radiant heat

What type of construction is it? If conventional framing, 2x4 or 2x6 stud walls with insulation and drywall, and an insulated attic, a warm air furnace type of heater MIGHT work okay.

but for most shops, it will be disappointing, as most shops tend to have lots of air leaks. And the high ceilings contribute to the problem.

Radiant heat is exactly what you want, but maybe not the 'in floor' radiant heat. As mentioned by 67dart273, it takes a LONG time to raise the temp. In Your home, it is generally less of a problem, since you normally want it to be comfortable all the time. Do you want your shop heated 24/7?

Airplane hangars are heated with radiant heat. Enormous warm air heaters wouldn't have a chance of doing it, cause warm air rises. Radiant heat can be directed sideways, straight up or down, and is not 'lost' with the movement of warm air which travels upwards.

I would consider radiant ceiling heat if I were you. You might want to check it out.