In this video, This Old House host Kevin O'Connor shows how to fill gaps and make a space cozier and energy efficient.
Steps for Installing Fiberglass Insulation
- Set an unfaced fiberglass batt into the stud bay, tight to the top plate. Press the batt into place, but don't compress it too tightly.
- Use a utility knife to trim the lower end of the batt along the bottom plate. Cut the batt a bit longer than necessary to ensure a tight friction fit between the studs.
- When you encounter an electrical box, pull apart the thickness of the batt and stuff the rear-half thickness of the insulation behind the box.
- Now cut the front-half thickness of the insulation along the top and bottom of the electrical box. Fold in the cut tab of insulation and press it lightly into the stud bay.
- If there's an air-conditioning line running vertically down a stud bay, peel the insulation batt down the middle, splitting it into two thinner batts.
- Slip one thin batt behind the air-conditioning line, and press the second thin batt over the line. Repeat the previous five steps to insulate the remaining stud bays.
- Insulate around all window frames with low-expansion aerosol foam insulation. Start applying the foam along the top of each window, then fill the spaces along the sides and bottom.
- Cut short pieces of paper-faced fiberglass insulation, called blockers, and set them between the floor joists and tight against the outside wall. Be sure the paper surface faces out into the room.
- Cover the unfaced fiberglass wall insulation with a 3-mil polyethylene vapor barrier. Staple the polyethylene to the wall framing with a hammer tacker and ¼-inch-long staples.