To properly install insulation, trim the batt so that it fits tightly into the wall cavity, then add a vapor retarder on the inside face of the insulation. If the batt is not faced, cover it with a breathable sheet, and tack the sheet every 12 to 24 inches.Continue Reading
Trim down the width of the batt by laying it on the floor in front of the wall cavity that you want to insulate. Line one edge up with the stud bay's inside face. Lay a 2 x4 straight line with the inside part of the stud that is next to the one you're working on, and press it down with one knee. Using a utility knife, trim the batt using several shallow cuts.
Place the insulation into its cavity tight against the stud bay's top part. Ensure that the batt is not tightly pressed on the stud; rather, let it run long, and cut it at the bottom with your utility knife.
If there are any wires, pull the batt apart in half, and slide one part behind the wire, while placing the other on the wire. If there is an electrical outlet box, install the batt, but cut out a section of it where the box is. If there are plumbing supply pipes, ensure you get the entire batt behind the pipe to keep it from freezing.
Use a vapor retarder on the inside face of the insulation if you live in a cold climate. If your batt is faced with paper or with foil, they already have a retarder built in. Cover batts that are not faced with 6-mil plastic or with a breathable sheet. Place a bead of the sealant on the top plate and on studs where sheets overlap.Learn more about Carpentry