The application of computational fluid dynamics to the assessment of green features in buildings: Part 2: Communal sky gardens

Sky garden is regarded as one of the green features in high-rise building design. Located in the mid-level of a high-rise, it serves as recreational garden for communal use. Amplifying the natural wind, and combined with the shading effect, a sky garden has its own thermal and wind environment. In this paper, CFD (computational fl uid dynamics) technique is applied to model the wind and thermal comfort of two possible confi gurations of a sky garden: one with 4 sides open and the other with 2 sides open. The wind data obtained from the Hong Kong Observatory are analysed and divided into three cases: i) summer, ii) winter, and iii) days affected by tropical cyclone (TC). For typical summer and winter wind conditions, thermal comfort is analysed, and for the tropical cyclone wind conditions, the wind comfort is analyzed. It is found that the thermal comfort with four openings is better than that with two openings in summer and vice versa in winter. The results also reveal that higher wind speed provides good thermal comfort in summer but poor thermal comfort in winter. The wind comfort level at typhoon days at communal sky gardens would be in the category of ‘uncomfortable’ or ‘very uncomfortable’. Finally, limitations of CFD simulation and its complimentary application with wind tunnel tests are briefly discussed.