Insulating Old Exterior Walls
Hi there,
I am renovating a 1890 cape in southern Maine and coming up against how to insulate old exterior walls in a one story kitchen ell and another exterior adjacent wall with standard depth 2×4 construction. This house has a a number of walls with blown in cellulose. The attic has one slope open enough to spray foam and the dormered side will have cellulose 16″
I am concerned about spray foam’s long term off gasing as i am recently diagnosed with some health issues. We have done one crawl space with spray foam on the walls and membrane and i have not noticed any irritation from that. In trying to come up with alternatives I considered roxul with 1″ polyiso as a further insulation and thermal break as there are lot of studs. but then read a post here about ‘wind-washing’.
MY partner suggested using tyvek type wrap on he inside against the sheathing prior to roxul as a way to reduce this. I’ve never seen anything like that mentioned here but don’t want to dismiss an idea that might work.
Is there an assembly that might offer a reasonable insulation for an older house where it will never be up to current standards? Cut and cobble(which I have read the threads here pro and con and with how to if you are doing it) might work but does use some spray foam and does require a lot of work but would mean considerably less offgassing.
I’m sorry if this has been gone over too many times. I have to make a rather quick decision and my time for research is running out.
Gayle
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Replies
Hi Gayle,
If spray foam isn’t on the table, this article by Andy Engel, Key Considerations When Insulating Old Walls, recommends tacking ½-in. vertical furring strips to the back of the siding, right next to the studs. Then pressure-fitting a water-repellant rigid insulation product from a manufacturer like Gutex or Stecio between the studs, and sealing any gaps with gun foam. The entire cavity can be packed with rigid insulation, or you can do an inch or two of that followed by batt insulation such as mineral wool—depending on your climate and insulation assembly thickness requirements. As Andy stresses, water management is imperative, so consider his tips for ensuring the assembly’s drying potential.