Passive Solar Design - Passive Solar has a slightly different priority in the part of the country that we live in (near Dallas, TX). We are in a predominately hot and somewhat humid climate. We want to capture free heat from the sun in the winter, but our primary objective is eliminating unwanted sun in the summer. We know enough about the movement of the earth relative to the sun that it is very easy to pinpoint exactly where in the sky the sun will be for any given minute of any day at any location on the planet. This location will vary over the months due to the tilt in the earth's rotational axis. In the winter, the sun rises more in the Southeast and is low in the sky. In the summer it will rise in the Northeast and move high overhead. 

By placing the walls, windows, and overhangs in the right location you can virtually eliminate any direct sunlight in the house during the summer and still gain a considerable amount of free solar heat in the winter. That's basically a passive solar design. The house just passively sits there and takes advantage of this natural cycle of sun movement.

Keep shape square or rectangular - two story is more efficient than one

Orient the long axis east - west

Place most windows on the north and south - minimize east and west glazing

Install the right size overhangs on the south windows 

There are also other passive strategies such as the color and materials of the walls and roof. The insulation value and the thermal mass of the building must be considered also. Again, most of these items do not really cost any additional money. The require no maintenance, replacement, or additional care. A design that takes advantage of the solar cycle is really so simple and elegant that I can't believe that more people don't take advantage of it.

See the free: Passive Solar Design Guidelines