1 INTRODUCTION Observations increasingly point to global warming and other changes in the climate system. The Inter- governmental Panel on Climate Change concludes that most of the warming observed over the last 50 years is attributable to human activities, and that anthropogenic climate change will persist for many centuries (IPCC 2001). Climatic impact from precipitation, wind, tem- perature and exposure to the sun causes extensive degradation and damage to the built environment every year. The understanding of how degradation and damage can best be reduced is of significant im- portance in the design and construction of buildings. Future building materials, structures and external envelopes will probably have to withstand even greater climatic impact in parts of Norway than to- day. The trend we have seen over the last 10 - 15 years, with mild autumn-winter seasons with heavy precipitation and frequent storms along the coast, is expected to intensify. Scientists in a wide range of disciplines are ex- ploring the possible impacts of climate change. Until now, few studies have focused on the possible im- pacts of climate change on the built environment in Norway. In other countries impact studies have been performed along with studies of climate develop- ment under global warming. A British study (Graves & Phillipson 2000) shows that an increase in wind speeds of 6% is likely to cause damage to 1 million buildings at a cost of £1-2 billion. The study also addressed the major impacts of increased driving rain quantities on the suitability of different types of building enclosures, and the likely increase of maintenance costs due to more extreme weather in parts of England. Dry summers in the south of Eng- land could cause a 50 – 100% increase in subsidence claims in vulnerable areas. A study published by the Building Research As- sociation of New Zealand presents climate change impacts on building performance in New Zealand (Camilleri et al. 2001). The study concludes that fu- ture performance of buildings in New Zealand may be significantly different from the current perform- ance with regard to coastal and inland flooding, overheating, and wind damage and flooding associ- ated with tropical cyclones. 2 RESEARCH BACKGROUND 2.1 Extreme weather events of the last ten years Coastal communities in Norway are vulnerable to strong winds. The hurricane that occurred in North- west Norway on New Year’s Day 1992 caused dam- age to buildings in the range of 166 million Euro. Wind speeds of 62 - 63 m/s were recorded, the high- est wind speeds that have ever been recorded on mainland Norway. The bulk of the damage was in- curred to roofs and roofing, due primarily to insuffi- cient anchoring. Large snow loads on roofs during the winter of 1999/2000 contributed to the collapse of five build- Building enclosure performance in a more severe climate K.R. Lisø, B. Time & T. Kvande Norwegian Building Research Institute (NBI), Oslo/Trondheim, Norway E.J. Førland The Norwegian Meteorological Institute, Oslo, Norway ABSTRACT: This paper gives an overall view of challenges concerning building enclosure performance in a potentially more severe climate, based on future climate development scenarios for different parts of Norway. Preliminary results from the Norwegian Research & Development Programme “Climate 2000 – Building con- structions in a more severe climate” indicates that there is a clear need to further develop our knowledge, methods, tools and solutions in principal concerning the planning and design of buildings in harsh climates, in order to ensure a reliable building stock in the future as well. Climate change will entail new conditions for the Norwegian construction industry. The presented climate change scenarios calls for a systematically identi- fication of areas in the Norwegian construction industry that are vulnerable to potential impacts of climate change, and the development of adaptation strategies.