Rockingham, NC -- I Have Crawl Space Vents--That's Good, Right?

Tuesday, March 6th, 2018 by Derek Moore


If you're a resident of Rockingham, NC or anywhere else in our coverage area, you may have crawl space vents.  A lot of people do, but that's good, right?  Well, first, let's take a quick look at what the term "relative humidity" really means. 

We define it by measuring how full of water the air is relative to the maximum amount of water it can hold at a given temperature.  With spring and summer comes warmer outside air.  You may have 84 degree air with 75% relative humidity that makes its way into your vents.  With a crawl space that is only 66 degrees, and a wall, dirt floor and floor joist temperature of 62, the problem is obvious. 

Yet, most believe that venting somehow removes moisture or keeps it out, making things better.  When in truth, the opposite is correct.  When we cool the air by one degree, the humidity rises by 2.2% because cool air holds less water than warm air.  So, looking at a different outside of 84 degrees, and inside being 62 degrees, it creates a 22 degree difference.  That results in a 48.4% increase in humidity!  So, in actuality, we start at 84 degrees and 75% humidity, but after cooling it to 62 degrees we must add another 48.4%.  Now we have 123.4%.  What does that mean?  Well, after 100% humidity (the dew point), the air can no longer hold the water, and begins to give up the moisture.  That's what causes condensation on our joists and wall surfaces, our cold water pipes, sill plates, girders, and insulation.  Porous surfaces like wood just soak up the moisture, and causes rot and eventually, mold. 

Knowing and understanding what goes on in our crawl spaces is key.  If we know, we can act appropriately.  Call Southeast Foundation and Crawl Space Repair today for a free estimate.  Crawl Space Encapsulation can improve the health of your family starting today.

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