In article .com,
wrote:

I am in the process of finishing our basement. Our home is 2 years old
with poured basement walls. We have started to put up 2x4 framing
against the walls, and planned to insulate with faced R-13 fiberglass
insulation, and put up 1/2 drywall. Recently a friend suggested that
we put plastic sheeting between the framing and the concrete walls to
keep out moisture, and use unfaced insulation.

My question is, what is the best way to do this? Our basement has had
a very small amount mildew appear in the summer, in the past.

Much depends on what climate you are in. Are you in Tucson, where it
is extremely hot and dry, or in Houston, where it is extremely hot and
wet, or in Minnesota? Is the humidity in the basement is from
groundwater infiltration? Or is it from warm, moist summer air,
coming into the very cold basement, and condensing on the cold walls?

Are your walls formed and poured concrete (pretty little moisture
transmission, unless there are cracks), or concrete blocks that have
been grouted with concrete (much more)?

Please consult a local expert who knows the local situation, in
particular with groundwater issues.

I'll make just one general comment. Consider doing this: Instead of
putting a vapor barrier (like 10 mil polyethylene, a.k.a. visqueen),
between the stud wall and the concrete wall, put a 1" or so layer of
foam insulation in. Some foam products can act as a vapor barrier,
and they have excellent R-values. And you can get a completely solid
layer of foam against the wall, with no penetrations at all (no studs
in contact with potentially moist exterior wall), which improves
insulation considerable (remember, wood is R-1 per inch, so the 2x4
studs are R-3.5, which is in parallel with the R-13 of the fiber
insulation between them. Also, like this the studs don't come in
contact with the potentially moise exterior wall. But make sure the
foam insulation can handle exposure to moisture (not all can).

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Ralph Becker-Szendy