Air sealing/insulation on top of stairs in a bungalow
Planning my air sealing project I’m most stumped by the stairs area. I tried some photos but they don’t help explain it. I’ve attached one of the second floor hall, the stairs top out just to the left, I’m talking about the narrow ceiling showing in the photo and the slant on top of the ceiling over the stairs.
If you were on top of the slanted ceiling for the stairs on one side is open to a small attic. On the other side is the ceiling shown in the photo, and then a sloped ceiling to a kneewall. Straight ahead to the center of the house is the back of 2 shelves that were built in to the void.
I also have access to the bigger section of attic more center the house because of an addition. So, I can see the top of the small ceiling in the photo from the big attic, and the top of the stairs from that same vantage point and from the small attic on one side.
So, if that’s at least somewhat clear:
I’m guessing the building envelope should be defined by the top of the sloped ceiling, since the attic it attaches to is a cold attic. They have stapled fiberglass batts over the top from the small ceiling shown horizontally across the stairs space. Am I correct that I should define the building envelope, then try to get insulation on all the borders of that envelope but open above it for ventilation?
If so I’ll probably use 2 layers of R60 on the vertical sections, then maybe rigid foam as if it’s the back of a kneewall?
I’m thinking I might be able to slide on my stomach on to that narrow ceiling to air seal, but would probably have more success dropping feet first from the attic addition on to the top of the slanted ceiling, then air sealing from there?
Thank you in advance for suggestions. If this is all confusing I can try to make a drawing or take some more photos.
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