High Humidity

Here in the Deep South North Mississippi, West Tennessee, and North Alabama. We deal with moisture in crawlspaces. We find many homes that leave there foundation vents open year round. As a result high humidity finds the way inside the crawl space. 

When your heating and air duct or equipment is installed inside the crawl space. The temperature of the air is being delivered thru the duct work is around 45 to 55 degrees. When that mix’s with the warm 100% plus humid air then condensation is the end result. Some homes have drainage issues and or rain water run off goes under the foundation walls and the moisture starts to mix with warm humid air. Either way it results in mildew growing in the crawl space. Which will result to heavy mold if nothing is done to stop the issue. 

To correct the issue you have to do 3 very important things:

Install a Moisture Barrier

Installing a plastic moisture barrier (minimum of 6 Mill thickness) will lay on the ground. First you need to clean any debris from crawl space. Then lay the material down on the surface. Roll the plastic up the wall a good 12”. Also cut around each foundation piers. Roll the plastic up 12” as well. Then foam the plastic to the walls and piers to keep moisture from seeping up moisture barrier.

Install a WHOLE House Dehumidifier

We used to tell our customers to go to your favorite big box store. And purchase a 65 pint dehumidifier. They are like window units they brake a lot. So now we rely on a Honeywell DR65. This is a whole house machine that goes in the crawl space and suspends from the floor joist. We duct the system to each end of the crawl space to warm and dry up the moist areas. We install an independent drain line either in the sewer line or outside away from the foundation.

Sealing Your Duct Work

Once that you have done step 1 and 2 then you are ready to seal your duct work. There are 2 rules of thinking around this. You can seal the duct work by removing the duct wrap insulation and painting the seams with a liquid mastic. And then install new Duct wrap insulation around each duct. Some customers decide to replace the entire duct system and seal it completely while installing the new duct work.


For more information you can reach me at kevin@harbinair.com