This essay proposes an inversion and productive complication of the familiar nomenclature of active and passive solar energy, as it pertains to architectural design methods and to solarity more generally: that is, to changes in economies, cultures, and ways of living in the present and future. I examine three houses central to the history of solar energy and its possible futures: the George O. Löf House (Denver, CO, 1957); the Douglass Kelbaough House (Princeton, NJ, 1974), and the Saskatchewan Conservation House (Regina, Saskatchewan, 1977) in order to assess the cultural and technical changes they elicited. At stake in reconsidering the distinction between active and passive solar energy is an attempt to understand how we experience simultaneously the resource conditions of our thermal interiors and the transformations of global climatic patterns. Which is to say, reconsidering active and passive in solar architecture (with heat storage as the hinge) also reconsiders the role of buildings in the production of the carbon zero future—less, at least relatively, as spaces of technological innovation, and more as spaces of social and species evolution. An active passive solar architecture aspires to lifestyles, habits, and expectations coming into line with the massive geophysical transformation of climate instability. By emphasizing the contingency of the built environment and of means of inhabitation, the solar house becomes a medium for epochal social change.