Climate Change and Urban Heat Islands
Adaptation Measures for Urban Planning
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Impressum
Authors
Alexander Storch (Austrian Environment Agency)
Wolfgang Schieder (Austrian Environment Agency)
Gundula Prokop (Austrian Environment Agency)
Linda See (International Institute for Applied Systems Analysis)
Maja Žuvela-Aloise (Zentralanstalt für Meteorologie und Geodynamik)
Brigitta Hollosi (Zentralanstalt für Meteorologie und Geodynamik)
Sandro Oswald (Zentralanstalt für Meteorologie und Geodynamik)
Stefan Guggenberger (International Project Management Agency Klagenfurt)
Daniel Johnson (ESCP Business School Berlin)
This brochure is a product of the research project ADAPT-UHI (KR17AC0K13693),
which was funded by the Climate and Energy Fund of the Austrian Climate
Research Programme (ACRP) from April 2018 to March 2020. Using three pilot
cities as an example - Mödling and the surrounding area, Salzburg, and Klagenfurt
- the ADAPT-UHI project developed tools to minimize the effects of urban heat
islands in the future. The aim of the project was to provide city planners with the
right tools to help them make decisions on climate change adaptation. All project
results can be obtained from the project website: adapt-uhi.org
Acknowledgements. Special thanks go to the city administrations of the three
pilot cities of Mödling, Salzburg and Klagenfurt, without whose support this
project would not have been possible. Unfortunately, we are unable to name all
supporters, so we would like to thank:
• Marita Widmann and her team (Head of the Planning Department Mödling)
• Cristina Polito (Office for Urban Planning and Traffic) and all supporting staff
from the city of Salzburg, and
• Stefan Guggenberger (International Project Management Agency Klagenfurt)
and all supporting staff from the city of Klagenfurt.
Image credits:
Illustrations by Natalie Sandner (n.c.sandner@gmx.de)
Photographs on pages 8 and 10 © proHolz Austria (proHolz.at)
Photograph on page 8 © Solana (solona-sonnenschutz.de)
Photograph on page 8 © urbadis (urbadis.com)
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This brochure is aimed at urban planners and provides
information on:
✓ General urban planning measures to reduce the UHI effect
✓ Costs and benefits of the various measures
Urban Heat Islands
Cities are particularly affected by climate change and rising
temperatures. Large, impermeable surfaces, lack of vegetation and
concentrated buildings drive up the temperatures in cities. This
effect is called the Urban Heat Island (UHI).
Extreme heat affects human health and well-being. Heat waves in
urban areas have already claimed many human lives. For example,
the 2003 heat wave resulted in 30,000 deaths across Europe.
Large cities such as Vienna have already examined the UHI effect
and developed climate protection and adaptation strategies. Less
work has been done in small to medium-sized Austrian cities, which
are also affected by heat waves during the summer. In addition,
with increasing urbanization, urban planners need solutions to
mitigate the impact of the UHI since cities will continue to grow in
the future.
In the ADAPT-UHI project, both the future heat load and potential
adaptation measures were modelled in the pilot cities of Mödling,
Salzburg and Klagenfurt. In a further step, both the effects and the
costs of these measures were compared.
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The ADAPT-UHI Project
Website
https://adapt-uhi.org/
Overview
Using three pilot cities as an example - Mödling and the surrounding
area, Salzburg, and Klagenfurt - the ADAPT-UHI project has
developed tools to minimize the effects of urban heat islands in the
future.
The aim of the project was to provide city planners with suitable
tools when making decisions on climate change adaptation. The
following products have been generated and can be obtained from
the project website:
• Urban Heat Island Risk Index for all of Austria. This map shows
the potential risk from Urban Heat Islands at a resolution of
100m x 100m.
• Modelling of three different adaptation scenarios for all three
pilot cities at a resolution of 100m x 100m, including a costbenefit
calculation.
• Urban Climate Quality Monitoring. For all three pilot cities, the
quality of the existing green and blue infrastructure (parks,
lawns, city trees, water bodies) was evaluated and rated.
General recommendations for urban planning were developed
based on the project results.
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ADAPT-UHI
Research Team
Alexander
Storch (UBA)
Brigitta Hollosi
(ZAMG)
Daniel Johnson
(ESCP)
Gundula
Prokop (UBA)
Linda See
(IIASA)
Maja ŽuvelaAloise
(ZAMG)
Sandro Oswald
(ZAMG)
Stefan Guggenberger
(IPAK)
Wolfgang
Hafner (IPAK)
Wolfgang
Schieder (UBA)
The Climate and Energy Fund of the Austrian
Climate Research Program (ACRP) funded the
ADAPT-UHI project from April 2018 to March 2020
for a total of € 250,000.
The Zentralanstalt für Meteorologie und Geodynamik
(ZAMG) modelled future urban heat islands for all three pilot
cities taking different measures into account.
The Austrian Environment Agency (UBA)
developed the Urban Climate Quality Maps
and the UHI Risk Index.
IIASA coordinated the project, created a UHI
visualization tool and was responsible for
knowledge transfer and dissemination.
The International Project Management Agency Klagenfurt
(IPAK) supported climate modelling and adaptation measures
for Klagenfurt.
Daniel Johnson from the ESCP Business School Berlin undertook the
cost-benefit calculations for all three pilot cities.
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One Tree per Resident
Cities should plan for one tree per
resident over the entire built-up area, or
the equivalent in terms of green or blue
infrastructure.
Both private and public spaces should be
considered. The planting of new trees,
the maintenance of existing trees and
any replacement measures should be put
into place within the next 20 years.
Replacement measures should have the
same cooling effect as an average
healthy city tree with an age of 30 years,
after 30 consecutive days of more than
30°C and no rainfall.
City trees provide cooling in two ways. First, through shading, and
secondly, through the evaporation of water.
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Evaporation
50 L/day
Water storage
The reflectivity (or albedo) of roof surfaces should be increased
continuously over time. An increase of 0.5 percentage points per
year over the next 40 years is recommended. This corresponds to
an increase in the reflectivity by a total of 20%.
"Cool roofs" are still largely unknown in Austria. In California, bright
roofs are part of their climate strategy. So-called "cool roofs"
should be placed on all new buildings - roofs whose materials are as
reflective as possible, e.g., through bright colors.
Increase the Reflection
from Roofs
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Amount of reflection
of solar radiation
White roof
Very high reflection of solar radiation
Metal roof
High reflection of solar
radiation
Black roof
Low reflection of solar radiation
The aim should be to continuously unseal public and privately
asphalted surfaces over time. An annual reduction in the sealed area
of 1.25% of the total over a period of 40 years is recommended. This
can be achieved by changing the sealed surface to a green area or
by installing different surfaces that have at least 50% water
permeability (see below).
Unsealing Surfaces
Green tram tracks
(Example from Mulhouse, Frankreich)
Partially unsealed parking lot
(Example from Munich, Germany)
Examples of surfaces with different infiltration
capabilities
(1) Macadam or water-bound surfaces
Permeability 50%, for parking spaces with light to
medium-weight vehicles
(2) Gravel lawn
70% - 90% permeability, for parking spaces with light
to medium-weight vehicles
(3) Lawn joint pavement
50% - 60% permeability, for parking spaces with light
to medium-weight vehicles
(4) Grass and lawn pavers
60% permeability, also suitable for heavy vehicles




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Effective shading of buildings and open spaces - for example by
trees, green facades, arbors or solar panels - should be used
wherever possible. In addition, other sustainable cooling measures
should also be used, with priority given to passive measures in
urban planning, architecture and building technology.
Shading from Buildings
and Vegetation
Everyday walks in public spaces should not be a burden for
pedestrians and cyclists, even on hot days. For those who do not
have a garden, the quality of the time spent in public spaces is
particularly important. A bench in the shade serves as a place to
relax and as a meeting point.
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Shading Measures
Shading of a public space
in Bittburg, Germany
(© Solana)
Shading of a public
square in Benicassim,
Spain
(© urbadis)
Shaded courtyard
(© Bruno Klomfar /
proHolz Austria)
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Existing green areas and water bodies should be protected from
obstruction, and new green areas and water bodies should be
created where possible. It is also important to maintain and set up
corridors that help to generate urban cooling.
Protect Cool Spaces
Identify cooling corridors and protect them from obstruction.
Austria's cities are particularly affected by increasing urban
sprawl. Here there is a risk that important cooling corridors will
be lost. These are often located in neighboring municipalities and
thus, are also outside of a city’s planning area. In this case, longterm
protection can only be achieved through good regional
cooperation.
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Cool area
protection zone
Wherever possible, attention should be paid to the selection of
building materials with regard to their thermal properties, and
classic concrete construction should be avoided (e.g., the thermal
conductivity of concrete is 16 times higher than that of wood).
Cool Building Materials
Above: Wohnhausanlage Mühlweg, Vienna
Below left: Kindergarten Schukowitzgasse, Vienna
Below right: Wohnbau Wagramerstraße , Vienna
All photographs by © Bruno Klomfar / proHolz Austria
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Private gardens can make a major contribution to the city's climate
and local biodiversity. City planning can achieve a great deal
through awareness raising and incentive systems. Trees on private
property should be protected against removal by legal means such
as an ordinance.
• Improvement of public relations between the city and relevant
target groups (private and institutional forest and garden
owners, companies in industrial and commercial areas, farmers,
forestry companies). The “Nature in the Garden” campaign
(www.naturimgarten.at) is a great example of how garden
knowledge can be conveyed in a manner that is easy to
understand.
• Establishment of a tree protection regulation for the sustainable
protection of the tree population - similar to the Vienna Tree
Protection Act (LGBL 71/2018: Gesetz zum Schutze des Baumbestandes in
Wien).
• Tree support program for new trees in gardens - similar to the
Graz model (Richtl. für die Förderung einer urbanen Begrünung, 2019).
Include Private Gardens
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Through regional cooperation between neighboring municipalities,
both costs and benefits can be optimized when applying climate
change adaptation measures.
Typical areas of cooperation in this context are: the protection of
forest areas (from construction on one side to prevention of fires
on the other), the development and design of industrial and
commercial areas, large construction projects, regional planning
programs, and common data sets that can be shared.
Regional Cooperation
Advantages of regional cooperation
In the ADAPT-UHI project, climate change adaptation measures
for the city of Mödling (urban area only) and the Mödling region
(the core city and 13 surrounding municipalities) were modelled
until 2050.
• If the measures are only applied to the core city, the number of
hot days can be reduced by 25%.
• If the measures are applied simultaneously in all surrounding
communities, the number of hot days can be reduced by 36% in
the entire region.
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As part of the ADAPT-UHI project, the costs and benefits of the
measures for reducing urban heat islands were assessed. Every
measure for reducing urban heat islands has an associated
investment and maintenance cost. In order to understand whether
the benefits of the measures outweigh the costs, the measures for
three pilot cities were assessed in monetary terms.
On the cost side of the equation are the investment costs for all
measures, which include, for example, the planting and
maintenance of city trees, the installation and maintenance of green
roofs, the unsealing of asphalt surfaces, the installation and
maintenance of white roofs, etc.
The benefits of ecosystem services were then evaluated, where the
advantages are obtained by using “green measures”. It was shown
that the benefits from ecosystem services outweigh the costs in the
long term.
Costs & Benefits
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• Green roofs reduce the outflow of rainwater to sewage
treatment plants.
• Trees reduce urban air pollution.
• The increase in green areas contributes to the storage of carbon
and improves regional biodiversity.
• Green walls and green roofs increase the thermal insulation of
buildings and thus increase property values.
• The reduction of hot days leads to positive health effects: there is
less absenteeism, fewer hospital stays and a lower heat-related
death rate.
The table shows the monetary valuation of ecosystem services
versus investment and maintenance costs. In all cities, the benefits
achieved are greater than the costs. The greatest benefit is achieved
by reducing heat-related mortality. The second largest benefit is
achieved through an increase in property values.
Costs & Benefits
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This brochure is a product of the research project ADAPT-UHI
(KR17AC0K13693), which was funded by the Climate and Energy
Fund of the Austrian Climate Research Programme (ACRP) from
April 2018 to March 2020. Using three pilot cities as an example Mödling
and the surrounding area, Salzburg, and Klagenfurt - the
ADAPT-UHI project developed tools to minimize the effects of
urban heat islands in the future. The aim of the project was to
provide city planners with suitable tools when making decisions on
adaptation to climate change. All project results can be obtained
from the project website: adapt-uhi.org