Buildings account for 40% of total energy consumption and emit 35% of the total CO2 in the EU and there is consequently an enormous energy saving potential. Therefore the EU-directive 2002/91/EU [1] requires from all EU Member States to save energy in this sector. Hence, the drive to reduce the energy consumption of buildings represents an essential component of environmental protection efforts. Furthermore, the new directive 2010/31/EU [2] requires that the Member States tighten national standards and draw up national plans to increase the number of 'nearly zero-energy buildings'. Well planned energy-saving strategies presume knowledge of specific characteristics of the current national building stock. Therefore, the implementation of process to support systematic data collection, classification and analysis of the energy consumptions of buildings will become increasingly important during the coming years. The following field survey analyzed the energy consumption of 68 school buildings in Luxembourg. A separate collation of electricity and heat energy consumptions allowed a detailed analysis of specific energy parameters. A statistical analysis and interpretation of new buildings differentiated by energy sources was completed as well as the definition of energy relevant parameters such as the energy standard, the purpose of the building or the presence of canteens. COVER LETTER Authors for correspondences:Andreas Thewes / Stefan Maas "nearly zero-energy buildings". Well-planned energy-saving strategies presume knowledge of specific characteristics of the current national building stock. Therefore, the implementation of a process to support systematic data collection, classification and analysis of the energy consumption of buildings will become increasingly important during the coming years.In the field study described below we analyzed the energy consumption of 68 school buildings in Luxembourg. A separate collation of electricity and heat energy consumptions allowed to make a detailed analysis of specific energy parameters. Clustered according to energy sources, the new buildings were analyzed from a statistical point of view. We defined the energy relevant parameters such as energy standards, the purpose of use of the buildings or whether they had canteens.

In Luxemburg hat sich in den vergangenen Jahren der nationale Energieverbrauch verstärkt zum Gebäudesektor hin verändert. Während 1990 noch 71 % des gesamten Inlandendenergieverbrauchs auf den Industriesektor zurückzuführen waren und nur 20 % auf die Gebäude, hat sich dies bis zum Jahr 2005 deutlich verändert. Demzufolge entfallen nur noch 44 % auf den Industriesektor, 25 % auf Verkehr und 31 % auf den Verbrauch des Tertiären Sektors [1], welcher die privaten und öffentlichen Haushalte sowie Dienstleistungsgebäude beinhaltet. Da in Europa sogar 40 % des gesamten Energieverbrauchs auf den Gebäudesektor entfallen und in diesem Bereich enormes Einsparpotential besteht, wurden durch die EU‐Direktive 2002/91/EG [2] alle Länder dazu aufgefordert Energie in diesem Sektor einzusparen. Die Energieeinsparung bei Gebäuden stellt somit eine zentrale Säule des Klimaschutzes dar. Die Direktive 2010/31/EG [3] fordert von den Mitgliedsstaaten die nationalen Normen weiterhin zu verschärfen und Pläne zu erstellen, um die Anzahl an Niedrigstenergiegebäuden weiter zu erhöhen. Um die Energieströme in Gebäuden besser zu verstehen, Sparmaßnahmen zu erarbeiten und mögliche Bewertungen über das Energieeinsparpotential für Gebäude durchführen zu können, sind jedoch aussagekräftige Verbrauchsdatenanalysen notwendig.Bei der folgenden Feldstudie konnten 47 Bürogebäude in Luxemburg energetisch erfasst werden, wobei Strom‐, Wärme‐ und teilweise auch der Kälteverbrauch getrennt vorlagen. Eine statistische Auswertung und Analyse der neueren Gebäude nach den unterschiedlichen Energieträgern (Wärme, Strom), sowie die Festlegung von energierelevanten Einflussgrößen, wie der Technisierungsgrad, der Fensterflächenanteil, die Bauweise oder die Nutzungsart zeigen die Probleme bei den Bürogebäuden auf. Eine abschließende Hochrechnung auf die Grundgesamtheit der Neubauten des Landes hilft das Einsparpotential zu verdeutlichen.Evaluation and analysis of energy consumption in office buildings. During the last years the national energy consumption of Luxembourg shifted noticeable towards the building sector. In 1990 71 % of the total domestic end energy consumption was ascribed to industrial sector and only 20 % to the building sector. The distribution changed significantly and in 2005 the energy consumption dedicated to industrial sector represented only 44 %, transport 25 % and the tertiary sector 31 % [1], which includes private and public households as well as non‐residential buildings. The buildings account for 40 % of total energy consumption in the EU and there is an enormous energy saving potential. Therefore the EUdirective 2002/91/EG [2] requires from all EU Member States to save energy in this sector. Hence the energy saving of buildings present an essential part of climate protection. Furthermore the new directive 2010/31/EG [3] requires from the Member States to tighten national standards and to draw up national plans for increasing the number of nearly zero‐energy buildings. But for a better understanding of energy flows in buildings and to develop energy saving concepts as well as to estimate possible energy savings of buildings a detailed analysis of energy consumption databases is an important precondition.The following field survey monitors 47 office buildings in Luxembourg. A separate gathering of electricity, heat and cooling energy consumptions allowed a detailed energetic analysis. A statistical analysis and interpretation of new buildings differentiated by energy sources as well as definition of energy relevant parameters like the window ratio, the construction method, the type of use or the kind of technical installations show the problems of typical existing office buildings. A final extrapolation to the population of all new office buildings in Luxembourg helps to estimate the energy saving potential.

Following the European directive to reduce CO2 emissions of existing buildings by improving energy efficiency, internal insulation systems play a central role in the renovation of historically valuable buildings which cannot be insulated from the outside for reasons of monumental protection, or in cases where no additional exterior space is available. However, besides the thermal property of insulation systems, there are other relevant properties to be considered before choosing an internal insulation system, such as the hygrothermal behavior which plays a particularly important role in diffusion‐open interior insulation systems. As the internal insulation layer reduces the temperature of the existing wall during the heating season, its drying potential after rain events is considerably reduced. In addition to the effects of moisture from the outside (mainly wind driven rain), the entry of humidity from the inside through diffusion plays an important role. In the presented study, high performance insulation materials with nanostructure based on silicon dioxide and polyurethane are compared to conventional material based on wood fiber from a hygrothermal point of view by analyzing in situ measurements and simulations.