I'm finishing up on putting together my crawlspace growroom and have been meaning to figure out my fan/ventilation situation. I have a speed controller that I use to dial the speed back and adjust as necessary. What I was hoping to find was some kind of inline Hi/Lo speed switch that I can install on a timer or something of the sort. I'm aware that I can get a climate controller that will adjust the fan speed to the temps but I was looking for a more hardline predetermined two speed set up. During lights on I want good ventilation of course to remove the smell and excess heat but since my grow room is in the semi conditioned crawl I don't want the fan running full blast at lights off and sucking heat out of the crawl. I want just enough negative pressure to keep the smell down and air moving but that is all. Any thoughts?