I have a window air conditioner in my grow room that has been working perfectly until the other night when the outdoor temp got down below 32F. The fan started making a loud noise (most likely froze with ice), so I shut it off and opened the window a little to cool the room off (fortunately the room is on the second story). So, I am thinking about buying a portable air conditioner that has an intake hose and an exhaust hose. But I am concerned that I may run into the same problem when the temps drop to sub-zero over the winter. Does anyone here have any experience with using a portable AC unit in below-freezing temps? Or if you have any other ideas on how to keep the room cool, please post them. I have four LEC/CMH315 lights in the room.