Building thermal performance and the urban heat island : optimization in temperate zones

Publication Type:
Thesis
Issue Date:
2014
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NO FULL TEXT AVAILABLE. This thesis contains 3rd party copyright material. ----- Optimized roofing considering cost and energy savings and external environmental impacts, was found for temperate climates. The best combination of roof solar absorptance, thermal emittance and sub-roof insulation showed low solar absorptance gave high energy savings without high R-values. Building simulation then pinpointed the optimum design, when select building design parameters, with all other parameters fixed, were changed simultaneously. This led to an optimum year round combination of design elements using examples of strong and weak cross–coupling between parameters which were exploited to save energy in summer and winter. A high solar reflectance, with capability of low infiltration and an intermediate R-value was the preferred year round combination in a single family house in Sydney. It was indicated that this approach to high energy savings could also reduce the heat island effect for more pleasant urban environments. A key task was to assess the limitations of AccuRate 1.1.4.1 simulation software as used in Australia for house energy rating when this project started, and then to design and test improvements. Simulation was validated against data on various structures and with alternative models, then applied to a range of building energy issues. The way convection and radiation combine in the “simple” algorithm in EnergyPlus (energy building analysis and thermal load simulation program) matched AccuRate 1.1.4.1 results but neglected night sky radiation losses. The AccuRate engine was then modified to consider variable heat transfer coefficients and external roof and wall radiation losses. This new engine provided more precise results. A simple low cost methodology to measure and calculate the atmospheric long-wavelength down-welling thermal radiation was developed to replace our fixed pyrgeometer which is expensive and less portable. The MLX90614, a low-cost infra-red thermometer at a particular orientation gave very satisfactory accuracy and hence data at remote sites. Other studies included (i) evaluating the impact and value of using phase change material in a roofing system (ii) how building layout, heights and façade materials in central business districts impact externally, especially via the heat stored overnight. Sky view aperture was the most influential parameter, followed by façade and road materials.
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