Designing Beyond Hot and Cold - Exploring Full-Body Heat Experiences in Sauna

The design of thermal experiences, often only associated with hot and cold sensations, encompasses a much wider range of qualities that can evoke emotional and sensory effects on users extending beyond this basic binary nature. Through a phenomenological study of a traditional Finnish sauna, we delve into how individuals perceive and express full-body heat sensations using both verbal and non-verbal methods and infer dimensions and parameters of heat that can inform future thermal experience design. Findings from participants' expressions lead to formulating experiential dimensions such as the dynamic nature of heat, the aesthetics of discomfort, considerations of texture and heaviness, interoception, and personal memories that expand our understanding what heat as a design material consists of and the various possibilities it may hold. Furthermore, we propose three thermal parameters of motion, timbre, and distribution which can contribute to designing more intricate heat experiences and pave the way for further research in temperature interfaces.