A wall fan includes a control circuit both controlling the wall fan and a temperature control unit comprising a heater, a cooler, or a Heating, Ventilating, and Air Conditioning (HVAC) system. The control system receives a desired temperature and compares the desired temperature to an outdoor temperature. When the outdoor temperature indicates that drawing outside air into indoor space will drive the indoor air temperature towards the desired temperature, the control system activates the wall fan, and de-energizes the heater, cooler, or HVAC system. When the outdoor temperature indicates that drawing outside air into indoor space will not drive the indoor air temperature towards the desired temperature, the control system de-energizes the wall fan, and energizes the heater, cooler, or HVAC system.