Photo of home insulation with a graphic of a cockroach in the middle of the general prohibition symbol of a red circle with a slash through it. There are a few types of insulation to prevent bugs.

The sight of a bug crawling up your living room wall gives you the heebie-jeebies. You’ve been noticing more bugs in your home lately, and you want them out. Did you know that your home’s insulation could also be a safeguard against bugs, depending on the type? It’s true! So, what’s the best type of insulation to prevent bugs and pests?

These types of insulation will stop bugs and pests in their tracks:

  • Cellulose
  • Spray foam
  • Polyurethane foam

In today’s article, we’ll talk further about the above insulation types and how they ward off pests. We’ll also delve into more pest-prevention measures you can take to keep your home virtually bug-free!

Tired Of Pests? Try These 3 Types of Insulation To Prevent Bugs & More

Cellulose Insulation

At the top of the list is cellulose insulation. Cellulose insulation is primarily composed of recycled plant materials, up to 80 percent, including post-consumer paper.

What’s the other 20 percent of cellulose insulation? Sometimes it’s acrylic binders, but more than likely, it’s a series of chemicals used to make the insulation fire-retardant. One of these chemicals is the reason why cellulose is regarded as the best type of insulation to use if you have insects and critters around the house.

That chemical is boric acid. Also known as hydrogen borate, boric acid serves all sorts of purposes. It can absorb neutrons, increase flame retardancy, and be used as an insecticide and antiseptic.

Boric acid gets added to cellulose insulation for its fire-retardant purposes. That the acid is also an insecticide is just a bonus. (Since boric acid is regarded as a weaker acid, its inclusion in cellulose insulation is not a health concern for you.)

It’s only the critters and insects that try to get into your home through your basement or attic that need to worry.

Once an insect consumes boric acid, it goes straight to its stomach. The bug’s nervous system usually feels the effects of the acid first, then death follows not too long after.

The inclusion of boric acid is not the only way that cellulose prevents pests. Sprayed cellulose can also block up damaged seals and other openings that small critters and insects use to slip into your home.

If a small animal decided to try to chew its way through the cellulose insulation, the borax in the cellulose would be able to kill them as well. Just FYI, though, that’s not necessarily the case for larger animals.

Spray Foam Insulation

If you read our post on spray foam versus cellulose insulation, you should recall that spray foam is made of isocyanate and polyol resin. The former helps for bonding and can make spray foam rigid.

A man in protective gear spraying spray foam insulation to prevent bugs on the underside of an attic ceiling.
Spray foam creates a tight seal against pests.

Let’s provide a recap on the difference between open and closed-cell spray foam insulation.

Open-cell spray foam is a malleable foam that’s softer. It will conform to the shape of the area it’s being sprayed in, which makes it a great choice for very tight and narrow corners as well as odd-shaped parts of an attic or basement.

Closed-cell spray foam is more rigid; this is due to its lack of moisture. Although closed-cell spray foam is durable, you can’t use it the same way you do open-cell spray foam, since it dries hard.

In the same way that sprayed cellulose insulation can close the gaps around your windows, doors, and other openings that let bugs in, that’s also true of spray foam.

Critters are often attracted to fiberglass insulation, but not so much to spray foam. Thus, once a bug or small animal realizes that it can’t get past the insulation barrier, the critter will usually give up.

Even if they don’t, closed-cell spray foam is rigid enough that it wouldn’t be easy for a hungry rodent to eat its way through.

Polyurethane Foam Insulation

The third type of insulation that could prevent bugs and pests is polyurethane foam. Polyurethane is a polymer linked by urethane or carbamate. It comes in different chemical varieties so you can buy polyurethane in fibrous form, as an adhesive, as a coating or varnish, or as a foam.

Like spray foam, polyurethane foam is available in both flexible and rigid foam varieties. You can use it in much the same way as you do spray foam.

Another way that polyurethane foam is like spray foam insulation is that it’s not an appealing type of insulation for pests. It’s not that the critters often eat insulation (although they will), but most of the time, they use it for their nests.

Since rigid polyurethane foam retains its shape and isn’t plush, it’s not a viable option for nest-building. Spraying polyurethane foam will also fill in gaps and openings, much like the other types of insulation materials we’ve discussed.

Polyurethane foam is very flexible and will leave almost no space for even a small bug to get into. As polyurethane insulation dries, it doesn’t shrink, so you don’t have to worry about bugs or critters making their homes here or starting a nest.

What Pests Does Insulation Protect Against?

If you decide to upgrade your home insulation to prevent bugs, which pests will you be helping to keep out? That all depends on which creatures are native to your area, but here are some insect and animal species that the above forms of insulation could prevent from invading your home.


Whether it’s the smoky brown cockroach, the Madagascar hissing cockroach, or the American cockroach, you don’t want any of them in your home. Cockroaches, if they spread enough, can cause asthma attacks and trigger allergies.

A cockroach infestation usually requires you to call an exterminator, which can be costly and inconvenient. If the insulation in your home can deter cockroaches from getting in, that’s a big plus!

Closeup photo of a brown cockroach on a gray concrete surface. If you use insulation to prevent bugs, cockroaches are one pest you can keep out of your house.
Grab a shoe!


Did you know there are around 2,500 different flea species? Although none can fly, they are great at jumping, especially from animal to animal. Fleas can leave your dog in agony, but they can affect us people just as badly.

Fleas can also transmit diseases, one of which is cat scratch disease from the Bartonella bacteria. This can’t affect your canine companions, but it can your feline friends. Fleas can even cause typhus and plague, so they should be treated seriously.

Foam insulation creates a tight enough barrier that even teeny-tiny insects such as fleas shouldn’t be able to get through.   


What kinds of ants do you have in your home? There are up to 10,000 ant species that could be the culprit, including carpenter ants, banded sugar ants, yellow crazy ants, pharaoh ants, and fire ants.

If you’ve ever battled ants in your kitchen, you know they are a force to be reckoned with.

But just like fleas can’t get into your attic or basement with insulation, ants should be unable to as well.


Every summer, it seems inevitable that you’ll end up covered in big, red, itchy mosquito bites. You should take this flying pest seriously. As it sucks your blood, a mosquito could pass along diseases such as malaria, dengue, Chikungunya virus, West Nile virus, and the zika virus.

Separate yourself from mosquitos with new insulation in your attic or basement. The bugs might be able to watch you through the window, but they can’t get through rigid foam insulation! Not quite ready to install new insulation? Here are some other ways to keep mosquitoes out of your house.

Mice & Rats

It’s a homeowner’s worst nightmare: seeing a mouse–or­ even worse, a rat–skittering across your living room or kitchen floor. Rat bites can lead to infections such as rat-bite fever. Even touching an infected rat can cause this condition. You’re also at risk of rabies.

Insulation might be able to keep mice, rats, and other small critters where they belong, which is outside!

More Tips For Keeping Critters Out Of Your Home

When you want to upgrade the insulation in your basement or attic, choose spray foam, polyurethane foam, or cellulose. These are the best types of insulation to prevent bugs, but they also do a great job making your home more energy-efficient as well.

But you can do more than re-insulate your home to safeguard your family from bugs and pests. Try these other measures today.

Keep Your Home Clean

A clean home truly is a happy home. When you tidy up dust, debris, food scraps, and the like, you’re providing fewer potential attractants to bugs and critters. Combine these efforts with your new insulation, and you’ll have far fewer creepie-crawlies around.

Photo of a woman wearing headphones and singing while vacuuming a living room.
Put on some music and your house will be clean and pest-free in no time!

Treat Interior Gaps

Your basement and attic are sealed for openings, but what about the rest of your home? With a caulk gun, check for any openings that allow bugs and even small animals in. You might also want to upgrade damaged or old seals and weatherstripping.

Upgrade To Eco-Friendly Windows & Doors

The gaps around your home’s windows and doors provide a perfect point of entry for pests. If the seals have deteriorated, you’re better off upgrading your windows and doors. That’s especially something worth doing if it’s been more than 20 years since your last replacement.

Today’s windows and doors are greener than ever. Energy-efficient windows with Energy Star certification prevent fluctuations in heat gain and heat loss. They feature low-emissivity or Low-E glass that can prevent 90 percent of the sun’s rays from entering your home.

The better temperature control makes it easier for your home to retain heat during the colder months of the year and stay cool when it’s hotter.


If your home has pests, the three best types of insulation you can choose are cellulose, spray foam, and polyurethane foam. Whether it’s through blocking gaps that pests use for entry or killing bugs with the inclusion of borax, these insulation materials are energy-efficient and practically bug-proof too!

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