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dekerbrian 12-30-2011 09:21 PM

Basement renovation with a partially insulated exterior
Would like some advise on how to finish my basement interior with insulation. I live in South East Michigan area.

I have 2" foam board insulation on the exterior of the poured concrete wall. The board stops approx 6" from the exterior grade. I assume it goes down to the bottom of the basement wall. I have only been in the house for 6 months, however the basement does seem to keep a consistent temperature with the rest of the house.

This leave 3' of the interior basement uninsulated at the top of the wall. I would like to finish the basement (drywall with probably steel studs), however I am unsure on how to approach interior insulation.
Options that I can think of;
1. No interior insulation
2. Foam board (2") on the upper 3' of the interior.
3. Foam board (2") on the entire interior. This option leaves me concerned that by insulated both sides of the basement wall I will be trapping moisture and giving myself a big problem in a couple years.

Only evidence of moisture was when my inspector exposed a tie rod holes. I am knocking out all of these and filling them in with cork/concrete first.

nealtw 12-31-2011 10:14 AM

Two inch foam dosn't give you much insulation. We build a 2x4 wall one inch away from the concrete, floor to ceiling. We insulate that and add vapour bearier.

dekerbrian 01-01-2012 07:23 PM

My concern about insulating in the inside also is I thought I would already have a vapor barrier outside with the 2" foam. By insulating and adding a vapor barrier on the inside, wouldn't I be creating a double vapor barrier, not allowing the walls the breathe either way?

nealtw 01-01-2012 08:25 PM

There are two reasons water travels thru concrete. High pressure on one side which should be taken care of with waterproofing and perimiter drainage. The other is moisture is drawn to warm. So if you have water on one side and heat on the other water can wick thru the concrete. Insulation on the inside will solve that problem and the interior moisture wants to be held in the structure away from the framing. Any moisture in the concrete that could still wick out thru the six inches exposed to the outside above grade.
If you have ever broke up an old sidewalk or anything you would not see alot of wet concrete because there is no reason for the water to go there.

dekerbrian 01-01-2012 09:09 PM

Appreciate the advise.

Do you paint the concrete with any type of water sealant?

How do you insulate the interior? Foam board in the framing or insulation batts? YOu then mentioned a vapor barrier, where would I apply that or would the foam board (I believe it would be XPS) be the vapor barrier?

nealtw 01-01-2012 09:53 PM

Batts to fit the framing 16" or 24" on center and 6mill poly stapled to the framing, don't forget to instulate above the wall between the joists

nealtw 01-01-2012 09:57 PM

Anywhere wood contacts concrete apply tar paper, poly or sill gasget.

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