Effects of urban context on the indoor thermal comfort performance of windcatchers in a residential setting

Abstract

The impact of urban district morphology on the ventilation performance of a residential windcatcher was assessed in three different urban scenarios through a series of wind tunnel experiments. Geometry of the urban context and external obstacles affect the characteristics of wind flow reaching the individual buildings. The ventilation performance of windcatchers has previously been studied, however the impact of surrounding urban configurations on the efficiency of a residential windcatcher has not been investigated in the literature to date. This paper investigates the comfort cooling performance of a residential windcatcher in different urban arrays. Three phases of work are reported: (1) wind tunnel experiments to measure pressure distributions over a scale model to compare the effects of different urban contexts on rates of indoor air movement. Three urban scenarios have been identified as a) isolated windcatcher building, b) windcatcher building located in the corner of a neighbourhood, c) windcatcher building embedded in a neighbourhood. (2) a climatological study to predict hourly indoor air speeds for Sydney's contemporary climate TMY). Corresponding indoor operative temperature for each hour in a year was estimated using DesignBuilder/EnergyPlus. (3) a thermal comfort simulation using Standard Effective Temperature (SET*) to compare the comfort cooling potential of the residential windcatcher within the three different urban morphologies. The results for each urban scenario were benchmarked against the default case of conventional through-window ventilation without windcatcher in the same urban scenario. Of the three urban configurations investigated the case in which the windcatcher building was located in the corner of the neighbourhood presented the largest indoor airspeed increment compared with baseline conventional window ventilation (∆0.39 m/s). The indoor air speed generated by windcatcher surrounded by neighbouring structures increased by ∆0.33 m/s above that obtained with just through-window ventilation. The corner-located windcatcher delivered a cumulative total of 5,281 degree hours of comfort cooling during Sydney's typical summer, comparable with 5,207 degree hours for the windcatcher surrounded by buildings. The incremental indoor air speeds would feel equivalent to an average ∆ -3.4°C comfort cooling relative to the default through-window ventilation mode for corner located windcatcher.