Basement Insulation

[kgc]

We built a new home 2 years ago in the eastern US mid-atlantic area. It has poured conc basement walls and geo thermal heat with very tight and well insulated duct work. The outside of the conc walls were coated (black sealant) before backfill and the joist cavities were insulated with fiberglass above the conc walls. The basement stays pretty cool in the winter (50º F). We are considering finishing some of the basement area, and would also like to insulate the unfinished parts. The heating system is adequate to handle any finished basement rooms but we will not be heating the unfinished parts. I have heard all kinds of stories about condensation, vapor barriers, etc. We have no water problems, and we painted all of the walls with "drylock" anyway. I am considering framing with 2X4's on the finished parts and using fiberglass batts with drywall. Should I use any additional treatment between the conc wall and the 2X4's? I have heard of using black roofing felt, but have also heard that you should not "trap" any potential moisture anywhere. And where I don't do any framing (the unfinished parts), are the "fiberglass blankets" a good idea? Do they have the potential to "trap" moisture also? I know there are other insulation products but I'm not sure if they're appropriate for this use (Styrofoam panels, foil covered poly rolls, etc.). I don't want to take a nice dry basement and create mold and mildew potential. Any advice?

[pushkins]

Check to see if the exterior of the basement walls are covered with a water proof membrane, if you dig down a little you should see a coating of a black substance and probably a rubber or fiber sheet all glued hard to the wall. (just the black tar doesn't always make it water proof.
Either way if you see that then you most definitely do NOT want to have any moisture barrier on the inside of the basement. So you cannot use batted insulation with paper facing, you would need batted unfaced insulation.
Styrofoam is an OK insulation, but offers much less insulation than batts or spray insulation plus it should be sealed in every stud cavity to be even remotely effective.
When building your 2x4 walls inside the basement make sure you keep them off touching the exterior walls 1" - 1 1/2" this allows air movement behind the wall.
As the interior walls should be built standing off from the basement walls you should attach strapping to the rear of the studs to ensure the installed insulation doesn't fall towards the wall and make contact with the wall.
Pressure treated lumber must be used when in any contact with concrete.

[kgc]

Thanks.... however I am still wondering what would be the best solution for insulating the walls in the areas of the basement that are NOT finished.

[pushkins]

Why would you want to insulate unfinished basement ? The finished walls of the rooms in the basement should be insulated.
The only way to insulate the unfinished part would be to build stud walls and insert the insulation into the stud cavity. Some might say glue foam panels to the basement wall but this is highly not recommended for a myriad of reasons ranging from trapped ambient moisture to wicking of moisture.
Ground temperatures at basement levels are roughly 50 F if you add in block insulation R values and ambient basement temps you sit at roughly 60 F.
The point would be if you not heating/cooling the unfinished section of the basement there really is no need to install insulation on the exterior walls.

[kgc]

Great question. The reason I was thinking of insulating the unfinished part too was to help to "warm up" the first floor. I realize that I could use batts in the unfinished parts of the basement ceiling, but there's a lot of stuff there (pipes, wires, ducts, etc.). So I'm looking at the options.

[pushkins]

The basement ceiling should have R13 bats already installed, your house is only 2 years old, this should have been done with the rest of the insulation installed during the building process. I'm surprised that it passed final inspection without it.
If you don't have insulation in the basement ceiling it would be much cheaper and far easier to install it rather than trying to insulate an unfinished basement.

[pushkins]

Dow make a Styrofoam panel for basement applications, the panels have spray foam applied to the rear and are then held in place by 2x4 treated material (also for future drywall attachment). The foam panel is held off the wall by the lines of spray foam applied to the rear. The biggest problem with "just" using this approach would be code compliance with exposed foam, for fire risk and fume inhalation code says it must be concealed behind drywall.