Home & Garden Architecture

How to Cut Fiberglass Insulation

By Home & Garden Last updated Tuesday, June/04/2024

1). Lay the batt of fiberglass insulation to be cut out on the plywood with the foil or kraft-paper backing facing up.
2). Lay the 2-by-4 inch board along the line you desire to cut into the fiberglass. The board should be long enough that it sticks out 6 inches beyond the edges of the fiberglass batt on each side or at least 12 inches longer than the line you intend to cut.
3). Weight down the board by kneeling on one end of it, then pressing down on the other end with one hand. This compresses the fiberglass and makes it much easier to cut.
4). Use the utility knife, in your free hand, to cut through the fiberglass along the edge of the board as you continue to compress the fiberglass. You should be able to cut through it in just one stroke.