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The Benefits of Foundation Vent Covers

October 30th, 2023 | 4 min. read

By Louis Greubel

A man using a yellow drill to install a black foundation vent cover over a foundation vent on the side of a brick house.

A hole in a home any bigger than the diameter of a nickel is going to cause problems. Animals will exploit that hole for shelter and warmth, and as they come and go, the hole can get bigger and bigger, leading to even larger animals getting in.

A foundation vent is a vulnerable spot for exactly this kind of hole and, as a result, critters often creep into a house’s crawl space through a foundation vent to wreak havoc. Foundation vent covers help to nip this issue in the bud, excluding animals from sneaking into the vent in the first place.

But how do these covers work? What are they made from? And how well do they work, anyway?

In this guide, we’ll examine those questions and more. By the time you’re finished here, you’ll understand all the animal-related issues to which a foundation vent is prone, and how putting on one of these vent covers now will save you from a lot of trouble in the long run.

What Are Foundation Vents?

A wide-open, uncovered foundation vent installed in a stucco wall on the outside of a home.

Foundation vents often come built-in with homes that have crawl spaces. These crawl spaces usually contain some of the home’s HVAC ductwork, plumbing pipes, or both for easy access in case repairs need to be made.

If left unventilated, the air in a crawl space will grow stagnant. Still air results in heating and cooling problems in the home. It also results in moisture accumulation, which in turn causes mold and mildew to grow in the crawl space and spread into the rest of the house.

Foundation vents solve these issues by allowing outside air to filter through. These vents are usually installed on opposite ends of the crawl space, letting the air pass in through one side and out through the other, promoting good circulation to keep mold at bay.

Do Foundation Vents Work?

Can foundation vents aid with air circulation? Absolutely.

But while they solve the ventilation issue, foundation vents lead to another problem: they can allow animals in. Most foundation vents come standard with a cheap, aluminum cover that doesn’t pose much of a challenge to even small critters.

Even if one curious mouse takes the time to squeeze through a cheap, stock foundation vent cover, that mouse will leave behind a big enough hole for a squirrel to fit through, which will leave enough space for a raccoon to invade, and suddenly your crawl space is host to an entire zoo.

Problems Posed by Animals in a Crawl Space

A mouse squeezing into a hole in a wooden wall that has four insulated electrical wires protruding from it

If animals do manage to get into a crawl space through a foundation vent, most homeowners don’t know about them until after they’ve been there for weeks (or even months). Critters can cause a lot of damage during that time.

Most homeowners are tipped off to the presence of an animal in a crawl space by smell — either the smell of an animal carcass or the smell of an especially potent animal like a skunk. Animals also leave feces behind, which results in its own issues, aside from the smell.

Bat droppings can lead to histoplasmosis, a fungal disease that is transmitted through the air. Waste from raccoons can contain roundworm eggs that can cause heart, eye, and brain damage in humans. Squirrel droppings can carry salmonella. If an animal gets into your home and leaves excrement behind, it could cause serious health problems.

Critters in a crawl space might track in other, smaller critters with them, too. Raccoons, opossums, squirrels, and other common wildlife nuisances can bring in fleas, lice, and ticks that will have no problem invading the rest of your home.

Finally, these invasive critters can cause structural damage. Mice or rats can chew through wires, possibly resulting in electrical fires. Animals might also claw through and nest inside of your insulation. They may even cause damage to the floor or the HVAC system, giving them access to the rest of the home.

Foundation Vent Covers

The black, gray, and white HY-GUARD EXCLUSION Foundation Vent Covers stacked on each other and displayed against a white background.

Foundation vent covers go a long way to stopping these issues before they even start by providing a sturdy barrier to exclude wildlife. There are plenty of great brands out there that make foundation vent covers, but at HY-C, we manufacture both the Foundation Vent Screen and the XL Foundation Vent Screen under our HY-GUARD EXCLUSION brand.

These covers are made from galvanized steel with 18-gauge, ⅜” mesh openings that still allow air to circulate while preventing animals from getting in. The screens come with eight pre-drilled ¼” holes around the edges, allowing them to be bolted directly onto a home over a foundation vent. They offer much stronger protection than the stock aluminum covers.

Do HY-GUARD EXCLUSION Foundation Vent Covers Fit All Houses?

These covers certainly don’t fit every house; they can’t possibly account for every size of every foundation vent. They are, however, crafted to match common foundation vent sizes. By our estimates, one of our two sizes will fit a foundation vent 90% to 95% of the time.

The original Foundation Vent Screen measures 10.5” x 18.5”, while the XL Foundation Vent Screen measures 12.25” x 19.5”. One of these two vents will fit most use cases.

What Kind of Animals Do HY-GUARD EXCLUSION Foundation Vent Covers Keep Out?

It would probably be quicker to list the kinds of animals these vent covers can’t exclude; it would be virtually impossible for an adult human to rip one off, let alone a small critter. They’re capable of excluding common small and medium animals from homes, including:

  • Snakes
  • Squirrels
  • Bats
  • Raccoons
  • Opossums
  • Mice
  • Rats

Are There Any Limitations to HY-GUARD EXCLUSION Foundation Vent Covers?

While these covers are sturdy, easy to install, and effective at preventing wildlife from invading a crawl space, there are two notable caveats to them.

For one, they tend to be more expensive than similar products on the market, sometimes by more than double. When it comes to these kinds of covers, you essentially get what you pay for; if you want to spend less up front, you may or may not have to replace the cover more quickly due to damage. HY-GUARD EXCLUSION vents may cost more, but they’ll almost certainly last longer.

Another caveat is that, on their own, these vents don’t provide protection against stink bugs, bees, wasps, or other insects. The ⅜” mesh openings provide room for bugs to squeeze in. There is a simple solution, though — just attach some bug screen to your foundation vent cover when you install it.

Should You Get Foundation Vent Covers?

The last thing you want as a homeowner is an animal in your crawl space or any of the problems that come with it. Smells, feces, diseases, and structural damage are enough to keep new and veteran homeowners alike up at night.

Foundation vent covers go a long way to alleviating — or even eliminating — these problems altogether. Not all homes have foundation vents on them, but if yours does, and they’re currently uncovered, foundation vent covers may be right for you.

If you do want to cover your foundation vents, you have plenty of options available. And, if you’re interested in giving HY-GUARD EXCLUSION a try, we’ll be more than happy to help you find a store that sells our covers. We’re confident that they’re sturdy, versatile, and will keep the critters out, providing you with some long-term peace of mind.

But what about the rest of your home? There are plenty of other vulnerable spots that wildlife can squeeze into — a chimney, for instance. If you have a fireplace and want to keep it nuisance-free, our guide to keeping wildlife out of chimneys is a great place to start.

Louis Greubel

Louis earned a bachelor's degree in English with a focus in rhetoric and composition from St. Louis University in 2017. He has worked in marketing as a content writer for over 5 years. Currently, he oversees the HY-C Learning Center, helping HY-C subject matter experts to share their decades of home solution products experience with homeowners and sales partners across the country.