Insulating basement walls
An insulated basement makes the space more comfortable and helps keep upper floors warmer too. Rigid foam is available in both urethane and polystyrene (plastic foam) in thicknesses from 1/2 inch to 2 inches. Urethane is more expensive but is easier to work with and is the better insulator. Both are flammable and must be covered by 1/2-inch drywall. If you like the look of wood paneling, apply it over the drywall. If you don’t want to install drywall, build a regular 2x4 stud wall and insulate with fiberglass between studs.
MATERIALS: Fiberglass insulation, 1x3 furring strips, construction adhesive, 6-mil poly, insulation stays or chicken wire, rigid insulation, tape, 3d nails, drywall, 1 -inch drywall screws, drywall tape and compound
TOOLS: Particle-resistant dust mask, utility knife, caulking gun, hammer, circular saw, straightedge, drill and screwdriver bit, level
1 BEFORE YOU INSULATE ON THE WALLS, INSULATE THE SPACES BETWEEN THE JOISTS ABOVE THE FOUNDATION. Wearing a mask and protective clothing, use a utility knife to cut fiberglass insulation to fit between the joists; pack loosely in place. Compressing insulation will reduce its ability to do its job.
2 TAPE A PLASTIC VAPOR BARRIER TO THE WALL TO KEEP OUT MOISTURE that may seep into the basement. The furring strips you will add in the next step will hold the plastic in place permanently.
3 NAIL 1x3 FURRING STRIPS BOTH HORIZONTALLY AND VERTICALLY OVER THE VAPOR BARRIER. The verticals bridge irregularities in the wall; the horizontals at the top and bottom support the edges of the drywall. Nail or screw the horizontal strips in place first then install the vertical strips on 16 inch centers just as you would regular wall studs.
4 SHIM THE VERTICAL STRIPS AS NECESSARY TO MAKE THE WALL PLUMB AND FLAT. Check the vertical grid of 1x3s with a straightedge, and shim as necessary to make sure they form a flat surface. Also use a level to make sure the furring strips are plumb. Cut the insulation panels to fit snugly between them as shown in Steps 5 and 6.
5 CUT THE PANELS TO FIT BETWEEN THE 1x3s. Make a jig to simplify the job. Begin by screwing a wide board to a narrow board. You'll guide the saw edge away from the blade along the narrow board's edge, rather than trying to follow a drawn line.
6 TO USE THE JIG, CLAMP IT IN PUCE WITH THE WIDE EDGE ON THE LAYOUT LINE. Guide the saw along the narrow edge. Once you've cut the panels, tape them in place until you put up the drywall.
7 SCREW THE DRYWALL IN PUCE, AND TAPE AND FINISH IT. If you're going to apply paneling over the drywall, leave the drywall unfinished and untaped and nail the paneling over it with 3d nails.
Insulating A Crawlspace
1 CUT INSULATION TO FIT BETWEEN THE JOISTS ABOVE THE FOUNDATION WALLS. Pack the insulation just tightly enough to prevent it from falling out.
2 INSTALL FIBERGUSS INSULATION BETWEEN FLOOR JOISTS OVER CRAWLSPACES OR UNHEATED BASEMENTS. Make sure the vapor barrier faces up, and install insulation stays (shown here] or chicken wire to hold the insulation in place.
3 CUT PIECES OF INSUUTION LONG ENOUGH TO DRAPE FROM THE MUDSILL, down the wall, and a couple of feet onto the floor. Hold in place by putting a 1x3 over it and tacking both to the mudsill, driving the nails enough to anchor the insulation while compressing it only slightly. Lay a 6-mil vapor barrier on the dirt floor, anchoring it with a few bricks.