The general purpose of this project is to encourage the use of innovative products. services and methodologies in the field of energy and environment-friendly efficient tertiary and mixed-used buildings among the business parks managers and among the business community at large. in such a way as to: o start a significant reduction in the emissions of greenhouse gases at NWE level; and o stimulate the competitiveness of the regional economies through bringing new technologies to market and developing new products. During the last two decades. the share of the energy consumption has shifted in Europe from the industry (originally. the major contributor) to the transport. housing and tertiary sectors. This shift from industry to tertiary activities is even more acute in regions that were formerly heavily industrialized. The share of the tertiary sector has increased substantially (e.g. in Wallonia. from 5.7% in 1990 to 8% in 2003. a 40% relative increase).The tertiary sector offers therefore a huge potential for energy consumption reduction. and correlatively for reduction of greenhouse gases emissions. provided some technical and cultural barriers are removed. The business and industrial parks are host to a significant part of the new investments in tertiary and mixed-used buildings. and in this regards. the industrial park managers have a key role to play in the removal of these barriers. Achievements: REGAIN has strengthened the link between the development of innovative and transferable products, services and methodologies in the field of eco-efficient building systems and their uptake, and by reporting back to policymakers, it has helped to enforce and also improve current regulations at local, national and European levels. The international market players (builders, architects, consultants, regulatory bodies) involved in the project tested innovative materials and technologies in terms of cost/benefit ratio, CO² reduction efficiency and reliability, and then integrated them in four eco-efficient tertiary and industrial pilot buildings, located in major industrial parks in the Namur Province (BE), Nord-Pas-de-Calais (FR), and Scotland and Wales (UK). In spite of a late start due to the initial difficulties encountered by the partners when selecting different materials and the time needed to adapt to the different national legislations, available skills, and local climatic conditions, four pilot buildings have now been built to the highest standards of energy-efficiency in the Project REGAIN.The most significant achievement and innovative aspect of our project was concerned mainly with new building technologies and materials, and is emphasized in the implementation of these technologies in the 4 pilots buildings (demonstration investments). These technical choices are illustrated in the Best Available Technologies Booklet, with 22 innovative BAT listed.