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