I am renovating my basement and the walls right now are 2 X 4 walls. I want
to insulate the walls and was told to use R20 which is 6 inches thick I
believe. Now I do have the room for the insulation and the foundation wall.
Here is my problem. I don't know if I should go with the 6 inch stuff or
the less thicker stuff. The 6 inch stuffis barely touching the concrete
wall. The foundation is dry and doesn;t leak. I was told that I need a
few inches between the insulation and the concrete wall for maximum
efficiency of th einsulation. Any comments??!!??

The description is confusing, where did the extra 2" of room come from
? Insulation IMO should be installed in such a way that it is not
compressed at all; I don't see the need for the "extra few inches" gap.

wrote:
The description is confusing, where did the extra 2" of room come from

I think he means he built his 2X4 wall about 2 1/2 inches away from the
basement wall. Thats where he got the 6 inches from.
I do not think the extra gap makes a difference. Unless you have severe
dampness on your basement walls, if you can get 6 inches of insulation
in there without compressing it, then do it. I

Any basement even visably dry may be to wet to close up resulting in
mold, get a moisture meter and test your walls after big rains. If dry
you don`t want an air gap, I used 2" R 7.2" foamboard for R 14.4. on
basement walls, much thinner than fiberglass, On damp areas it is all
designed for easy removal and future repairs. Another consideration for
foam is pipes brake , basements flood.

The description is confusing, where did the extra 2" of room come from
? Insulation IMO should be installed in such a way that it is not
compressed at all; I don't see the need for the "extra few inches" gap.


Is your "IMO" anything other than a wild-assed guess, though?

(A)What's the R-factor for 6" fiberglass in a 2x6 studwall?
(B)What's the R-factor for 6" fiberglass stuffed into a 2x4 studwall?
(C)What's the R-factor for 4" fiberglass in a 2x4 studwall?

I suspect that you will find that ABC.

In any case, OP would be better off spraying in
Urethane foam. and not using fiberglass at all.

Note to OP: If you're really sure that you won't
get any groundwater wicking through the foundation wall,
then you shouldn't need the airspace, but you should
be really anal about the vapor barrier on the inside
surface of the wall. If you're NOT sure, then I
strongly recommend a closed-cell foam product against
the wall.