Topos 127

no 127
2024
to po s.
heat

COVER
IMAGE: Alexander Weiß
The compound responsible for the heat in chillies
is called capsaicin. It binds to receptors in the
mouth and skin, causing the sensation of heat or
burning. To reduce the burning sensation from
eating hot chillies, dairy products like milk,
yogurt, and cheese are effective because casein
in dairy can bind to capsaicin and help wash it
away. In this issue of topos we want to know what
is our cheese to our hot cities? What helps to
reduce the Urban Heat Island Effect? Oh and
BTW: This picture was AI generated. It doesn't
leave you feeling good, does it?
Heat can kill in three major ways: organ failure,
heart attack or kidney failure. Heat is hard work
for the human body. It has to ensure that the
body temperature does not rise too much, otherwise
the structure of the body's own proteins will
be altered, resulting in organ and tissue damage.
Humans produce sweat to counteract the damage
and cool the body. What is more, the blood
vessels also dilate, which in turn lowers the blood
pressure, and the heart increases its pumping capacity
to regulate it. This can lead to a heat
stroke. If left untreated, this will lead to death.
In 2017, researchers at the University of Hawaii
defined that outdoor temperatures of 37 degrees
and above can be dangerous for us. In principle,
however, an increased risk of death can be assumed
from an outdoor temperature of 30 degrees.
The tricky thing is that researchers from
the Insituto de Salud Carlos III in Madrid discovered
in 2017 that people die so quickly during
a heatwave that they do not make it to hospital.
This is why a heat warning of 72 to 48
hours in advance is so important.
In 2021, the number of heat-related deaths
worldwide was 100,000. According to the
WHO, the consequences of climate change are
expected to claim 250,000 victims a year between
2030 and 2050. Malnutrition, malaria, diarrhoea
and – heat – are cited as the cause of
death. Vulnerable groups are particularly at risk
from the heat – including elderly people, pregnant
women and children. According to UNI-
CEF, more than 559 million children were frequently
exposed to heatwaves in 2022. By 2050,
this figure is expected to rise to two billion children.
Two billion, ladies and gentlemen.
The increase in extreme heatwaves is a huge
problem. In May 2024, it made headlines around
the world. In Tabasco, Mexico, several black
howler monkeys dropped dead from the trees
during a heatwave of 45 degrees. Animal welfare
organizations counted 78 dead specimens of the
endangered species at the end of May. In Pakistan,
temperatures of up to 50 degrees were expected
at the same time. Schools closed and
clinics went on alert. It was the third year in a
row that Pakistan experienced an unusual heatwave.
And for several weeks, the officially longest
heatwave in decades swept across Southeast
Asia. In Thailand, at least 61 people died - more
than twice as many as in the whole of 2023. In
Vietnam, hundreds of thousands of dead fish
floated on the surface of the Song May reservoir
and in the Philippines, 53 degrees were measured
in the province of Zamblas. Man-made
climate change is to blame for this, exacerbated
in Southeast Asia by a strong El Niño.
Due to the Heat Urban Island effect, our cities
and metropolitan areas are particularly affected
by the increasing heat – with far-reaching consequences:
the health risks already mentioned,
elevated air pollution levels, increased energy
consumption, water quality issues, compromised
infrastructure, reduced livability but also
climate change amplification.
What I find particularly astonishing is that we
as a society have been aware of the dangers of
increasing heat for decades, but we are still doing
far too little in terms of heat management in
our cities. This is despite the fact that numerous
solutions, innovations and strategies are already
available. For this reason, in this issue of topos
magazine, we discuss the topic of heat in the city
from different angles and present current best
practices – in the hope that we will finally make
significant progress in climate adaptation.
TOPOS E-PAPER: AVAIL-
ABLE FOR YOUR DESKTOP
For more information visit:
www.toposmagazine.com/epaper
THERESA RAMISCH
Editor-in-Chief
t.ramisch@georg-media.de
topos 127 005

CONTENTS
OPINION
Page 8
THE BIG PICTURE
Page 10
CURATED PRODUCTS
Page 100
REFERENCE
Page 106
METROPOLIS EXPLAINED
Page 12
URBAN PIONEERS
Page 14
EXPOSING THE HIDDEN KILLERS
Page 54
MELTING CITIES
How urban heat kills minorities
and what can be done about it
Page 18
FIGHTING THE HEAT WITH
GREENERY AND CLAY
The value of traditional construction
Page 26
KUALA LUMPUR
How to cool a tropical city
Page 32
UNLIVEABLE IN EAST ASIA
A pessimistic outlook
Page 38
EUROPE'S HEAT-PROOF CITIES
An overview
Page 60
MADRID
Turning an urban heat island into
an urban cooling island
Page 66
FRANKFURT
Heat in the city
Page 72
URBAN HEAT
VISUALIZED
a Picture Series
Page 78
CITY GAMECHANGERS
Page 112
EDGE CITY
Page 114
IMPRINT
Page 113
PROJECTS
Green and blue ideas to counter urban heat
Page 42
THE ART OF FIGHTING HEAT
Artful projects to combat heat
Page 86
MERGING CITY AND NATURE
Mitigating urban heat islands
Page 50
EXPOSING THE HIDDEN KILLERS
How heatmapping could help cool our cities
Page 54
LET’S BEAT THE HEAT!
Join in and become part of the initiative
Page 58
BOSTON
How it tackles the heat
Page 90
THINK VERTICALLY
FOR A CHANGE!
A commentary
Page 96
CONTRIBUTORS
Page 98
PICTURE SERIES: NASA
Page 78
Photos: Toby Elliott on Unsplash, NASA/JPL-Caltech
006 topos 127

OPINION
MIND THE
HEAT GAP
Will the urban heat island effect in future only be a burden for poor people in?
Studies show that poor people in cities already suffer much more from heat
than wealthier sections of the population. Could the fight against heat islands
therefore increasingly become a kind of devilish marketing tool?
008 topos 127

Opinion
It seems to be a well-known phenomenon. Poverty
attracts yet more poverty. Or: financially
disadvantaged people struggle more with the effects
of climate change or other climatic challenges
than people who have more money or
live in better neighbourhoods. The same seems
to be true of the urban heat island effect. Poorer
neighbourhoods are affected by this effect more
often and more severely than others. Accordingly,
poorer people are also confronted with
the negative effects of heat islands much more
often and more intensely.
The devil runs in circles
Strictly speaking, it's a vicious cycle. The vast
majority of the world's metropolises prove day
after day that the focus of urban development is
much more on well-known or already better-off
neighbourhoods. As a result, these neighbourhoods
are the first to benefit from the greening
efforts of the administration. As a rule, only
these neighbourhoods become the recipients of
new architecture, which contributes to the general
cooling of the location thanks to green roofs
and façades. Poorer neighbourhoods are generally
not developed. This has a considerable impact
on the sections of the population who, of
course, are unable to obtain any real relief from
the heat due to a lack of money. We are talking of
course about immigrants, older people, the
group of residents formerly known as the working
class and, increasingly, families with children.
Those families who can afford it are moving
to the suburbs or living in high-quality flats
near the city centre. This is certainly not the case
everywhere, but occurs far too often.
As early as 2021, the U.S. Environmental Protection
Agency (EPA) found that people below
the poverty line and immigrants are much more
likely to be affected by the urban heat island effect
than other population groups. Using Baltimore
as an example, joint research by NPR.org
and the University of Maryland's Howard Center
for Investigative Journalism found similar
results. They were able to prove that the hottest
areas of Baltimore are also among the poorest.
This fact is worsened by the fact that heat in metropolises
is a significant health risk. Poorer
population groups are almost defenceless
against this risk. For older people, this can mean
acute danger to life and limb. For children and
young people, this could lead to even greater
difficulties for their start in life than they already
have due to their financial position.
The language of money – climate protection
with $$ in their eyes
Rebuilding our metropolises is expensive.
Health is expensive in many regions of the
world. It seems that climate protection is also
expensive. Of course, there is a lot of truth in all
these statements and especially in the basic idea.
It costs money to transform a large car park into
a green, cooler refuge of tranquillity. It also
costs money to green roofs and build better
public transport infrastructure. Many metropolises
and cities are making these investments in
isolated areas.
However, if you look at our metropolises with
open eyes, you quickly see that heat protection
degenerates into a marketing tool. Cities boast
about heat protection projects that all too often
only benefit the very wealthy city dwellers. An
honest look at the structurally weaker corners
of metropolises shows how much investment is
lacking. One could be forgiven for thinking
that urban development has more to do with
the marketing term ‘return on invest (ROI)’
than with honestly improving the living conditions
of all people.
Thanks to state-of-the-art mapping methods,
however, cities can no longer hide. If we look 15
years into the future, we will increasingly find
metropolises whose wealthier neighbourhoods
are on average up to ten degrees cooler than
traditional working-class or poor neighbourhoods.
It will therefore be impossible to hide
the issue from those wanting to promote heat
protection and climate protection for everyone,
to close the heat gap.
TOBIAS HAGER is a journalist and Chief Content
Officer and member of the management board at
GEORG Media. Responsible for all GEORG brands
such as topos magazine, BAUMEISTER and
Garten + Landschaft, his focus is on the areas of content,
digital, marketing and entrepreneurship.
topos 127 009

THE BIG PICTURE
Photo: JAM STA ROSA by gettyimages
010 topos 127

The Big
Picture
Summer Heat Hits Asia
South and Southeast Asia are being hit by an extreme heatwave this year. The hottest season has not yet
begun in countries like India, the Philippines, Cambodia and Thailand, but the temperatures are already
soaring up to 50 degrees Celsius. The perceived temperatures are even higher and worse is feared for the
months of May and June, which are considered particularly hot. Experts warn of massive health issues and
many people report that breathing becomes close to impossible. Authorities are warning people not to stay
outside for long periods and schools are closed in some places. Many countries in the region have already
suffered fatalities and sustained high temperatures will cause further deaths. Experts warn of more dire
consequences, such as extreme drought in some of the world's most densely populated regions. They are
therefore calling on governments to take further measures and preparations against human-caused global
warming. It is the poor in particular who are suffering from the heat and who will continue to do so. Due to
government restrictions that limit outdoor activities, farmers and construction workers are particularly
affected in their daily work. Of course, this also means a loss of income, which in turn may lead to hunger.
TEXT: JULIA MARIA KORN
topos 127 011

Cities
Our increasingly hot cities and metropolises affect everyone, regardless of their origin,
skin color or other characteristics – or so you might think. But far from it, because
as with many other things, marginalized groups that are already weakened
suffer particularly from the increasingly hot cities. How urban heat kills minorities
and what can be done about it.
MORGANE LLANQUE
topos 127 019

heat
In 2018 and 2019 the streets of Los Angeles were
dyed white, making for bizarre pictures of dancing
palm tree shadows on chalky avenues. Yet it
was not snowflakes covering the streets, but paint.
In an experiment to tackle urban heat islands
(UHI) in cities, the City of Angels decided to coat
some streets in CoolSeal, a bright paint designed
originally for the military to disguise airplanes.
The very costly paint is aimed to reflect back sunrays
and heat to the atmosphere, in contrast to the
dark-colored asphalt of a usual street, which absorbs
between 80 and 95 percent of the sun's rays,
heating up not just the streets themselves but the
entire surrounding area. This heat also leads to a
higher demand of energy, since more air conditioning
is needed, which in turn is bad for the environment.
This so-called urban heat island effect
can add up to 22 degrees Fahrenheit to the average
air temperature in a city, compared to the surrounding
area, according to the U.S. Environmental
Protection Agency EPA.
This heat is deadly.
When young children, old or sickly people are
exposed to extreme heat, they can suffer heat
exhaustion and heat stroke. Hot temperatures
can also contribute to deaths from heart attacks,
strokes, and other forms of disease. These
impacts are made worse by humidity. Normally
the human body can cool down by sweating,
but this mechanism is compromised by increasing
levels of moisture in the atmosphere,
itself a result of global warming. According to
data from NASA's jet propulsion lab, heat stress
has been the leading cause of weather-related
deaths in the United States, the country with
the most extensive research on the subject,
making Urban Heat more deadly than hurricanes
or earthquakes. In the United States the
number of heat related deaths rose to 1700 in
2022. In Europe, where air conditioning is very
rare in residential housing, 60,000 people died
as a consequence of heat related health issues in
2022 according to the WHO.
But what most statistics don’t tell you is that it is
not only age that affects the risk of dying from urban
heat, but also race, gender and wealth.
The gender and race gap of urban heat
As far back as 2013, a US study documented
that not only countries in the global south but
also western neighborhoods with minorities
and underprivileged populations experience
higher temperatures. The study of 108 urban
areas in the United States suggests that predominantly
non-white neighborhoods were
hotter than the neighborhoods with a white
majority, some by nearly 13 degrees Fahrenheit.
This inequality is exacerbated by the fact
that non-white and lower income households
not only contribute less to global carbon
emissions, they also have fewer resources to
020 topos 127

heat
FIGHTING THE HEAT
WITH GREENERY
AND CLAY
JULIA TREICHEL
026 topos 127

1
Located in a hot
climate, the bustling,
concrete-built center of
Ouagadougou heats up
quickly when the sun
shines. Traditional
materials are being
tested to cool down the
city in future.
Photo: Helge Fahrnberger via Wikimedia Commons, CC BY-SA 3.0 DEED
topos 127 027

Monsoon and Harmattan – these two powerful winds primarily determine the climate in
Burkina Faso. And thus also the changing scenery of the landscape. While the monsoon
blowing from the southwest brings warm, humid air and precipitation in summer, the
trade wind Harmattan from the Sahara causes the long dry season in winter. How a
country where the sun shines frequently and rain is a rare resource tackles the challenges
of global warming with clay and green.
Burkina Fasos’ climate zones reflect these influences. In the far north, in
the Sahelian zone, there is a warm desert climate in which rainfall can be
less than 600 mm per year. The rainy season here sometimes lasts less
than two months and temperatures often rise to over 40 degrees during
the dry season. The Sudanese zone in the south, on the other hand, is
characterized by a tropical savannah climate. Here, the rainy season lasts
six months and the monsoon brings rainfall of up to 1100 mm per year to
the southern regions. Between the two extremes, the Sudano-Sahelian
zone - about half of the country - is subject to a warm, semi-arid climate.
Monsoon and harmattan and the balancing act of subarid and subhumid
zones from north to south determine the country's biodiversity and ecological
systems. But in the age of the Anthropocene, these powerful factors
are not the only ones: "Beside these factors, undoubted in their effect,
man is nowadays the main determinant affecting biodiversity with regard
to: demographic growth, pressure on natural resources, socio-cultural
practice, ect.", is how Adjima Thiombiano and Dorothea Kampmann, editors
of the Biodiversity Atlas of West Africa, describe the relevance of human
influence.
The human impact
According to UN Habitat, the African continent has the fastest urbanization
rate in the world. In 2010, the report 'State of African Cities 2010,
Governance, Inequalities and Urban Land Markets' stated that the urbanization
process in the regions south of the Sahara was particularly rapid. At
that time, UN Habitat predicted an 81 percent increase in the population
of Burkina Faso's capital Ouagadougou by 2020 - from 1.9 million in 2010
to 3.4 million in 2020. A rapidly growing population within a short period
of time inevitably has an impact on the shape of the city. In Ouagadougou,
for example, there is an increasing fragmentation of rural areas and the development
of informal housing estates on the outskirts of the capital. This
urbanization process has unavoidable consequences for the ecosystem.
In their paper 'Intensity Analysis for Urban Land Use/Land Cover Dynamics
Characterization of Ouagadougou and Bobo-Dioulasso in Burkina
Faso' from 2023, Valentin Ouedraogo, Kwame Oppong Hackman, Michael
Thiel and Jaiye Dukiya criticize, among other things, an increase in
impermeable surfaces at the expense of natural vegetation and water bodies
with serious consequences: "The urbanization process causes the
transformation of permeable surfaces into impermeable surfaces, including
concrete and asphalt, which reduce the infiltration capacity of the soil
and increase runoff and the amount of flooding.“
To understand the changes in Burkina Faso, the four scientists examined
the change in land use in the country's two largest cities between 2003 and
2021. They found that rapid urbanization over this period had led to a
78.12% increase in built-up areas in the capital; at the expense of agricultural
land, 42.24% of which was lost over the same period. As the human
footprint in cities increases, so does the risk of environmental hazards.
These include flooding, for example, but also the urban heat island effect.
Ouagadougou, in the center of the country, has a tropical climate with
average monthly temperatures between 20 and 30 degrees Celsius. The
results of climate simulations for the period 2010-2050 predict an increase
in the average annual temperature of at least 1 degree. This was
the conclusion of the international EU project CLUVA (Climate Change
and Urban Vulnerability in Africa), which ran from 2011-2013. The scientists
also described an increase in both the frequency and the duration
of droughts. Heatwave episodes could increase from the current average
of 6 days to 17 days.
The situation is particularly precarious in the informal outdoor areas
without formal infrastructure. These areas have the hottest temperatures
028 topos 127

heat
both during the day and at night. In the northeast of the city center, on the
other hand, is the Bangr'weogo City Park, a large area of community forest
that borders the central reservoirs. This area in turn connects to the
river vegetation zones that lead out of the city. The linear canals allow
fresh air to reach the northern part of the city center.
Measurement results for the Urban Heat Island effect
A 2013 study by Jenny Lindén, the University of Gothenburg and the Direction
de la Météorologie Nationale in Ouagadougou took a closer look at
the temperature development in the city. Measurements in areas with different
vegetation, buildings, road surfaces, open terrain and bodies of water
were used to determine which areas of the city heated up the most.
They were able to register the most significant temperature differences at
night. Areas with vegetation were five to nine degrees Celsius cooler than
those without vegetation. The strong effect in the evening hours is attributed
to evaporative cooling. The researchers also found that the heat island
in the city center was less than two degrees Celsius warmer than the rural
surroundings. The most striking finding of the study was that areas with
vegetation within the city were cooler than the open cultivated landscape
outside the city center. The analysis of the results shows that vegetation is
therefore the most important factor for the night-time urban climate in
Ouagadougou, while the impact of built-up and paved areas is limited.
During the day, the temperature differences recorded at the individual
measurement locations were generally smaller. Overall, the researchers
were unable to detect any effect of shading in the city center. In principle,
taller buildings absorb and reflect more heat, which increases the temperature
of a street, but from around 3 storeys upwards they begin to cool the
street by shading it. Today, Ouagadougou is a melting pot of different architectural
styles. You will find elegant glass office buildings next to colorful
markets covered with corrugated iron. International influences are
unmistakable, but are combined with traditional building styles. In general,
Ouagadougou has a rather open building structure. This may therefore
have neither a particularly positive nor negative effect on the urban
heat island effect of the capital, the researchers assume in their paper.
The added value of traditional construction methods
This is astonishing in comparison to other metropolitan areas around the
world. Last year, for example, the New York City Council published a report
according to which inner-city temperatures in places away from
large green and water areas are 4 to 8 degrees Celsius higher than the average
value. Although temperatures in Ouagadougou are higher than in
New York, the urban heat island effect is lower in Burkina Faso's capital.
This may in fact be related to the traditional building materials used.
Like mirrors, fully glazed façades deflect most of the solar radiation
downwards, towards other buildings or the road surface. Depending on
the material, this absorbs the radiation and emits it again as heat. Depending
on factors such as the facades of other buildings and the width of
the street, the heat is literally trapped at street level. In a study by the École
de Technologie Supérieure, researchers investigated the extent to which
the composition of asphalt has an influence on surface reflection and thus
on the heat island effect. They found that the use of yellow clay brick as a
chip seal aggregate increases reflectivity by 250 percent and can therefore
reduce the surface temperature by 23 percent. In Burkina Faso, the main
building material is clay – this may have a negative impact on the urban
heat island effect.
"Earthen construction is our heritage," the National Geographic quotes
Sanu, head of the village of Koumi in the southwest of the country, in an
article from 2023. "For thousands of years, these houses have enabled us
to live a good life. Why should we change that, especially now when we
urgently need them?" He rightly speaks out against supposed modernization
processes that are detrimental to local conditions. In their paper 'Development
of Bioclimatic Passive Designs for Office Building in Burkina
Faso', Abraham Nathan Zoure from Tianjin University and Paolo Vincenzo
Genovese from Zhejiang University also criticize the general application
of "inappropriate standards that were originally developed for the
needs of other (Western) environments". These include, for example, the
increasing use of concrete and steel, but also the intensive use of air conditioning
systems. Around 45 percent of the energy consumed in buildings
is used to maintain thermal comfort inside. Instead, they recommend
relying on natural ventilation through shading devices and using
building materials with high thermal capacity - such as clay - to maintain
generally moderate temperatures during the day. These are all aspects that
can have a lasting impact on the city's indoor spaces, but also on its outdoor
spaces in the long term.
As Jenny Lindén's study makes clear, however, the greatest potential in
the fight against urban overheating lies not in the building construction
sector, but in the consistent expansion of blue-green infrastructure. In
topos 127 029

BATLLEIROIG
MERGING CITY
AND NATURE
Designing open spaces as pleasant and comfortable areas that enhance
environmental quality and are free from pollution is essential. Leveraging
seasonal climate variations in the design of these spaces is key to
moderating temperatures during the hottest and coldest periods, allowing
for the enjoyment of public spaces throughout the year.
050 topos 127

commentary
1
Image: Batlleiroig
1. Three projects were
carried out in Esplugues
de Llobregat: The
urbanization of the
Finestrelles sector (1),
the transformation of
the Avinguda dels Paisos
Catalans (2) and the
remodelling of the
Elisabeth Eidenbenz
roundabout (3).
The primary objective of these designs is to mitigate
urban heat islands, thereby addressing the
climate emergency and enhancing health and
well-being in urban areas. This is achieved
through the use of various tools, including primordial
geography, water, vegetation, permeability,
and materiality. By integrating these elements,
the designs create sustainable urban environments
that not only reduce rising temperatures
but also improve the overall quality of urban life.
Prioritizing the creation of large green areas improves
air quality, ventilation, and reduces noise
pollution. Incorporating trees and landscaped
areas into urban design helps regulate environmental
hygrometric conditions, relative humidity,
and the feeling of air freshness. Planting deciduous
trees in public spaces is advisable to
maximize sunlight in winter and provide ample
shade during summer.
The distribution of large tree masses should enhance
ventilation corridors in public spaces. Additionally,
it is important to manage the topography
to optimize rainwater capture and retention
in green areas. Hard paved surfaces should be
minimized, and synergies with nearby natural
spaces should be established through green corridors,
thereby promoting biodiversity in the city.
Green infrastructure plays a crucial role in the
resilience of cities against the urban heat island
effect. Open spaces, as major structural elements
of the city, have the potential to become bioclimatic
areas capable of regulating temperature
and humidity. Connecting these green infrastructures
with the original geography, grouping
them into areas with sufficient critical mass, and
managing their vegetation are key aspects that
can reduce temperatures by up to 3°C.
For over 40 years, Batlleiroig has implemented
various strategies and solutions in our projects
aimed at enhancing the resilience of our urban
fabric. One example is the planning and urbanization
project of the Finestrelles sector in Esplugues
de Llobregat (Fig. 1). This proposal
aims to extend the natural park of Collserola.
topos 127 051