BH&G Five Star Home #2507

Though it looks like a one-story structure, this home is actually a full two stories high. The big advantage is that with the first floor four feet below grade, you utilize space that's dug for foundation. There's fine separation of activities, too. 

Main entry is below grade level, halfway between floors to minimize stair climbing. Bedrooms are more remote from noise and traffic of the living areas than in a one-story house.