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Before and after comparison of the facade insulation.
© RWTH Aachen, E.ON ERC
Untapped savings potential in refurbishment

Tracking down the rebound effect

Researchers at RWTH Aachen University have been investigating the implementation of a district energy concept in Karlsruhe across a period of three years. An evaluation of the measurement data has shown that the theoretical savings potential has not been fully achieved on completion of the refurbishment there; a so-called rebound effect has been created. A new project as part of the "EnEff:Stadt" research initiative now intends to get to the bottom of this phenomenon.

The phenomenon of reduced saving potentials has been debated for some time under the term "rebound effect". This is usually caused by the increased use of energy services. When this specifically relates to the energy requirement of buildings, the term "performance gap" is frequently used. However, a lack of data until now means that there have been no detailed quantitative analyses of the rebound effect. The current research project is therefore using the already existing comprehensive measurement technology in Karlsruhe-Rintheim and the simulation models of the buildings in order to close this gap. The measurement values will be supplemented with discussions with tenants and questionnaires. By examining the efficiency of the systems and the actions of tenants in detail it is intended to divide the rebound effect into economic, structural and technical effects that can be caused by changes in the heating system or expanding the usable living space.

Analysing the measured energy consumption in the Rintheim flats (including the internal temperatures measured in them) has partly revealed the reason for the high consumption, since the internal temperatures in some rooms are as high as 24 °C. This circumstance is, for example, one reason for the discrepancy between the calculated demand and actual energy consumption. Increased energy efficiency in the building sector does not necessarily lead to a reduction in the total energy consumption and is therefore only of limited use as an instrument of energy and environmental policy. Additional measures are required here. A reduction in the theoretically expected energy savings caused by the performance gap and the rebound effect has to be taken into account in future when planning the structural and system-based components. The research project is scheduled for completion at the beginning of 2015.

Aspects in urban districts

As part of the "Energy-efficient city" research initiative funded by the German Federal Ministry of Economics and Technology, assessment criteria, concepts and design tools are being developed for local authorities, the housing sector and the energy industry, and are being tried and tested in typical urban districts. The aim is to reduce the primary energy consumption in the entire district by at least 30 per cent.
The BINE-Projektinfo brochure "Integrated energy concept for a residential neighbourhood" (01/2010) focuses on the energy-based refurbishment and sustainable urban development of the residential district in Karlsruhe-Rintheim.



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