Thermal radiation, being the infrared spectrum of electromagnetic radiation, shares many characteristics with visible light, and thus is highly dependent on surface geometry. Much research effort has been dedicated to characterizing the behavior of visible light in the built environment and its impact on the human experience of space. However, longwave infrared radiation’s effect on the human perception of heat within the indoor environment is still not well characterized or understood within the design community. In order to make legible the embodied effect of radiant surfaces’ geometry and configuration, we have developed a Mean Radiant Temperature simulation tool which is based on a raytracing technique and accounts for the detailed geometry of the human body and its surrounding environment. This paper is meant to provide an overview of the geometric characteristics of radiant heat transfer with a dual purpose: 1. the integration of these principles into a Mean Radiant Temperature simulation technique in order to better characterize radiant energy exchanges and 2. the development of architectural design strategies based on these principles, which are tested in a case-study prototype. The MRT simulation method and results for the experiment are discussed.