The Texas Hill Country house pictured is 2x6 walls for all of the exterior (either stone or stucco or both) and any interior wall that has plumbing. It's 4600 square feet with about 500 on the second level as a game room. Ceilings run from 12 to 15 ft. It is now all LED and we use about 500 gallons a year in propane (house heat, water heat, drier heat and cooking heat) and about 1/2 - 1 cord of oak a year in the insert.
