Paper 8
Book Review
Tropical Urban Heat Islands - Climate Buildings and Greenery
Nyuk Hien Wong and Yu Chen
First published
by Taylor Francis 2009-01-24.
ISBN
10:0-415-41104-1 Printed
ISBN 10:0-203-93129-7 Electronic
Approximately 50% of the
world’s population live in the tropical climate region, the vast
majority of which live in urban areas of high temperature and humidity. In
these areas the problem of high temperature is exacerbated by the impact
of urbanisation itself. This book is aimed at highlighting the problems
and solutions associated with such urban areas.
In the first Chapter the
authors highlight the characteristics of urban climate in the tropics. Not
only is day-time temperature high but also extensive cloud cover can
result in high night-time temperatures too. This therefore reduces the
potential for night cooling. As a result, classical architecture has been
used to dissipate excessive heat and take maximum advantage of natural
ventilation. Examples include steep roofs, extensive overhangs, low heat
capacity walls and the use of light colours.
Following from climate,
Chapter 1 also considers the issue of thermal comfort. The authors point
out that temperatures are easily above the comfort zone as defined for
temperate climates. Despite this the authors advocate the use of natural
ventilation. This, they argue, is because evidence shows that tropical
architecture enables fairly comfortable thermal conditions to be achieved.
They also state that sick building syndrome is more easily found in
air-conditioned buildings.
Chapter 2 looks more
closely at tropical buildings. The authors express concern that much
modern architecture is based on imported or “transplanted” designs
from temperate climates. Very importantly, this failure to recognise
tropical conditions means that passive measures to control indoor climate
in these buildings are not possible and that full reliance must be placed
on air conditioning. Air conditioning has subsequently become the main
consumer of energy in the tropics. However, this continuing demand and
growth in energy need is proving to be unsustainable. It is argued,
therefore, that improvements are needed in urban planning and design. Key
considerations are reducing solar gain and promoting natural ventilation.
This Chapter also explores the architectural development of buildings in
the tropics from vernacular, colonial to modern good and modern bad.
In each case examples are given.
Chapter 3 considers the
important role that can be played in urban areas by vegetation. Plants are
considered in their roles of providing economic, environmental and
aesthetic advantages. Many illustrations and examples are provided to show
how horizontal and vertical planting can be integrated into the urban
environment.
Chapter 4 introduces the
concept of the urban heat island. It explains how the interaction of
buildings, heat sources, urban canyons and modified wind patterns
contribute to inflated temperatures. Negative factors include smog, high
night-time temperatures and increased cooling energy consumption.
Mitigation methods include the use of vegetation and choice of building
materials. The authors especially stress that vegetation, “no matter how
it is arranged”, plays a very important role in regulating the urban
climate. The optical and thermal characteristics of building materials are
also vital in mitigating the effects of urban heat islands. A further
important issue is urban ventilation. Aspects such as “breezeways”,
variations in building heights, street orientation and void decks to
improve permeability are vital parameters.
Further discussion on the
role of vegetation is presented in Chapters 5, 6 and 7. Important
environmental advantages include shading and cooling. Environmental
benefits include the ability to retain rainwater and hence reduce peak
runoff. Plants in the vicinity of buildings can maintain a
construction’s integrity by lessening the impact of weather. As an
example, green roofs can lessen stress due to expansion and contraction.
Consideration is also given to the role of plants in terms of aesthetic
and social benefits. This culminates in the concept of a
plant-climate-building model.
The second part of this
book is devoted to case studies and experiments utilising this
plant-climate- building model concept. This essentially relates to the
heat island effect experienced in Singapore. Satellite imagery and
ground-based measurements are first used to measure the magnitude of the
urban heat island, which is found to be between 3 to 5 °C above the
surroundings. Various measures to reduce this impact are then assessed and
measured. Regional solutions include the benefits of urban parks in which
cooling effects are demonstrated with as much as 1.3 °C of cooling. On a
more micro scale the benefit of trees is considered and results show that
housing areas with 22% vegetation cover had lower ambient air temperatures
than those with less coverage. On an individual building basis,
“intensive” and “extensive” roof top gardens, as well as
“vertical landscaping”, were shown to have beneficial cooling effects.
Full quantitative cooling information is presented in the book.
This is a very thorough book, which is aimed not only
at highlighting the problems of urbanisation in the tropics but also
devotes much content to solutions and case study examples. Although
addressing the tropics, this book has applications for highly urbanised
areas in almost any climate and should therefore prove to be of value to
architects, developers, designers and policy makers involved in urban
planning.
(Review – Martin W Liddament)
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