In its different forms, the built environment is the single largest energy consumer in the EU, and one of the largest carbon dioxide emitters. Green buildings and smart technologies are two of the most important elements to reach this goal. In a situation where the use of new technologies and new knowledge becomes more important as well as the news flow increase the role of the technical consultant becomes more important. Also, the client/developer role become increasingly important when buildings turn from storage facilities to service generating entities. A closer alliance between client and consultant is necessary to align business models with new technologies. Contracts are the most important instrument to shape incentive structures for optimal economic outcomes, as well as for shaping incentives for optimal operation of smart and sustainable buildings. In this paper we propose a contract design that incentivise consultants to fully use their knowledge to make sure that planned systems are installed and operated in an optimal manner. There are in general two approaches to this type of contract design. The first is to write a detailed contract setting out how to deal with possible outcomes going forward. The second, and the approach used in this paper, is to write a less detailed contract that sets out a framework of incentives for continuing cooperation and to keep a good reputation.