The European Union has taken a strong leadership role in promoting energy efficiency in buildings. This is among other things highlighted by the Directive on the Energy Performance of Buildings, which is designed to promote the improvement of energy performance of buildings in member states. One of the benefits of this directive is that it provides an integrated approach to different aspects of buildings energy use, which until now only a few member states were doing, and that all aspects are expressed in simple energy performance indicators. In order to achieve such reductions of the energy use in new buildings it will require development of new construction solutions, new types of building envelopes, and development of new building materials. It will also require the development of more holistic building concepts, sustainable buildings where an integrated design approach is needed to ensure a system optimization and to enable the designer(s) to control the many design parameters that must be considered and integrated. It is therefore important to understand how this design process works and how the architect can be enabled to integrate sustainable design solutions. Computer-based modeling and simulation is becoming more and more significant for the prediction of future energy and environmental performance of buildings and the systems that service them. Modeling and simulation can and should play a vital role in building and systems design, commissioning, management and operation. Although most practitioners will be aware of the emerging building simulation technologies, yet few are able to claim expertise in its application. In the design of sustainable buildings it is therefore necessary to identify the most important design parameters in order to develop more efficiently alternative design proposals and/or reach optimized design solutions. This can be achieved by applying sensitivity analysis early in the design process. Previously, environmental simulation of building performance was only done by engineers at the end of the design process. Any weak points in the performance of the design could then be ‘fixed' by adding heating, cooling, shades, vents, fans, panels, etc ... However, at the end of the design process it is too late. The decisions made early on in the design process have the largest impact. In addition, environmental issues are becoming more important, the complexity of the building design is increasing, and simulation tools are becoming more architects friendly. Therefore, in the design of sustainable buildings it will be very beneficial to be able identify the most important design parameters in order to develop more efficiently alternative design proposals and/or reach optimized design solutions. Communication between architects and engineers paper will become more common but also more important. Digital architecture has to take these challenges into account and develop a common language for architects that enable integrated design in order to tackle the problems stated above
