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What Relative Humidity Means for Your Georgia and South Carolina Crawl Space

Friday, September 30th, 2011 by Jason Simmons

Crawl Space Humidity Savannah, Georgia

Jason Simmons, Lowcountry Basement Systems

 I’m sure that, if you’re like me anyways, most of you check the weather the night before or the morning of your work day. We probably all hear it again on the radio while driving into work. I’m wondering how many of us actually pay attention to what we’re hearing? Do we really understand what it means when the temperature is 74° and the relative humidity is 92%? Why should we even care?

 If you have a vented dirt crawl space then you should be worried over these numbers. Let me show you why. When you have a vented dirt crawl space the air outside and inside your house is constantly being exchanged. Air carries moisture with it wherever it goes. The ground underneath your space also emits moisture to the tune of 5 gallons of water vapor per 1,000 square feet. When we heat or cool this air we change the ability of the air to hold moisture. Relative humidity is the amount of moisture in the air compared to what the air can "hold" at that temperature. The relative humidity of air goes down by 2.2% for every degree we heat it and up by 2.2% for every degree we cool it.

 So let’s take our numbers from earlier, add a few more things in, and see what this equation equals for our crawl space. The average temperature we see in a crawl space is around 70°. The average floor joist and dirt floor temperature is around 67 degrees. If we take the outside temperature of 74 degrees and bring that air into our crawl space we cool it down by four degrees. 4 degrees multiplied by 2.2% equals an 8.8% rise in relative humidity. 8.8% added to 92% equals 100.8% humidity. At 100% humidity the air can do longer hold all of its moisture and it begins to fall out of the air in your crawl space. This causes condensation on all of the areas, especially the cooler ones, in your crawl space.

 This high crawl space humidity in Hilton Head Island, SC and surrounding Georgia areas can lead to serious problems. The condensation build up on your HVAC ducts can cause mold problems on and around your duct work. Pipes that are not insulated can also begin to grow mold. Paper backed insulation that was installed in your crawl space may begin to hold moisture, fall, and mold. Your floor joists also may mold or begin to rot due to the high moisture content in the wood.  

 There are a few ways that we can take care of this nasty problem. First, we can seal up the vents to our crawl space. There are a few easy ways to do this yourself, but the humidity problem and mold still remain in your crawl space. Second, we can buy some plastic and place it down on the floor of our crawl space to block the ground moisture. The problem with this solution is that we build up moisture underneath the plastic, which grows more mold, and leaves the humidity and mold issues that we already have unaddressed.


 There is a solution that will solve all of the issues with humidity, moisture, and mold. It’s called CleanSpace®. Our 20 millimeter think liner is laid down in your crawl space and blocks the ground moisture. Our liner is also antimicrobial, which means it won’t grow mold on the side against the ground. We deal with the moisture underneath and any water seepage problems by installing one of our SuperSump® or TripleSafe® sump systems to pump away the water. Next we seal the vents of your crawl space to lock out that humid outside air. Finally we install one of our awesome SaniDry dehumidifier units to keep the humidity in our new CleanSpace® under 70% humidity which stops most mold growth.  

 The CleanSpace® Crawl Space Encapsulation System® satisfies all of the repair criteria and transforms your crawl space into a healthy, useable space.

 “Water does very little to ruin a home with a dirt crawl space. It’s the water vapor that kills the house.”  Lawrence Janesky

 “A vented dirt crawl space raises your heating and cooling cost 15% (to 25%) every month, and makes it very likely you’ll have a big expense for mold removal and/or rotted wood replacement.”      ~Lawrence Janesky

 Lowcountry Basement Systems is a member of the Basement Systems, Inc. and Foundation Supportworks Dealer Network. Information in this article is contained in Crawl Space Science by Lawrence Janesky. To schedule a free quote on crawl space repair in Georgia and receive a free copy of this book, please contact Lowcountry Basement at 912-927-7827 or visit www.LowcountryBasement.com




our service area

We serve the following areas

  • Girard
  • Keysville
  • Sardis
  • Waynesboro
South Carolina Our Locations:

Lowcountry Basement Systems
145 Commercial Ct.
Rincon, GA 31326