"And I'll ask again. What is the difference between a Barndominium and an attached garage? I specifically asked my insurance agent this question and he said none, as long as the shop space is not used for a business."
Out in the real world (where you, me, us, and TBN live) we know there is essentially no difference.
When you get code, regulations, insurance, FEMA and lenders involved, things get downright spooky in a big hurry.
Insurance companies can change their underwriting criteria and what is insurable today may not be tomorrow. If your insurance guy is an independent agent, hold on to him, he can place your coverage with any number of "more cooperative" companies. If he is a one company agent (works for one company only, such as Hartford or State Farm) if the HQ decides not to cover your type of building or use or maybe they don't like the color you painted it, they won't renew and you have to start all over again explaining your "unconventional structure" to companies which HATE uncertainty and are really much more comfortable insuring cheaply built stick homes, 3/2s with shingle roofs and an SUV in the driveway.
Here in Floriduh the homeowner's insurance situation is an unmitigated disaster, a total clown show, and seems to have been organized by Franz Kafka while he was on some very poor quality recreational pharmaceuticals.
My insurance has been non-renewed because: You didn't take all your hurricane shutters down and we don't think you live there full time, If you lease 15 square feet of your 4.6 acre property for an internet relay box (2' by 4', all wiring underground) that's a commercial use and we not only won't cover it but now we are not going to renew because YOU ASKED US before you entered into the deal. Turns out there WAS no deal to be made, they still declined to renew (I guess the power and phone company equipment on the property isn't a commercial use.), Your utility building is bigger than your house, that isn't acceptable to us, We don't understand how steel trusses can possibly be much stronger than wood trusses and also won't burn or get eaten by termites, so we won't insure you, Our records show your address is in a business district even though you are telling us that you are looking out the front window and see nothing but houses in every direction, our records are infallible . . . and it goes on . . . and I have NEVER had a claim in over 55 years of home ownership anywhere.
So the State of Florida, instead of doing anything to ameliorate this mess and possibly keep the citizens from getting hammered by insurance companies, is seriously talking about passing a law which would make it illegal for your dog to stick its head out of your car window as you drive around . . .
FEMA - I could get carpal tunnel syndrome relating my experiences with FEMA. I'm half the emergency response team in our town, and the pair of back to back hurricanes we just had were less trouble to deal with than FEMA. Personally, I received seven identical letters asking for information which I had already supplied, and the last question on each identical form was "Where were you born?" I was tempted to say "In a log cabin" but I have no political aspirations.
NAHB (National Association of Homebuilders) says 24.9% of the cost of the average house is regulatory compliance and paperwork. If you can do some of this paper-pushing yourself (and actually, you can) you can put a lot more of your money into your home, and a lot less into reams of useless paper which "has to be on file" and which no one will EVER look at again.
I think the key here is to avoid "Imperial Entanglements" as much as possible - every agency has their own set of contradictory rules and regulations, and if you read through them you may be able to avoid much of the garbage they insist on having - refer to my earlier comments about "It is a BARN, right?" from our very helpful building inspector.
(Lets see, the fire department says I have to trim back foliage to establish a 30 foot fire break buffer around my home, and DEP says I can't cut anything in the resource corridor, which is less than 30' from my home. I ought to let them fight it out while I eat popcorn and enjoy the show of an immovable object (bureaucracy "a") tangling with an irresistible force (bureaucracy "b".) I'm so confused . . . )
Do your paperwork first, get all the official meddlers to say yes, THEN start building.
With best regards,
Mike/Florida
If you want to transition wealth to sons or daughters, make a conventional house with a huge detached, open pole barn for all the big equipment. 
