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Crawl Space Vent Covers: Good Or Bad Idea?

Crawl Space Vent Covers_ Good Or Bad Idea
Crawl Space Vent Covers_ Good Or Bad Idea
If you’re considering installing crawl space vent covers and wondering if they are a good or bad idea, this is the article for you. Crawl spaces should be dry and free of moisture, rodents, and bugs. By the end of this blog, you’ll learn what to do about your vents and some professional crawl space waterproofing methods.

Are Crawl Space Vent Covers A Bad Idea?

No. Crawl space vent covers are not a bad idea. Vents cause more problems than they were initially intended for. Most encapsulation professionals recommend sealing any crawl space vents in your home. The only case where an open vent is acceptable is if a dehumidifier or fan is blowing outwards constantly (like an attic fan).

What’s The Purpose Of Crawl Space Vents?

Crawl space vents were initially meant to promote air circulation underneath your home. This was supposed to prevent moisture from building up in your crawl space. Unfortunately, vents are very counterintuitive. Instead of promoting clean airflow, they allow heat and frost to fill your crawl space. Hot air can rot your floorboards, beams, joists, and anything else wooden under your home. Frost can crack your pipes during the winter, leading to plumbing leaks. Overall, allowing outside air to enter your crawl space is a bad idea. Here are more downsides to crawl space vents.
crawl space vent
  • Waste of energy – Once hot air fills the space below your home, it has nowhere else to go but up. If your air conditioning is constantly battling the increase in humidity below your home, your energy bills could soar in the hotter seasons.
  • Bad air quality – In case you didn’t know, you actually breathe the air from the floor below you. If your crawl space is humid or musty, you could start to smell and breathe in strange odors or mold.
crawl space vent covers graphic

Should You Close Crawl Space Vents?

Most professionals recommend closing any crawl space vents with covers. Each city has different building codes, but experts always recommend closing any open crawl space vents. If you’re unsure if your crawl space is affected by outside moisture, here are a few notable signs.

  • Musty odors – Once your crawl space starts to smell, odors can rise into the rest of your home, making your living space feel damp and musty.
  • Condensation – Look for any condensation on your crawl space walls, floors, beams, and pipes.
  • Mold – Standing water can lead to mold growth and health issues.
  • Rodents or insects – Raccoons, mice, rats, and other small creatures love to make dark and damp environments their home.
  • Efflorescence – When water seeps into your crawl space walls, it can leave behind a white, powdery substance called efflorescence. This is a good indication your crawl space has moisture problems.
  • Rust on pipes, wiring, or ductwork – The plumbing, wiring, and ductwork underneath your home shouldn’t be exposed to any moisture or frost.
  • Rotten wood – Wood rot can grow on the wooden beams and joists beneath your home if they’re exposed to moisture. This can lead to serious structural issues.

If Your Crawl Space Has Moisture

If sealing your crawl space vents doesn’t solve your moisture problem, experts have a few other solutions.
  • Crawl space encapsulation – Encapsulation involves sealing your crawl space walls and floors with a thin layer of impermeable polyethylene sheeting. This 10 to 20 mil thick barrier keeps moisture from seeping through your walls and prevents your crawl space from becoming too humid. Many studies have shown that an encapsulated or sealed crawl space creates a healthier and more energy-efficient home.
  • Drain tile system with a sump pump – If groundwater is building up around your crawl space, experts recommend installing a drain tile system and a sump pump. If water seeps through your crawl space walls, the vapor barrier will catch the moisture, allowing it to drop down into a perforated pipe at the base of your walls. This pipe (the drain tile) will channel any collected water to a sump pit where it will build up. Once the water reaches a certain level inside the sump pit, the sump pump activates and ejects the water away from your home. This waterproofing system is one of the most effective solutions on the market.
  • Dehumidifier – A dehumidifier is perfect for circulating clean and dry air inside your encapsulated crawl space. Experts will choose the most optimum position so that it can keep humidity levels down in your entire crawl space. Note: If you decide not to close your crawl space vents, a dehumidifier will have a harder time filtering intruding outside air.
sump pump in crawl space

Who Can Help With Your Crawl Space Issues?

If you have a crawl space underneath your Chicago home, call The Real Seal. We’ll come out and inspect it for any signs of moisture or structural damage. Our crawl space experts will find a solution that works for you, providing you with a clean, dry, and energy-efficient foundation. Reach out to us today for your free inspection and quote.


Austin Werner

Austin Werner is the Owner of The Real Seal LLC, a basement waterproofing and foundation repair company. Austin believes that having a highly trained and happy team is the key to success. This is reflected through hundreds of 5 star customer reviews his company has received online.

2 Responses

  1. Live in North Carolina, and I have foundation vents that closes automatically in the winter months. I guess that’s what they are called. The home was built 19th years ago and for the pass year or two several of them doesn’t close. I don’t see anywhere that batteries or needed so can you give me any info on why no closing.

    1. Hi Adel,

      You’re halfway there! You should replace all of them with permanently closed vent covers. Unless you have a fan/dehumidifier hooked up and blowing out, there is no reason to have static open vents in the crawl space. You actually end up getting more moist air in the crawl that leads to all the problems in the summer months. Close them up permanently and you’re good!

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