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Toplighting

Light from above is a classic theme of architecture. Skylights and clerestories have long histories as apertures.
 
Toplighting differs from sidelighting in several significant ways. Exterior views are replaced with views of interior sunlit surfaces, such as Pantheon, Rome. There is less potential of glare compared to sidelighting, especially at low sun angles. Toplighting also provides, more light per unit area of opening than sidelighting.
 
Openings for toplighting can be oriented independently from building orientation and can distribute light deeply into single-story space. This makes toplighting  very efficient. For example, roof openings can provide three times the light level of sidelighting openings of identical size. By locating the openings where they are needed, the best distribution can be achieved without excessive illumination and accompanying negative impact on heating, ventilation, and air conditioning.
 


Shape

The shapes, surface reflectances, and proportions of top lit spaces are critical. Increasing the ceiling height will improve the light distribution so fewer openings will be required.
 
Light is best used in directly. For top lighting, vertical elements such as walls are typically the best light-receiving surfaces. The ease of illuminating walls with toplighting explains why it is often used for illuminating artwork. In some cases , light from top lighting can be reflected back up to the ceiling as in Kimbell Art Museum.
 
Tilt and Bearing
 
Tilt
 
Set the glazing tilt to match the seasonal lighting needs. Associated heat gain can be regulated with exterior shading. Horizontal skylights receive the maximum amount of light and heat when the sun angles are high, and minimum amount of when sun angles are low. The sky will be seen with the most of them, therefore they are best for overcast sky conditions. 
 


Bearing
 
Adjust the bearing orientation of clerestories for optimum quantity and quality of light. Vertical clerestories act as windows because they are highly depend on bearing orientation. East- facing clerestories collect morning light; west facing collect afternoon light. South facing clerestories collect more light from low sun angles than high sun angles. This light is in warm color, intense and variable. North facing clerestories require minimal shading because the collect more skylight than sunlight. This light is in cool color and varies little.

Response to Natural Light
 
 


Skylights are best for overcast sky conditions. Vertical clerestories favor low sun angles and work best for sunlight and reflected light.
 


Large translucent skylights can simulate gloomy overcast skies, regardless of weather conditions, using several small areas of carefully located clear glazing can improve the distribution of light.




Using high ceilings can also improve distribution of light.




Using slope ceiling up to opening can improve distribution and reduce contrast.




 






Locating openings to direct light against walls or other light-redirecting surfaces such as light wells helps controlling glare by keeping direct light off the work surfaces.




Follow us on our next article “ Sun Catchers&Atria ”.

Sources;
Architectural Lighting by M. David Egan and Victor W. Olgyay

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Planlux Lighting Design

A virtual lighting design identity who celebrates 10th age