Natural & Efficient Lighting
As well as minimising solar gain, design elements should reduce the need for artificial light – which will result in significant energy savings for commercial buildings in particular.
Minimising solar gain and improving natural lighting might appear to be at cross-purposes. However, solar gain is dominated by direct solar radiation – which occurs when the sun shines directly through a window.
Windows facing away from direct sunlight admit almost as much daylight, but with significantly less solar gain.
Minimising direct solar radiation whilst maximising exposure to diffuse light helps improve energy efficiency.
Large windows protected by horizontal shading on the north side of buildings in Rio de Janeiro would admit light whilst avoiding direct solar radiation.
South facing windows would admit diffuse light for most of the year – though may require shading from the rising and setting sun during summer. These measures would minimise solar gain while maintaining good levels of natural light.
Such windows would also maximise the potential for natural ventilation, since they would take advantage of the prevailing breeze in Rio de Janeiro.
The glass and glazing systems used in a building can affect the amount of light transmitted through windows – some glazing systems can reduce the heat entering the building whilst allowing light to penetrate. This element of design should be carefully evaluated . For a thorough description of how glazing can improve energy efficiency, see the glazing guide produced by the Australian Department of the Environment.
Other measures to improve natural lighting include:
- Light shelves, white painted shelves which reflect low light onto ceilings
- Celestory windows, which allow low light to enter but prevent light entering when the sun is high
- Light tubes, which transmit light from roofs into the building interior
- Central atria, which can be combined with natural ventilation systems and solar chimneys 
- Brightly painted interiors, possibly using luminous/reflective paints
- Efficient light fittings should be specified, with energy saving controls.
More Information and Resources
- Glazing Information from the Australian Dept. of the Environment
- Daylighting Factsheet (PDF) from the Initiative for Renewable Energy in Architecture.
- The Daylighting Collaborative
- Windows and Daylighting resources from the Lawrence Berkeley National Laboratory
- Lighting Research Center of the Rensselaer Polytechnic Institute
- Commonwealth of Australia | Department of the Environment, “Your Home Technical Manual – 4.10 Glazing.” [Online]. Available: http://www.yourhome.gov.au/technical/fs410.html. [Accessed: 17-Nov-2012].
- “Building Envelope Design Guide – Atria Systems | Whole Building Design Guide.” [Online]. Available:http://www.wbdg.org/design/env_atria.php. [Accessed: 23-Oct-2012].