The facade is the building’s interface with its environment. It is here that building physics parameters such as heat, humidity, sound and light interact with the building. All these influences need to be controlled by the building envelope in order to ensure the comfort of the user and the functional performance of the architecture. This introduction explains the most important phenomena and then relates them to design and building practice – which materials react in which way to these factors? How do facade systems deal with heat, humidity, sound and light? This practice-oriented book, which is the result of cooperation between an architect and a structural engineer, describes the most important facade materials and constructions under the aspect of their building physics performance.