Insulation for Walkout basement

sandtkay

Hi all,

I have thoroughly searched this forum, and I still can't quite find the answer to my question, I hope you can help. Please look at the picture of my basement, and let me know how you would approach insulating it. My plan was to cover the concrete wall portion with 1" or 2" XPS, but not to go all the way to the ceiling with the XPS, as this seems very expensive and unnecessary. Then build 2x4 walls up against the XPS, but go all the way up to the ceiling with the walls. I want a flat wall from top to bottom. Then filling the walls with unfaced insulation. I know that if I were using XPS from floor to ceiling, I would not use a vapor barrier based on pervious posts. But if I am only using XPS part way up the wall to cover just the concrete portion of the wall, how should I handle the vapor barrier issue? How should I seal the concrete portion of the wall vs. the above grade portion of the wall? This home is a bit north of Salt Lake City in Utah.

Thanks!

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jklingel

Were this mine and I felt I needed additional insulation, I'd run EPS floor to ceiling and tape/goo all edges and penetrations. Forget the vapor barrier; air seal. Nail sheet rock through the EPS into the studs, and either use concrete anchors for the bottom part, or fir some 2x2's locked to the wall and screw the sheet rock to them. Or, if you have the room and desire, you could put an additional wall inside the EPS, then fill it was wires, pipes, etc, and Roxul batts if you feel you need more insulation. Give thought to trimming that window, regardless of what insulation scheme you come up with. Good luck; many ways to skin this cat.

sandtkay

Thanks for your input. I too was initially thinking of putting dry wall right up against EPS or XPS boards with no additional framing, but then I wouldn't have electrical outlets at standard heights and other issues with running pipe. So that led me to go ahead and plan to frame and build interior walls, which led me to plan on filling those walls with Roxul. But if I do that, it seems that the insulation already in the exterior walls, plus the the Roxul in the interior walls, plus full sheets of XPS from floor to ceiling was overkill and too expensive.

So unless anyone thinks its a bad idea, my plan is to use short XPS boards to cover only the concrete wall portion sealed with spray foam top and bottom, use Roxul in the walls I build, no vapor barrier, drywall, and that's it.

Windows on Wash

Sounds like a pretty good solution.

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