Living envelopes, such as biological skins and structures built by animals, are functional and sustainable designs resulting from years of evolution, conditioned by biological and physical pressures from the environment. When building a home, animals demonstrate inspiring strategies to protect themselves from predator threats and external climatic conditions. As for human buildings, temperature, humidity, air quality, light, are some of the various factors they have to manage for optimal conditions. Facing the climate emergency, growing efforts to build durable designs have led designers to search for more efficient or alternative solutions by observing Nature. The emerging field of bioinspiration including animal architecture has already brought few but rare exemplary innovations that were integrated into building designs. Data on animal architecture are scattered among various biological domains, from observation of species habitats by zoologists such as entomologists or ornithologists, to bioindicator studies by climatologists. Data collected by scientists is available in eclectic idioms, a challenge to be fully comprehended by building designers. This chapter presents a characterization of living envelopes aiming at facilitating the transposition of some relevant biological features into innovative and sustainable architectural designs. The approach is architecture and engineer oriented, assessing biological functions and strategies, using criteria that are meaningful to building designers: functional and temporal analyses of spaces and materials, physical factors regulated through envelopes, behaviors, and interactions of species. Applied to a sample of species and animal-built structures, the characterized biological role models put forwards multi-functionality and efficiency through relevant construction techniques, the use of local resources, as well as behavioral adaptation. Examples of applications inspired from the characterized species are described, from theoretical proposals to a very practical application of an adaptive envelope skin inspired by the Morpho butterfly.Read less <