Predicting thermal comfort in office buildings in a Brazilian temperate and humid climate. Energy and Buildings

This paper aims to compare thermal comfort responses from office workers in both fully air-conditioned and mixed-mode buildings against both the analytical and adaptive models of thermal comfort of ASHRAE 55-2013. Occupants were asked to record their thermal perception in questionnaires delivered online while instantaneous instrumental measurements were taken in situ (air temperature, radiant temperature, air velocity and humidity). Three buildings were investigated in a temperate and humid climate, i.e., in Florianópolis, southern Brazil. Two buildings have mixed-mode operation and one building has central air-conditioning. Almost two thousand six hundred questionnaires were collected during field studies. Actual thermal sensation and acceptability votes were compared against two predictive models of thermal comfort: the analytical model and the adaptive model. The 80% and 90% acceptability limits of indoor operative temperature used in the adaptive model were calculated using the prevailing mean outdoor air temperature. The analytical model overestimated the cold sensation of users, mainly for natural ventilation mode, and did not properly predict the percentage of thermal dissatisfaction of users. The analytical model could be used only when air-conditioning is operating; and a wider range of indoor thermal conditions than recommended by ASHRAE 55-2013 is recommended to be adopted during air-conditioning operation. The application of the adaptive model seems to be inappropriate for fully air-conditioned buildings. This work was not conclusive about the use of the adaptive model when the air-conditioning is on in mixed-mode buildings due to few data collected in this mode of operation. Under natural ventilation operation in mixed-mode buildings, occupants adapted to temperature fluctuations as predicted by the adaptive model, however, occupants appear to be more tolerant to cool conditions. The adaptive model may be used in mixed-mode buildings, when the air-conditioning is not on.