Does it make sense to install rigid foam insulation on only one wall?
I live in an area where temperature’s varies from -40 to +38 deg Celsius. I have a home built in the 1940s and I have a question about increasing the insulation in exterior walls. Note, my foundation footprint is a rectangle.
At construction, loose coconut fibre was placed between the studs, and no vapour barrier was installed. I’ve done some research and have found that about 4″ of loose cocounut fibre equates to about an R3.
The sheeting is made up of 1×6 tongue and groove wood planks, covered with builder’s felt. The original exterior wall seems to be some sort of parging that was applied to a wire mesh, about 1″ thick.
Most of my home has since been covered with aluminum siding (no insulation added between siding and original exterior). That said, my attached garage (not insulated, no foundation) wall is still original.
I’d like to know if it would be worthwhile to install XPS (or EPS) rigid board on the exterior side of this wall to improve the household’s overall insulation.
My concern is that without a thermal break between the attached original walls/siding, that I wouldn’t really realize any benefit because the cold/heat will still transfer through the attached walls to a large degree.
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