Cutting fiberglass insulation is a messy and potentially dangerous job, but a necessary one for many tradespeople and homeowners. Fiberglass batts—one of the most popular types of insulation—is best used for flat surfaces, such as walls, floors, and ceilings. Because this style comes in a continuous roll, it must be cut into sections and often trimmed around the contours of wall outlets and other obstacles. This cutting is done by hand.

It pays to find the safest way to cut these batts. But how? Cut fiberglass insulation with a safer knife, of course (this is a Slice® post, after all). We’ll get to that, but first let’s look at all the risks associated with this activity and how to mitigate them.

Why Cutting Fiberglass Is Hazardous

As the name of the material implies, fiberglass insulation contains thin glass fibers. Because the glass pieces are so small, you can’t see them easily. They can go airborne and easily work their into skin and other tissues. And like any small bits of glass, if they get in your skin, eyes, throat, or lungs, you’re going to experience irritation and pain.

There’s also the fact that cutting any material involves potential lacerations, mostly to your hands. To insulate a structure, you’re going to do a lot of cutting. Like any job you do repetitively, especially in a workplace setting, you run the risk of overuse fatigue or injury.

Given these hazards, there are five primary points of protection to consider when you’re deciding how to cut fiberglass insulation rolls safely.

  • Hands
  • Skin
  • Throat and lungs
  • Eyes
  • Muscles

Let’s take a closer look at how to protect each of these five vulnerable areas while cutting fiberglass insulation. Techniques to protect yourself (or your workers) vary, and it’s important to use them all.

Protect Your Hands

Let’s look at the risky business of using cutting tools. The greatest concern here is accidentally cutting yourself, and your hands are most at risk.

Whether you’re working alone or you’re an OHS professional in charge of worker safety, it pays to find the safest knife for cutting insulation batts. We recommend the Slice long-blade industrial knives. The 4-inch blade extends to a maximum cutting depth of 3 inches, so it easily cuts through thick, soft materials like insulation. We offer the 10559 Manual Industrial Knife and the 10560 Auto-Retractable Industrial Knife.

Unlike overly sharp metal blades, Slice industrial blades have a patent-pending finger-friendly® edge design and are safe enough for you to touch. This greatly reduces the risk of lacerations.

You also won’t have to change the blade often like you would with a metal blade. Abrasive materials like fiberglass insulation are notorious for dulling standard blades quickly. Slice blades last up to 11 times longer than their metal counterparts.

Like all Slice tools, the industrial knives work for lefties and righties. Just flip the orientation of the blade’s cutting edge to change the handedness. These tools ship with a rounded-tip blade, as these work for most applications and are our safest blade design. Optional pointed-tip replacement blades are also available in the line, and will soon be joined by rounded-tip serrated blades.

The below video demonstrates how the Slice industrial knives cut through fiberglass. 

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Protect Your Skin

A very common complaint resulting from cutting insulation batts is itchiness. This happens when those pesky bits of glass getting stuck in your skin. Always wear gloves, a hat, long sleeves, and long pants. Some even suggest wearing disposable coveralls because it’s tough to get glass fiber out of clothing.

Wherever your skin is exposed, or any place where a gap could form—like at your waistline or where your gloves and shirt sleeves meet—apply baby power. This will help prevent the fibers from sticking to your skin.

This goofy but very useful video covers the best ways to prevent skin irritation from handling fiberglass insulation. 

Protect Your Lungs

When you’re cutting insulation batts, there’s a high likelihood you’ll inhale small bits of airborne glass and other insulation dust if you don’t wear protection. This can cause discomfort and unpleasant irritation in your nose, throat, and lungs. Inhaling these irritants can exacerbate breathing difficulties like asthma and bronchitis; those so affected should be particularly careful.

To help keep your airways free and clear, always wear a disposable dust mask or respirator. No exceptions.

Protect Your Eyes

Eye protection is paramount when cutting insulation batts, for two primary reasons. First, whenever you use cutting tools, you should wear safety glasses. Second, airborne glass pieces and dust can get in your eyes when you’re cutting fiberglass insulation. Do you want glass shards in your eye? Does your company want to deal with the resulting worker’s comp claims from this kind of injury? I didn’t think so. Wear eye protection, and mandate safety glasses for any workers under your jurisdiction.

Protect Your Muscles

Insulating a space requires you to cut a lot of material. When cutting fiberglass insulation, techniques can vary—you can cut on the ground or on a table, for instance—but however you do it, make sure your set-up is ergonomic. This means that the cutting motion should feel natural. You, or your workers, should not have to move in any way that is awkward or uncomfortable.

The same applies to your cutting tool: it should feel like an extension of your hand. All Slice tools are ergonomically designed, so we have you covered there.

Enjoy the Wonders of Fiberglass

Fiberglass insulation is a fantastic material. It helps keep your spaces warm in winter and cool in summer. Additionally, it’s great for dampening sound and, to top it all off, fiberglass insulation is fire-safe.

While handling this material can have long-lasting negative effects, some simple planning can negate those risks. Follow the tips here to make cutting fiberglass insulation safer for everyone.


Originally, this post stated to “keep in mind that workers who deal with fiberglass every day are at risk for more serious cumulative effects from breathing in particles over time.”

Slice was contacted by the North American Insulation Manufacturers Association (NAIMA), and the organization wrote, “Insulation glass fibers are not durable and do not pose the risk . . . that there could be ‘serious cumulative effects.’” The organization further specified that “established work practices recommend the use of a dust mask (N95 respirator) to protect against exposure to fibers when the PEL would likely be exceeded [a voluntary Permissible Exposure Limit, PEL, of 1 fiber per cc is in effect] or for the comfort of the worker. But if fibers do enter the lung, it is important to remember that these insulation fibers are biosoluble and will dissolve in the lungs.”

Slice thanks NAIMA for bringing this to our attention.