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We're doing 4x8' wood panel sheets to serve as walls in the basement (mainly to serve as a media and kids play room). The carpenter framed/furred out with 2x4's due to the wonkiness, bowing and varying heights of walls and basement. We (the homeowners) didn't really think about insulation before starting this project which was a mistake. Based on the wall details below and the pictures provided, what are our options to insulate this space at this point?

  • The walls' height range from 80" to 86" (to ceiling joist)
  • The walls' being paneled (furred from) are exterior and made up of concrete wall on the bottom and timber framing on top and the latter sits back roughly 2 1/2" from the front of the concrete
  • The concrete portions are below ground level, their height varies from 40" to 46" throughout and they bow in most areas
  • The timber framing portions are above ground level, are uninsulated, their height varies from 37" to 43" throughout and there's shiplap boards and then cedar siding as the finish on the exterior side
  • Again to save space the carpenter framed with the 3 1/2" side of 2x4 studs facing the wall
  • Because of the bowing and wonkiness of the concrete walls, the distance between the concrete walls and the start of the framing are 0" to 1" on one wall, 3/4" to 1 3/4" on another and 3" to 4" on another. The timber portion of the walls are 7" to 8 1/4" from shiplap to the start of the framing
  • We're in Seattle, WA and the house is over 100 years old

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So I'm just an electrician, but I'd use closed cell spray foam at least on the concrete. From what I've seen it's a different type used on concrete, usually a light blue, I'm assuming for moisture, though I had thought closed cell also was already a moisture barrier. But anyway, closed cell spray foam is the most efficient (more "R" value per inch of thickness) type of insulation that I'm currently aware of. I'd even recommend spraying the upper half with closed cell, for at least the thickness of the original framing, and then either open cell or the common fiberglass Batts over that.

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Two problems need to be solved with this walls.
1 Cold from the exterior getting to the back side of the inside panel, house moisture can condense on the panel inside surface and cause mold on the living space side.
2 warm moist house air leaking in the wall and getting to cold surfaces which can cause mold in the wall.
For both the answer is a really good fitting insulation and a wall that is sealed against air leaks in or out of the living space.
Spray closed cell foam may be the best answer but expensive and things can go wrong with the mix that cause off gassing into the space.
If there is room to slide a foam board behind the studs against the concrete, I would do that and then fill the lower space with 1 1/2" foam board and tape all joints and to the studs.
I would do the top of the foundation with foam board and then I wood fill the top space with good fitting rook wool.
 

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I don’t see the problem. He maximized the living space at the expense of thinner lower walls. So buy 2 different thicknesses of roll insulation. Home depot sells r-7 insulation in rolls, its advertised as 2” thick. It will be squished a little…
 

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Make sure you waterproof the exterior at least 12“ above finish grade.
Make sure you have good ventilation.
furr out the flat stud walls by sistering a new 2x to the edge of the 2x4’s like an L the bigger the 2x the thicker the insulation use fiberglass insulation bats. Go through all this if your going to add 6 minimum 6” of insulation, smaller than that you are wasting money and you may as well pay for the higher heating and cooling costs.
good luck
 
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