Skylight

Skylights are light transmitting (elements filling building envelope openings) forming all, or a portion of, the roof of a building's space for daylighting purposes.

Open skylights were used in Ancient Roman architecture, such as the oculus of the Pantheon. Glazed 'closed' skylights have been in use since the Industrial Revolution made advances in glass production manufacturing. Mass production units since the mid-20th century have brought skylights to many uses and contexts. Energy conservation has brought new motivation, design innovation, transmission options, and efficiency rating systems for skylights

Skylighting types include roof windows, unit skylights, tubular daylighting devices (TDDs), sloped glazing, and custom skylights. Uses include:

A fixed skylight consists of a structural perimeter frame supporting glazing infill (the light-transmitting portion, which is made primarily of glass or plastic). A fixed skylight is non-operable, meaning there is no ventilation.

An operable (venting) unit skylight uses a hinged sash attached to and supported by the frame. When within reach of the occupants, this type is also called a roof window.

A large (20' x 20') steel and glass retractable skylight, seen from the roof. Note the steel tracks that the skylight rolls on, to retract.

The same retractable skylight, seen from the interior. This is a bi-parting skylight, meaning that it parts in the middle to open.

This ridge skylight wraps over the highest point of the roof - the ridgeline.

This is that same skylight, from the inside. Steel allows large spans, without a grid of supporting tubes and cables.

A retractable skylight rolls - on a set of tracks - off the frame, so that the interior of the facility is entirely open to the outdoors, i.e., not impeded by a hinged skylight. The terms retractable skylight and retractable roof are often used interchangeably, though skylight implies a degree of transparency.

TDD skylight on the roof terrace of Liverpool Central Library

Active daylighting uses a tubular daylight device—TDD

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