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engineer_ryan

Insulation in Walkout (mixed-walls)

engineer_ryan
15 years ago

So I've thoroughly digested the Building Science piece on basement insulation, and I'm almost ready to go. I'd like some feedback on one area, though.

We have a walkout basement - so the entire back wall of our basement is normal framing. The front wall in completely concrete. The builder has insulated everything in the basement with unfaced batting (where there's framing) and foil-faced rolled-fiberglass insulation that is attached to concreted and framing.

So I intend to remove the foil-faced insulation everywhere, and on concrete: glue 2" EPS to the walls, frame, insulate further with unfaced batting, then 1/2" drywall.

On the framed wall I will leave the existing batting and apply drywall to the framing.

It's the mixed walls on the sides that I'd like advice on - the foundation stair-steps down on both sides, such that there is no framing on the front side, and it steps down so that there is 50/50 framing and concrete at the midpoint, and then a completely framed wall towards the back.

Should I apply EPS only to the concrete portion of the wall, and then build the framing on top out with furring strips so it sits flush with the EPS, and then frame normally? Or use EPS top to bottom, again with furring strips to make the framed portions flush? My instinct is that it doesn't matter - the latter will just give me more insulation. I'm not sure if there's a moisture issue I'm not thinking of, though.

Sorry for the long (first) post, just trying to get my head around this one.

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