The construction of a new office building in the woods surrounding Zeist is promoting the interests of two organisations that promote the interests of their members. Upon its completion in 2011, the staff of CBW Mitex will not only enjoy a panoramic view of the surrounding woods through the fully (triple-)glazed façades. They will work in one of the most energy-efficient and environmentally-friendly buildings in the Netherlands. The building is CO2 neutral and produces enough energy to meet its own needs (net zero energy). An integral system of sensors ensures that the building is only ventilated, warmed, cooled and lit in those parts of the building where people are actually present. This system saves up to 40% of the building’s energy needs.The design focused on the interaction between man and the natural environment. This was achieved in form as well as by the sustainable measures included in the design. The new building has a square floor plan with two storeys. The wings are designed around a courtyard. The ground floor in the wing facing the woods is left open to create an immediate connection between the courtyard and the adjoining scenic landscape.The design is based on an interplay of three elements. The first of these is the members. Visitors enter the building in its northwest corner where they immediately find themselves in the centre of the building. The west wing, on the side facing the courtyard, has a double-storey entrance lobby, reception desk, waiting room and a small information centre. Conference rooms are located in the south wing on the first floor. From here, a view through to the pond in the adjoining English landscape-style park provides visitors with tranquil surroundings. Having the largest part of the building made from glass makes the structure of the organisation transparent.The second element consists of the users. Offices are on the outsides of the wings and oriented toward their surroundings. Using so much glass makes other users and the entrance always visible from the workstations. The rooms for facilities face the courtyard and encourage social interaction.The third element is interaction with the natural environment. By means of the ‘open’ wing, the natural environment penetrates the courtyard and makes it an extension of the surroundings. Through the open glass facades with wooden blinds, the natural environment can be admired from every room. The building also makes maximum use of daylight and thus reduces its consumption of electricity for lighting.The building is designed with sustainability in mind so that it can give as much as possible back to the natural environment. This satisfies the needs of the current generation of users but does not limit future generations either. Two examples: the acoustic material is biodegradable and only a minimum of copper was used. A reduction in energy consumption also contributes to sustainability. One of the elements in this is an underground heating and cooling storage facility combined with concrete core activation. The system also responds to the number of people present in the building, thus improving efficiency even more. The building not only interacts with its natural surroundings, but it also displays a respect for nature. For users, these measures impart the ultimate in comfort.