Building or buying a home is a long-term financial commitment. Good passive solar design offers big payoffs in thermal comfort, energy efficiency, and conservation, with miniscule monetary commitment. Poor design has the opposite effect—it can obligate a homeowner to unnecessarily high energy bills and living in an uncomfortable house. The same holds for environmental performance. Over a structure’s lifetime, well-designed buildings have less impact on the environment, while poor design results in a lifetime of high energy use and resource consumption.
Although solar designs have improved, an awareness of the lessons learned from the past is vital to the future of passive solar heating and cooling. By understanding the common problems, builders, architects, and designers can work diligently to avoid them—either in building new homes or when retrofitting existing ones.
In the late 1970s, I purchased my first home, an attractive bungalow built in 1925. It wasn’t a passive solar structure, but it had good southern exposure. Soon after moving in, I started to work on the house. I purchased solar collectors to heat domestic hot water. I removed some rather large, leaky north-facing windows, beefed up the attic insulation, and sealed air leaks. Next, I attached a small sunspace on the home’s south side, my first attempt at passive solar heating. I based the design not on science and solar engineering, but on pure speculation.
Not surprisingly, the sunspace failed miserably. The reason? It was far too modest to meet my home’s heating requirements. It did provide some warm air, but not enough to noticeably affect the home’s temperature. Had I known more, I would have constructed a space commensurate to the home’s square footage and installed a system to move air out of the sunspace that was more sophisticated than a portable fan.
Many other people experimented with passive solar heating in the 1970s and 1980s. Venturing boldly into the field, many of us designed intuitively. What could be so difficult about passive solar design? You concentrate windows on the south side of a house, provide overhangs for summer shade, insulate well, and then sit back and bask in the benefits of your labor. Trouble is, good passive solar heating design requires more than intuition—it requires understanding the concepts of orienting a home properly, balancing glazing and thermal mass, and allowing for good insulation and ventilation.