Case Studies: Seattle Justice Center

NBBJ

Architects must be mindful of multiple concerns in designing building facades. There are always trade-offs that must be made in optimizing building facade performance and the challenge lies in balancing conflicting criteria. A desire to maximize transparency, daylight, and views, for instance, can often be at odds with the need to minimize solar heat gain and reduce air-conditioning loads. Orientation is also an important factor. Site constraints or features, such as surrounding buildings or vistas, often dictate easterly or westerly facades, which are difficult to shade from low-angle morning or afternoon sun.

For the design of the Seattle Justice Center, NBBJ had a public client with high expectations. The project brief emphasized daylight penetration, views, and outdoor connections, but they were not to be achieved at the expense of increased air-conditioning or energy expenditure. The project goals were to create a work environment that provided high occupant satisfaction, set an appropriate, open image for the City of Seattle, and address sustainable building design principles.

Existing research illustrates that vented, double skin facades are an appropriate approach to maximizing the positive qualities of glazing while minimizing its negative energy impact and it potential for thermal discomfort, especially on easterly or westerly glazed facades. Simply put, a shading device within the double skin can absorb solar gain and re-radiate it as heat trapped in the cavity. Apertures at the wall's top and bottom induce air movement. The heat's natural tendency to rise pulls fresh, cool air in at the bottom while exhausting hot air out the top. Controlling the capture or venting of this trapped heat dictates cavity air temperature and, in turn, the inner glass surface temperature.