Heat Islands: Understanding and Mitigating Heat in Urban Areas

215 Pages·2008·6.65 MB·English

by  Lisa Gartland

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HEAT ISLANDS
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HEAT ISLANDS
UNDERSTANDING AND MITIGATING
HEAT IN URBAN AREAS
Lisa Gartland
London • Sterling,VA
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First published by Earthscan in the UK and USA in 2008
Copyright © Lisa Gartland,2008
All rights reserved
ISBN-13:978-1-84407-250-7
Typeset by MapSet Ltd,Gateshead,UK
Printed and bound in the UK by Cromwell Press,Trowbridge
Cover design by Rob Watts/RogueFour
For a full list of publications please contact:
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Earthscan publishes in association with the International Institute for Environment and Development
A catalogue record for this book is available from the British Library
Library of Congress Cataloging-in-Publication Data
Gartland,Lisa,1960–
Heat islands :understanding and mitigating heat in urban areas / Lisa Gartland.
p.cm.
Includes bibliographical references.
ISBN-13:978-1-84407-250-7 (hardback)
1.Urban heat island.I.Title.
QC981.7.U7G37 2008
551.5'25091732–dc22
2008001740
The paper used for this book is FSC-certified and
totally chlorine-free.FSC (the Forest Stewardship Council)
is an international network to promote responsible
management of the world’s forests.
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Contents
List of Figures and Tables vii
List of Acronyms and Abbreviations xiii
Chapter 1 What is a Heat Island? 1
Heat island definition 1
Impacts of heat islands 2
Characteristics of heat islands 2
Chapter 2 Causes of the Heat Island 15
Introduction 15
Energy balance 16
Reduced evaporation 17
Increased heat storage 18
Increased net radiation 20
Reduced convection 21
Increased anthropogenic heat 22
Interplay of heat island causes 23
Chapter 3 Measuring and Modelling Heat Islands 27
Measuring heat islands 27
Modelling heat islands 35
Chapter 4 From Heat Islands to Cool Communities 43
Typical land use characteristics 43
Typical roofing materials 46
Cool roofing materials 48
Typical paving materials 49
Cool paving materials 51
Thermal properties of materials 52
Cooling with trees and vegetation 52
Potential for cooling 53
Chapter 5 All About Cool Roofing 57
Introduction 57
Cool roofing definition 57
Types of cool roofing 63
Benefits of cool roofing 71
Other cool roof considerations 79
Chapter 6 All About Cool Paving 85
What is cool paving? 85
Types of cool paving 85
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vi Heat Islands
Benefits of cool paving 100
Other cool paving considerations 103
Chapter 7 Cooling with Trees and Vegetation 109
Introduction 109
Benefits and costs of trees and vegetation 109
Effective landscaping for cooling 121
Green roofing,or garden roofing 128
Chapter 8 Community Benefits from Heat Island Mitigation 139
Introduction 139
Temperature reductions 139
Energy savings 140
Air quality improvements 141
Human comfort and health improvements 146
Stormwater run-off reductions 148
Maintenance and waste reduction 150
Quality of life benefits 151
Chapter 9 Cool Community Action Plan 155
Motivate 155
Investigate 158
Educate 162
Demonstrate 164
Initiate 167
Legislate 172
More action opportunities 177
The cool revolution 183
Index 187
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List of Figures and Tables
Figures
1.1 Luke Howard (1772–1864) of London,an amateur meteorologist,was the first
serious practitioner of urban climatology 1
1.2 Summer and winter air temperatures in the central business district (urban) and
airport (rural) of Melbourne,Australia 3
1.3 Summer and winter differences in air temperature between the central business district
and the airport of Melbourne,Australia 4
1.4 Minneapolis–St Paul,Minnesota Metropolitan Area:(left) locations of 26 weather
stations (numbered crosses),(right) contours of cooling degree–days in degrees
centigrade above the 18.3°C threshold temperature 5
1.5 Map of Tokyo,Japan,showing the train line network along which heat island
measurements were made 5
1.6 Air temperatures measured along the central Chuo Line in Tokyo,Japan,in August 1990
(~10:30pm) and in November and December 1990 (~5:30am) 6
1.7 Tokyo temperature contours derived from mobile traverse measurements made in
August 1990 (~10:30pm) and in November 1990 (~5:30am) 6
1.8 Air temperature contours in Granada,Spain,on winter nights with clear skies and
light winds.Pattern A:buildings with 7–10 floors and broad streets,B:2–4 floors,
narrow streets,C:9–10 floors,broad streets,D:gardens,E:7–10 floors,broad streets,
F:principal roads,white:rural areas 7
1.9 Air temperature variations along the dashed line AB in Figure 1.8 measured successively
over a single winter night in Granada,Spain 7
1.10 Surface temperature contours (in degrees centigrade) over a map of Buffalo,New York,
on 6 June 1978 at 2:00pm EDT derived during the Explorer satellite’s heat capacity
mapping mission 8
1.11 Thermal image of downtown Sacramento,California,on 29 June 1998 at noon,derived
from a flyover in a Lear jet by NASA’s ATLAS program 9
1.12 Temperature difference between the urban Filaret and rural Banasea areas of Bucharest,
Romania.On the left,cloudy and windy conditions (solid – spring,dashed – summer,
dotted – summer with morning clouds).On the right,calm and clear conditions (solid –
winter,dashed – spring,dotted – summer).Time is relative to sunset,so 0 is sunset,2 is
two hours after sunset and –2 is two hours before sunset 10
1.13 Differences between the monthly averages of maximumtemperatures at Phoenix’s Sky
Harbor airport,and in urban Phoenix,urban Mesa and suburban Tempe,Arizona,and
the rural desert of Sacaton,Arizona,over the past century 10
1.14 Differences between the monthly averages of minimum temperatures at Phoenix’s Sky
Harbor airport,and in urban Phoenix,urban Mesa and suburban Tempe,Arizona,and
the rural desert of Sacaton,Arizona,over the past century 10
1.15 Typical daytime potential temperature profiles over rural and urban areas;potential
temperatures have been corrected for changes due to altitude 11
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viii Heat Islands
1.16 Typical night-time potential temperature profiles over rural and urban areas;potential
temperatures have been corrected for changes due to altitude 12
1.17 Map of New York City area showing the flight path taken by an instrumented helicopter
on 16 July 1964 12
1.18 Actual vertical and horizontal temperature distributions in degrees centigrade at
sunrise along the New York City flight path on 16 July 1964 13
1.19 Rural (above) and urban (below) actual temperature profiles in St Louis,Missouri,
on 26–27 July 1975 around sunrise and sunset 13
2.1 Daily energy balance measurements under clear sky conditions in a rural Vancouver
area during the summer of 1983,a suburban Chicago area during July 1992 and an
urban Mexico City area during December 1993 17
2.2 Thermal conductivity,heat capacity and thermal diffusivity of various materials 19
2.3 Solar reflectance and thermal emittance of various natural and construction materials 20
2.4 Change in heat island intensity (urban minus rural air temperature) just after sunset
(time=0) for varying ratios of building height to width in a scale model experiment,and
for a concrete slab versus a wood slab (representing a rural area) 21
2.5 Energy consumption in the US from 1950 to 2000 22
2.6 Daily anthropogenic energy generation in urban,suburban and rural areas of Brisbane,
Australia,in December 1996 23
2.7 Summer and winter energy balance in Tokyo,Japan,showing anthropogenic heat gains
in relation to other energy terms 24
3.1 Wavelengths of electromagnetic radiation 30
3.2 Black body emissions at different temperatures,solar energy reaching the Earth and the
five energy wavelengths typically measured by remote sensing 31
3.3 Solar energy reaching the Earth in the ultraviolet,visible and infrared wavelengths,plus
the two energy wavelengths that are typically used to measure reflected solar energy 32
3.4 Absorption of infrared energy by different constituents of the Earth’s atmosphere (carbon
monoxide,methane,nitrogen dioxide,ozone,carbon dioxide and water vapour) plus all
constituents combined (bottom) 33
3.5 Typical daytime potential temperature profiles over rural and urban areas;potential
temperatures have been corrected for changes due to altitude 33
3.6 Typical night-time potential temperature profiles over rural and urban areas;potential
temperatures have been corrected for changes due to altitude 34
4.1 Coverage of roofing,paving and vegetation in residential areas of Chicago,Houston,
Salt Lake City and Sacramento 44
4.2 Coverage of roofing,paving and vegetation in non-residential areas of Chicago,Houston,
Salt Lake City and Sacramento 44
4.3 Average land cover in Chicago,Houston,Sacramento and Salt Lake City 45
4.4 Satellite images of Atlanta,Georgia,metropolitan area showing changes in land cover
between 1973 and 1997 46
4.5 Types of low-slope roofing used in the US for new building construction,2004 47
4.6 Types of low-slope roofing used in the US for re-roofing of existing buildings,2004 47
4.7 Sales of steep-slope roofing in the US for new building construction,2004 48
4.8 Sales of steep-slope roofing in the US for re-roofing of existing buildings,2004 48
4.9 Percentage of road surfaces in the US covered with asphalt,concrete and a composite of
concrete and asphalt,corrected for the number of lanes per road type 50
5.1 Solar energy versus wavelength reaching the Earth’s surface 58
5.2 Solar reflectance of different roof materials 59
5.3 Combined effects of solar reflectance and emittance on roof temperature 60
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List of Figures and Tables ix
5.4 Application of an elastomeric cool roof coating 64
5.5 A cementitious cool roof coating 65
5.6 This PVC roof in the background was originally as white as the paper on the clipboard 66
5.7 A roll of standard black EPDM single-ply roofing 67
5.8 Bright white cool roof on a home in Florida 68
5.9 Cool coloured clay tiles and their solar reflectance values 69
5.10 Cool metal roof coatings and their solar reflectance values 69
5.11 Temperatures of 3M’s cool black shingle versus a traditional,hotter,black shingle 70
5.12 Infrared photograph of a light grey asphalt roof in Gilroy,California,at the edge of a
bright white cool coating 71
5.13 Temperature of an uncoated light grey asphalt roof versus a bright white cool roof
coating on a Gilroy,California,rooftop during the week of 26 August to 1 September 1996 72
5.14 Effect of a bright white coating on the cooling energy use of a building in Gilroy,
California,during the week of 26 August to 1 September 1997 73
5.15 Land cover and tree shading in Sacramento,California 77
5.16 Coated and uncoated portions of an asphalt shingle roof in Pennsylvania 79
5.17 A cool roof in Connecticut shows less snowmelt on the right,where SPF insulation
has reduced the heat transfer from the building 81
6.1 Variation of the solar reflectance of asphalt and concrete pavements over time 86
6.2 Tucson,Arizona,parking lot pavement with a solar reflectance of around 15 per cent 86
6.3 Tucson,Arizona,parking lot pavement temperature fluctuations 87
6.4 Asphalt pavement temperatures over one day 87
6.5 Asphalt pavement heat flow over one day 88
6.6 Concrete pavement temperatures over one day 89
6.7 Concrete pavement heat flow over one day 89
6.8 Porous pavement temperatures over one day 90
6.9 Porous pavement heat flow over one day 91
6.10 Cooler Portland cement concretes 93
6.11 Ultra-thin white-topping being applied over an existing asphalt road 94
6.12 Interlocking concrete paver construction detail for an airfield 94
6.13 Porous concrete parking lot at Bannister Park in Fair Oaks,California 95
6.14 Solar reflectance of various types of aggregate used in pavements 96
6.15 Roadway outside of Union Station in Los Angeles surfaced with a coloured asphalt
emulsion sealcoat 97
6.16 Asphalt pavement in a Hialeah,Florida,furniture store’s parking lot textured to
resemble paving stones 98
6.17 Resin-based pavement used in the Land’s End Coastal Trail alongside the
San Francisco Bay 99
6.18 Porous pavers being filled with aggregate for use in a parking lot at the University of
California Merced Campus 100
6.19 Porous pavers filled with soil and grass used as emergency fire lanes around buildings at the
Microsoft campus in Washington State 100
7.1 Predicted energy savings in typical homes in seven US cities due to tree shading and
wind shielding effects,assuming one tree is planted to the south and one to the west 112
7.2 Total stored carbon and annual carbon sequestration in metric tons per square mile as
a function of tree coverage percentage in five US metropolitan areas 113
7.3 Net reduction in CO production (kg per tree) in five climate regions when a
2
medium-sized,40-foot-high,deciduous tree is planted in various positions around a
residence built after 1980 114