What are the Effects of Open Crawl Space Vents in Winter?

Leaving crawl space vents open in the winter is an invitation for moisture to harm this space.

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Winter in Columbia, SC, can be rough. Freezing temperatures and rain can take a toll on your home. Your open crawl space won’t be spared. During this time, everyone weather strips their home. Some homeowners ignore or overlook the need to close off vents and pay the ultimate price. To avoid problems, you need to close off the vents in a smart way. 

If you dally too much, you’ll be staring at costly and potentially disruptive repairs when the ice thaws. 

Before we look at how to seal off crawl space vents, it’s also important to look at the effects of open vents in your home. 

open crawl space vent problems

Crawl Space Problems in Winter 

While venting the crawl space theoretically creates an escape route for indoor moisture, a cool, open crawl space draws outside moisture in via vents. The unabated airflow will lead to these problems. 

Low energy efficiency. Leaving the crawl space vents open during winter months makes your home less energy efficient. And that’s because cold air keeps leaking in from the outside. Your heater will work extra hard and for long hours just to warm up your home. 

Frozen/burst pipes. When temperatures drop below the freezing point, water pipes in the crawl space are bound to freeze if the vents remain open. It’s a good practice to close off the vents in winter. Doing so prevents the dry, cold winter air from freezing the pipes inside the crawl space. 

Crawl space condensation. Many homes built on crawl space foundations experience condensation due to open vents and poor moisture management. 

The stack effect. Another reason you’d want to close the vents is to prevent the stack effect. This phenomenon occurs when warm, upward-moving air exits your home via the ceiling, leaving cold air from the crawl space to replace it. Leaving vents open promotes this effect, meaning cold air will continue flowing into your home. 

Toxic air. The stack effect doesn’t just make your home cold; it also brings up harmful dust, mold spores, and bacteria. All these have the potential to cause respiratory health problems. 

Rotten/bowing floor joists. With moisture building up, wooden structures like rim joists and beams will soak up some of the moisture and start decaying. This winter moisture ends up weakening your subfloor and wooden supports. 

Insect infestation. Moisture makes the crawl space an attractive nesting place for pests and vermin, including termites and other wood-destroying insects. 

Insulation damage. If your insulation is defective, evaporating moisture will collect on it and destroy it. 

Should You Seal the Crawl Space Permanently? 

This is a hotly debated question among homeowners, as many homes are built with crawl spaces instead of basements. Numerous studies show that venting perpetuates moisture problems like the ones above. If you live in a city like Columbia, SC, where the relative humidity is usually high, you would benefit more by sealing the crawl space. 

Recommended Crawl Space Sealing Solutions 

Vents on the outside of the crawl space allow air, water, and pests into your home. You can prevent these nuisances with durable vent covers. These fixtures are built to last and you won’t need to repaint the cover or worry about rotting or rusting. They’re simply installed over existing vents.  

Your crawl space needs to be airtight so outside air won’t get inside. To create an airtight area, your contractor will encapsulate the crawl space using a 20-mil plastic vapor barrier to cover the floor and masonry walls. Gaps and holes going outdoors are sealed and the crawl space doors will be weather-stripped. Once the floor and walls are sealed, insulation is applied to the perimeter walls. 

Are you ready to seal your crawl space for good and are interested in what repair solutions might be best for your home? Schedule a free crawl space inspection with Mount Valley Foundation Services’ moisture management experts and discover how you can keep the crawl space dry and healthy in winter.

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