I'm a Restoration Contractor, we do insurance work, water and fire damage. What ever heat source you decide to use check with your insurance company first. Your insurance company may have restrictions as to what you may use to have your coverage in effect. Example my carrier will only allow radiant baseboard heaters, why is a mystery but those are their rules.
I've seen first hand, claims being denied on out buildings such as workshops due to heat source.
Also if you have a free standing shop make sure your coverage is appropriate. Out buildings if not so identified are capped as a percentage of the value of your home. Example $250,000 home out buildings are (usually) 10%. So you may only have $25,000 to rebuild.
Greg