The ambulance station in Zeist is the 4th building we designed for the Regional Ambulance Service Utrecht (RAVU). The buildings share a number of distinctive family traits. They all have wooden facades and a curved roof. In this design that pedigree is extended with extra attention for energy efficiency and the use of natural materials. The building is located on the outskirts of town, against the edge of the forest. The L-shaped plan is carefully positioned between the existing trees. A large beech tree shades the 4 meter high window in the main staffroom. An ambulance post has no public function, patients will never enter this building. We decided to keep the main facades closed, the green sloping walls rise from the ground and transform into in the curved line of the roof. The building is almost energy neutral thanks to an highly insulated shell. Heating and cooling are provided by an all-electric system with a heat pump and a solar water heater. Wood has many advantages as a bio-based and healthy building material. We opted for a laminated timber construction. The timber-frame facades, the siding and the window frames are also made in wood. The curved shape of the roof is the main theme of the interior. The wooden trusses remain visible in the entire project.