Vented Crawl Space Best Practices for North Carolina

New home with vented crawl space

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Why should you open and close your crawl space vents?

The biggest challenge with traditionally vented crawl spaces is generally going to be moisture management. The purpose of crawl space vents is to promote drying (dehumidification) through natural ventilation. Correct positioning of the vents may vary based on climate, but a major tip for vented crawl space success is remembering when to open and close your vents.

For our North Carolina homeowners and builders, close the vents in the spring when you start using the AC and open vents in the fall when you switch the heat back on. Keep reading for more crawl space tips and tricks!

Exterior view of a closed crawl space vent

Summer: Vents Closed

During the summer, outdoor air is warm and humid. Relative humidity (RH%) means that warm air carries significantly more grains of moisture than cooler air at the same RH%. 

The crawlspace stays cooler than the outdoor air during the summer so it naturally carries less moisture. Ventilating the crawlspace with warm humid air, which is carrying more moisture than what is already in the crawlspace, is not an effective drying method. This is why you should keep your vents closed in the warm, summer months.

Exterior view of an open crawl space vent

Winter: Vents Open

As the weather cools off in the fall, there is a noticeable decrease in outdoor humidity. Open the vents in the fall when the temperature and humidity drop. This will ventilate the crawl space with cool dry air through the winter, keeping the crawl space and equipment as dry as possible. 

More Vented Crawl Space Tips and Tricks

Pro Tip 1:
Install a vapor barrier in your crawls!

A polyurethane (poly) plastic vapor barrier is installed to reduce ground moisture from entering the crawlspace. It is important that this poly remains in place and completely covers the ground throughout the year. Try to avoid storing tools or equipment in the crawlspace which may puncture or damage the poly barrier.

Pro Tip 2:
Pay attention to your vents to extend the life of your equipment!

When air conditioning equipment and ducts are located within the crawlspace, there is also significant potential for condensation because of the cold surfaces. The buildup of condensation (water) in the crawlspace can shorten the life of equipment, and extended wetting of building materials can promote unwanted growth of mildew and mold.

Pro Tip 3:
Be careful what you store in a vented crawl space!

It is also advisable not to use your crawlspace for the storage of any potentially hazardous or noxious chemicals such as paint or gasoline. Even in a well-air sealed house, there is often connectivity between the air in the home and the crawlspace. Don’t store any chemicals in the crawlspace that you would not store inside of your home. 

Not sure about your crawl space strategy?

Controlling moisture in your crawl space is essential for your home’s health so close up those vents in the spring and open them up in the fall to take advantage of that natural ventilation. 

If you have other questions about your crawl space or building strategy, don’t hesitate to reach out! Schedule a meeting with one of our building science specialists or fill out the form below to get started.

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