The building envelope is the physical separator between the interior and the exterior environments of a building. Building envelope design is a specialized area of architecutal and engineering practice that draws from all areas of building science and indoor climate control. The envelope controls the air flow and is important to ensure indoor air quality, conserve energy consumption and avoid condensation (ensuring durability) and providing comfort.

The physical components that make up the envelope include foundation, roof, walls, doors and windows. The dimensions, performance and compatibility of materials, fabrication process and details, their connections and interactions are the main factors that determine the effectiveness and durability of the building enclosure system. This concept is also described as “the house as a system” whereas all parts of the building must be designed in such a way so that they work together in providing a healthy, comfortable and energy efficient space.