My shop is around 14x20, lap siding with a bit of daylight showing through, open rafters. Don't want to insulate it because it was my grandfather's/father's before me and the nostalgia factor has me over a barrell. I use either a twin tube electric quartz heater just to know the chill off, or a 10,000 btu radiant kerosene heater when it is colder. With the kerosene heater, I place a fan behind and above it to help circulate the heat. I have far less problems with rust than I did when I was working out of my garage. I keep stationary tool tables waxed and occasionally wax my planes and stuff. I keep a rust eraser handy to touch up the ones I have not used frequently that may get a bit of rust here or there.