Impact of increasing the height of Tel Aviv buildings on pedestrian comfort and building energy efficiency

This study examines the potential effects of adding several additional floors to existing buildings on the microclimate of Tel Aviv streets, and hence on pedestrian thermal sensation and on energy consumption for space conditioning. The research employs computer simulation, using three numerical models: First, the Canyon Air Temperature (CAT) model is used to generate site-specific weather data from time-series measured at a meteorological station in the region, accounting for urban geometry, materials and surrounding hydrological conditions. These data are used as inputs for assessing: a) Pedestrian thermal comfort, using the Index of Thermal Stress (ITS), which estimates pedestrian thermal sensation under warm conditions based on radiative and convective exchange, as well as humidity and physiological responses, and is calculated as the evaporation rate in terms of equivalent latent heat which is required to maintain thermal equilibrium. b) Building energy performance, using ENERGYui, a graphic user interface for EnergyPlus. ENERGYui was developed to generate building energy efficiency labels according to the Israeli building standard IS 5282. The paper reports on the effect of different building heights in N-S oriented street canyons. Results suggest that deeper streets are likely to create more intense nocturnal heat islands. However, the total number of hours in which a pedestrian is likely to experience thermal stress is reduced in deeper N-S canyons, creating a net positive effect. Additionally, building energy modelling shows that elevated air temperature plays less of a role in energy efficiency than do other aspects such as the proportion of building envelope exposed to the sky and mutual shading by adjacent buildings, making taller buildings more economical under the conditions simulated.