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Thinking of Venting the Crawl Space? Read This First!

Crawl space vents make it impossible to control moisture and create a dry, usable space under your home.

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Close to 20% of newly built homes in the U.S. have crawl space foundations. They’re cheaper to build than basements yet more functional than slabs, offering homeowners a convenient space for their wiring, plumbing, and ductwork.

Vents have been a common fixture in these spaces. Local codes even encouraged homeowners to vent their crawl space. But there’s a problem: Venting the crawl spaces opens it up to moisture, especially in humid climates. When this air gets in, it condenses on the walls, framing, and other cooler surfaces.

Some home builders and remodelers try addressing these problems by bringing in more outside air, either actively through fans or passively by creating more foundation openings. If you have vents, you seriously need to rethink your ventilation because venting doesn’t work.   

crawl space ventilation

Is Crawl Space Venting Useful?  

A ton of research across homes with vented crawl space has shown time and again, venting is a bad idea. Venting brings in moist air year-round, but mostly during summer and spring. You can’t control this air as long as the vents stay open. So after a while, you’ll start dealing with these problems:

  • Termites and crawling pests
  • Mold, bacteria, and fungi
  • Crawl space condensation 
  • Wood rot and decay 
  • Air pollution
  • Funny smells and odors

Why Sealing Vents Makes Sense

Anyone who’s had the misfortune of living in a home with a vented crawl space knows what problems moisture can cause. It really pays off to have the vents sealed and the crawl space encapsulated. Isolating the crawl space cuts off warm outside air, preventing condensation and air contamination.

We all want to live in energy-efficient homes. But with the vents open, that’s wishful thinking. The constant airflow will force you to run your heater for hours during winter months, resulting in higher utility costs. You can cut down your energy use by blocking vents and sealing the crawl space.

If temperatures drop below zero in cold weather, the crawl space pipes will freeze and burst. You can avoid leaks and flooding due to frozen pipes by sealing the vents and insulating the water supply lines down there.

Remember that the condition of your crawl space affects the comfort and the quality of air indoors. Almost half of the air you breathe comes from the crawl space. By blocking vents and isolating the crawl space, you will stop particle-filled air and moist air from becoming a nuisance.

Creepy crawlies are drawn to damp basements. And venting gives them a free pass. When these critters come in, they can tear down the insulation, chew wood, and contaminate the crawl space with their feces.  That’s not really what you want, so seal your vents.

Taming Crawl Space Moisture  

Many homeowners use groundcovers and air exchange to regulate the conditions in the crawl space. Other measures you can take to beat back moisture include:

  • Installing a crawl space dehumidifier
  • Sealing ventilation ducts and increasing air pathways 
  • Clearing water on the floor
  • Properly insulating the crawl space 
  • Adjusting the thermostat correctly 
  • Finding and sealing leaks around plumbing or electric wires
  • Sealing the crawl space door

Sealing the Crawl Space

Warm, moist air will keep causing problems in your home unless you install Crawl Space Vent Covers. These fixtures will block outside air and bolster your waterproofing efforts. Once they’re attached, they’ll form an airtight bond. Installation takes a few hours. Take it a step further and encapsulate your crawl space. This will create a large storage area. The long and short is, you can forestall crawl space problems and prevent water damage by sealing up this low-lying space in your home.


If you have a vented crawl space and would like to have the venting closed, get in touch with Indiana Foundation Service. We’ll assess the crawl space and tell you what sorts of repairs are due.

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Foundation Repair, Basement Waterproofing & Crawl Space Repair and Encapsulation, Serving Central Indiana & Indianapolis

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