Microclimatic implications of a large-scale green roof and high-rise redevelopment in New York City

Abstract

This paper quantifies the impacts of the Jacob K. Javits Convention Center (JJCC) green roof and the nearby redevelopment of Hudson Yards (Midtown West, Manhattan, New York City, NY) on the local microclimate. The analysis was performed using ENVI-met, a grid based, three-dimensional (3D) computational fluid dynamics model commonly used to simulate surface-plant-air interactions in urban settings. Using air temperature, relative humidity, and wind speed and direction measured onsite on July 22, 2014, a total of six simulations were run, comprising three different stages of redevelopment (e.g., in 2014, 2018, and 2021), with and without the JJCC green roof in place. Under the simulated climate conditions, the green roof reduced air temperature over the no-green roof (NoGR) condition, primarily on the north side of the JJCC. However, because of the nearby redevelopment, the cooling benefit provided by the roof decreased slightly over time. For example, at 1:00 p.m. the air temperature dropped from 0.75 K at roof level in 2014, to 0.65 K and 0.64 K in 2018 and 2021, respectively. Similarly, though to a lesser extent, the same trends were evident in the simulations at pedestrian level. The redevelopment of Hudson Yards reduced the sky view factor (SVF) and provided shading during the day, reducing daytime mean radiant temperature (MRT). However, the same buildings raised nighttime MRT. Together, the study provides insights into the growing understanding of how green roofs can impact the microclimate of complex urban environments.