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 following parameters are studied: - Climate: temperature, wind, solar radiation, rain, relative humidity - Air tightness of the building envelope - Thermal insulation of the building envelope - Windows/glazing type, size and orientation - Shading and daylighting systems - Solar collectors and BIPV The preliminary 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 robustness, energy efficiency and comfort.