The Federal Office for Building and Regional Planning

Publication Recommendations for the integration of energetic differentiation characteristics in rental tables

Editor: BBSR Series: BBSR-Online-Publikation Issue: 04/2010 Published: October 2010 ISSN: 1868-0097


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For several years now, increasing energy costs and the necessity for climate protection have led to a strong growth in the energetic modernisation of buildings. In this way, many landlords want to increase the value of their property, limit the heating costs burden for their tenants and thus avoid vacancies. At the same time, they are making an important contribution to climate protection and saving resources. As a result of this energetic modernisation and the improving of standards for new buildings it is expected that the rent will be influenced by the energetic quality of buildings - in particular against a background of rising heating cost burdens. The effects of these price changes can be examined empirically and, when statistically significant, reproduced by integrating energetic differentiation characteristics into the rental table. This leads to a better founded monitoring of typically paid rents. A useful side-effect here is an improvement in the refinancing of energetic modernisation.

The following methodical steps are necessary if energetic differentiation characteristics are to be considered when compiling the rental table:

  • The energetic building quality for the rental table sample must be assessed by a valid method and classified if necessary.
  • The energetic building quality is taken into account in the rent determining factors.
  • The price effect of the rent determining factors are examined empirically and the significant influencing parameters are displayed in the rental table. This analysis has to be done for every town individually.

The energetic building quality can be assessed by energy performance indexes or energetic building features. Energy performance indexes are shown for example in the energy certificates required by the Energy Conservation Ordinance (EnEV). However, energy certificates were not developed for determining energetic building quality in rental tables. Their use in this connection is not without problems. There can be a considerable discrepancy between the energy performance index determined by an energy balance calculation and the energy performance index determined from measuring the actual usage for a building. Therefore, the unambiguity of characteristics, necessary for rental tables, is only present to a limited degree. Another, more pragmatic approach for energetic building assessment is an energy points system based on energetic building features. A main part of this expertise deals with the design and development of such a comparatively simple assessment and classification scheme. As a result a proposal for an energy points system based on energetic building features is presented.

The additional time and costs for obtaining the energetic building data are different depending on the nature of the rental table survey - which has to be carried out in any case. If a rental table is based on a landlord survey, questions relating to energetic building features can simply be added to the usual questionnaire. The situation is more complex with rental tables which are derived from tenant surveys. A very simple general questioning about energetic building features can probably be carried out within the scope of the tenant survey. However, from a technical energy-related point of view this is not accurate enough. Information is required concerning for example the thickness of the insulation, which has been subsequently added to a building or the year of construction of the heating system. For a survey with this degree of detail, an additional landlord questioning will be necessary. This can lead to an increase in costs.

In the rental table, energetic differentiation characteristics can be displayed as purely energetic rental price determinants or as mixed rental price determinants composed of energetic and other characteristics of housing quality.

With purely energetic rental price determinants the influence of the energetic building quality on the net rent is examined directly and is shown in the rental table, e.g. in the form of an addition. A higher incentive for energetic modernisation is thus achieved because the realisation of the measures and the price effect are more directly coupled.

In many rental tables mixed rental price determinants made up of energetic and other characteristics of housing quality are shown. Common practice here for example is the aggregation of energetic and other modernisation measures like sanitary, ventilation or electrical installations to form the rental price determinant "modernised". The advantage is that the information about energetic building quality does not necessarily have to be gathered in the same detail as would have to be the case for using the proposed energy points system. Through the aggregation with other characteristics often, an identifiable rental price effect still can be found.

Against a background of climate protection needs and increasing heating cost burdens the integration of energetic differentiation characteristics in rental tables may provide an important incentive for energetic modernisations. The integration of energetic characteristics in rental tables should be supported by further research work, particularly with respect to the energy point system which as yet has not been applied in practice.

Institute for Housing and Environment (IWU), Darmstadt
Dr. Jens Knissel, Dr. Christian v. Malottki, Roland Alles
Forschung und Beratung für Wohnen, Immobilien und Umwelt (F+B), Hamburg
Dr. Michael Clar

Federal Institute for Research on Building, Urban Affairs and Spatial Development (BBSR), Bonn
Wolfgang Neußer

This abstract is part of the German publication "Integration energetischer Differenzierungsmerkmale in Mietspiegel",
BBSR-Online-Publikation 04/2010.

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