In the popular imagination, energy-efficient design has been understood to be a byproduct of the oil embargo initiated by the Organization of Petroleum Exporting Countries (OPEC) on 19 October 1973. On that date, Western consumers of fossil fuels became painfully aware of the energy-intensive nature of their built environment and their fragile dependence on foreign energy sources. The practice of energy-efficient design gained public recognition only after the related conditions of overconsumption and scarcity became so dramatically apparent. The political drama of the mid-1970s, however, only documents the prior suppression of long-emergent scientific doctrines. The German physical chemist Rudolf Clausius (1822–88) was one of the first to articulate the second law of thermodynam-ics, which he expressed in 1865 as the concept of ent ropy. On the basis of his observation of thermal transfer, Clausius argued that one could not finish any real physical process with the same amount of ener...