Field survey of occupants thermal comfort in rooms with displacement ventilation

Field survey of occupants´ response to the thermal environment in eight office buildings with displacement ventilation was performed. The response of 227 occupants (94 males and 133 females) was collected and analysed. A neutral thermal sensation was reported by 37% of the occupants, and between slightly cool and slightly warm by more than 85% of the occupants. The occupants´ thermal sensation was close to the predictions by the PMV index. About 24% of the surveyed occupants complained that they were daily bothered by draught mainly at lower leg. Presence of draught discomfort was verified even amidst persons feeling warm or slightly warm for the body as a whole. The predictions by the Draught Rating model incorporated in the present indoor climate standards were close to draught discomfort identified from the occupants´ response. Vertical air temperature difference measured between head and feet levels was less than 3 deg.C at each visited workplace. However, almost one half (49%) of the occupants reported that they were daily bothered by uncomfortable room temperature (half of them experienced sensation of cold and the rest sensation of warm). The main conclusion of this survey is that in rooms with displacement ventilation draught is a major local discomfort factor for the occupants. The effect of vertical temperature difference on occupants´ local discomfort was not evidenced.