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Daylighting

The sun is an extraordinary source of natural light: we only need one hundredth of the amount of direct midday sunlight falling on a desk for us to be able to see very well. Buildings should be designed to use this free resource even where electric lighting is available. As our workspaces and schools become more dependent on computer screens the levels of ambient light can be reduced and too much glare can cause discomfort. Ideally some flexibility is therefore required to control the quality of natural light we admit into our buildings.

Even Distribution

Place windows at regular intervals on both sides of the room to achieve even distribution of daylight. Avoid direct sunlight by adequate shading.

In the absence of electrical light, good quality diffuse daylight is required on working surfaces within a building. In a school this means ensuring that the blackboard, desks and benches where children are working are sufficiently illuminated. Light entering from opposite sides of a room will create a balanced and even distribution of daylight. Windows on the north and south walls are preferred to those on the east and west, as they offer good levels of diffuse lighting throughout the day with minimal direct glare.

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RLS Dormitory  Each bed space in each row of the dormitory rooms is equipped with its own personal glass block window

Daylight Control

Blinds and shutters can control the quality of sunlight and turn glare into diffuse light. Moveable controls allow daylight to be adjusted.

Curtains, blinds or shutters can be used to reduce and diffuse the impact of daylight when it is too bright outside. This is particularly important on east and west facing windows, which suffer from direct solar gain during the early morning and late afternoon. The simplest solution is a louvred or bamboo clad shutter which can be closed to reduce intense sunlight and reopened when more daylight is required. Woven perforated screens can shade direct sunlight while maintaining air movement.

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Lake Bunyonyi Secondary  Windows are fitted with wooden shutters that can be open or closed to control the quantity of light.

Rooflighting

Roof lights admit two to three times as much light as windows but can cause glare and solar gain if designed incorrectly

Roof lighting is very useful in deep plan spaces, while work surfaces may be a long way away from windows. A source of light at. the central ridge of a roof can bring daylight into a otherwise dark space but it should be protected from direct sunlight. 

Diffuse lighting can be achieved by screening clear roof sheets with a perforated material material or creating a light shelf on the underside of the roof light. Placing a roof light nearby to the backboard wall will ensure that it is kept well illuminated.

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COF Primaries  Polycarbonate is placed on top of perforated metal sheeting to allow light to enter while avoiding excessive glare.

Reflectivity

The quality of natural lighting in a space is highly dependent on the reflectivity of walls, floors and surfaces within the space.

Bright sources of daylight from outside can be transmitted around a space internally by using light coloured walls, floor finishes and working surfaces. This is particularly true of window reveals where highly reflective and light coloured surfaces will amplify the impact of daylight. Conversely dark window reveals can highlight the contrast between light and dark and increase the sense of glare. Light shelves provide shading from direct sunlight, but transmit this back into the room as diffuse lighting.

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Ruhehe Primary Vibrantly decorated light shelves are hung below the ceiling to bounce diffuse light around the classroom.

Artificial Lighting

Where spaces are used outside of daylight hours, it will be necessary to provide energy efficient artificial lighting.

Artificially-lit spaces need to be designed for maximum efficiency to minimise operational running costs. Directing artificial light towards reflective surfaces will ensure efficient and uniform distribution. A room with a light reflective ceiling, for instance, will benefit from up-lighting, whereas in a room with a dark ceiling, luminaries should be focussed on lighting working surfaces. LED bulbs are twice as efficient as fluorescent fittings and ten times as efficient as tungsten light bulbs.

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NTC Kaliro Classrooms have light coloured walls to optimise daylighing and artificial lighting when in use.