vapor barrier?

[Fred Perreault]

I am framing and finishing the basement in my house. The poured concrete walls and the basement in general is quite dry, no leaks, dampness or other issues. As a precaution I used Drylock sealer on the concrete walls. When I frame up the walls along the perimeter I want to insulate with fiberglass batts. Should I use unfaced insulation to let the walls breathe rather than Kraft faced insulation? I am concerned that there may be a possibility of condensation forming and having it develop at the bottom of the walls. Also I was wondering if putting insulation in the form of batts between the floor joists along the perimeter of the sills at the top of the foundation would reduce drafts and such? Foam would probably be better and tighter, but I am on a budget :-) Thanks for any suggestions........

[Lee Schierer]

Two things. First be sure you put poly under the boards that touch the basement floor to stop moisture absorption. I would also recommend that any wood in contact with the floor be treated lumber.

If you are wanting insulation, why not spray foam the walls instead of using fiberglass insulation. Closed cell foam would have less moisture issues.

[Fred Perreault]

Thanks Lee, I did use PT on ther floor to support the framed walls, but i just don't have the budget for closed cell foam even though I am aware that it would be the best choice.

[Shawn Pixley]

I am favorable towards over-insulation. I would not insulate only the walls, but the rim joists and probably the joists of the first floor. Not knowing the precise construction of the basement, I would use a vapor barrier on the hot side. Drywall finish in the basement?

[Jim Becker]

Yes, I would use a vapor barrier on the conditioned side of the wall for sure.

[roger wiegand]

check out the green building advisor forums. Current wisdom suggests that fibreglass batts and blown cellulose are always a bad idea below grade (this is consistent with my experience). Vapor barriers are the subject of endless debate and discussion. Poly on the inside with a damp concrete wall outside is seen as a recipe for a wall full of water.

Spray foam on the outside or XPS or spray foam on the inside without additional vapor barrier is the most widely accepted solution. Our basement has spray foam on the outside, XPS on the inside then a framed 2x4 wall. So far it keeps things warm and comfortable with no evidence of moisture issues.

[Chris Padilla]

Fred,

Look into using "Foam It Green" and see what you think. This is a DIY spray foam kit. I used it for a bathroom remodel and found it very easy to use and I was very happy with the results. For smallish areas, I think it is very affordable. Heck, it might work into your budget for a large area, too!

[Ole Anderson]

As the OP stated, the walls have no moisture problems, not all basement walls do. I insulated mine 40 years ago with kraft faced fiberglass with no problems. We have sandy/gravely soils with the water table 10 feet below the floor. Some walls, including those on the open walkout side have drywall, others have OSB (shop area), a couple in the shop remain bare concrete where I can't loose 4 inches of floor space. Just use a can of foam to seal any cracks at the rim joists, and then cover with fiberglass.

[Fred Perreault]

Thanks all. I used Drylok on all the concrete walls, and spray foamed the sill box/plates with 3" of closed cell foam. Then I framed the walls and used Knauf Eco Batts unfaced. It is a dry walkout basement, with typical sandy soil backfill. I expect that with no moisture entering from the foundation walls, that I would not use a vapor barrier towards the heated side so that there would be no trapped moisture and the walls could breathe. I did this similarly to my last home 30 years ago, and never saw any sweating or moisture problems. I will keep my fingers crossed. :-) The ceiling to the first floor is open and uninsulated, so after all the wiring and plumbing is completed I expect to insulate the ceiling as well.