Review and Critical Analysis of International UHI Studies

This paper applied a model to calculate the amount of carbon that could be saved by the existing
vegetation in two residential areas in the Chicago, US. The simulation programs used were
Shadow Pattern Simulator (SPS) and MICROPAS. SPS creates data relating to the shading
patterns from trees on entire building surfaces, the software uses sun‐tree‐building geometry to
compute the surface shading coefficients and can calculate for a monthly, daily or hourly time
period. The SPS data is produced in a MICROPAS friendly format so that this program can go on
to estimate the building’s energy use based on its thermal characteristics, residential lifestyle and
any weather data relevant. MICROPAS can also compute on an hour by hour basis. MICROPAS
receives its climate data (temperature, radiation and wind speeds) from a local weather file by
ENERCOMP which is loaded into the program [041].
3.1.6 Urban form/planning
The studies found in this area are scare, some acknowledge the importance of urban design in
cities but there are few papers devoted to testing and simulation. Four papers that specifically
consider this area are discussed below. The papers cover three continents; Australia, Asia and
North America.
The paragraphs below lay out the types of models used in these studies:
The study in Japan considers the best design method in an urban area, buildings and trees, to
achieve the optimum outdoor environment using simulations and genetic algorithms (GAs). The
optimum outdoor thermal environment in this study is specifically focused on human comfort
levels. GAs are coupled with simulations of convection, radiation and conduction to achieve the
brief. In the first part of the study the optimum design method is considered, the second part of
the paper looks at human comfort levels using Standard Effective Temperature (SET), and how
meteorological conditions effect these levels such as wind speed, air temperature, humidity and
mean radiation temperature (MRT). The third part of the study considers the optimum results for
part 1 and 2 and checks they are compatible. In terms of the coupled simulation of the outdoor
thermal environment, the composites (spatial distribution of air, wind velocity, air temperature,
humidity and MRT) are calculated as follows: MRT uses the Monte Carlo Method; radiation
analysis using Gebhart’s absorption factor and conduction analysis is used to calculate ground
and wall surface temperatures; and CFD simulation is fed with surface temperature data. GAs
are simulations used to mimic humans and as such are considered living organisms, the fitness of
the human simulation is calculated using genetic operations and the model with the highest
fitness is considered to be the optimum model. After all the simulation components are tested on
the human simulation the optimum design method can be selected based on the human
simulation’s design parameter. The final stage of this study is to test the optimum design system
on an arrangement of buildings and trees to test for pleasant outdoor thermal design [085].
This study looks at urban design as a way of mitigating the urban heat island in Phoenix Arizona
along with water. The heat island in Phoenix has been studied intensively, as Phoenix
experiences daily summer minimum temperatures over 32°c, making it an ideal study/testing
area for mitigation strategies. Obvious mitigation measures such as urban reforestation and green
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