Hello Bill.

I don't know if I qualify other than having forced air HVAC in my shop. I have a Trane heat pump that keeps the shop at 74 in the summer and 68 in the winter. Yes, it isn't a Pennsylvania winter, but the summers can be nothing to sneeze at.

One consideration is how much insulation you are willing to throw at the project. How good are the windows and doors? Are you going to heat it day and night? If you go with a central heating system, 'the more insulation the better' is the mantra. IMO, the best thing to do is to price all the components that would go into a forced air heat system, and then look at the payback; you probably did that for your home heating system. It isn't clear to me, but you don't plan on running underground duct work from your home furnace to the shop do you?

Another option would be to dig the ditch and put in a pipe of the appropriate size under the new driveway and just leave it until you decide what you truly want to do.