foam and above the ceiling okay? Would it be advantageous to put something fluffy like fiberglass in that void?