Any frame walls in the basement (as with a "walk-out" basement above ground level) should be insulated with fiberglass batts installed between the studs. If the insulation has a facing or vapor retarder, it should face inward (see "Exterior Wall Insulation"). For unfinished concrete walls, there are several options.

What happens if you don't insulate basement walls?

When a basement is finished but not properly insulated, warm air from inside the finished space can come into contact with the foundation walls, behind the insulation. ... Condensation in your finished basement can build up in insulation and the wood framing, and even pool on the floor behind finished walls.

How do you insulate an unfinished basement floor?

What's the Quickest, Most Effective Way to Insulate an Unfinished Basement? Having closed-cell spray foam insulation applied to the entire basement (walls, header, and floor) is the quickest, most effective way to insulate a rough stone basement like mine. I had a continuous 4-inch layer applied in a single day.