In the late sixteenth and seventeenth centuries, northern Europeans witnessed remarkable experiential transformations in their secular architecture resulting from the proliferation of a once rare material: transparent, colourless window glass. This essay traces the aesthetic effects occasioned by the new relationship between early modern glazed spaces and their surrounding environments, introducing the concept of synthetic vernacularism to describe the dynamic geographical factors that shaped the local use of this industrial material in northern Europe. By allowing builders in frigid climates to simulate the open, light-suffused spaces found in classical architecture, glass facilitated the site-specific reinvention of a foreign style. It also fed the ever-growing thirst for interior illumination in bustling commercial cities, which in turn engendered culturally specific modes of visual perception and expression. Before the global triumph of architectural modernism, the localized application of glass constituted a regional ecology in the early modern built environment.