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28 Feb 2014 - News
Thermal Impact of the Designed Environment on the Urban Heat Island
A pilot research program evaluating the thermal emissivity of elements in the designed environment and their transience to the urban air was carried out in the summer of 2010 in the Victoria Park medium-density residential precinct, Sydney. At question is the degree to which components of the built environment and associated urban landscapes contribute waste heat to the urban climate and heat island. The intention is to contribute knowledge of thermal performance at a micro-urban scale - to design decisions: aimed at adaptively counteracting global and urban warming phenomena, and mitigating noxious consequences by cooling urban environments.
Although generic sustainability rating schemes are in use, and basic thermal mass insights are acknowledged – and urban climatologists undertake a raft of complex simulation studies – practical application in the ‘cool’ design of city buildings and precincts is minimal. Empirical insights are lacking; and the emphasis is on energy - essential but insufficient in itself to affect the excess heat stored in the built form and transferred to the urban air mass. Critically, it is heat which changes the carbon cycle and climate, rather than the gases themselves. This research aims to fill that paradigm gap.
Moreover, acknowledging that greenhouse gases are present in the atmosphere at concentrations likely to persist for a century and more, the only logically realistic resolution appears to be: to take the heat out of the equation. The methodology followed in this research was to obtain thermal imagery of radiant emissivity at micro-urban-climatic scale, at different times of day and night and on different facade orientations in a case study site - by means of a hand-held thermal camera. Ambient conditions were logged simultaneously, and correlated with the radiant emissions.
The results have been tabulated in a Thermal Performance Index in the Final Report below, representing the transience contribution of elements, ranked from hottest to coolest (radiators to coolers); where maximum and minimum radiant emissions are associated, and interpreted as rules of thumb.
Although the thermal imagery indicates that albedo reflects heat and cool coloured elements apparently contribute less heat, and water stores heat as expected, unless the thermal energy is transformed, essentially, by living, vegetative greenery the dilemma of excess heat in the urban environment and climate persists. This is a conceptual interpretation drawn from this research – and demands further research.
This thermal imaging technique can be readily applied in urban environments of any scale – since the metric is micro-urban climatic. To undertake evaluations of designed environments - from the CBD via medium-density to outer suburban configurations - is a next logical step.