Green Building Project - The Salt & Light Company, Inc.

The design of our green building project includes both passive and active solar design. The difference between these two concepts is rather simple. The principles included in active solar design are those that people typically think of when they hear the words "solar" and "house." Our project will include solar energy panels in the roofing system with the installation of a converter that allows the energy collected by those panels to be returned to the grid, thus actively providing energy to the house and the rest of the electric system. It is wonderful technology, but does not, by itself, cover all of the principles involved in efficient solar design.

Passive solar design incorporates those principles that make the house more energy efficient just by the way it is built. More specifically, the concept is in the way the house receives the sun. On the cold days of winter, the sun can add much desired warmth to a home just by the radiant heat of its rays. (Have you ever seen a dog or cat lay in the sunlight cast through a window on a cold February day? If you have pets, you're likely quite familiar with this sight.) The summer sun is quite bright and very hot, and although it provides great amounts of energy for an active solar panel system to collect, it also adds a good deal of unwanted heat to the home if not property diverted.

The walls and roofing include more than sufficient insulation to keep the warm and cool air separate. But one of the worst culprits of energy loss, even with the most efficient products, is a home's windows. Most people think of this concept in terms of the warm air lost to the outside on cold days, but it applies in the reverse as well. The bright sun shining through windows in the summer add heat, and even layers of blinds and curtains won't stop it. This is where our passive solar design system fits in.

Passive solar design incorporates the orientation of the building to the solar radiation. Solar south is different from true south (remember that the earth is tilted on its axis). During the winter solstice on December 21st, the earth has rotated furthest south and so the sun is lowest in the horizon. During the summer solstice on June 21st, the sun is highest in the horizon. The exact height of the sun during these times depends on the latitude of your location. Locations closest to the equator are least affected by the earths rotations, since they continue to remain nearer to the sun at all times. The farther you go from the equator, the more the seasons are affected by this change. In the Northern Hemisphere, southern locations experience more (if not entirely) warm weather, more hours of daylight and longer periods of summer. Northern locations experience longer, darker and colder periods of winter. This matters when you are trying to figure out how to keep a house cool in the summer and warm in the winter for the least cost possible.

In Mt. Holly, the sun's orientation to the earth is 27 degrees in the winter and 74 degrees in the summer (think angles, not temperatures here). Thus our building is designed to include large windows that take full advantage of the winter sun and maximize its warmth, as well as carefully designed overhangs that fully shade the windows only in the summer, allowing no sun exposure. This allows for radiant heat when it is cold and none when it is warm, all for free from God's solar heater.

If you see the shadow lines in the photos below, you will notice that the windows were receiving full sun at solar noon (11:57a.m.) on December 21st, 2005. As the year progressed, the windows were fully shaded at solar noon (1:01p.m.) on June 21st, 2006.

WINTER SOLSTICE - DECEMBER 21st	SUMMER SOLSTICE - JUNE 21^ST

Angle of the sun determined by latitude and longitude for Mt. Holly, NJ.	Angle of the sun determined by latitude and longitude for Mt. Holly, NJ.
SUNLIGHT CAST DURING WINTER SOLSTICE	SUNLIGHT CAST DURING SUMMER SOLSTICE

During the winter solstice and surrounding months, the sun is at its lowest arc in the sky.	As the summer solstice approaches, the sun climbs higher in the sky until it reaches its maximum height on June 21st.
FULL SUNLIGHT ON WINDOW AT WINTER SOLSTICE	FULL SHADE ON WINDOW AT SUMMER SOLSTICE

Windows receive full sun during the Winter Solstice, December 21st, taking advantage of the heat of the winter sun.	Windows are fully shaded during the Summer Solstice, June 21st, shielding the home from the heat of the sun's rays.