Review and Critical Analysis of International UHI Studies

EXECUTIVE SUMMARY
The U.S. Department of Energy (DOE) has funded this project with the overall objective to
support the Secretary’s initiative on cool roofs through a review of international literature on
urban heat islands (UHI) and the identification of a panel of scientific experts to develop a
research priority plan founded on the findings from this research study. The study is desk based
and is composed of two principal tasks.
The first was to collect, review and critically analyze the international UHI literature published in
the past two decades with the scope of identifying the potential to save energy and CO2 through
implementation of UHI countermeasures; summarize the documented understanding of the
opportunity for scale‐up national and international UHI mitigation efforts; review of the UHI
countermeasures in various climates examining where the value of the energy savings justify the
implementation of mitigation efforts or if incentive schemes are required; assessing the urban
planning issues and how they affect the deployment of UHI countermeasures; and finally
developing a set of recommendations on the next steps required to support the development and
deployment of the UHI mitigation efforts. The second task was to identify the most prominent
scientific leaders in the UHI field to serve on an international scientific panel that will develop a
research priority plan to validate the CO2 mitigation potential of cool roofs as well as debate the
recommendations emerging from this study.
The research conducted has reviewed a total of two‐hundred and thirty‐eight papers across the
entire UHI value chain with the greatest interest (descending order) from the following
continents: North America, Asia, Europe, Australia, and Africa. The predominant focus was in
warm, arid and equatorial climate types with a majority of the seminal studies relating to UHI
emanating from the Lawrence Berkley National Laboratory, UHI Group.
The UHI phenomenon itself was well documented and universally interpreted by all research
groups. It is apparent that the focus of climate on the global scale has shifted from the global to
local scale with most of the research groups and studies addressing the urban climate. The
research conducted to identify the UHI causal factors and measuring the impact of UHI clearly
demonstrates that the impacts have greater implications than simply temperature increases. The
research in this field was found to be comprehensive in identifying the causal factors; however,
their collective interaction upon the urban heat island as a system appears to be less well
understood.
The studies that used modeling and simulation were found to be a useful method for modeling
individual buildings/cities experiencing the UHI phenomena and in evaluating UHI mitigation
countermeasures. Much of the focus appeared to be on the micro (single building) to macro (city
scales) with great emphasis on the micro‐scale phenomena, it was however, noted that such
models were often highly constrained to effectively break free from the micro scales, and in
certain cases under developed to cope with the macro/global scale required to produce accurate
mass UHI countermeasure assessments. It was demonstrated that the modeling and simulation of
mitigation scenarios is an important step in regulatory planning as it acts as a low cost, low risk
test of the effectiveness of the mitigation technology.
Review and Critical Analysis of International UHI Studies
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