Towards a theory of adaptive thermal comfort - The pleasure principle

Designing for natural ventilation became permissible across a vastly increased range of climate zones in 2004 with the incorporation of an adaptive model into ASHRAE's comfort standard (Std 55-2004). This mainstreaming of adaptive comfort was further reinforced with the introduction in 2007 of a European standard (EN 15251) that closely followed the ASHRAE 55-2004 precedent. Despite this broad international acceptance, there remains a gap in the theoretical underpinnings of adaptive comfort. The question left begging is: "How can a single set of thermal environmental conditions deemed unacceptable in a conventional HVAC setting be regarded as acceptable and even pleasant in a naturally ventilated setting?" A related question is directed specifically at the role of air movement: "How can an air speed of, say x m/s be experienced as an unpleasant draft under one set of conditions, and yet induce pleasant sensations under different thermal conditions?" In this paper the physiological phenomenon of alliesthesia is applied to the specific context of thermal comfort to provide a deeper understanding of why adaptive comfort actually works.