Sorry to hear of Doug Kelbaugh’s passing. I met him at Seaside when he was involved in the New Urbanism movement, but I first heard of him in 1973, in connection with a solar house that he built for himself in Princeton. It made an impression because unlike most solar-heated houses of that period, which had sloping solar collectors and resembled wedges of cheese, the Kelbaugh House had real architectural qualities. The house was passively solar heated by means of a Trombe wall, named for its inventor, Félix Trombe (1906-85), a French engineer who was in charge of building a 1000 kW solar furnace in southern France. I was doing research on solar stills, and I heard Trombe speak at a UNESCO conference in Paris in the Seventies. The basic principle of his device was simple: a south-facing thick masonry wall painted black, an air gap, and a glazed wall. The sun warmed the masonry, which at night radiated heat to the interior of the house. No fans or pumps (hence the “passive” moniker), and no angled solar collector, just a masonry wall. There was a bit more to it, but that is the idea in a nutshell. Doug added glazed windows to the wall, which meant that, unlike a collector, view was not entirely blocked. Very elegant.