I did a crawl space inspection yesterday at a house in South Charlotte where I discovered a humidistat controlled power vent used by the homeowner to help control the crawlspace air quality. The unit was set on 30% Relative Humidity so the fan was running continuously sucking air out and pulling unwanted air in from the outside through the other open vents. With cooler temperatures, low humidity and dew point levels present now there is no reason for this fan to be running. Passive air movement through the open vents is adequate to ventilate the crawl space in the winter. If the air is too cold outside this device would draw in cold air and make the floors colder and perhaps freeze the water pipes. If you have one of these old style units under your house inside the crawl space change the setting to 70% and give me a call to discuss alternatives that actually work. This homeowner was spending an extra $5 per month for a fan that made the problem worse. Humidistat devices don’t work in the winter time!!! Either Replace them or turn them off!!!! Either Replace them with the current state of the art crawlspace environmental control system or turn them off!!!! Call me to upgrade your system to one that works and saves you money – (704) 787-6972