Insul-Knife Insulation Knife Review
Cepco Tools' Insul-Knife is designed specifically for cutting insulation, including sheet foam and fiberglass batts
In 1989, I went to photograph a top-notch crew installing fiberglass insulation in a new addition. The foreman hadn’t shown up yet with the key to the house, and the lead installer was sitting on the curb, slowly dragging a kitchen knife back and forth across the rounded corner of the concrete edging. “This concrete curb acts like a file and can put a good edge on a knife for cutting the insulation,” he said, “but this method can sort of upset the neighbors.” If the neighbors were concerned about the kitchen knife, wait until they see the Insul-Knife.
Looking like a cross between a handsaw and a vegetable knife, the Insul-Knife is designed to cut insulation. You can saw through sheet-foam products with the knife, but its real forte is slicing fiberglass batts.
The key to a first-rate fiberglass-insulation job is eliminating air gaps, and that means tight fits with square edges. I’ve tried all the tricks: kitchen knives, utility knives, and even garden shears. None of those approaches yields crisp, square cuts as reliably as the Insul-Knife.
For best performance, you need to keep the knife sharp. I use a diamond hone to restore a razorlike edge. The manufacturer also sells a sharpener just for the Insul-Knife.