Windows and doors, an important source of daylight in themselves, can be further lit through the inclusion of transom and fanlight windows around them.
What are transoms?
Before artificial light was everywhere, even before there was electricity, transom windows were a popular and effective way of harnessing sunlight and dispersing it throughout the home. Transom windows are typically smaller windows built above other windows or doors, which allow more light in while also maintaining the same level of security.
Transoms are particularly good for brightening up small spaces (such as foyers), and like most forms of daylighting, they help save energy by reducing dependence on artificial light.
What are fanlights?
Sometimes hinged to a transom is a fanlight. While it serves a similar function – to provide additional light through a traditional window or door – a fanlight is semi-circular in shape and can, through the inclusion of bars, be used to 'fan' the light out through a room.
The purpose of a transom window or fanlight is also to let out the hot air that's pooled at the top of the room. This, as well as effective cross-ventilation, can be achieved by placing a small vent closer to the floor on the other side of the room. For the purpose of ventilation, a transom window or fanlight that can be opened is more useful than one that can’t.