Along with my co-author, the architect, Michael Pellegrino, I wrote this piece on the green-energy practice called daylighting for the SAGE publication on Green Energy. The publication itself is crazy expensive and neither I nor Michael get any compensation if you purchase it, but please follow the link in the picture if you’re interested.
by Ron Keith and Michael Pellegrino
Daylighting is the practice of using natural daylight to illuminate the interior of buildings, reducing the need for artificial light and, as a result, increasing the energy efficiency of those buildings. Though, primarily thought of as a source of illumination, daylighting can also serve as an adjunct to heating and cooling systems, further reducing a building’s artificial energy requirements.
Often a necessary element of pre-modern building design, and an aesthetic element in the late nineteenth and twentieth century, daylighting as implemented in contemporary architecture is used as an innovative solution to energy efficiency and sustainability problems.
The use of daylight as a primary or complimentary means of illumination for the interior of buildings is, of course, not a modern phenomenon. Pre-modern architecture often used natural light for illumination. This usage was not always driven strictly by necessity, as might be thought, but also could be both functionally and aesthetically innovative.
The Pantheon in Rome, dating from the second century, is an innovative design, incorporating what might be the world’s most famous skylight. A simple, yet elegant, design, the only source of interior illumination is the daylight which shines in through the oculus, essentially a simple hole in Pantheon’s dome.
Paris’ Sainte Chappelle, built around 1240, makes extensive use of daylight as an aesthetic element of its Gothic design. Natural light is used throughout the chapel, most strikingly in the upper chapel, where stained glass windows surrounding the entire upper chapel, diffuse and color sunlight passing through to the interior.
The use of daylight as an architectural design element became more prominent beginning in the nineteenth century with the widespread availability of steel and glass. Building designs, once more restricted due to structural limitations of traditional building materials and cost factors, started making greater use of daylight, as the use of glass became more commonplace.
In 1851, Sir Joseph Paxton’s Crystal Palace ushered in this new era of architectural design. The Crystal Palace, essentially an enormous greenhouse, was originally designed to house Great Britain’s Great Exhibition. According to Hermione Hobhouse, in her book on the Crystal Palace and the Great Exhibition, it was constructed from iron, wood and 896,000 square feet of glass.
Since Paxton’s Crystal Palace, the modern era of architectural design has been replete with examples of structures incorporating natural illumination in their design. Some notable examples include:
- Bibliotheque Nationale de France, Paris, France, Henri Labrouste, 1868
- Pennsylvania Station, New York City, New York, McKim, Meade and White, 1910
- Bauhaus, Dessau, Germany, Walter Gropius, 1925
- The Glass House, New Caanan, Connecticut, Philip Johnson, 1949
- Crown Hall, Chicago, Illinois, Ludwig Mies van der Rohe, 1956
- The East Building, National Gallery of Art, Washington, DC, I. M. Pei, 1978
While the use of daylight as an illumination source was a design element in all of these buildings, it is likely the architects of these buildings incorporated the use of daylight principally as an aesthetic element. Energy efficiency and environmental sustainability were perhaps secondary benefits, but were probably not principal concerns for the architects, as these issues were not principal concerns for society as a whole.
Today, concerns about global warming, pollution and environmental sustainability have fostered “greener” building designs, which strive to be more environmentally friendly. The American Institute of Architects (AIA) now promotes architectural designs which are energy efficient, environmentally sustainable and as carbon neutral as possible. As society’s environmental awareness has increased, the design and construction of greener buildings has also increased. Contemporary architectural design, now, frequently incorporates design elements focusing on greater energy efficient and environmental sustainability, and the use of daylight is more than an aesthetic element.
Daylighting is one of the principle tools used in green building design. The use of daylighting in a building’s design has many benefits:
- Daylighting increases energy efficiency by reducing the need for artificial sources of illumination.
- Daylighting can also reduce the need for artificial heat, though this might be offset by the need for greater use of artificial cooling in warmer months.
- Since daylight is available during common working hours, the period of highest electricity demand, it’s use reduces strain on the electricity grid. Reduced demand during peak hours, means a reduced need for building more power plants, principal sources of greenhouse gases and other pollutants.
- Daylighting reduces the life-cycle cost of a building by reducing the usage of lights, fixtures, and other related items, thus extending the usable life of those products and reducing the maintenance and replacement costs.
- Daylighting reduces overall building operating costs through reduced use of artificial energy consumption.
- Daylight helps improve working and learning conditions. Studies have indicated greater use of daylighting techniques in workplaces has improved worker productivity and satisfaction, and its use in schools has led to improvement in student scores.
Daylighting solutions can be as simple as the installation of skylights or windows, allowing more light into a building, but contemporary green building design often employs a wider array of daylighting strategies. These include:
- Site orientation – A building must be properly oriented to efficiently employ available daylight.
- Climate studies – It is important to understand the availability and direction of daylight for the region where a building is constructed.
- Toplighting – Efficient use of toplighting allows daylight into interior spaces and provides indirect natural illumination throughout the building.
- Exterior and interior shading devices – Help reduce heat gain as well as increase diffusion of light.
- Glazing – Window glazing enhancements, such as films and coatings, optimize the light allowed into a space, absorbing and reflecting back excess light and harmful radiation.
- Interior reflectance – The higher the reflective quality of interior surfaces, the greater the penetration of daylight into the building, however good daylighting techniques employ indirect light so interior reflectance should be employ strategically.
- Lighting integration – Lighting can be integrated with daylighting to raise and lower artificial light as necessary without human intervention, preserving function illumination levels.
- Heating, ventilation and cooling (HVAC) integration – Daylighting can be used to offset heating and cooling costs. Smart HVAC systems integrated into new construction complement the use of daylighting in building design.
Daylighting by definition is as simple as employing windows and skylights in a building, but daylighting used efficiently in contemporary green building design requires innovative construction techniques complemented with integrated artificial lighting and HVAC systems to realize its greatest energy efficiency gains.
See Also: Alternative Energy; Energy Conservation; Green Energy Certification Schemes; LEED Standards; Sustainability
Hobson, Hermione. The Crystal Palace and the Great Exhibition of 1851: Art, science and productive history. A History of the Royal Commission for the Exhibition of 1851., New York, NY, Continuum Press, 2004
ArchitectureWeek, “Great Buildings Collection” Available online at: www.greatbuildings.com (Accessed January, 2009)
American Institute of Architects, “50to50: Sustainability 2030” Available online at: www.aia.org/SiteObjects/files/50to50_20071212.pdf (Accessed January, 2009)
Ander, Gregg D., “Daylighting” The Whole Building Design Guide, 2008 Available online at: www.wbdg.org/resources/daylighting.php (Accessed January, 2009)
Romm, Joseph J. and William D. Browning, “Greening the Building and the Bottom Line” The Rocky Mountain Institute, 1998, Available online at: www.rmi.org/images/other/GDS/D94-27_GBBL.pdf (Accessed January, 2009)
Heschong, Lisa “Daylighting in Schools: Reanalysis Report” California Energy Commission, October, 2003, Available online at: www.newbuildings.org/downloads/FinalAttachments/A-3_Dayltg_Schools_2.2.5.pdf (Accessed January, 2009)
New Buildings Institute, “Lighting” Available online at: www.newbuildings.org/lighting.htm (Accessed January, 2009)