The central European construction sector has shown that the renovation of existing buildings to the Passivhaus standard is achievable. The two-fold challenge for Norway and Norden in general is to first, build the knowledge and skills capacity for the bro ad implementation of this extreme energy efficiency technology and design technique, and second, find innovative and cost-effective technical solutions for achieving the standard in our climate and construction/property industry context. Challenges includ e new Norwegian building and planning regulations in force from 2009 mandating greater energy efficiency, stricter construction site control, renovating buildings in tight, urban contexts, policies to reduce CO2 production, and the scatter of data on iden tical building energy use. Since the existing stock of buildings is 97% of all buildings, all buildings use 38% of all energy, and most of them no longer meet energy regulation levels, the opportunity is in the existing buildings to potentially save 8 - 1 2 TWh every year by 2020, while Energy21 calls for the research and implementation competence to achieve such radical energy efficiency by 2015. This project will study energy efficiency renovations in Norway in cooperation with industry stakeholders OBOS Prosjekt, Undervisningsbygg KF, and Grønn Byggallianse, from an interdisciplinary and case study method to account for the complexity of the data and to include the users and the industry in the setting of the research agenda , metodology, and selection of case studies, and compare these cases to Nordic and European examples with a European research network. This research will thus produce scientifically based innovation and new knowledge of how the Passivhaus type energy efficiency for existing building s can be reliably introduced to Norway, researchers and engineers that can continue this R&D and implementation activity in an international context, and help to develop opportunities for Norwegian industry.