If it is possible, insulate the walls and ceiling, either with proper insulating board, or polystyrene sheet covered by hardboard, or better, plywood. It will retain whatever heat applied whilst the shop is occupied.
My shop was built without windows, and insulated with 50mm glass fibre behind 12mm ply, with 19mm wood outer cladding on the walls, 12mm ply each side of 50mm glassfibre under mineral felt (now a rubber roof membrane) for the ceiling.
Normally it is unheated, unless occupied. When frosty (in Eastern UK) a 60 watt tubular heater leaves metal benches not cold to the touch within 24 hours of switch on.
When working in there, a thermostatically controlled 2Kw fan heater is used. The shop is 3m x 2m and just over 2m floor to ceiling. The heater runs for less than 10 mins each hour.
Lighting is by one or two 65 watt ceiling mounted fluorescents, plus LED lights on the machines, so no great heat input there.
Ventilation, when needed, is by a weatherproofed 6" fan mounted high up with two or three fixed 50mm dia vents near to floor level. Obviously, it gets ventilated when the door is opened . Whenever possible, I try to work with the door open.
Rust is almost unknown.
My old uninsulated shop, with windows, often left the oil on the machines turning milky with condensation each morning, unless some heat was applied. Hence my love of insulation
60 watts will raise the temperature above the dew point in temperate climes. Colder climes, obviously will require greater heat input. Locating the heater (60watt bulb?) under the sheet or blanket covering the machine (tools need to be in drawers) will go along way to preventing rusty beds or tables.
Howard