Help with drafty home/basement insulation
Hoping to get some advice on the right strategy for insulating/air-sealing a basement. Briefly: Have a two-story home in New York State (Zone 6A) built circa the 1920s. For the past few years, I’ve noticed an increasing draft–not moving cold air, but a cool feeling within moments of the gas forced-air furnace shutting off. Decided to top off some ancient attic insulation with 15 inches of R-49 but didn’t notice any real difference. Windows are new and doors are weather-stripped. Not sure about insulation in the walls.
I suspect I’m getting some cold air infiltration in the basement, which has a concrete block foundation. A couple of things stick out: The foundation seems to extend well above grade, past the basement windows and well over the first floor. The cells of the concrete blocks that are exposed over the four windows are filled with batt insulation, which is dirty and moving air. Taking some of the insulation out to inspect the cavities, I could feel cool air coming in. These voids seem to be at least two or three feet deep, putting them well above the floor overhead. I’m wondering if I should remove the ancient batting and fill these voids with foam, or if expanding foam might affect the structural integrity of the foundation by “pushing” against the concrete blocks.
The other problem is the rim joist–or what I think is the rim joist. Along the left and rides sides of the house, it’s wood that “floats” slightly over the foundation. Someone stuffed batt insulation in here, too, and I’m again wondering if I would be better served pulling it out and putting in spray foam–but also concerned the foam could push the rim joist away from the foundation.
I don’t seem to have a conventional sill plate to speak of. The joist looks more like photos I see online in the front and back of the house, but there’s still no “bottom” that would hold a piece of rigid foam insulation.
Basically, I think air is getting in via the concrete block cells, between the blocks and the sill plate, and I’d like to stop it if possible. Thanks in advance.
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