Passive solar design uses and anticipates the heat energy from the sun within its predictable movement to create an energy efficient building that seeks to be warm in the winter and cool in the summer.
In doing so, there are several building characteristics that are fairly common and work in conjunction with one another in passive solar design.
Passive solar design works with regular preexisting patterns. The photo shows a time lapse photo over the duration of one year. The highest arc is the sun’s path on the summer solstice. The lowest arc is the sun’s path on the winter solstice. Passive solar homes are built to face the sun. They have an overhang to block the high summer sun, while allowing the low winter sun to enter and warm the house.
The diagram below illustrates the same principles: how the sun travels differently on the summer and winter solstices.
On June 21st at 9am, the sun is at a 49 degree angle from the ground and travels a high arc across the summer sky. On December 21st on the winter solstice, at 9am, the sun has risen to a 17 degree angle and travels a short, low arc across the winter sky before setting. In order to benefit from the energy given by the sun, the building must face as close as possible to true south.