In architecture, a lightwell,[NB 1]sky-well,[NB 2] or air shaft is an unroofed or roofed external space provided within the volume of a large building to allow light and air to reach what would otherwise be a dark or unventilated area. Lightwells may be lined with glazed bricks to increase the reflection of sunlight within the space. Lightwells may have sunlight reflecting mirrors on the top of light well.[1]
Lightwells serve to reduce the necessity for electric lighting, add a central space within the building, and provide an internal open space for windows to give an illusion of having a view outside.
A subterranean lightwell by any frontage of a building for light to a basement is also called an area (or areaway in North American usage). This may also allow pedestrian access to the building separate from a main door.
^[1] Environmental assessment of light well in high-rise apartment building | Hisashi Kotania; ∗, Masaya Narasakia, Ryuji Satob, Toshio Yamanakaa | Department of Architectural Engineering, Graduate School of Engineering, Osaka University, Suita Osaka 565-0871, Japan | Department of Architecture, Osaka Institute of Technology, Osaka, Japan | 17 January 2002| Building and Environment 38 (2003) 283 – 289 | Size of light well (m) 13m × 12m × 62m (height)