Using Tools to Specify Glass

Glass manufacturers have developed easy-to-use tools using advanced software for glass and glazing system analysis combining performance and visualization to aid in the glass specification process. Users can explore the aesthetic and functional possibilities of building with glass while meeting complex energy, daylighting and LEED requirements.

Various types of “calculators” can be used to determine the best product. Three types of calculators are a performance calculator, a building energy calculator, and a sustainability calculator. A performance calculator provides comprehensive center-of-glass performance metrics and color information on largely open-ended glazing compositions. A building energy calculator offers schematic-level direction on the comparative whole-building energy-efficiency influences of prospective glazing selections. A sustainability calculator facilitates the generation of application-specific reports on prospective LEED and other sustainability credits associated with the use of one manufacturer’s products.

Another option is to use a building information modeling (BIM) content generator, which allows one manufacturer’s products to be integrated into 3-D project models that offer rendering, coordination, analysis, takeoff, and building operation advantages.

A final option is a glass visualizer which provides photorealistic digital renderings of many prospective glazing compositions in a range of project application and sky conditions.

Getting the Right Light Inside

Studies show an increase in performance as well as health and safety of occupants in well-lit buildings. However, there’s a common misperception that attaining the highest visible light is always the right choice. Excessive glare can negatively impact the health, safety and welfare of occupants. Direct sun can cause eyestrain as well as disability glare, which prevents an occupant from being able to see, much less work. Disability glare happens anytime the brightness of the background exceeds the brightness of the task. These factors can affect occupant health by causing eyestrain, fatigue, tension, and headaches.

In addition to affecting occupant health, safety, and welfare, too much visible light can also allow for unnecessary solar heat gain, which can reduce energy efficiency.

It may seem that 50 percent visible light is too dark, when in reality 50 percent visible light allows a lot of bright natural light in the building without being overwhelming or harmful to occupants.

When visible light transmission is lower, it reduces glare and improves occupant comfort. A lower amount of visible light transmission also eliminates, or reduces, the need for blinds. When blinds become closed they tend to stay closed which defeats the purpose of the window, and electric light becomes the substitute, using valuable energy and raising energy costs. Specifying the right glass for a project is key to allowing the right amount of light inside without the need for blinds, curtains, or other shading materials.

Visible light transmission also affects building design and aesthetics. A lower amount of visible light transmission tends to cloak the window treatments and therefore provide a more uniform appearance to the building when viewed from the exterior. A lower amount of visible light transmission also tends to create a better visual color match between spandrel and vision glass and actually increases the potential for daylighting. High visible light transmission creates glare and the need for window treatments, such as curtains or blinds. These window treatments are often closed by occupants and therefore there is no light transmission from the window into the space, which defeats the purpose of the original design.

When specifying glass and coatings for the glass, architects and designers must consider the needs of the occupants as well as the facade and the intentions for the building’s aesthetics. In some cases, the building’s exterior is designed to provide symbolism for what occurs within the building. Modern architecture not only provides the latest technological advancements for lighting and occupant safety and comfort but it can also be a means of expressing great symbolism

In the following case study, the German Bundestag in Bonn was intentionally designed to not only house the government but also make a statement.

Conclusion

When considering glass for a project, architects and designers must understand the benefits of high-performance glass and best practices for specifying glass. The transparency of high-performance glass allows for abundant daylight and views, which can promote the health and well-being of occupants; at the same time, the material can manage solar heat gain for a range of climate zones. With a high-level understanding of glass manufacturing and coating processes, as well as knowledge of the tools available to help with the specification process, architects and designers can achieve their desired aesthetic while providing performance solutions that allow daylighting and views that have been proven to improve the health, safety, and welfare of occupants.

End Notes

¹Schittich, Christian; Staib, Gerald; Balkow, Dieter; Schuler, Matthias; and Sobek, Werner. Glass Construction Manual. Birkhäuser. 1999.

²Foster+Partners. Web. 24 Oct. 2018. www.fosterandpartnerns.com

Resources

List of Approved Software for Calculating the Energy Efficient Home Credit. Office of Energy Efficiency & Renewable Energy. U.S. Department of Energy. Web. 24 Oct. 2018 www.energy.gov/eere/buildings/list-approved-software-calculating-energy-efficient-home-credit

"Green schools are better for budgets." The Center for Green Schools. U.S. Green Building Council. 1 Aug. 2018. Web. 24 Oct. 2018. www.centerforgreenschools.org/green-schools-are-better-budgets