How to Insulate a Cinder Block
- 1). Measure the cinder block walls with a tape measure to determine the total length of each side. Add up all sides' measurements and divide by two to find the width of the foam board insulation you will install. Record the number, which represents the number of sheets needed to install over the entire cinder block.
- 2). Inspect the cinder block to ensure the foundation has no cracks. Caulk around the gaps or cracks in the plumbing and pipes with silicone sealant. Fill all visible holes.
- 3). Position the first piece of foam board vertically in the first corner of the room. Place a level vertically, and adjust the foam board until it is square. Butt the second piece up to the first. Place a 1-by-3 furring strip between the two pieces. Drill in self-tapping two-inch masonry screws through the furring strip and into the cinder block to secure the insulation to the wall. Insert one screw every 8 inches up the furring strip.
- 4). Set the third piece of foam board next to the second, and place a furring strip between the two. Attach it just as you did the previous furring strip. Continue down the entire side of the wall until reaching the end. Measure and mark where you must cut the insulation.
- 5). Line up a framing square on the mark. Score along the framing square with a utility knife. Snap the insulation in two, and install it in the same manner as you did the previous pieces. Move on to the next wall, and install the insulation on the cinder block just as you installed the other pieces.
Source...