Single-Source and Performance

Single-source fabrication—not to be confused with sole-source specifications—can provide improved control of many variables that contribute to aesthetics, building durability, occupant comfort, and operational costs. The impact of recent trends in building design imply stricter requirements for glazing and IGU performance in such areas as:

▶ Energy control. Such advances as low-emissivity (low-E) coatings, graduated patterns, and triple insulating units have served more rigorous energy codes and green building goals.

▶ Larger enclosure units. Increased size capabilities have followed the trend among many architects to specify larger glazed openings to increase daylighting and views or mainly for a “glass box” aesthetic effect.

▶ Ceramic frit and low-E coatings. To meet a particular design vision without sacrificing performance, glass treatments can now combine low-E coatings with ceramic frit or ink options as well as silk-screening and digital printing.

▶ Sustainability and codes. In addition to LEED and other certifications such as Living Building Challenge, energy codes have stricter requirements for enclosure U-value, for example, complicating the design challenge.

There are other considerations, of course. For example, building design criteria begin with basic aesthetics—punched openings, for example, or ribbon windows or curtain wall. Then architect and client consider what the glass itself should look like: transparent (neutral), opaque, colored, or a combination of those? These choices may work together by coordinating a palette of glass colors for transparent and spandrel sections, as well as silk-screen patterns such as lines or dots and perhaps even the colorful graphics achievable through digital printing.

Then there are basic envelope performance requirements (see “Four Key Metrics” on the previous page). These include solar heat gain coefficient (SHGC), visible light transmittance (VLT), U-values, and sound transmission class (STC), as well as the light-to-solar-gain ratio, abbreviated as LSG, which is the ratio between the SHGC and VLT. These are among the factors that affect occupant comfort, too—heat and cold near the building perimeter, for example, and the potential for glare from direct or reflected sunlight. In general, however, glass is appreciated for bringing in the outdoors, so to speak, as well as sunlight and views.

Photo © Hoachlander Davis Photography, courtesy of Viracon

United States Coast Guard
Location: Headquarters (USCG), Washington, D.C.
Architect: Perkins+Will; WDG Architecture