DESIGN: Parameters

Interior and Exterior Shading

Project or co-planar shading are important variables affecting energy performance in a building. Exterior and/or interior shading will have impacts on the building's heating, cooling, and lighting, as well as relating it to the natural environment in terms of access to daylight, ventilation and views.

Sun control is fundamental for preventing overheating and diffusing bright sunlight. Sun control solutions should offer shading of direct sun and reduce glare from sky brightness. More advanced approaches improve the daylight illuminance and increase the illuminance deeper into the space.

Fixed Exterior Shading Devices
The sun's seasonal altitude and orientation impact shading device design. Horizontal shading or light-control elements perform best on south facades, due to the high sun angles at those orientations. Vertical elements, in contrast, perform better on east or west facades—overhangs on the east and west are not effective in blocking the very low rising and setting sun. Overhangs on the east and west do provide shade, however, when the sun is higher in the sky. The classic shading solution for east and west orientations is vertical fins, however, egg crate, brise soleil, or other architectural expression can be even more effective in blocking the low sun that impacts these facades.

Shades and Blinds
While passive controls such as overhangs are fixed, other controls allow for adjustment or change. Blinds, drapes, and awnings can allow the user to more readily customize light levels. The effectiveness of sun-control elements is increased when they are adjustable, to better account for the inherent daily and seasonal variability of the sun and sky.

Interior shade options range from the traditional roller shades, venetian blinds, drapes, and blackout screens to blinds located between the panes of an insulated glazing unit. The finish options are similarly diverse. Various shading materials and finishes, when matched to a glazing’s visible light transmittance, can combine to control excess brightness and glare while maintaining a view to the outside.

Exterior shade options also range blinds, screens, roller shades, and awnings. Similar to the interior devices, exterior shades have diverse, operability, finish and material options.

Advanced Light Control Systems
Advanced technologies such as automated shading or light redirection have become integrated solutions for controlling light and solar heat gain. When used in combination with daylighting controls, these systems can substantially reduce the electricity loads as well as address the human comfort issues such as comfort and glare. Daylight typically penetrates a room by 1.5–2 times the window height. Advanced light control systems, such as light shelves and prismatic glazing, capture and redirect light even deeper into the space.

Curved exterior light shelves on the Hoffmann-La Roche Ltd. Office Building in Nutley, NJ, with prismatic transom windows above the shelves. Photo: Philippe Dordai

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