Evaluation of microclimatic conditions in urban environment from the human comfort perspective

Abstract

The paper presents a new assessment method for microclimatic conditions in the urban environment. The proposed model defines quantitative and qualitative features of the study area from the human comfort aspect. Two main elements of the urban environment, weather conditions and urban development are evaluated. To determine whether the environment is comfortable for inhabitants, a simple criterion of comfort has to be established. This criterion must take into account the complex nature of heat exchange between a man and environment. In the light of extensive research carried out in many countries it can be demonstrated that there is a correlation between the intensity of heat fluxes with air temperature and wind speed, which allows approximations to be applied. This parameter can be used for the relative comparison of different environmental conditions. Taking into account the efficiency ranges of the thermoregulatory systems (applied in thermophysiology), criteria for thermal comfort can be established. For the assessment of weather conditions, a weather typology is proposed. Human thermal sensation caused by the reaction of the thermoregulatory system to atmospheric stimuli (air temperature, wind speed) are related to the specific type. The second important element affecting the final assessment of microclimatic conditions is the structure of the urban area i.e. participation of the various urban structures, tall vegetation and open area in the total surface as well as zones with wind comfort and discomfort. The above estimation is carried out using numerical simulations, assuming wind speed 4m/s and by simultaneously taking into account frequencies of wind flow occurring from 8 or 12 directions and related air temperature. The proposed method in its current version constitutes an approximation only. Many parameters, such as land profile, shadow fall, or heat loss by the external surfaces of the building, are not included. However further future developments and incorporation of other parameters are possible.