This dehumidistat is a key element in all moisture management plans outside of just plugging in your dehumidifier. The unit acts as a switch, turning power on and off to a dehumidifier and suppliment fans as the humidity rises and falls. It allows a "whole crawl space" approach to dehumidification. With this dehumidistat, most quality dehumidifiers can control moisture in double the space as what they were originally rated for if properly installed. For example- The Compact Air Plus is rated for 1600 sq ft at 3' high. With a dehumidistat and the proper amount of suppliment air movement (supplied by fans) the Compact Air Plus can dehumidify nearly 3500 sq ft. *Note- For this to work efficiantly, a proper moisture managment plan must be formulated. It can be complicated to get the right results, please consult with us at the time of purchase.