Architecture has advanced over the years and the days of the drafting table are over and the computer with CAD software has taken its the place.
The one and one half story house that is sometimes called the cape cod is essentially one story with a steeper roof which allows for expansion of the attic.
Dormers are usually added to provide additional light and ventilation. This has two distinct advantages: the economy in cost per unit of habitable living space, and built-in expandability.
Generally, bedrooms and a bath are provided in the attic space. Since any space with less than five feet headroom is considered unusable the total square feet of space in the attic is about one half that of the first floor. Dormers, stairs, and a slightly steeper roof are the principal additional costs required to build the one and one-half story.
The one and one-half story is quite versatile. It can begin as a two-bedroom, one-bath house with the upper area left unfinished. This minimum house will meet the needs of a newly married couple or a retired couple. As the family of the younger people expands, the expansion attic can be finished to provide a more livable room.
Heating costs are minimized due to the small outside wall area compared to the amount of interior space. Cooling may be accomplished through the use of interior space. Cooling may be accomplished through the use of louvered ventilators at each end of the structure and the generous use of insulation. Adequate ventilation and insulation is necessary since about one-third of the ceiling area is directly under the roof. This area tends to be quite warm in the summer.