Wow, Ladia. I missed your responses (several, along with others) over the past several days.
Now, I'm wondering if this is even something that I should attempt here (small town) with local vendors. When I first thought about this in '01, the ONLY outfit doing it within 35 miles didn't instill lots of confidence. The sold the HP and would install it...but (pre-pond) argued amongst themselves for a couple weeks as to how much tubing (digging & $$$) would even be required. I walked away...
I'm only 40 mins from Iowa City, so maybe there are others there I can talk to about this.
My shop will not be attached, but sit perhaps 50 feet from the house. It will have in slab radiant, I've installed it before, and will this time. Home has LP fired forced air...not sure how these 2 systems will (or even could) be tied together. Shop radiant can easily be supplied by 60 gal HWH, AC, perhaps just a window unit - I won't live in the thing!
...probably simpler to keep the systems separated.
Geothermal is supposedly very popular now. Especially for new construction. The guy who sold the system to me told me (he installs the ground loops) that he was booked up for several years in advance. Now they have new drill that can pull the tubes underground without major digging. I also think that the installers got much more skilled, since I installed my system, (well there is a software) in calculating all the required specs. If you don't need AC (you can always add it later) the floor heating with geo is not much more expensive than forced air especially if you can lay the tubes by yourself.
By the way most of the utilities also sell the geo system.
Obviously the best and cheapest heating is insulation. Combined with HP it might also be the least costly to operate. If you use geo for heating only it is about as complicated as forced air.
The two system could coexist several ways. I would use two separate heat accumulators each with its own temperature control and circulation pump. One could be set to floor heating temp 90 - 110 F and the other to forced air temperature 160 F with house heating demand priority. Then you would have to replace the furnace with an air handler or add the air handler in series with the furnace so you will have a back up heating.
