Urban development poses multiple problems, including environmental pollution, a reduction in biodiversity, and the disappearance of the natural environment. Man-made environments and structures... Show moreUrban development poses multiple problems, including environmental pollution, a reduction in biodiversity, and the disappearance of the natural environment. Man-made environments and structures consume a large amount of limited natural resources through their extensive use of energy and materials. This research explored the use of vegetation in building facades as a potential solution to the problems of urban ecology and the excessive energy consumption in buildings. Vegetated facades have the ability to reduce building energy use, reduce the urban heat island effect, improve air quality, and increase the biodiversity of plants and animals in cities. The goal of this research was to evaluate the effects of plants on thermal performance and energy consumption of buildings by developing a thermal model of a building facade covered with a layer of plants. The developed mathematical model accounts for thermal physical processes in a vegetated exterior wall, including solar radiation, infrared radiative exchange between the facade and sky, the facade and ground, the facade and vegetation layer, convection to and from the facade, evapotranspiration from the plant layer, heat storage in the facade material, and heat conduction through the facade. The model calculates vegetated facade surface temperature and heat flux through the facade for multiple weather conditions, plant physiological characteristics, and facade properties. The model was validated with the results of a week-long experiment measuring the thermal properties of bare and vegetated facades on a building at the Illinois Institute of Technology campus. The experiment and subsequent sensitivity analysis demonstrated that a plant layer can effectively reduce the facade exterior surface temperature, daily temperature x viii fluctuations, exterior wall temperature gradient, and, as a result, provide as much additional thermal insulation to the facade as a 2.5 cm layer of expanded polystyrene insulation, depending on a range of plant parameters. The vegetated facade model was also used to analyze the reduction in energy consumption in generic office and residential thermal zones for multiple parameters. The simulations showed that energy reduction could be as high as 6.2% of annual total energy use and 34.6% of cooling energy use in residential thermal zones, depending on building characteristics, plant parameters, and climate zone. Overall, the vegetated wall model developed and validated herein provides a new tool for evaluating the impact of plant layers on facade thermal performance in existing buildings retrofitted with green walls and for designing green walls for optimal energy efficiency in new construction. Show less
