Passive Solar Design

Environmental Mission > LEED Gold Welcoming Center > Energy Conservation

Passive solar design is a general term for making use of various passive solar technologies to maintain a comfortable temperature range inside a building throughout the sun’s daily and annual cycles. By implementing passive solar design in our building, we minimized the need for traditional heating and cooling technologies such as a HVAC (heating, ventilation and air-conditioning) system, which would rely on power from our PV cells or grid power. Passive solar systems are an ideal use of the sun’s energy because they have little or no operating costs, very low maintenance costs, and emit zero greenhouse gasses when in operation.

For a year before ground was broken on the Welcoming Center project, surveyors came out to the site and did a sun path analysis. They looked at where the sun rose and set and at the altitude angle of the sun throughout the seasons. This analysis allowed the architect to design the building to absorb sunlight during the cold, winter months and to block sunlight during the warm, summer months. The Welcoming Center has a series of large, floor-to-ceiling windows that face due south for absorbing sunlight. However, the awnings over the windows, which house our solar thermal collectors, are designed so that they completely block the high-angle, summer sun while letting in the low-angle, winter sun.

The second part of our passive solar design is the large thermal mass present in the building in the form of the plastered straw bale walls, the concrete floor, and the living roof. Thermal mass is any mass that absorbs and holds heat. Properties of a good thermal mass are high specific heat, high density, and a low thermal conductivity, though not as low as for insulation materials. Because the walls, floor, and roof have a high thermal mass, they can take in excess thermal energy during sunny periods when you don’t want the interior of the building to be hot, and then release it during overcast periods or during the night. Basically, you can think of thermal mass as a “shock absorber” for the fluctuations in temperature outside the building, keeping the inside temperate at all times.

As you can see, both of these technologies utilize the energy from the sun directly, without complicated semiconductors, electronic systems, or even any moving parts.