The importance of sample grouping; Exploring thermal sensitivity of occupants within one building type and ventilation mode

Occupants’ thermal response is influenced by their sensitivity to temperature variations, i.e. the rate of change in occupants’ thermal sensation per unit change in indoor temperature. Thermal sensitivity is commonly taken as constant (Griffiths constant) in the calculation of occupants’ comfort temperature. This constant is based on small differences found between buildings’ ventilation modes [naturally ventilated (NV) vs. air conditioned (AC)]. However, recent research found significant differences depending on building type, ventilation mode, age, gender and climate. This paper reviews thermal sensitivity within the same building type and main ventilation mode using longitudinal surveys and monitoring data from school buildings, two in the UK (U1 and U2) and one in Sweden (S1). Results show that in two of the schools (U1 and S1) children were half as sensitive as in school U2 and the difference is statistically significant. A similar result with slightly different thermal sensitivities was derived from comparison by clusters derived from the classrooms’ indoor temperatures. This outcome suggests that building ventilation mode (AC/NV), which is typically considered the main determinant of occupants’ thermal experience and often the only building information recorded in field surveys, is inadequate to explain this important occupant response factor.