Daylighting in architectural design is the controlled use of natural lighting in a working or living environment in order to reduce or eliminate the need for electric lighting. Historically, before the electric light was invented, designing buildings so that daylight could enter interior spaces was a necessity yet, despite a long history of using daylighting as a design strategy, building owners, architects, engineers and lighting designers are only just learning how to use it effectively and new glazing technology is opening up a wealth of opportunities in these areas.
The art and science of good daylighting design today is not so much how to provide enough daylight to an occupied space, but how to do so without any undesirable side effects. It is a careful balance between heat gain and loss, glare control and the variations in daylight availability. The increased use of glass in building design combined with innovative technological advances in glass and glazing could reduce the cost of energy whilst reducing carbon emissions and our individual carbon footprint.
Why the renewed interest in daylighting?
1. The high cost of fossil fuels
2. The realisation that sources of electricity have a finite life
A good daylighting design can save up to 75% of the energy used for electric lighting in a building. Additionally, electric lights also generate significant heat in a building and, in summer, savings can be made in the energy used to cool a building. The use of solar control and low emissivity glass can help to reduce capital outlay, running costs and the associated carbon emissions of a building. Solar control glass is used to minimise solar heat gain by rejecting solar radiation and help to control glare. Low emissivity glass can reduce heat loss while allowing high levels of free solar gain to heat buildings with no significant loss in natural light.
3. Human factors – daylight contributes to a feeling of well-being
We have a natural human desire for change which is brought about by the seasons, the weather and the time of day. The direction of natural light provides shadow patterns which give objects and surfaces the appearance that we associate with the natural world. Sunlight has a therapeutic effect and lifts our spirits as does a view from a window. Natural colour may vary throughout the day but it is the standard by which colour is judged. Have you ever worked in an office with no natural lighting – what affect did it have on your productivity and your enjoyment of your working activity? Do shopping centres devoid of natural lighting make you feel disorientated and confused about the passage of time?
The Code for Sustainable Homes awards points for good daylighting design under category 7, Health and Well-Being. As a national standard for use in design and construction, The Code for Sustainable Homes is an environmental assessment method for rating and certifying the performance of new homes and through this standard aims to encourage continuous improvement. There are three points available, one awarded for an average daylight factor of a least 2% for kitchens, one for an average daylight factor of a least 1.5% in living rooms, dining rooms and studies and the final point is awarded if at least 80% of the working plane in these rooms receives natural light. For further information go to http://www.planningportal.gov.uk/uploads/code_for_sustainable_homes_techguide.pdf
Whilst windows and doors are the most obvious method used for daylighting, other devices such as skylights, rooflights, clerestories and light tubes can provide light which penetrates deep within the building.