Project Statement Waterfowl Pavilion of Beijing Zoo is a net-zero energy building locating on the Waterfowl Island which owns extremely high ecosystem and landscape biodiversity and serves as a multi-functional building for bird breeding, exhibition and science advocacy. It's both a practical case of public architectural design and construction, and an experimental platform for sustainable design strategies based on the Cold Zone in north China. Facing the particularities both on site and function, a sustainable design target was set up at the initial stage of project: to create a demonstration net-zero energy building under the limit construction budget. The design process of Waterfowl Pavilion involves three phases: planning layout, architectural design and detail design, emphasizing being 'invisible' in the natural environment. Invisibility is not solely reflected in visual level, but also the minimization of interferences toward ecological system and wild environment of Waterfowl Island. Vanishing in the nature The Waterfowl Island owns superior natural environment which vegetation coverage reaches more than 90% with luxuriant arbors and shrubs. In order to 'plant' a building inside the site, its form should adjust to communicate with the natural environment leading to the visual invisibility. According to the functional demands, the pavilion is separated into two parts, the bird house in the south and the surrounding human zone. The two higher inverted funnel-shaped wind towers of bird house and the lower zigzag exterior walls of human zone imply the forest and grass mixture, arbors and shrubs alternate on the island. The zigzag walls use renewable coarse-grained wooden panels while the exterior gallery wall is knitted by dry vulgar reeds, which make the pavilion more corresponded to the environment in color and texture. The arbors surrounding the building are accurately positioned before construction and protected carefully, which can shade the pavilion and make it invisible. Minimizing of environmental interference. Waterfowl Island is an independent and intact micro-ecosystem which requires the idiosyncratic architecture to minimize the interferences toward environment. That is the deeper meaning of 'Invisibility'. When choosing the site, architect leaves the large area poetic wetland on the south side alone, but chooses a small void place in the north avoiding the old black poplars and pines. This decision can not only shorten the path and shrink the work-yard which help to reduce the carbon footprint, but also avoid creating too much artificial shadow area on the island. An integrated wetland system including collecting, guiding, cleaning and draining is employed through a minimally invasive reform of the site section, which creates an excellent habitat for the waterfowl and the vegetation. The absorption of aquatic plants such as reed and the fixation and infiltration processed in the soil help to remove the N and P. The green can also absorb the carbon dioxide and release the oxygen while their evaporation can help to balance the temperature and humidity. Invisibility also requires carbon balance. The pavilion employs steel structure and renewable materials to reduce the carbon emission during manufacture and construction. By combining passive design methods (natural ventilation, lighting, sun-shading and high-performance building envelop) and active technologies (ground source heat pump, radiation air-conditioning, heat recovery system) together, the carbon emission during operation is remarkably cut. After carbon calculation, Waterfowl Pavilion will release 745 ton carbon dioxide in material manufacturing, construction, operation and disassembly during its 50-years lifecycle, while reduce 2756 ton carbon dioxide through using renewable energy and landscape compensatory. The latter is much more than the former which mean Waterfowl Pavilion reaches the goal of real invisibility, net-zero energy and net-zero carbon.