Correspondence: David Steixner, FHS Kufstein Tirol BildungsGmbH, University of Applied Sciences, Andreas Hofer Strasse 7, Kufstein A-6330, Austria. Tel: +43 (0) 5372 718 19 129; Fax: +43 (0) 5372 718 19 104; E-mail: David.Steixner@fh-kufstein.ac.at; Web: www.fh-kufstein.eu and www.immobilien-benchmarking.at

¹finished his studies of Facility Management at the University of Applied Sciences in Kufstein in 2005. Since 2005, he has been a research fellow at the University of Applied Sciences in Kufstein, where he is currently carrying out a Research Project in the field of Real Estate Benchmarking. In parallel, he started his PhD studies in 2006 at the University of Innsbruck.

²started his PhD studies at the University of Innsbruck in 2004, where he also began his studies of Economics and Mathematics following his studies of Facility Management at the University of Applied Sciences in Kufstein. Since 2005, he has been a research fellow at the University of Applied Sciences in Kufstein, where he is currently carrying out a Research Project in the field of Real Estate Benchmarking. Wolfgang Brunauer was awarded several prizes, for example, the Emerald Gerald Brown Award 2006 and awards by the IFMA, Gefma and DVP.

³earned his diploma in statistics in 1997 and his PhD in Statistics in 2001, both at the University of Munich, where he habilitated in 2004. Having worked as a research assistant until 2002, he became an assistant professor at the Department of Statistics of the University of Munich. In 2005, he became a Professor of Statistics at the University of Leipzig. In 2006, he became a Professor of Statistics at the University of Innsbruck.

Received 3 August 2007; Revised 3 August 2007.

Abstract

The directive 2002/91/EC of the European Parliament and the Council of 16th December, 2002 (Energy Performance of Buildings Directive, EPBD, 2002) requires member states to introduce an energy certification in order to reduce energy consumption in buildings. For the appraisal of the energy, key-figure paragraph 2 of the directive generally allows both the theoretical calculation of energy demand and the collection of the real energy consumption; however, these two approaches do not always lead to the same result, but rather to substantially different values. Naturally, this leads to lively discussions among the involved persons. This paper is the first survey of a study whose goal is to explain where the differences between the two approaches arise from. The first results, for example, show that external walls, ceilings and roofs with a theoretically poor thermal quality are expected not to be as 'bad' in practice as the theoretical calculation would lead us to believe...