The building envelope is the shell that helps protect the interior of a building from the elements. Key components include the roof, walls, windows, and doors. Optimizing the design of the building envelope dramatically improves energy-efficiency in new and existing buildings by reducing heating and cooling loads. It may also enable the building owner to downsize mechanical equipment.

With a new building project, it is important to incorporate building envelope design criteria during the planning phase. The first steps in improving energy efficiency in an existing building are to analyze existing conditions and develop criteria for improvements.

Thermography, a testing procedure that uses an infrared camera to determine heat loss from an existing building envelope, can be used to analyze existing conditions and identify areas for improvement.