Impact of Building Design and Operating Strategies on Urban Heat Island Effects Part II: Sensitivity Analysis

Abstract

This study investigates the mutual thermal interactions between buildings and the microclimate within urban area centers. Buildings are the primary energy consumers in cities, and one of the main causes of the urban heat island (UHI) formation. In this article, a flexible simulation environment is developed and used to model the mutual thermal interactions between building energy systems and their urban surroundings in Phoenix, AZ, characterized by its hot climate. The impacts of various operating strategies for both commercial and residential buildings are assessed on both UHI effects and energy consumption. Specifically, the study evaluates the impacts of indoor temperature settings, precooling strategies, and air infiltration/exfiltration rates. It has been found that heat rejected by air conditioning systems significantly impacts UHI formation in urban centers located in hot climates. Specifically, commercial buildings were found to cause more UHI effects than residential buildings due to higher cooling loads. The impacts of heat rejected from heating, ventilating, and air conditioning (HVAC) systems are found to be more dominant than that from air exfiltration on the microclimate of urban centers. For urban center made up of commercial buildings with a street aspect ratio of 2, heat from air exfiltration is estimated to be as low as 10% of the heat rejected by HVAC systems.