To cut thick batts or rolls of fiberglass insulation easily, use an extendable utility knife that has snap-off blades. Extend the blade all the way out to provide a long, sharp edge that perfect for cutting through thick insulation.

Use a board to compact the insulation and provide a straight edge for cutting. Watch this video to find out more.

Further Information

Joe Truini: One of the best ways to save energy around your house is install your own insulation. It’s a pretty easy job, too, although it does require a lot of cutting.

Typically, if they can be cuts like every three or four feet, or six or eight feet, depending on where you’re installing insulation. So, the best thing is to set up outside if you can, so you keep the dust out of the house. And to use… First you put a board down that you can cut against, and you have a straightedge that you can cut along.

Now, even with insulation—this is only R13, but it’s about four inches thick. If you use a standard utility knife, you can see the challenge, the blade’s only about an inch long. So what I prefer to use is a utility knife that has a snap off blade.

Now, the way these are designed to be used is, you extend the blade, when it becomes dull, you snap it off, and you extend another blade. But you can also extend it three or four inches. What you end up with is this beautiful insulation cutting weapon that will slice through the thickest insulation.

So, just roll it out, get the length you need. And then, what I like to do is kneel on the board to compress it. Then with the long blade, you can very easily slice right through it.

There you go, through the insulation and paper. Now, if I can just get someone to help install it.

Editorial Contributors
Joe Truini

Joe Truini

Radio Show Co-Host

Joe Truini is a contractor, author, and the host of “Simple Solutions” on Today’s Homeowner TV and the weekly Today’s Homeowner radio show. He has worked on both large commercial projects and residential remodeling, and has written for national publications such as This Old House and Popular Mechanics. He has also written eight books, including three best-selling shed-building books. Joe lives in Connecticut with his family and enjoys hiking, traveling, and baseball in his spare time.

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