Roof-to-Street Cooling and Day–Night Radiant Response around the Javits Green Roof during Hudson Yards High-Rise Completion

Abstract

Green roofs with large areas can contribute towards reducing roof level temperatures, although their effectiveness in densely populated urban environments is conditional upon the extent to which this cooling is experienced at pedestrian height and influenced by nearby high-rises. This study evaluates the impact of the Jacob K. Javits Convention Center green roof and the adjacent Hudson Yards area in New York City for 2014, 2018, and 2021 urban geometries. The numerical framework consists of a 27316 m² extensive green roof, a horizontal grid of 6 m by 6 m, vertical grid spacing of 2 m, building heights of 82 m and 740.08 m, and typical weather conditions. The maximum roof-level cooling decreases from 0.75 K in 2014 to 0.65 K in 2018 and 0.64 K in 2021, whereas the maximum pedestrian-level cooling reduces from 0.52 K to 0.45 K and 0.44 K. The transfer fraction of roof to street cooling stays almost the same at roughly 0.69, implying reduced cooling capacity without the disruption of vertical transport of thermal energy. Maximum median sky view factor is 0.184 for 2018 and 0.194 for 2021. For the 2021 form, the mean radiant temperature reduction during the day is estimated to be 1.65 °C, while the increase.