Crawl space ventilation system

A multiple ventilation system for multiple crawl spaces under a building structure with exterior wall vents to reduce the moisture content of the air within at least one crawl space, said multiple ventilation system comprising:

• a fan unit having a fan operated by an electrical motor centrally located and orientated within said at least one crawl space;
• a timer unit associated with fan unit that is set to transmit a first electrical signal for ventilation time periods that are determined to optimally reduce the moisture content of the air in a respective crawl space;
• a temperature sensor to determine a temperature within the at least one crawl space and transmit a temperature electrical signal that generally indicates a temperature value in the crawl space used to determine if said fan unit should be activated;
• an outside humidity sensor to determine the percent moisture value of the ambient air and generate a second electrical signal to indicate the ambient air moisture value to further determine if said fan unit should be activated;
• an inside humidity sensor to determine the percent moisture value of the at least one crawl space air and generate a third electrical signal to indicate a percent moisture value for the at least one crawl space air to also help determine if said fan unit should be activated;
• and
• a controller unit associated with each crawl space having a main switch, a transformer, a plurality of logic control circuits and a control switch that receives said temperature, second and third electrical signals and compares these signals with predetermined limits of temperature and humidity, whereby the fan unit may be activated.