- 1). Cut a three inch wide piece off the foam board to go right next to the stud. Score it straight down with a utility knife and snap it off from the full sheet of foam board. Run a bead of silicone sealant on the back of the piece with a caulk gun and set the three inch strip into the wall at the first corner between the first two studs.
- 2). Press down firmly on the foam board so the strip can adhere to the wall. Repeat the process for a strip at the other end of the stud. This will help prevent moisture from building up in the foam board. Measure the length and width between the studs and cut the first piece of foam board with a utility knife.
- 3). Set the board in place between the studs and run a bead of foam at each edge along the inside of the studs to hold it in place. Set a spray foam gun at the top of the insulation and run it down to the bottom in the gap between the stud and the foam. Repeat the process for the other side of the foam board.
- 4). Cut the three inch strips of foam board for the next section between the studs and install them the same way they were previously installed. Cut the foam board to size and install it. Repeat the process of installing the foam board between the studs until the room is completely insulated.
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