I N S I G H T :
H igh - P e r f o r man c e
Facade Solutions b y L E A H B . G A RR I S
Adapted from the April 2006 edition of Buildings, published by Stamats Business Media. According to the Lawrence Berkeley National Laborator y in Berkeley, Calif., high-performance commercial building facades are comprehensive systems that incorporate daylighting, solar heat-gain control, ventilation, and space conditioning. Examples include: Solar-Control Facades
Spectrally selective solar control is window glass that permits some portions of the solar spectrum to enter for daylight purposes while blocking others associated with solar heat. Low-E coatings control solar heat gains in summer, prevent loss of interior heat in winter, and reduce electriclighting use. Solar filters, such as overhangs, fins, light shelves, or secondary exterior skins made of filter material, indiscriminately absorb or reflect a portion of both direct and diffuse solar radiation and are applied to exterior walls to reduce solar radiation levels and diffuse daylight. Exterior solar control helps to stop direct sun from entering the building and can be provided by overhang, fin, or full window-screen geometries. Examples include louvers and blinds. Daylighting Facades
Sunlight-redirection systems rely on reflection, refraction, diffraction, or non-imaging optics to modify the distribution of incoming daylight. Benefits include not only the potential to offset lighting requirements, but to improve lighting quality and visual comfort. Light shelves, one example of a sunlight-redirection system, are horizontal, exterior projections that use a highreflectance, diffuse, or semi-specular upper surface to reflect sunlight to a certain interior depth from the window wall. Skylight redirection systems, designed for diffuse skylight, are intended to increase overall interior daylight levels with less emphasis on the depth of light redirection. Double-Skin Facades and Natural Ventilation
Heat extraction double-skin facades systems consist of a single exterior layer of heat-strengthened or laminated safety glass, with exterior air inlet and outlet openings. A second layer, the interior
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facade, consists of fixed or operable, double- or single-pane casement windows. In between these two facades are retractable or fixed blinds, or roller shades. During cooling conditions, the blinds/shades cover the full height of the facade and are tilted to block direct sun. The heat absorbed is released within the intermediate space and drawn off through the exterior skin by natural or mechanical ventilative means. Nighttime ventilation can be used to cool a building, reducing air-conditioning loads. Heat
gains generated during the day are absorbed by furnishings, walls, floors, and other surfaces and released over time. With nighttime ventilation systems, the building is often shaped to minimize air-flow obstructions. Mixed-mode ventilation is a space-conditioning approach that combines natural (passive) ventilation with mechanical (active) ventilation and cooling. to draw in fresh air at a low level and exhaust air at a high level.)
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Published on Oct 18, 2011
Texas Architect is the official publication of the Texas Society of Architects, each edition features recently completed projects and other...