The building envelope is the single most crucial element of any building. A building envelope includes all components of a building that enclose conditioned space. Building envelopes create a separation between the interior and the exterior environments. The building envelope also serves as the outer shell to protect the indoor environment from outdoor weather conditions. 

A building envelope design must include a solid, well formed structure, a drainage plane, an air barrier and a thermal barrier. If any one of these building envelope components fail, is damaged or is not constructed properly, minor to serious building damage can occur. Should these problems occur, this situation will degrade the structural integrity of the building and may pose serious health risks.