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Want to Avoid Moisture Problems? Get Crawl Space Humidity Levels Right

Keeping track of your crawl space humidity level is critical to prevent expensive structural damage.


Outdoor humidity in Kansas City is always in flux. That’s not to mention summers are typically hot and humid, while winters are cold and dry. Such fluctuations in temperature and humidity have a huge impact on the home, especially the crawl space.  

If you are grappling with moisture management issues or wondering what humidity level is right for your crawl space, you are in the right place. Here, we will look at the ideal humidity levels for the crawl space and how low is too low. We’ll finish off by examining how best to maintain optimal humidity in this low-lying area of your home. 

control crawl space humidity

Does relative humidity affect the crawl space? 

Your crawl space health depends on how much vapor is present relative to existing temperatures. At 50 degrees, the air inside the crawl space is cool, as it tends to draw its temperatures from the surroundings.  

The problem starts when moisture-laden air from the outside enters the crawl space. It will raise the humidity level and cause condensation. The higher the relative humidity the higher the risk of wood and mold infestation. Mold will grow once the humidity level goes above 60%.  

Can crawl space humidity be too low?  

While you cannot really over-dry a crawl space, you can bring down its current moisture levels. A drastic reduction will impact the health of your crawl space and can just be as dangerous to your property as high humidity.  

All buildings, whether new or old, require some level of moisture to operate effectively. Drying out your crawl space completely can lead to various issues. One of these is a drop in the wood’s moisture content, which causes wooden beams or supports to dry out. This isn’t good. Your wooden structures may start showing signs of stress due to dehydration. Gaps may form between trim joints and hardwood flooring.  

Wood shrinkage may also occur once the moisture content in the crawl space drops below 25% to 30%. Anything above this range, your wood remains dimensionally stable. For you to maintain an ideal crawl space environment, you need to maintain a relative humidity between 30% to 50%. This will preserve wood moisture yet remain below the threshold for mold growth and wood rot. 

How to maintain optimal crawl space humidity levels 

Here are three effective ways of maintaining the optimal humidity levels in your crawl space. 

Fix cracks and gaps in crawl space walls 

Start by inspecting the crawl space foundation for cracks, gaps, or openings that could be letting in moisture from the outdoors. Seal them to stop water from entering your crawl space. Plumbing leaks are also a major source of water in the crawl space, so look out for any plumbing leaks and have them repaired.  

Encapsulate the crawl space 

As long as the crawl space stays exposed or open, it will remain a hotbed for moisture and other unpleasant things. You won’t have control over what happens inside it. You can avoid such a scenario by encapsulating it. Encapsulation involves installing a 20-mil vapor barrier system over the crawl space walls and floor to keep water, moisture, and pests out.  

We normally use a thick plastic material that is tear-proof and puncture-proof. It comes with a mold-resistant additive that prevents the growth of mold and mildew. Once the vapor barrier is installed, the crawl space stays clean, dry, and free of mold and pests. 

Install a dehumidifier 

Get a self-draining dehumidifier and have it installed on the crawl space to rid the air of excess moisture. This appliance will help keep moisture levels in check. When there’s a moisture spike, it kicks in and starts drying out the air. The dehumidifier turns off automatically as soon as moisture levels go down. This feature helps you maintain steady humidity levels in the crawl space. It also makes your AC system energy efficient. 

Need help taming crawl space moisture? 

If you have a crawl space and are struggling with moisture buildup, contact the experts at Foundation Recovery Systems for a free basement waterproofing inspection and quote. Our team in Kansas City, Missouri, will help you identify the sources of moisture and recommend the best solutions to bring the moisture under control. 

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2401 SE Creekview Dr.
Ankeny, IA 50021

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211 SE State Route 150
Lee's Summit, MO 64082
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Moberly, MO 65270
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Fenton, MO 63026
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