We have a 4 zone heating system - natural gas. In summer when we run the air the basement gets frigid. We do not put the air on in the basement. The upstairs zones are set at approx. 74 and the basement zone is not turned on but the temp down there is 64. This is a full walkout basement with rec. room, bedroom, bathroom and storage area. Why is the basement so cold? If I set it to auto on the thermostat the heat kicks on for that zone. Is that OK?