Urban heat island effect on energy application studies of office buildings

Abstract

Because of the urban heat island (UHI) effect a metropolitan area is typically warmer than its surrounding rural area. This has led to a growing concern that the use of standard (mostly rural) weather data leads to inadequate decision-making with regard to the energy efficiency of buildings in metropolitan areas. This paper conducts a series of computational studies that explore the UHI effect on two routine applications of building energy simulation: (1) predicting the magnitude of energy use and (2) predicting energy savings. We present the results based on case studies of office buildings in 15 representative cities across different climate zones in the U.S. The results show that the UHI considerably modifies the urban climate measured by cooling and heating degree days. As a consequence, ignorance of the UHI effect remarkably underestimates building total energy use in hot climate zones where cooling energy use is dominant, yet causes overestimation in cold climate zones where heating energy use is prevalent. In mild climate zones, the UHI effect only has a moderate effect because the effects on cooling and heating mostly average out. When building simulation is used to assess energy savings that is measured as the ratio to the corresponding baseline such as in a comparative analysis of retrofit measures, the UHI effect is less of a factor.