I think thats why most people run these air cooled lights from outside to outside but that doesn't help me during weather extremes. The guy before me was pulling cool air from his first floor up to his lights on the second floor and directly outside. It was an out building so he didn't really care...had no secondary use for the building.A negative air pressure is difficult to maintain like that. I've always seen it the other way around. You create a positive pressure and let it force the hot air out. My brother was an HVAC guy and that's how he 'splained it to me. It has something to do with preventing mold. I think he said a low pressure environment allows it to propagate faster.