One inch of XPS = R5. It will make a big difference in comfort. One-inch expanded foamboard (EPS) is also acceptable, though the R factor is somewhat lower, typically 3.85 per inch. Instead of Liquid Nails, use a foamboard adhesive made especially for the purpose, such as PL300.

If the adhesive doesn't do the job--because the wall is too irregular for instance--you can use concrete fasteners or furring strips. You can place the strips horizontally across a number of boards, then put the concrete fasteners through the wood and the insulation in one shot. You can then use the strips to anchor drywall later. Be sure to make them thick enough to permit the installation of further insulation and any electrical boxes you might want to mount.

By Code, any type of foamboard in an area of combustible construction is usually required to be covered by a fire resistant material.

sounds good, is my basement an area of combustibile construction.....?

I do not understand...my basement is below grade, and it is always the warmest room in the winter, and coldest in the summer...what is the need for a high R value insulation in the first place? Also, the anchoring the foam with wood is hard when you have thick boards, when you add in the wood thickness and the foam, plus the distance to get into the concrete, you will be limited on what is available.

Up to 50% of the heat loss in a tightly well-sealed home is through the basement. It's less--20%-35%-- in other homes only because there is even greater heat being lost everywhere else.

The biggest source of heat loss is the portion of the basement that is above-grade, including windows.

Concrete screws come in lengths up to 6". There are lots of ways to secure the foam. Whichever works best for you and suits how you're finishing basement is the one to use.

For instance, I just came across thisway of securing foamboard. Other methods include: gluing the foam board to the wall, then gluing the drywall to the foam; or securing slotted XPS to the wall with furring and attaching the drywall to the furring strips.

combustibile construction

If there's exposed wood, it's combustible, and typically is required to be covered by at least 1/2" drywall.

Well....our basement is pretty much a constant 60 degrees. Maybe a tad warmer or colder depending on the weather outside. It is not finished at all. The ceiling does have insulation bats (exposed) in the rafters. I am unsure if any cold air is getting into the basement and permiating upstairs. The main reason for putting up the foam would be in hopes of getting the temp up a little bit in the winter. Maybe then we'd add some heat. I'd hate to add heat now since I figure it would permiate out thru th efoundation walls....maybe I am wrong. Also, things get real dusty down there.

As far as combustible....the entire ceiling is exposed wood rafters....does this imply homes built new today must come with these rafters covered in drywall?

our basement is pretty much a constant 60 degrees

If that's without adding heat, either direct or indirect, I wouldn't bother with insulation.

As far as combustible....the entire ceiling is exposed wood rafters....does this imply homes built new today must come with these rafters covered in drywall?

worthy wrote:If there's exposed wood, it's combustible, and typically [any foam insulation]is required to be covered by at least 1/2" drywall. Note added qualification in Bold.

(I wondered if anyone would notice that! There should be an editing function here.)

If you running tight on cash, the biggest bang for your buck would be to use 2" XPS and insulate the rim joists.

yes it was without heat....usually 60 degrees. Funny the AC quotes we got to eventually repalce our 20 year old heat pump said not to bother adding duscts in the basement as it would not make a huge difference,,,now I am starting to wonder why not!

Hell I could easily paint the walls white, add a dropped ceiling, epoxy the floors and add some area rugs. I just thought in order to warm it up a bit I needed the insulation. It has been 10 - 15 degress here in Pa the last few days...unusually cold for this area....I think the basement was 57 degrees. When the temps are in the 30s it is usually 60 down there.