Building envelopes are the separating and filtering layers between outside and inside, between nature and adapted spaces occupied by people. In historic terms, the primary reason for creating this effective barrier between interior and exterior was the desire for protection against a hostile outside world and adverse weather conditions. Various other requirements and aspects have been added to these protective functions: light transmission, an adequate air change rate, a visual relationship with the surroundings, aesthetic and meaningful appearance etc. Accurate knowledge of all these targets is crucial to the success of the design as they have a direct influence on the construction. They determine the amount of energy and materials required for construction and operation in the long term. In this context, transparent and translucent materials play an important role for the building envelope as they not only allow light to pass through but also energy. Besides glass, a variety of other translucent materials have attracted architects from the very beginning: plastics, perforated metal plate and meshing but most of all membrane materials which can also withstand structural loads. Earlier applications of membrane materials have served the purpose to keep off sun, wind, rain and snow while offering the advantage of enormous span widths and a great variety of shapes. The development of high performance membrane materials on the basis of PTFE (poly-tetra-fluoro-ethylene), e.g. PTFE coated glass fabrics, and transparent ETFE-foils (also a fluoropolymer) were milestones in the search for appropriate materials for the building envelope. As early as 1976, first solar balloons and solar warm water collectors could be manufactured from ETFE-foils thanks to new bonding and application technologies. In more recent times, rapid developments in material production varieties (e.g. laminates) and surface refinement of membrane materials (e.g. coatings), along with advanced CFD and other computer simulation methods, have been a constant stimulus for innovation. As a result, modern membrane technology is a key factor for intelligent, flexible building shells, complementing and enriching the range of traditional building materials. The Membrane Projects presented below are examples for a forward-thinking and resource friendly technology which is able to merge different aspects, from high quality design, to function and comfort.