Effect of urban built form and density on building energy performance in temperate climates

Abstract Urban built form and density are crucial parameters for the optimization of building energy performance on an urban scale. However, a lack of a cohesive framework exists in the literature which correlates building energy with urban built form and density, with no unified determination for the concept of urban density. This study establishes the sensitive interrelationship of urban built form, density and building energy performance using two density indicators, specifically, site coverage and plot ratio. The paper initially considers geometrical variables of four customary urban built forms to investigate their relationship with the density indicators. Energy analyses are then performed on geometrical models representing residential buildings. The city of London, as an example of a temperate climate, is considered as a case study. Annual building energy demands of masterplans consisting of pavilion, terrace, court and tunnel-court forms are calculated. The findings are used to make a heat map of energy intensity on the Form Signature graphs. Results show that high-rise buildings with greater plan depths achieve higher energy efficiency. Moreover, greater cut-off angles correspond to higher energy demands under London climatic conditions. An energy indicator, termed Energy Equity is introduced which represents the ratio between Photovoltaic (PV) energy generation installed on roofs with respect to the total energy demand of the building. Further analyses show that by considering energy demand and PV energy generation simultaneously, low-rise buildings with greater plan depths provide improved total energy performance. Finally, a comparative analysis of the energy performance of different built forms with similar geometrical variables demonstrates that the tunnel-court and the pavilion built forms represent the best and the worst energy performance, respectively. However, when keeping the density constant while changing geometrical variables, this trend is reversed. Graphical displays of the analyses provide urban planning guidelines that can be used by urban designers, planners and architects to facilitate the most energy-efficient built form and density for promoting more sustainable cities.