Passive Solar House Design Using a Two-Story Trombe Wall

Architect Douglas Kelbaugh built his family's solar heated and cooled home with a passive design using a collector wall.

| January/February 1977

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    This passive solar home is heated and cooled by a two-story Trombe wall. Sunlight is converted to heat and trapped between the glass windows and the wall and used to heat the house and its attached greenhouse.
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    A diagram of the Trombe wall.
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    The low winter sunlight (1) passes through the glass surfaces (2) of the Trombe wall and hits the black concrete slab (3) which absorbs some of the light as thermal energy, or heat. When the heat is radiated from the slab it is trapped by the glass and rises (4), drawing cool air (5) into the collector wall via floor vents on the bottom of the home’s two stories. The sun-warmed air then exits through vents (6) near the ceiling of both stories into various rooms of the house, where it mixes with cooler air, descends and is drawn back through the collector. At night, the massive slab radiates (7) the heat it absorbed during the day warming the home. In the summer, sunlight (8) strikes the house at a higher angle and “bounces off.” Small electric fans (9) exhaust any hot air that accumulates in the collector, which rare because the vents between the wall and the rest of the house keep air circulating.

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Up in New Jersey, a guy by the name of Doug Kelbaugh designed (and moved his family into) a passive solar home that's not only cozy in winter and cool in summer, but aesthetically pleasing to boot!

Yes, Virginia, a solar heated and cooled house can be beautiful. That, among other things, was what architect Douglas Kelbaugh set out to prove when he designed and built his family's all-new Princeton, N.J., solar home, and it shows!

The split-level dwelling's major design element — as you can see in the Image Gallery — is a massive, south-facing "collector wall" made of 15-inch-thick poured concrete that has been painted flat black and faced with 600 square feet of double-pane glass. (The two layers of glass are mounted in greenhouse-type aluminum channels, set 6 inches in front of the slab.) This passive collector not only heats the three-bedroom house in winter and helps cool it in summer, but lends aesthetic appeal to the structure as a whole, something that, until recently, has been missing from too many solar home designs.

How the Solar Heated Home’s Collector Wall Works

In the diagram of the house design, the rays of the low winter sun (1) strike the glass surfaces of the collector wall nearly perpendicularly and (2) readily pass through to impinge upon the concrete slab (3), which, because it's painted black, absorbs slightly more thermal energy than it reflects. And, since glass is transparent to light but opaque to heat, about two-thirds of the warmth that is radiated from the slab is retained within the collector.

OK. As the air between the glass and the concrete becomes heated, it rises (4), drawing cool air into the collector wall via floor vents (5) on both of the home's two stories. The sun-warmed air then exits through vents (6) near the ceiling of both stories into various rooms of the house, where it mixes with cooler air, descends, and is ultimately drawn back through the collector again.

(Thanks to an adjustable damper halfway up the solar wall, each floor of the house can be heated independently. Without the damper, most of the warm air generated by the glass-and-concrete "heater" would go straight into the upstairs rooms.)

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