What’s the Best Insulation Knife of 2021?

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Whether you work in the industry, you want to start a career or you simply enjoy doing everything around your house yourself, choosing specialized knives over improvised alternatives is by far the best way to ensure good final results. When it comes to working with insulation, chances are most knives could help you cut through it. But if you want quick and efficient results and a straight cut, you will need a professional insulation knife – specifically designed for such operations.

Going out there to find the best insulation knife can be tricky. If you go to local shops, some sellers may not even know what they are. As for shopping online, you will find lots of different options. Generally speaking, those knives seem quite similar, but quality standards make the difference in efficiency and durability. Apart from knowing what to look for, it also pays off going for a product with great ratings and reviews. So, what kind of options do you have?

About Insulation Knives

DA71000 KLENK TOOLS Dual Duct / Insulation Knife - Rosewood HandleWhile this is not a general rule, many insulation knives look like survival knives. They come with a relatively long blade. Some of them have serrations, while others come with straight blades. There are also options with two edges – one of them has serrations, while the other one is smooth. Most of them are particularly designed to cut through mineral wool and other specific types of insulation.

You can, however, cut through insulation without an actual insulation cutting knife too. You can get one of your kitchen knives, make sure it is super sharp and go ahead. Insulation is not that hard, so pretty much any knife can cut through it. Then, why would you get a fiberglass insulation knife? Such knives are built for this job.

Cutting insulation with a regular job can bring in some issues. For example, you could end up splitting the insulation apart, rather than actually cutting it. This is when serrations come in handy. Then, some knives do not have the capability to cut through mineral wool. Instead, you would have to put more pressure, so you will practically crush the insulation in the attempt to cut it.

Some types of insulation can be cut with a straight blade designed for such materials. Some others require a sawing motion, so serrations are more efficient for a clean and straight cut. Other than that, different types of insulation come with different thickness standards, so this is another aspect to keep in mind when hunting the best insulation knife.

Now, what are the most appreciated insulation knives in commerce and what kind of features do they come with?

2021’s 5 Best Insulation Knives

Fuller Tool 320-0100

Fuller Tool 320-0100 Insulation Knife - Double SidedVersatile applications – Featuring Fuller’s limited lifetime warranty and being advertised to be Fuller’s best insulation knife, this product is likely to tackle all your needs. It brings in quality and it can be used for a wide plethora of applications – not just insulation. It is suitable for amateurs who like to engage in DIY projects, as well as professionals and commercial businesses dealing with insulation.

Easy to use – While many insulation knives come with specific recommendations regarding the materials they can cut through, this one is quite general. It can cut through most types of insulation with no issues at all. If you are worried about mineral wool, it will slice through it without too much pressure. There is no experience required – the knife is stable, comfortable, and easy to use.

Superior blade – The blade is less likely to let you down. It measures 11 inches, so you can cut through thick modern insulation. It has tiny serrations on one edge for a clean and easy cut. On the other edge, you will find larger serrations for bigger cuts. Made of stainless steel, this blade will last without requiring maintenance. It is rust and corrosion-resistant.

Comfortable handle – A comfortable handle is mandatory when dealing with such activities, especially as they often require some effort from your side. This knife comes with a composite handle, which is nicely shaped for a comfy grip. It has a hole at the end, so you can hang it on the wall in your shed, but it also features hand guard protection to prevent accidents.


  • Different types of serrations on each side
  • Suitable for any type of insulation
  • Easy to use by both professionals and beginners
  • Comfortable composite handle
  • Super sharp blade


  • Not suitable for dishwasher cleaning, as the blade might go dull
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Everhard MK46300

Everhard X-Long Cut Insulation Knife 5Specific design – Based on the design and appearance, this product is specifically developed to cut through the insulation. It is not as versatile as other units in this segment, yet it can be used for other applications too. But overall, its simplistic design makes it pretty obvious – it will support all your insulation related cuts with no issues at all. Furthermore, it brings in excellent value for money.

Quality blade – The blade is what makes the difference. When you cut insulation, chances are you have plenty of it. Even if you only insulate your own home, there will be lots of work required. All in all, the blade measures five inches, which is usually enough for more types of insulation – even the modern thick IsoBoard styles. It is precision ground and double-beveled on all edges.

Superior materials – Everything is based on quality, from the handle to the blade. The handle is made of hard plastic and it has an unusual shape. It ensures a good grip and it will definitely last. It is double riveted. As for the blade, it is made of high carbon steel, which ensures great edge retention and can get razor sharp. It is hardened and tempered for extra flexibility.

Care and maintenance – Sharpening this knife is relatively simple, as there are no serrations. Each edge must be sharpened at the same angle. You can use a sharpener or a stone. As for cleaning and maintenance, never do it in a dishwasher. Instead, wash it manually. Since it is made of high carbon steel, it pays off oiling the blade when not in use for long periods of time.


  • Extremely sharp and great edge retention
  • Excellent value for money
  • Flexible and strong blade
  • Long enough to cut through most types of insulation
  • Durable


  • While the handle is less likely to slip, there is no handguard protection
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Klenk DA71010

DA71010 KLENK TOOLS Ergonomic Dual Duct / Insulation KnifeGreat value for money – You do not fool around with Klenk’s best insulation knife. The product looks like a survival knife. It has a solid blade, a durable design, and a good grip. It can obviously be used for other applications as well. More importantly, given its versatility, it comes with excellent value for money and will ensure many years of daily use.

Top-notch blade – The blade is what draws the attention straight away. Simply put, you get a relatively thick blade. It comes with serrations on one side. It is smooth on the other. It is made of stainless steel and it has a sharp tip. Stainless steel is rust and corrosion-resistant. Plus, it does not require any maintenance at all. The blade measures six inches in length.

Excellent handle – The handle will not let you down. First of all, it has an ergonomic shape, so each finger will go in the right place. You have a good grip, but there is also some hand guard protection to prevent injuries. Although it is not textured, it feels rough, so it is less likely to slip out of your hands, even if they get sweaty. The handle measures around five inches in length.

Extras and maintenance – You can take this knife anywhere without having to worry about injuries or accidents. You do not have to store it along with a bunch of tools and get it dull. Instead, the manufacturer also includes a reinforced nylon sheath. It can hang from your belt for easy access too. In terms of maintenance, clean it manually and never in a dishwasher, as the blade will dull.


  • Excellent blade with two edges
  • Durable stainless steel blade
  • Ergonomic and comfortable handle
  • Great value for money
  • Comes with a reinforced nylon sheath


  • Sheath feels like it will wear out quickly
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Grip-Rite Insulation Knife

Grip-Rite Stone Wool Insulation KnifeSpecialized profile – Grip-Rite’s insulation cutting knife is built to deliver. It is particularly developed like a classic saw – a big handle, lots of serrations, and a super sharp blade. While suitable for most types of insulation, it is one of the best choices for roxul stone wool insulation. Other similar knives might be able to cut it through, but definitely not that easy.

Quality blade – The blade is relatively long and ensures an easy and effortless job. It measures just over 12 inches. It is made of 420-grade stainless steel and the edge is serrated, so cutting through installation will be a piece of cake. The stainless steel construction eliminates the need for constant maintenance, as the material is both rust and corrosion-resistant.

Safe handle – If you have used a saw before, this knife comes with a similar handle. It is shaped like a triangle and it has a specific shape for your hand to grab it firmly. It is ergonomic, thick, and easy to hold. It measures just over four inches in length. Once you grip it, the knife will feel like an extension of your arm. Since it features a closed shape, your hand will never slip on the blade.

Care and maintenance – Stainless steel does not require any oiling or other treatments to prevent rust, as it is less likely to get it anyway. You can clean the knife after each use. While it is advertised to be dishwasher safe, dishwashers tend to dull blades, so it is better to clean it manually and let it dry before storing it. Sharpening a serrated edge is more difficult than sharpening a smooth edge though.


  • Simple and efficient design
  • Excellent value for money
  • No risks to cut yourself if the handle out of your hand
  • Durable stainless steel blade
  • Super sharp out of the box


  • The handle could have been a bit more comfortable
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Milwaukee 48-22-1921

Milwaukee 48-22-1921 Smooth Blade Insulation KnifeValue for money – The Milwaukee insulation knife is built with insulation in mind. It is engineered to last longer than other similar products, but also to retain its sharpness for ages. It is mostly recommended for HVAC and mechanical insulation, yet it is versatile enough to be used for other types too. Given its price, it comes with great value for money and many years of regular usage.

Excellent blade – The blade is not massive or wide. Instead, it measures about six inches in length. It is sharp, thin, and can cut through insulation like a hot knife through butter. It is made of stainless steel and will resist corrosion and rust. Furthermore, it is engineered to get super sharp and stay sharp for longer. The blade is smooth and has a pointy tip. It is sharp out of the box, so be careful when you unpack the knife.

Ergonomic handle – The handle is slightly shorter than the blade. It has an ergonomic design and an unusual shape to ensure your fingers rest comfortably. It is rounded for a good grip, while the textured shapes on it ensure it will not slip out of your hand – even if it is sweaty or wet. The handle also comes with a lanyard hole. It is rounded and allows smooth applications.

Design and maintenance – The knife features a full metal tang. It is strong and sturdy and the blade is less likely to break when putting too much pressure on it. It allows tough cuts with no issues at all. It also comes with a durable blade cover for storage and transportation. In terms of maintenance, make sure you never clean it in a dishwasher or the blade will go a bit dull.


  • High quality for the price
  • Durable blade
  • Comfortable handle
  • Full metal tang for tough cuts
  • Comes with a durable blade cover


  • The lack of serrations will make some types of insulation a bit more difficult to cut
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Frequently Asked Questions

Are serrations needed in insulation knives? 

There are many types of insulation out there and each of them comes with various specifications. As you might have noticed already, some insulation knives come with serrations, while others come with smooth blades.

Serrations are ideal for mineral wool insulation and other similar types of wool insulation. On the other hand, a straight and smooth blade is more appropriate for HVAC and mechanical insulation. Since insulation is not necessarily made of hard materials, most knives will manage to get the job done. But if you work in this industry, a specialized blade will save your time and money.

What else can I use to cut insulation?

Generally speaking, you can cut insulation with almost every sharp knife, but you may not get a professional, clean, or straight result. If this is a random fix, you could cut through thick rolls of fiberglass insulation with a utility knife and snap off blades, for example. You need a sharp edge to go through the cut insulation. You can also rely on board to compact the roll and come up with a straighter final result.

On the other hand, if you work with insulation, chances are you will require a professional insulation knife.

How can I get a straight cut on an insulation board?

Getting a straight cut on an insulation board may seem difficult with a smooth edge. At this point, a serrated edge will provide much better results. You will use the respective blade with a constant sawing motion. This is the best way to achieve a clean and precise cut.

You can also score the rigid insulation with a utility knife before snapping it over an edge, yet the result may give you rough edges.


Choosing the best insulation knife depends on a few different things. Consider the type of insulation you normally work with, as well as your future projects. There are more options out there that can dominate the market, but most of them come with specific uses. Obviously, you are likely to find a few general knives that can tackle most types of insulation.