Window Design – Details

Setting Priorities with Daylight

Window design caters to supply daylight and provide views of its surrounds.
It is an air quality ventilator with mass cooling, and a climate moderator, insulator, noise barrier or glare protector.
Windows also have an important impact on the energy efficiency of a building.
The designer will not always be able to reconcile the conflicting demands of these roles.
Prioritization is important to address such issues.

The primary purpose of window design is to provide light to enable a building to function.
This demands high levels of light as in a workspace.
However, the level or intensity of light is less important than its quality.
Light allows a building to function and also the role of creating a pleasant visual environment.
Windows thus create a feeling of well-being which in itself stimulates individual performance.


Throughout history, daylight has been a crucial factor in the design of buildings.
An ideal definition of a well daylit room is difficult to determine due to many variables.
However, a quote from Louis Kahn (20th century architect), indicates its importance:
‘I can’t define a space really as a space, unless I have natural light.
Natural light provides atmosphere with its essences in the daytime and the season as it enters and modifies the space’.

Daylight is critical in some building types such as design studios where the ability to judge colour accurately is important.
Daylight is the colour reference as all other forms of light change the perceived colour within a spectrum.
The assumption that daylight gives true colours persists, but skylight varies daily and sunlight expands it further.
Special lamps, rather than daylight suits colour matching tasks.

Sunlight

It is important to recognize the benefits of sunlight.
Sunlight increases the overall level of light and helps to provide a constant variation in the
intensity, pattern and colour of light.
There is little doubt that entering a sunlit space is a pleasing experience and the interior of
the great cathedrals, where the rays of the sun create shafts of light, is unforgettable.
Sunlight should be encouraged at home for some part of the day and cases exist where this is not so.

Where access to direct sunlight is not possible, the impression of sunlight may be derived from an exterior view: sunlight on buildings at a distance, sunlit trees or a sunlit landscape.
Humans have a strong desire to be able to perceive sunlight when it is known to be available, and occupants of a building are disappointed when this is denied.

With sunlight, however, come other consequences.
Sunlight is an energy source, heating buildings.
This assists with poor performance energy buildings and where internal heat gains are low in winter.
In well insulated building, internal gains are high, and in spring, summer and autumn, the heat gain can be a nuisance unless carefully controlled.
Control of sunlight glare is important.

Latitude also affects the ease of solar control.
In Mediterranean regions, sun paths are higher in the sky, making sunlight easier to control.
In Nordic countries, sun paths are lower and sunlight is more difficult to control.
With most daylit buildings, the control of incoming sunlight is critical at the strategic planning stage.
The only exceptions are buildings such as greenhouses where sunlight is always welcome.