Don’t let the fuzz trick you—cutting batts of fiberglass insulation is easy
Though you don’t physically see it in your day to day, you owe a great deal of gratitude to your insulation. Insulation works hard year-round to keep your home cool in the summer and warm in the winter.
If you’re planning to DIY your own insulation installation, you’ll first need to know how to cut insulation. Luckily, cutting batts of fiberglass insulation is one of the easiest parts of installing home insulation. Learning how to insulate an attic or another space after learning how to cut insulation may be a little more challenging.
Correctly installing insulation can be difficult. Health and safety risks are involved; therefore, we highly recommend contacting a pro to ensure the job is completed safely and correctly.
Before we cover how to cut insulation, let’s go over the safety protocols. Fiberglass—composed of, well, tiny fibers of glass—can easily irritate your skin and eyes if you come into contact with it. And that’s just the start of fiberglass dangers. You can also easily inhale fiberglass, which can cause breathing problems, and exposure to fiberglass may also pose an increased risk of cancer.
To avoid these issues when cutting fiberglass, we highly recommend suiting up with:
A long-sleeve shirt
Safety gloves
Protective eyewear
A face mask
The first step in cutting a batt of insulation actually starts with cutting something else: a 2x4. Using a circular saw (or any other saw you have on hand), cut a 2x4 roughly 12 inches longer than the width of your roll of insulation.
You’ll use this 2x4 to get a clean cut when it’s time.
Next, find a spare piece of plywood and lie it down on the ground. The plywood will protect your floor if working inside, and it will also protect the blade of your knife if working on concrete.
Then unroll a portion of the insulation on top of the plywood vase. Put the fuzzy side facedown, with the foil or vapor barrier facing toward you.
Use a tape measure to determine where you’ll want to make your cuts. Use a pencil to mark the cut line.
Then lay your 2x4 along the cutline. Press the 2x4 down as hard as you can so it flattens out the “fluffy” fiberglass beneath. Place a knee on one of the 2x4 and your non-cutting hand on the other end; this will ensure the 2x4 stays pressed down firmly against the batt.
Pro Tip: Measure out your piece of insulation to be a little larger than the space you need to fill. Fiberglass insulation is malleable, so you can use it to fill tight spots fully.
Cut the insulation along the line using your utility knife. Then repeat the process as needed for more pieces of insulation.
How much insulation you need to cut depends on the size of the space you’re insulating. Learn more about some of these spaces in our guides to:
Attic roof insulation
Dryer vent insulation
Learning how to cut insulation on your own is easy, but it doesn’t make sense to do unless you’re handling the entire insulation installation process by yourself. Installing insulation can be challenging if you’re not savvy around the house, however—it’s certainly more complicated than just cutting the batts.
If you don’t want to DIY insulation for your home, you can contact an insulation company near you. Get quotes from at least three different contractors, and ask family and friends for recommendations. You can read reviews online to help narrow down your choice when hiring someone to install insulation in your home.
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