The Climate Dimension in the Design of Resilient Urban Neighborhoods in Norway: A study on materials, outdoor thermal comfort, and building energy demand in the context of the urban microclimate

Abstract

One of the 17 Sustainable Development Goals proclaimed in the 2030 Agenda for Sustainable Development by the United Nations is Sustainable Cities and Communities. In the view of urbanization and a rising world population, the ambition is to create and transform cities into climate-resilient, safe, healthy, climate-friendly, and livable environments for its citizens. This thesis aims to contribute to this goal in the context of Norwegian climate conditions. For that, multiple approaches and methodologies are used. First, an extensive literature study is conducted to synthesize the characteristics of the urban climate, focus areas, and research gaps from scientific publications addressing cold and polar climate regions. Second, numerical tools including computational fluid dynamics (CFD) and building performance simulation (BPS) are used to create models for studying the effect of different climates and design scenarios particularly with regard to people’s outdoor thermal comfort and building energy demand. Field measurements of relevant climate variables from a network of fixed and temporary weather stations are used to provide input and validation data for the numerical models predicting the local climate conditions in an urban neighborhood (microclimate). Finally, a coupling methodology for CFD and BPS is presented that allows investigation of the energy demand of different floors of a high-rise building considering vertical temperature gradients derived from CFD simulations. For most of the thesis work, the Gløshaugen campus of the Norwegian University of Science and Technology which is currently under redevelopment served as a case study. From the literature review, it was found that the urban climate in cold climate regions is strongly affected by the presence of the urban heat island (UHI). Mostly, observational methods were used and only 22 % of the reviewed studies used numerical tools to replicate, predict or investigate different scenarios of the urban climate. The numerical simulations in this thesis show that solar access is key for improving the outdoor thermal comfort in urban areas during the cool and cold seasons in Norway. Also, wind sheltering proves to be an effective measure, however, only at relatively high wind speeds and on a smaller scale than solar access. Changing the material properties of the urban surface in a dense urban environment only presents a negligible effect on outdoor thermal comfort during cool or cold weather conditions. Moreover, solar access is favorable in buildings, as in Norwegian climate conditions, south-oriented, unshaded windows can lead to more useful solar energy gains than detrimental energy losses, on an annual basis. The benefit of wind sheltering to lower a building’s energy demand is found to be small, as new buildings according to the Norwegian building regulations get increasingly airtight. Furthermore, it is shown that especially during a summerly heat wave in Norway, the cooling energy demand and indoor overheating can be reduced effectively with vast urban greening compared to a concrete-sealed urban surface. While in summer the effects of different material compositions of the urban surface on the microclimatic conditions are very distinct, they are less pronounced in autumn and marginal in winter during the investigated conditions. Resulting from the proximity to the urban surface, the effect is strongest in the lower floors of a building. This thesis underlines the importance of including urban microclimate in the planning process of buildings and neighborhoods, as well as giving it a stronger role in study syllabi. It shows that numerical modeling is a valuable resource for the understanding of the urban (micro)climate and gives detailed examples for its application. The results are intended to provide useful knowledge for researchers and practitioners in architecture, building engineering, and urban planning, as well as decision-makers in public authorities.