I built my in-laws a 1200 foot house with an 1100 foot garage right behind mine last year. We did all ICF to ceiling level, then trusses on top. Added sheeting and 2" of foam to gable ends, gasketed the walls before drywall, finished the exterior walls with hard coat stucco. I chose hard coat because we have Flickkers here, kinda like a big woodpecker that is a protected species, and they love the EFIS style stucco. That 1/2" of concrete put a stop to them pecking right away. Radiant heat in the floors with a mini split for A/C. Mother in-law loves having warm feet in the winter. Father in-law wanted a basement so he could have an aging room for his game, 72 years old and still would rather hunt than anything else. We ICFd hthat as well, and ran 2 6" ducts to the outside. One duct has a in-line fan that is thermostatically controlled to bring in cool air at night, and dampers to keep out warm air during the day. Insulated fiberglass entry door for access. Haven't tried it out yet, I kept him too busy last year to go hunting. One thing I didn't do but might be worth the extra $ is to put 1/2" of foil backed foam (polystyrene) on the roof. The foil helps bounce heat back into the atmosphere and keep your attic cool in summer, and the foam provides a thermal bridge.