What Should Humidity Be in a Crawl Space

"What should the humidity be in my crawl space?" This question comes from many homeowners across the country. Most are asking, "is it normal to have moisture in my crawl space," as well. We feel the best answer is to have the humidity between 45% and 55%. But keep in mind that temperature also affects moisture levels of the crawl space.

Humidity chart

When you mix temperature and humidity this is called the dew point. Having high temperatures and lower humidity can still cause your crawl space to be wet if the temperature is high enough. Also, having high humidity and low temperatures can create a dry crawl space. We see this in really cold areas of the country. This is where grains of moisture is helpful.

What is Grains of Moisture

Grains of moisture is a measurement used by water damage professionals to determine how much moisture is in the air. Most of us use relative humidity as a guide to determine the health of your crawl space, but there is way more to it. Grains per moisture (GPM) is the best and most accurate way to determine if your home or the air in your home is wet. Click here to learn more about What is Grains of Moisture.

Can My Crawl Space be Too Dry?

If your crawl space is too dry it can cause dry rot and even affect your health to some degree. Viruses and bacteria can grow unchecked in low humidity homes as well as in high ozone levels. Some people will even get nosebleeds if the humidity is too low. Remember, a proper humidity level is about balance. Having humidity levels between 45% and 55% in the crawl space creates a balance that can affect the rest of your home.

What Happens if Humidity is too High?

Humidity that is too high can cause wood rot fungus to grow as well as dust mites. Dust mites can grow unchecked in high humidity environments. High dust mite concentrations are apparent in moist homes with lots of dust. Lowering humidity can help control dust might colonies, which is the number one cause of asthma among children.

Should I Dehumidify My Crawl Space?

You may be thinking, "The crawl space doesn't matter, it's not even a part of my home. Why should I care about its humidity level?" Believe it or not, 50% of the air in the crawl space makes its way into the living space. Most homes have a loose-laid vapor barrier and that's it, but is it enough?

If your crawl space is damp, wood rot fungus can begin to grow and destroy your sub-floor. Mold that is growing in the crawl space can travel into your home through the duct system. Air gaps in the sub-floor can allow high humidity and mold to enter your home as well. Making sure your humidity is between 45% and 55% in the crawl space is a great way to prevent indoor air quality problems.

Correcting Crawl Space Moisture

Do you need help fixing your crawl space humidity problems? If so, we can help. Please contact us to schedule your assessment. Also, let us know in the comments below if you'd like to suggest a future blog post.

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About Michael Church

Michael Church has been involved with indoor air quality since 2005 and feels the unhealthy crawl space is one of the major problems causing poor indoor air quality.

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