Feature Article

Passive Solar Heating

Using the sun for most of a building's heating needs is in the DNA of green building. But in an age of superinsulation, does it still make sense?

The 20,000 ft2 Congregation Beth David Synagogue in San Luis Obispo, California, was completed in 2006 at a cost of $161/ft2. Measured energy consumption shows 82% savings compared with a standard Title-24 building in California—and a 90% reduction in CO2 emissions. A combination of direct gain and water walls, with effective shading, provides passive solar heating, daylighting, natural cooling, and natural ventilation.

Above: David Bainbridge, Below: San Luis Sustainability Group

I was fortunate to have been involved in the glory days of the passive solar energy movement. In the late 1970s I worked in Santa Fe for the New Mexico Solar Energy Association, which was at the epicenter of the burgeoning movement to create buildings that relied on south-facing glass, integrated thermal mass, and carefully designed building geometries to deliver heat in the winter and maintain natural cooling in the summer. We thought we had the answers to the world’s energy woes. It was a heady time.

In some ways, passive solar was a low-tech response to the first wave of solar energy systems that emerged following the 1973 energy crisis. Those early active-solar systems were complex and prone to failure, and many of them were only marginally successful when they operated as designed. Passive solar systems were far simpler, with no moving parts. The buildings became the solar heating system, with solar collection, heat storage, and distribution handled passively and by virtue of the geometry, materials, and design.

While passive solar remains in the DNA of green building, we’re now more likely to hear about high-performing buildings with R-5 windows and R-40 walls, with rooftop solar-electric systems and high-tech energy recovery gadgetry. Is passive solar still relevant? I decided to find out.

Published June 29, 2012 Permalink