First I want to say I'm VERY envious! I plan to do something similar
in the next year to 18 months, but I really wish I had it NOW!
Where are you located and what temps do you expect to see? You didn't
say anything about doors and windows and they probably wouldn't be a
huge factor anyway. You do mention R4 insulation, which isn't much.
Generally I've heard that every dollar spent controlling heat or cold
infiltration equals $6 spent heating or cooling, so I'd consider
more/better insulation first. We're in the middle of building about 60
miles NE of Austin and we're having the house foam insulated.
Basically we'll have the world's largest styrofoam cooler. I'll
probably do the same with the shop. In your case, I'd say additional
insulation would be the first step.
Also I'd take a serious look at propane, especially if you see really
cold temps for prolonged periods. Electric heaters aren't cheap to buy
and operate, and unless you already have a very healthy electrical
service installed you might have to get it upgraded to handle the
additional load. Regardless of which way you go with the heaters, I'd
consider leaving the heat on, maybe using a programmable thermostat to
keep the temps in the shop reasonable 24/7, then warming things up an
hour or so before you start working. Yeas, that's going to cost you,
but If you don't do something like that and it's really cold outside
(and in the shop) most of the time, it won't get warm quickly enough
in the evenings to do much good anyway.
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