ExoBuilding explores the novel design space that emerges when an individual‟s physiological data and the fabric of building architecture are linked. Developed in early 2009, ExoBuilding is a tent-like structure that externalises a person‟s physiological data in an immersive and visceral way. This is achieved by mapping abdominal breathing to its shape and size, displaying heart beat through sound and light effects and mapping electro dermal activity to a projection on the tent fabric. The research is positioned in relation to previous work and the iterative development of ExoBuilding from to-scale to full-size prototype is described. The design process, feedback gathered alongside and observations allow the discussion of wider issues: the different scales possible, the temporal nature of the data, ownership and ambiguity of that data, ranges of control and the aggregation of data in a building context. This leads to the presentation of directions for future research at this exciting boundary between Architecture, HCI and medical science.