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Crawl Space Vents: Open vs. Closed?

open crawl space vent allowing moisture inside

When it comes to crawl space vents open or closed, the right answer is very clear. Your crawl space vents should always be closed and sealed off from the outside elements.

Venting your crawl space leads to a variety of issues. First and foremost, open vents allow moisture to enter your crawl space. This creates the perfect environment for mold growth and mildew. Furthermore, unsealed vents could lead to wet insulation, wood rot, and higher electricity bills at the end of the month.

Reasons to Keep Your Vents Closed

1. The Stack Effect

Why do open crawl space vents spell trouble for you entire home?

Air is typically cooler in your crawl space than it is outside. Once the outside air enters your crawl space and combines with the cooler air, humidity is created. As you can see, combining the two creates moisture problems, which is your crawl space’s greatest foe.

To make matters worse, the warm air that enters your crawl space will rise into the living areas of your home, dragging anything light enough to travel with it. This includes mold spores, dust mites, and the humidity already wreaking havoc in your crawl space. This process is known as the stack effect, and it’s a continuous cycle that will cause various problems for your home and family.

illustration demonstrating the stack effect

2. Utility Bills

woman turning up thermostat

Open crawl space vents invite outside air and its accompanying moisture into your home, directly impacting your energy consumption and bills. This moisture increases the humidity level in your crawl space, leading your heating, ventilation, and air conditioning (HVAC) system to exert more effort to maintain a comfortable climate.

The extra work is due to the energy-intensive process of cooling or heating humid air, which is more challenging than conditioning dry air. In summer, the air conditioning must cool and dehumidify the air, requiring more energy. In winter, heating moist air also demands more energy to achieve the same level of warmth, leading to increased utility costs.

Sealing off crawl space vents prevents this influx of moist air, helping to stabilize the crawl space environment and reduce the strain on your HVAC system.

3. Mold Growth

Mold thrives in moist and damp environments, making an open crawl space a perfect breeding ground. When vents are left open, they introduce exterior air, raising the humidity levels inside the crawl space.

This increased humidity is the key factor in mold proliferation. Mold is not only a structural concern but also poses serious health risks. It can trigger allergic reactions, asthma attacks, and other respiratory issues. By keeping crawl space vents closed, you significantly reduce the moisture that molds require to grow, thus safeguarding your home’s structural integrity and the health of its inhabitants.

mold growth on crawl space beam

4. Wet Insulation

wet insulation inside damage crawl space

Insulation in your crawl space plays a crucial role in maintaining your home’s energy efficiency. However, when crawl space vents are open, moisture can infiltrate and saturate the insulation, diminishing its effectiveness.

Wet insulation loses its thermal resistance, meaning your heating and cooling systems have to work harder to maintain comfortable temperatures. This not only leads to increased energy bills but can also cause the insulation material to deteriorate over time. Keeping vents closed prevents moisture entry, ensuring your insulation remains dry and effective in preserving energy.

5. Wood Rot

Wood rot is a fungal decay that occurs in timber that has been exposed to moisture for extended periods. Open crawl space vents allow moist air to enter, which can be absorbed by the wood structures of your home. This creates an ideal environment for wood rot fungi to thrive, which can compromise the structural integrity of your home.

Wood rot can be difficult to detect in its early stages, and by the time it’s noticed, significant damage may have already occurred. Sealing off crawl space vents helps keep the wood in your crawl space dry, protecting it from rot and extending the lifespan of your home’s foundation and structural elements.

pencil piercing dry rot wood

Secure Your Home’s Foundation and Energy Efficiency

Interested in reducing your home’s energy use by 15%? According to a study by Advanced Energy, homes with closed crawl spaces have used an average of 15% less energy for space conditioning. Imagine the savings and the enhanced comfort in your home. JES offers a comprehensive solution to your crawl space moisture problems, including encapsulation and vent sealing.

Take Action Today with JES

Groundworks certified field inspector greeting homeowner

Don’t let the crawl space vents debate keep you from protecting your home. Contact JES to schedule your free, no-obligation inspection today! Our experts are ready to work with you to ensure your crawl space is properly sealed, contributing to a healthier, more energy-efficient home. Let’s put an end to your crawl space concerns once and for all.

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