Guest Blog: Five Tips for Specifying High Performance Glazing

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Date: June 8, 2015

By Alan KinderGuardian Industries Corp.

Guardian Science & Technology Center SNX 51 23 Spandrel HT Photo by Ara Howrani

As architects consider specifying and designing with glass for building facades, the possibilities are vast. Manufacturers offer products in a greater variety of colors, textures and performance options than ever before for interesting and beautiful design. Architects can specify high-performance glass, delivered through greater light transmission, improved U-factor, or desired levels of solar heat gain, or a combination of all of these. Creating a clear plan to the right glass can be streamlined by following these critical steps:

1. Identify design intent

What is the desired exterior appearance? Consider the following:

  • Color: Color and appearance can be achieved through coatings on glass or tinted glass, or both. Color can also impact the desired transparency and reflectivity.
  • Transparency and reflectivity: Light transmission options are available from 30 percent or below to above 60 percent. Reflectivity levels can vary from low reflectivity (more transparent) to medium or highly reflective.
  • Building shape and orientation: Determine how direct and indirect daylight will impact energy use and occupant experience. Rooms on the building perimeter require daylighting and glare control.

2. Consider the coatings

  • Low-E (low-emissivity) glass reduces heat gain or loss by reflecting infrared energy (heat), while letting in larger amounts of visible light. The coating lowers the U-value and, if desired, the solar heat gain; and in doing so, it improves the energy efficiency of the glass. Because of this and its relative neutral appearance, low-E glass continues to grow in popularity in commercial and residential projects.
  • By blocking solar heat and making maximum use of daylight, spectrally selective glass – defined by the U.S. Department of Energy as glass with a light-to-solar gain of 1.25 or better – can significantly improve building energy consumption and peak demand related to heating, cooling and electric lighting load, allowing downsizing of HVAC equipment. This will reduce initial capital investment and energy costs going forward.

3. Examine performance

While new coatings do an excellent job of letting in light and lowering solar heat gain, energy codes and LEED requirements may dictate even greater solar control. Fortunately, there are many options, including medium light transmitting coatings (40-50 percent) and silk screened glass with or without coatings.

The higher the transparency, the easier it is to see in, and the more light penetration. Daylighting is proven to improve mood, however, higher light transmission could result in glare or high solar heat gain, depending upon the product specified. A solution may be a glazing with higher reflectivity or use of a tinted float glass with a coating that still permits daylighting, but not as much direct light penetration. Also, consider the reflectivity from the inside looking out. Different glass options may be more reflective on the inside, making it harder to see out. Mockups or samples will demonstrate this effect and help architects understand that light transmission in the 30-50 percent range still permits a great deal of light into a structure.

4. Take advantage of glazing technologies

  • When considering the light-to-solar-gain ratio, or, how efficiently the glazing is letting in light but blocking solar heat gain, triple silver (three layers of silver sandwiched within other metal layers) offers best-in-class performance.
  • Performance can also be improved even more with the addition of a fourth surface coating, providing an enhanced thermal barrier. These coatings are very durable and are designed to be exposed to the interior of the building.
  • If safety is an important consideration, laminated glass, a combination of two or more glass sheets with one or more interlayers of plastic (PVB or ionoplast), minimizes the risk of injury. In case of breakage, the glass will tend to remain in its frame, reducing injury from sharp edges and flying or falling pieces of glass. Laminated glass also blocks UV light, can provide excellent solar control and reduces sound transmission.

5. Look at all the angles

Architects must look carefully at the samples to gain the best perspective on what the glass will look like when installed.

  • Glass in outdoor or natural lighting, preferably in slightly overcast conditions, shows the most accurate rendering of transmitted and reflected color. Consider angle of observation, interior lighting and potential effects of glare.
  • View glass outside during various times of the day, and under varying lighting conditions, e.g., cloudy versus sunny. This will provide a truer indication of how varying light conditions impact design intent.
  • When evaluating samples indoors, use a black background to observe the glass reflection, which is the best indication of what it will look like from the outside.
  •  Utilize new online digital tools that help provide a more comprehensive review. For example, the Glass Visualizer from Guardian Industries Corp. guides you through the process of selecting the glass substrate, coating, building type and then allows you to view the products under varying light conditions.

6. Do it digitally

A glass visualizer is just the tip of the iceberg when we talk of how architects can now Build With Light® online. Guardian Industries has developed easy-to-use, advanced software for glass and glazing system analysis. Guardian Glass Analytics offers a comprehensive suite of engineering and analytical reports that demonstrate the advantages of high performance glass in building facades:

  • Customize product options using the Performance Calculator
  • Visualize under varied lighting conditions using the Glass Visualizer
  • Analyze building performance using the Building Energy Calculator
  • Design using Guardian’s BIM Generator

Specifying high performance glass is increasingly complex with energy, daylighting and LEED requirement considerations. I look forward to discussing these and any conditions of building with glass.

Alan Kinder is Guardian Industries’ Architectural Design Manager for North Carolina, South Carolina and Georgia. For more information about high-performance glass and glazing, contact Alan at (704) 572-7280 or, or visit