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A previous edition of Explainer described how exterior sunshading devices, or brise soleils, have the ability to greatly reduce the solar heat gain of a building. When this particular architectural element is used in tandem with a double-skin facade, energy performance is optimized. Consisting of two building envelopes, an outer and inner layer, a double-skin facade creates an intermediate space that serves as a ventilating cavity, supported naturally or mechanically. The system acts as a thermal buffer that moderates occupant comfort, promoting air flow through the cavity and reducing energy consumption by providing heat in the winter and shading in the summer.
The concept of the double-skin facade was first explored and employed by Swiss-French architect Le Corbusier, who inserted heating and cooling pipes between large layers of glass, a system he called a mur neutralisant (neutralizing wall). Architects experimented with the system around the world but it never quite penetrated the industry to reach mainstream status. However, a recent drive for energy-efficient and environmentally friendly buildings has sparked a renewed interest in double-skin facades, with high-profile skyscrapers like 30 St Mary Axe and Shanghai Tower adopting the practice.
Compared to a conventional glazing configuration, double-skin facades generally achieve a higher insulative value, regulating the temperature and acoustic properties of a building. The solar heat gain captured within the cavity can be circulated throughout the occupied space to offset heating requirements in cooler climates, while the cavity can be vented out to reduce heat buildup in warmer climates. But the efficiency and performance of the system is highly dependent on consistent maintenance.
The former Occidental Chemical Center in Niagara Falls, New York, essentially a nine-storey glass cube, implemented the first double-skin facade in North America. An independent energy analysis predicted that the structure would use only two percent of a conventional building's energy for winter heating and 19 percent annually for cooling. But grossly inadequate maintenance meant that the mechanized louvers would stop functioning, and air-intake grilles were covered to prevent the cavity from accumulating dirt and particulates from a nearby excavation site. The system was effectively rendered useless and now serves as a cautionary tale for owners who habitually ignore and defer building upkeep.
Critics contend that similar insulative values can be attained by using conventional high-performance, low-e windows, instead of having to sacrifice usable floor space for the cavity. The material and design costs of enacting the system can also be prohibitive; as a result, double-skin facades continue to be found almost exclusively on high-profile and big-budget projects.
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