The house isn’t technically round, but with 20 sides, it’s close. And it looks unusual enough that strangers sometimes drop in just to ask about the place Elmer ’64 and Marianne Kennel built in 2007 a few miles outside of Harrisonburg, Virginia.

Built with 20 prefabricated panels made by a company in North Carolina, the house includes a number of green features, beginning with the shape itself. The round design gives the home an improved surface-to-volume ratio – and consequently, improved energy efficiency – over a standard, boxy house. Simple ways the Kennels maximize the efficiency of their house: passive solar design, orienting the house to maximize and minimize the effect of sunlight at the appropriate times of year, thick insulation, reflective roof shingles, well-built windows and doors, and “window quilts” to minimize heat loss.

The house also includes some higher-tech green features, including solar collectors to heat the house via radiant floor heat and the water system (on March 1, a sunny but chilly day, their tank temperature reached 120 degrees). A separate, 4.8 kW photovoltaic system at the house generates about half the electricity the couple uses.

Elmer’s and Marianne’s previous house, built in 1980, also had solar collectors for hot water and a passive solar design.

“It seemed like the right thing to do years ago, and it still is,” says Elmer, who retired in 2010 from his career as a general surgeon affiliated with Rockingham Memorial Hospital.