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1. INTRODUCTION
A sustainable built environment is a precondition for sustainable development of a society. Buildings which offer comfortable and affordable housing and functional space for work are as important as an efficient infrastructure which provides reliable transport of people, goods, water, energy and information. Depending on the state of development of a society, the challenges regarding the built environment are very different. In many developing countries the focus lies on the establishment of a basic infrastructure and housing for everybody while in the developed world the focus is on the transformation of the existing built environment towards a much more sustainable one.
The key elements driving this transformation process in developed countries such as Switzerland are climate change, energy policy and substantial demographic changes of the society in the coming decades. As a midterm goal, Switzerland is committed to reduce the overall CO2 emissions during the period 2013-2020 by 15.8 % compared to 1990. Within the new energy policy which has been formulated in the aftermath of Fukushima the nuclear phase-out, large improvements in energy efficiency and increased use of renewable energy are planned. Presently, the Swiss building stock is responsible for roughly 50 % of the national CO2 emissions and for 40 % of the end energy demand (1, 2). The building sector is therefore required to reduce its environmental footprint dramatically over the coming decades.
This is not only a challenge for the construction sector but also a unique opportunity. Deep renovation of existing buildings, replacement of old and unsustainable buildings by new ones and the increased use of renewable energy in buildings will fuel the development of the sector over the coming decades. To make all of this happen, an acceleration of the innovation speed is mandatory. Switzerland is well positioned to follow this road since the Swiss research community ranks amongst the best worldwide in the construction area. However, the transfer of new ideas and concepts from the research world into practice takes far too long. The main reason is the risk aversion of planners, contractors and clients. There are two main reasons for this: high investment costs and lifespans of 30 years and more. As long as new solutions have only been proven at the lab scale, the direct...