Temporary basement insulation questions
Climate Zone 6, almost 7 in Ontario
I’m in the process of completely renovating our 700 ft^2 house. I have R60 in the attic, and my goal for the main floor walls is a minimum of R34. It’s currently R12. I’d like to match the R34 in the basement above grade and taper down to R20 near the footing (I think). I want to insulate the exterior of the basement and carry the insulation about 4 inches above the rim joist. I was planning on using the exterior insulation as a vapor barrier and tying it in with the interior vapor barrier on the main floor. The main floor walls are double 2×4 with 2-3 inches between them. I planned on using closed cell spray foam on the bottom plates to connect the interior and exterior vapor barrier.
For the basement, initially I was planning on using reclaimed XPS but I am now considering a Rockwool product because I need insulation now. I have a 50k BTU/hr wood stove in the basement and it can not heat the basement above 15*c (59*f) with outdoor temps at -10*c (14*f). I’m expecting a heat loss of 15k BTU/hr once I’m done all my renos but right now I’m likely over 60k btu/hr. We are using electric space heaters to keep the house livable but that’s costing near $300/month.
My basement is cinder block wall and I’ve built a 2×4 wall in front of it. The cinder block is poorly done. It wonders off course and is not plumb. It also has a weird 10″ horizontal section that looks like it is a poured slab about 5′ up the wall. All that to say, it will not be easy to put rigid insulation on it.
Since I ultimately want my insulation on the exterior but I need insulation for this winter, I’m wondering what I should do. The 2 thoughts I’ve had are to hang XPS on top of the studs and then temporarily put 1/2 drywall on top of it for a fire barrier, or to just hang some Rockwool panels on top of the studs. I’ll then transfer this insulation to the exterior when the time comes.
The basement does leak, fairly bad although I’ve improved it a fair bit with some exterior grading. I plan on water proofing the foundation this summer, which is when I plan to do the insulating. RH in the basement is 50-40% although since running the wood stove (only installed last week) it’s staying around 40%. Later down the road I plan to put vapor barrier on top of the slab, add R15-R20 XPS and then pour 2-3″ of cement with embedded PEX.
Presently the exterior is stone clad from slightly below grade right to the bottom of the roof deck. I have pretty bad ice dams already and am in the process of removing the top course of stone. I plan on completely removing the stone.
Sorry for the long post, I just wanted to try and cover all the details. Thanks for any comments.
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