Insulating a Stone Foundation
We’re buying an old house (circa ~1850) in zone 5b (Hudson Valley, NY), and are considering some level of energy retro-fit as the first part of our renovations. We’re weighing our options (and budget) on how far to go with the retrofit. Because the roof and the roof deck need to be completely replaced, we have the opportunity to do a substantial retrofit with insulation on the outside and inside, and are planning to start there. However, my question is about our stone foundation basement, and what we should consider doing there. Currently, the house has fiberglass insulation on the ceiling of the basement in between the joists. However, most of it is deteriorating and/or missing, and there is no air sealing. At some point, the dirt floor was covered with a layer of concrete (and I’m fairly sure, because there are a few places where holes have been cut, that there is no insulation or vapor barrier below). Is it worthwhile to insulate the walls and rim joist (say with closed-cell spray foam), but not insulate the floor? The basement is damp, and we have no plans of finishing it, but we’re thinking we’d like to at least keep it somewhat conditioned since our current furnace (oil, forced air), duct work, and electric water heater are down there.
Additional info: I believe the house had some cellulose insulation blown into the wall cavities at some point (these walls have no exterior sheathing, just the siding. Interior walls are mostly plaster—we have less options here because both the interior and exterior have historic elements.) Many details are to be worked out, and the articles on the site are extremely useful, but I’d love some high level thoughts on how far to go with our retrofit. Many thanks in advance. -Curtis
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