The impact of occupant's thermal sensitivity on adaptive thermal comfort model

Occupants' thermal sensitivity influences comfort temperature, thermal comfort models, and building energy simulation. To date, a universal thermal sensitivity estimate (i.e. 0.5/degrees C), the so-called Griffiths Constant, has been widely used to estimate comfort temperatures. However, recent field evidence indicates that the constant is actually a variable that changes according to context. The objective of this study is to explore the impact of different thermal sensitivity values on adaptive comfort models using the ASHRAE Global Thermal Comfort Database II. The method followed five main steps: i) subset Database II to include entries with the requisite parameters; ii) estimate neutral temperature using the standard Griffiths method; iii) iterate step "ii" using different thermal sensitivity values; iv) derive adaptive comfort models for air-conditioned and naturally ventilated office buildings considering global and European datasets; v) compare resulting models. The results highlight that occupants' thermal sensitivity varies according to building ventilation type. Occupants in naturally ventilated offices were about half as sensitive to temperature changes as occupants in air-conditioned buildings. The most important outcome of this study is that thermal sensitivity and geographic region significantly affect the adaptive model relationship between outdoor temperature and indoor neutral temperature for occupants of naturally ventilated buildings; Occupants of European buildings are more sensitive to temperature changes than counterparts in other regions. The significance of this finding is that the adaptive model relationship forms the basis of the adaptive comfort standards, and so it has implications for both the design and operation of naturally ventilated and mixed-mode buildings.