Member States of the European Union are obliged to present a calculation method and certificate for the energy performance for buildings according to the guidelines 2002/91/EG und 2010/31/EU. In Luxembourg it is obligatory to add the real final energy consumption to the certificate after 3 years. The measured real final energy consumptions and the calculated ones were compared for 125 single-family homes and 105 multi-family homes with 870 dwellings in total. The mean calculated values for single-family homes were 74 % higher, the mean calculated values for multi-family homes 103 % higher than the actual measured data. The older the buildings, the higher the deviations, as the input parameters, which were partly assumed and partly predefined, diverge between calculations and reality. Sensitive parameters of interest are the indoor room temperature, the U-values, the used assessment for thermal bridges and the air exchange rate.
The public building stock of a country, consisting of schools, offices, accommodation facilities, single-and multi-family homes, accounts for a high consumption of electrical and heat energy. Therefore, this stock is often object to actions with the goal of lowering this energy usage by increasing the efficiency of those buildings. This is usually done by applying measures to the building envelope like insulation and/or new windows and by using more efficient HVAC technology. But often, in the initial state, the current energy consumption of such a stock is unknown or only known for single buildings. In this case, the calculation of energy and costs savings is either impossible or not exact. This paper shows a way to quantify and categorize the end-energy for heat use of the public building stock in Luxembourg, which consists of 1,744 Mio. m 2 gross area, while the information about this stock was incomplete in the first place.This analysis was done in cooperation with the national administration of public buildings.A certain amount of sample buildings was analyzed and then separated into three groups of low, normal and high end-energy use. The boundaries of these groups were chosen according to literature values, derived from European retrofit projects, which also served as the source for possible costs of renovations. This data was extrapolated to the whole stock. This information serves as a basis for future decisions concerning the retrofit of those buildings and makes a
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