Last summer, while the sun rode high in the sky, I evaluated the solar potential of a building site here in western Maine. Specifically, I wanted to know how much unrestricted sunlight would come pouring through any south-facing windows in those months when it was most needed - December through March.
The task was made easy by a recently developed sun plotter, a simple acrylic card which, held two inches from the eyes, shows exactly what path the sun would trace between 9 a.m. and 3 p.m. on Dec. 21, when it was lowest in the sky. Those trees that would have to be removed if the site were to live up to its potential showed up clearly. Just as important, the card showed what trees need not be removed.
I returned to the site in December and, sure enough, the sun traced a path right where the Solar Card, as it is called, had predicted it would many months earlier.
The card indicates the sun's path on the 21st day of each month.
The use of sun-path indicators is an important first step in deciding where to locate solar panels, sun rooms, or even large windows on or in your home.
In the past, most of the available sun-path indicators have been expensive (from $50 to $150). The Solar Card, by contrast, sells for $12.95 (from Design Works, PO Box 489, North Amherst, Mass. 01059).
Because the sun's path varies with latitude, be sure to state the region where it will be used so you get the proper card.