The document discusses various aspects of building facades and envelopes. It defines facades and envelopes, explaining that facades are the exterior walls of a building and envelopes refer to the exterior parts that separate the indoor and outdoor environment. It describes the key functions of envelopes in providing weather barriers and light transmittance. Various materials that can be used for facades and envelopes like concrete, glass, metal and polymers are discussed. Different types of facade systems like curtain walls, double skin facades and cladding are also summarized. The document provides a comparative analysis of conventional and new facade materials.