Key issues in energy-efficient building envelopes of Norwegian office buildings Matthias Haase, Research Scientist, SINTEF Building and Infrastructure, 7465 Trondheim, Norway; matthias.haase@sintef.no and www.sintef.no/byggforsk Inger Andresen, Dr.ing, Senior Scientist, SINTEF Building and Infrastructure, 7465 Trondheim, Norway; inger.andresen@sintef.no and www.sintef.no/byggforsk KEYWORDS: building envelope, climate, energy efficiency, sensitivity analysis, simulation, survey SUMMARY: This work is part of the project “Climate Adapted Buildings” (CAB) run by SINTEF Building and Infrastructure. The project’s principal objectives are to develop more energy-efficient building envelope assemblies and new methods for the design of building envelopes in harsh climates, resulting in more accurate and geographically dependent design guidelines. The project includes analyses of building envelopes applied in different kinds of climates, different uses, and different construction methods. Nine energy-efficient office buildings in Norway were studied in order to get an overview of the state-of-the-art of low energy office buildings in Norway. This paper includes a description and classification of the energy concepts and the corresponding technologies for reducing energy consumption in the buildings. Then, the implications of these technologies are studied with the help of a simulation model and the key issues that influence the energy performance of these buildings with special emphasis on envelope performance are reported. The results show that a very airtight envelope is an important step towards low-energy buildings. The supporting effect towards other energy concepts as heat pumps, natural/hybrid ventilation should be fully explored in order to realize sustainable energy-efficient buildings in Norway. A careful design of climate adapted and super- efficient envelope systems can further enhance energy-efficiency. 1. Introduction More efficient use of energy in the built environment is essential to reach political goals within Norway and the European Union on reliable energy supply and reductions of emissions of greenhouse gases. The built environment affects nature through energy use, emissions and use of raw materials. The total energy use in buildings accounts for about 40% of the total energy use in the country, excluding the energy sectors (Statistics Norway 2006). The construction industry may thus make significant contributions to environmental improvement through energy efficiency and utilization of renewable energy. In order to realize energy performance requirements of a higher standard in the new Technical Regulations, it is necessary to develop new design strategies to meet these requirements - without sacrifices in other performance codes, standards or guidelines. Prior experience related to the introduction of new energy performance requirements has shown that the design energy performance levels are either not met, or they are fulfilled at the expense of indoor climate, technical quality (e.g. moisture related problems), or architectural quality. Facing the future risks of climate change, Norway also provides a unique “laboratory” for testing of the robustness of new building envelope solutions (Lisø et al. 2005). Therefore it seems appropriate to determine the parameters of building design that have the biggest influence on energy consumption of buildings. Special focus was put on the building envelope and some parameter that have an influence on the building load (Andresen et al. 2005). The starting point was to focus on office buildings but other building types will be studied in the near future.