Heating a shop with an outside water-less furnace or boiler is both simple and safe and at a lower cost than typical fossil fuels or electricity because you are likely to have waste oil that you normally have to pay to get rid of, in an automotive shop.
Waste oil burners can be added to any boiler or forced-air furnace. We can add a sleeve or pipe, with a flange, that goes from the outside of the colored steel, through the insulation ands water or air jacket (depending on the model) and into the firebox, where it will provide the heat instead of wood.
Many owners prefer the simplicity and lower cost of the forced-air waterless model because you do no need insulated Pex Pipe plus heat exchangers (usually hanging), with fan on them. All that is needed is a 110V power wire, a thermostat wire and inexpensive snap-together ductwork than you can get locally to get rid of that sky-high propane bill!
Most shops or garages are not allowed to have any wood boiler or furnace INSIDE due to flammables and sparks, etc. Some states and insurance companies will not allow a wood boiler in a space that CAN be occupied by a car!
With an outdoor boiler or water-less furnace, wood or waste oil is your inexpensive fuel source.
Radiant heat should always be considered for new construction. That means warm floors to lay on and high ceilings are possible without heat loss at the ceiling because radiant heat stays in the lower 8-10 feet!
Even in winter, repairs must go on and an outdoor heater makes it possible at a much lower cost than propane and other fossil fuels.