What about the garage?
An unheated garage is technically not part of a home for the purpose of calculating form factors and surface areas. Garages are kind of an “in-between space” that is neither interior nor exterior. It turns out, though, that the integration of the garage into the structure plays an important role when it comes to energy-efficiency. If there is heated space above an attached garage, or if the garage is integrated into the home such as it is often the case with older split-level type homes, the form factor increases and energy efficiency goes down.
If there is a choice between putting the garage at the basement level (under) or at the first floor level (attached), the garage under the house is be preferred. The configuration in the picture above with a master bedroom suite above the garage is less desirable, because the space above the garage loses heat to the environment on all sides except for the one wall that is shared with the house. This area will be uncomfortable in the winter and difficult to heat.
