The Endlessly Frosty American Indoors

That first summer, however, staffers found themselves increasingly hot, limp and damp, their experience captured by daily surveys that included this plaintive report from one suffering soul: “I am physically melting.”

More fans were brought in, employees were encouraged to work early in the morning — before the day got too hot — and the dress code was relaxed. Clients who visited, including State Department officials (at the time, the firm was working on an American embassy in London) were forewarned. Witold Rybczynski, writing of the experiment in Architect magazine, imagined a scene from a P.G. Wodehouse novel: diplomats in short pants!

It was a grand experiment, and not exactly a failure, since the building, which is now cooled by what’s known as mixed mode operation — that is, using a bit of conventional air-conditioning when needed — is still a model of energy efficiency. Switching to mixed-mode has added only 1 or 2 percent to the building’s total energy load, according to Roderick Bates, a Kieran Timberlake principal.

Mr. Bates said that one of the reasons natural cooling wasn’t fully successful was that Philadelphia’s nighttime temperatures during the peak summer months weren’t low enough to allow natural ventilation to cool the place down. Passive house systems work really well in climates with big diurnal temperature swings, like the desert.

A byproduct of the experiment was the evolution of the survey process, now a cloud-based app called Roast, that revealed something rather illuminating: While there were slightly more survey responses from female staff, the differences in thermal comfort between sexes were insignificant. (Are women just more inclined to participate in surveys?)

It turns out gender is less a predictor of thermal comfort than other factors, like age, activity level or, tellingly, the relative wealth of the society surveyed, according to studies conducted by researchers at the Center for the Built Environment at the University of California, Berkeley.