Since the 2000s, several international studies have shown that housing is an unevenly distributed determinant of physical and mental illness. To understand how social inequalities in health are linked to social inequalities in housing, the SAPHIR research program is studying buildings sampled according to their date of construction, subject to different thermal and noise standards. Through individual and group interviews, it identifies "places and issues," "critical situations" and "trade-offs" resulting from "residential stress." Using three buildings located in the center, periphery and southwest suburbs of Paris, two forms of social inequality in housing health are analyzed: fuel poverty and poor soundproofing. When incorporated with the quality of the built environment, factors such as housing choice, control over the environment and ability to plan for the future are reflected in residents' literacy, which is highly developed at opposite ends of the socioeconomic spectrum. This leads us to question the notion of "spheres of justice" in the field of social housing, and the third-party role of researchers working with tenants and landlords.