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Installing A Crawl Space Dehumidifier


Your dehumidifier should be located in an area where the discharge airflow is not blocked. It best to place the dehumidifier on concrete blocks (hanging the dehumidifier can transfer noise to the space above). Locate the dehumidifier where it can be easily drained (a condensate pump can be added if drainage is not available). The unit should be level to insure no standing water is held in the internal drain pan. None of our dehumidifiers will have a bucket that needs to be dumped. They are all equipped with a drain hose (some will have a built-in pump). Locate the dehumidifier in a convenient location for humidistat adjustment and seasonal filter change /cleaning. Once your humidistat is properly set, you should rarely have to adjust it again.


Some crawl space dehumidifiers will offer an optional duct kit. If you have a large, unusually shaped or divided crawl space, the duct kit can be used to direct the discharge air a greater distance away from the unit.  Ducting a dehumidifier will prevent it from sampling local air and give you longer, more energy efficient running cycles. Creating a longer distance from intake to discharge will create a cross current that will help dry the entire space more efficiently. Using insulated flex duct on the discharge side will also significantly reduce noise. Here are some sample duct layouts:

U-Shaped Crawl Space

Place the dehumidifier in the middle of the "U", and separate the intake from the exhaust with flexible ducting. 

Rectangular Crawl Space

Place the dehumidifier at either end of the crawl space, and use flexible ducting to separate the intake from the exhaust.

Divided Crawlspace

Use ductwork to extend the exhaust from one section of the crawl space to the other. You may have to create holes in dividing walls to create a path for return air to circulate between the divided sections.

Monitoring Crawl Space Temperature & Humidity

Crawl space humidity should be kept between 50-60% rh. A wireless hygrometer can be used to keep an eye on the humidity without you having to enter the crawl. A data logger can be placed in the crawl and be set at various time intervals. It will record temperature and humidity history. It can then be removed and connected to your computer via USB to display a detailed graph.