The oil price shock of 1973 sparked a burst of interest in “solar houses.” During the 1970s, owner-builders all over the U.S. erected homes with extensive south-facing glazing — sometimes sloped, sometimes vertical. Many of these houses included added thermal mass — concrete floors, concrete-block walls, or 55-gallon drums filled with water.
Some of these houses had passive solar features, while others included active hardware: space-heating systems that circulated water or antifreeze through roof-mounted collectors, or arrays of solar air collectors connected by ductwork to insulated rock bins in the basement.
Responding to a growing interest in all things solar, publishers came out with dozens of solar-house books in the late 1970s and early 1980s. It’s fun to re-read these old books — to see the photos of pony-tailed carpenters working on systems they claim will provide “free heat.” Once the warm glow of nostalgia fades, however, one begins to notice what’s missing from these books: any understanding of air leakage.
Most of these “solar houses” were built with little attention to air tightness and were insulated with fiberglass batts. Moreover, descriptions of homes with extensive ductwork never mentioned the need to seal duct seams.
Understanding air leakage
While these early solar houses were being built, researchers in several locations were making pioneering discoveries about how air leakage affects residential energy consumption: