How To Insulate Floor Joists In Basement

Use a box cutter to cut the insulation to length.

How to insulate floor joists in basement.

Properly insulating and air sealing rim joists band joists takes patience so most builders simply stuff in some fiberglass and walk away. Joist bays the open spaces between floor joists are prime hosts for insulation under specific circumstances. Once the ceiling is buttoned up insulate the rim joist the floor framing around the perimeter of the house directly above the foundation wall. Department of energy recommends r 11 3 insulation under floors in warm climates and an r 25 6 to 8 in cold climates.

Fiberglass insulation batts or rolls are the most economical and easiest diy choice for insulating between the floor joist in a crawl space. Also insulate 4a any portion of the floor in a room that is cantilevered beyond the exterior wall below. When the basement or crawl space has vents installed insulating joist bays. 4b slab floors built directly on the ground.

The insulation should extend all the way down to the basement floor or at least to below the frost line the depth to which the ground freezes in winter. If you need to insulate these rim joists it s best to hire a cellulose insulation contractor. Rigid foam is affordable. 4c as an alternative to floor insulation foundation walls of unvented crawl spaces.

Here s how to insulate under a floor. 4d extend insulation into joist space to reduce air flows. When insulating basement walls don t forget the band joist the piece of wood at the top of the wall that extends around the perimeter and encloses the ends of the floor joists. If you have an unfinished basement you can properly insulate the rim joists in two or three hours.

Cut the insulation to length using a square and sharp utility knife. Hold the batts in place by stapling their paper faced vapor retarders to the lower edges of the joists.