The Invention of the Roofpond System

The Phoenix Prototype and Atascadero house

The 1967 Phoenix Prototype (120 sq ft, built with passive-solar engineer John I. Yellott) was a rigorously measured demonstration: interior temperatures held between 68–82°F, comfortable roughly 91% of the year in Sonoran Desert conditions — credibility came from third-party-verifiable performance data, not publicity alone. The follow-on Atascadero, CA house (completed 1973) escalated the story: Hay testified before Congress the following year, and in 1976 the American Revolution Bicentennial Commission named Skytherm one of the “200 most promising inventions” in the US.

The 1975 evaluation

A 1975 evaluation report called Skytherm “a unique and invaluable national and worldwide asset” — despite this, congressional testimony, and national recognition, Skytherm never scaled commercially.

Why it didn’t scale

• The late-1970s return of cheap fossil fuels killed the economic urgency driving interest in passive solar.
• Real, unglamorous engineering/maintenance problems: leaky bladders, deflection of the movable insulation panels, edge-seal thermal leaks, and the structural cost of supporting a roof-load of water.

Why it matters for this archive

The essential counter-example for this KB’s promotion research: congressional testimony plus a national “invaluable asset” evaluation plus strong measured performance data are necessary but not sufficient for scaling. Unresolved maintenance/engineering weaknesses and a macro energy-price shift can sink an otherwise well-publicized technology — directly relevant to stress-testing Double Play’s own maintenance and reliability story before over-investing in publicity. See Harold Hay and Promoting passive thermal technology.