Abstract: The topic of solar orientation and urban form is both perennial and, once again, timely. The discourses and practices of “ecological urbanism” have turned our focus to the terrestrial topics of hydrological connectivity and ecological function. Heliomorphism proposes to revise and extend the ecological urbanism agenda by returning to solar performance. Recent projects of a number of leading architects and urbanists have suggested new forms of urban order through solar orientation. In many of these projects, designers correlate the shape of the city to a complex and contradictory economy of solar performance. The topics of solar orientation and social order, public health, and political economy were fundamental questions for many protagonists and projects of modern planning. In the wake of the collapse of modern planning, singular models of social urban order based on latitude and solar equity have given way to neoliberal models of market driven urbanization. The seminar returns to this archaic aspect of urban order, and presents its potentials through a range of planning policies and precedent projects. Independent of location or latitude, access to the sun is considered an ancient and inviolable right in many cultures. The seminar reconsiders solar access in relation to social equity and it examines, accordingly, the tensions that exist between built form through capital accumulation and access to sunlight through environmental consensus. The energy crisis and economic shocks of the 1970s led to experimental and counter-culture practices of architecture and urbanism. The current environmental crisis embraces zero-carbon responses and has pushed the scale of operation to the scale of urban form. Ralph Knowles’s concept of the “solar envelope” proposed a design tool that anticipates contemporary interests in parametricism and relational modeling. The envelope offered a projective form through which urban morphology was indexed to solar performance. The technological developments of the last decade have enabled an unanticipated degree of precision and feedback, potentially infusing new possibilities into an idea that has a half-century of history. The seminar considers the changes, conceptual and projective, that contemporary models of computational geometry have brought to this design model.