Environmental Engineering Reference
In-Depth Information
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Bourbia and Boucherbia (2010) studied the thermal comfort conditions in the
street canyons of Constantine (Algeria), where the impact of the streets geometry
was analysed. Both air and surface temperature were measured in various streets in
order to assess the interrelation between the urban streets geometry and thermal
comfort. The physical parameters for the representation of the urban geometry
were the height to width (H/W) ratio and the sky view factor. The authors showed
that the larger the sky view factor, the higher the air and surface temperature
measured and the higher the H/W ratio, the lower the air and surface temperature.
Therefore, open spaces with no vegetation are exposed to the sun for most of the
day, leading to discomfort problems. As a result, the geometry of urban canyons
plays a critical role in urban heat island mitigation.
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In a study at the campus of University Putra (Malaysia), Makaremi et al. (2012)
assessed the outdoor comfort conditions in shaded outdoor areas under hot and
humid tropical climatic conditions. The research in this case was based also on
subjective and objective measurements, including wind speed and direction, and
temperature and humidity in the open campus areas, from which the PET index
was extracted. In addition, a survey questionnaire was circulated among students.
Analysis of the outdoor comfort survey indicated that although the PET values of
the areas under study were higher than the comfortable range, a significant number
of students declared that the comfort conditions were acceptable. There were thus
some differences between measured outdoor comfort and people's perceptions,
showing the ability of people to adjust to less comfortable environments.
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The outdoor comfort conditions in Dhaka (Bangladesh) were studied by (Ahmed,
2003) The methodology used was based on a survey questionnaire and measure-
ment of environmental parameters, i.e. air temperature, globe temperature (mean
radiant temperature) and relative humidity. The urban spaces were categorized in
terms of their position and sheltering. The study showed that comfort boundaries
varied significantly with: (i) presence of air flow; (ii) a person's activity; (iii) varia-
tions of globe and radiant temperatures; and (iv) shading. Shading was considered
to be the most important aspect between noon and 3 p.m. in the specific climatic
conditions. From the study, the author recommended that “drinking water, pedes-
trian access and street furniture-shading should be considered as a public amenity
in the Tropics''.
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Seven European cities - Athens (Greece), Thessaloniki (Greece), Milan (Italy),
Fribourg (Switzerland), Kassel (Germany), Cambridge (UK) and Sheffield (UK) -
were studied for their outdoor comfort conditions in the framework of the RUROS
(Rediscovering the Urban Realm and Open Spaces) project (Nikolopoulou and
Lykoudis, 2006). The results of the microclimatic and human monitoring were
based on field surveys in which meteorological parameters were measured, assisted
by the subjective results acquired from nearly 10,000 interviews. The comfort
temperature range varied significantly among the various European regions; for
example from around 23
◦
C for Athens to 13
◦
C for Fribourg. The study proved
the strong relationship of outdoor comfort with air temperature, solar radiation
and wind speed patterns, although comfort adaptation influenced the responses
from pedestrians.
Analyses of the various case studies for outdoor comfort are tabulated in Table
19.3.1.
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