I was wondering if using a dehumidifier in the workshop will be expensive to run? The workshop is around15ft square. I am currently insulating the flatroof with fiberglass and plasterboarding it out. There will be airspace above the insulation for ventilation. I need to seal around the up & over door. Windows are double glazed. Two walls are 4" breezeblock, the others are single brick. The floor is concrete. I don't expect the workshop/gargage to be at room temperature at anytime as I can put up with a little cold. What I need to do is keep humidity down to stop everything going rusty. Do dehumidifiers work down to freezing? Do they have any defrost functions to keep the workshop from freezing? Would just a dehumidifier work to keep things from going rusty? Would it have to be on all the time? What sort of power do they take ? Are they expensive to run? I can't afford an expensive dehumidifier, so would a cheapish (£150) one be okay? Any suggestions would be greatly appreciated.