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Crawl Space Vents – Why Closing Them Makes More Sense

Closing your vents and sealing the crawl space with a plastic vapor barrier is the best way of keeping moisture and insects at bay.

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If there’s one debate that will last more than a lifetime, it’s whether homeowners in Minneapolis, MN, should vent their crawl spaces or seal them. Local codes have for a long time vouched for crawl space vents. The understanding was that these fixtures were instrumental in airing out the crawl space in hot and humid summer months. But are they really what they seem? Are there any downsides? 

Homeowners have always had the option to close their vents or leave them open. At least, that’s what local codes say. However, they have to meet some conditions. We encourage homeowners to shut their vents as they won’t control moisture if this area stays exposed. 

open crawl space vent problems

Are Crawl Space Vents Really Worth it? 

The short answer is no. They are not something we’d recommend to any homeowner. When the temperatures outside soar, you may be doing what everybody does, which is running your HVAC unit for a short period to cool down the interior. You innocently open your windows to air out. Warm, moisture-laden air gets in. Here’s what you may not know. The most air from the outside will condense when it sweeps past cold surfaces, a phenomenon known as condensation. 

The motive behind crawl space vents is noble. But the logic behind it is faulty. At the end of the day, venting instigates moisture and other problems — the very thing we all believed it would address. Sealing vents will help lock out moisture and improve the condition inside your crawl space. 

Why You Shouldn’t Vent the Crawl Space 

A lot of studies and tests on homes with crawl space vents indicate these fixtures are harmful. During hot and humid summer months, they encourage moisture to get in and buildup. This is the reason crawl space vents are moist or damp. 

Another thing is almost half of the indoor air in your home comes from your crawl space. If the crawl space measures 1,000 square feet, you can expect no less than 10 gallon of moisture in the peak of summer. All this air can trigger moisture problems and turn your HVAC into a workhorse. 

You may not have given this much thought. Crawl space vents can also reduce the quality of indoor air. The air from outside may be polluted by dust, mold spores, or mites. Every breath sends toxic and stuffy air down your lungs. Within no time, you will experience breathing problems. 

Where there’s water, wood will rot. Wood decay can weaken your crawl space beams and joists. Eventually, these structures won’t be able to support the load above. 

Let’s not forget the impact of moisture on your interior heating and cooling. Costs will go up as cold outside air keeps causing drafts. The cold air will create a temperature imbalance. And your heater will be constantly working to regulate your home’s condition. 

Mold will also thrive in your damp crawl space. You will also notice an influx of pests escaping the searing hot weather outside. Why? They can quench their thirst and seek refuge in the cool crawl space. 

What’s the way forward? 

Seal your crawl space vents with vent covers. There are no two ways about it. We also encourage you to encapsulate this area. We normally use a 20-mil plastic vapor barrier that goes on the walls and to the crawl space floor, leaving roughly two inches for termite inspection. 

Leaving your vents open lowers the quality of indoor air. It also encourages mold and wood rot, which can eat the wooden joists and beams. Both can lead to structural failure. From our experience, we can tell you that homes with sealed crawl space vents are much cleaner, energy-efficient, and less moldy than their non-encapsulated counterparts. Best of all, they remain relatively dry throughout the year. 

Want to seal the vents in your crawl space? Need help with dehumidification? Get in touch with Innovative Basement Authority for a free crawl space repair inspection and quote. Our friendly and knowledgeable experts will recommend the best fixes for your crawl space, including waterproofing options.

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