Foto: Frontansicht des Einfamilien-Passivhauses in Pettenbach

KELVIN - Reducing the urban heat island effect via improving the reflective properties of buildings and urban areas

The aim of this project is to estimate the potential to reduce urban heat islands via low-tech measures such as the variation of the surface albedo, using the City of Vienna as an example. The project will also assess the energy savings and greenhouse gas emission reductions due to the decreased energy demand for cooling as a result of such measures.

Short Description




Starting point / motivation

Increased intensity or frequency of heat waves due to a changing climate could have far reaching implications for Austria. It is expected that the phenomenon of Urban Heat Islands (UHIs) observed in cities will further contribute to heat excess, leading to higher need for energy for cooling and ventilation. Even with good insolation, buildings absorb solar radiation and release it to their surroundings in the form of thermal energy.

Contents and goals

Exposed building surfaces may be designed so that they reflect incoming radiation rather than absorbing it. The improvement of the reflection properties of roofs and other surfaces is one possible way to increase energy efficiency in the urban area and at the same time contribute to climate change adaptation by addressing the problem of UHIs. The visual impression, such as coloring of tile roofs should be kept the same so that the usual appearance of the historical cities remains unchanged as far as possible.

In this project, the potential of climate adaptation as a measure to reduce the UHI effect through changes in properties of the urban surfaces (roof albedo, green roofs, facades etc.) and related emission-reduction through decreased cooling demand will be examined using the city of Vienna as an example.


The required input parameters for climate modeling such as surface albedo will be determined based on the satellite images for Vienna covering the period 2000 to 2014. Urban climate model simulations will be conducted based on the high-resolution topography and land use data for Vienna. Potential changes in local climate in the urban environment resulting from the changes in surface albedo will be examined and the potential to reduce the heat load on a city scale will be quantified.

The work will also include a calculation of the potential for reducing electricity demand for cooling (including CO2-equivalent savings based on the results of the city climate modeling). In addition, the project will estimate the potential change in radiative forcing by changing the variation of the surface albedo. This will also be converted to CO2-equivalent savings.

Expected results

The project meets the operational program objectives of the call by contributing to urban development targets through high resource and energy efficiency, improved quality of life and minimization of greenhouse gas emissions. It serves as a "stepping-stone" for future industrial developments by investigating the intelligent use of building coverings (façades, roofs) as a climate change adaptation strategy in urban regions.

Project Partners

Project management

JOANNEUM RESEARCH Forschungsgesellschaft mbH
RESOURCES - Institute for Water, Energy and Sustainability

Project or cooperation partners

Contact Address

JOANNEUM RESEARCH Forschungsgesellschaft mbH
RESOURCES - Institute for Water, Energy and Sustainability
DI Dr. Hannes Peter Schwaiger
Elisabethstraße 18/II
Tel.: +43 (316) 876 1316
Fax: +43 (316) 876 9 1316

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