Quantifying the impacts of air conditioning on the thermal sensation of pedestrians in terms of changes in microclimate

Abstract The study analyzes the effects of air-conditioning (AC) usage on thermal sensation due to interferences in acclimatization in outdoor spaces, from field data in Rio de Janeiro. Field monitoring campaigns have been carried out in warm periods between 2012 and 2015, with microclimate monitoring and concurrent comfort surveys according to ISO 10551, to which questions on the use of AC were added. The thermal index employed for interpreting microclimatic data was UTCI (Universal Thermal Climate Index). Results showed that the frequent use of AC could have an impact on the thermal perception of passersby, thus confounding the definition of thermal comfort limits. A drop of 2°C was estimated in terms of UTCI units for the onset of heat thermal stress for the less acclimatized group (typical users of air-conditioned spaces), which suggests a reduction in thermal tolerance to heat in such population stratum. From results obtained and towards the development of the field area outdoor thermal comfort in Brazil (with mostly tropical climate conditions) it is recommended the introduction of questioning as regards time of residency in outdoor comfort surveys.