Abstract

Global warming and rapid urbanization have intensified the urban heat island (UHI) effect, and its effect on human comfort in urban spaces has attracted widespread attention. The UHI effect increases the risk of heat-related mortality and building energy consumption and reduces outdoor human thermal comfort. A comfortable outdoor space supports sustainable urbanism by making the outdoor environment more comfortable and usable, thereby helping reduce the time spent indoors and the energy consumption of buildings.

There are thermal, visual, and acoustic features that influence outdoor comfort in terms of human physical, psychological, and social behaviors. Building façades, a common component of the physical factors that are part of the urban form, are often overlooked as climate factors that affect pedestrian outdoor behavior and public health. Research to date has mainly focused on green façade techniques, combining different materials, and the various properties of façades. However, very little research has investigated the relationship between building facades and outdoor comfort as experienced by human subjects.

To fill this knowledge gap, this dissertation utilized a combination of field measurements and questionnaires to investigate the effects of building facades composed of different materials and window-wall ratios on human outdoor comfort and behavior. Same-size spaces in front of three different facades on the Washington University campus in St. Louis were utilized as experimental sites to measure the mean radiant temperature (MRT) under low temperature, cloudy, and clear sky conditions. Student participants were invited to sit at three distinct distances in front of the three building façades on a cool cloudy day, a cool sunny day, and a hot sunny day to collect their perceptions and actions regarding their comfort in relation to the various characteristics of the facades (building materials, window-wall ratios, aesthetics, and heat reflection); the microclimate conditions (temperature, wind, and solar radiation), and the features of the sites. Their adjustments or seating distances reflected their attitudes toward their outdoor comfort in each setting; and the results revealed four insights. First, on cold sunny days, solar radiation increased the surface temperature of the building façade. The thermal radiation from the building façade and the reflection from the sun raised the MRT by about 4.5°C to 6.5°C, which affected outdoor comfort due to the heat and brightness. Second, on cloudy days, the facade materials had less impact (MRT fluctuation of 2°C); but on sunny days, the Indiana limestone panel walls, which had lower surface temperatures, had a higher impact than glass curtain walls and combination walls (MRT fluctuation: 7°C) and the façade materials also influenced the psychological comfort of the participants noticeably. Third, the participants’ distances to the wall and view satisfaction affected their outdoor visual and thermal comfort. The impact of the facades on the MRT decreased (Max MRT difference: 6°C) as the distance from the façade increased due to the view factor. Fourth, comparing the different MRTs, solar radiation significantly impacted the outdoor comfort of the participants than did the different materials and distances (MRT Difference: Weil Hall, glass curtain wall, 11°C; Art Museum, glass and Indiana limestone panel combination wall, 9.3°C; and Givens Hall, Indiana limestone panel wall, 12.6°C). These results confirmed that outdoor comfort is a complex subject that is influenced by many aspects and requires more research.

Not enough attention has been paid to how building facades affect outdoor comfort in the past. This dissertation contributed a new viewpoint and suggested that an outdoor comfort assessment that considers the impact of building facades can promote more appropriate and satisfying building designs.

Committee Chair

Hongxi Yin

Committee Members

Ming Qu; Ian Trivers

Degree

Doctor of Sustainable Urbanism (DrSU)

Author's Department

Graduate School of Architecture

Author's School

Sam Fox School of Design & Visual Arts

Document Type

Dissertation

Date of Award

Summer 8-17-2023

Language

English (en)

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