Even if you enclosed the rack with something, I still wouldn't keep it in a room that gets that cold. My Boaphile rack is fully enclosed and I would not trust it to hold good temps with ambient temps outside the rack any lower than 65 and that is pushing it. I try to keep the temp outside the racks at least 70 in the winter and that will keep my cool side in the tubs at 74.
Edit: Also, humidity in racks is not a problem. You will usually start with the humidity to high and drill holes to bring it down to where it needs to be.