I have an 85 year old house(New England salt-box) in SW Washington, that was built by my grandfather in 1924. It has a finished attic with two dormers built in. Around ten years ago, the rain got in and damaged the sheetrock and insulation below. My mother, who had the house at the time had a contractor repair the roof, but nothing was done about he ceiling. My daughter and I arrived a couple years ago and I have gotten tired of the sagging ceiling. I tore it out thinking this to be a simple remove and replace job. Silly me!
The area above the ceiling is sloped to around 5/12, versus the rest of the roof which has an 11/12 pitch, and has Owens Corning fiberglass insulation batts with paper vapor barriers between the rafters. The spaces between the joists below have what appears to be loose fill fiberglass(?) insulation, but it's sporadic. (It's a dark grey fuzz) Won't the lower insulation adversely affect the upper, being as there is a vapor barrier between them? There is a variable air gap between the two layers, of between three inches at the low end and and three feet at the upper. Should I strip out the upper insulation and install new barriered insulation below? It can get pretty cold in the winter here and my daughter wants that area for her bedroom.
In addition, this summer, I intend to reshingle the roof. As shiplap ceder is no longer allowed here, I'll have to replace it with OSB. Is this going to adversely affect the existing insulation, as the OSB does not 'breathe' like the shiplap does? There are no soffet or ridge vents, but the upper one quarter of the rafters are exposed to a three by eight foot triangular space above the finished ceiling, and running the length of the house (about 45 ft.) That section also has the batts between the rafters, and the loose-fill between the joists of the ceiling.
Re: Insulation questions.
Howdy, the air gap what is holding one insulation off of the other? Never want to install vapor barrier between layers of insulation as it traps moisture. Is the ceiling and the roof rafters insullated allowing this gap?
When re roofing add ridge cap vent or individual roof vents and consider adding gable vents and or soffit, eve, vents to allow roof to cool in summer extending shingle life and moisture to escape...
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