Vitro Certified® Newsletter

When specifying glass in buildings, sometimes architects and owners seek high levels of transparency and visibility. Other times, a building design calls for low transparency, or reflectivity, to provide privacy, reflect the building’s surrounding environment and/or hide messy mechanicals.

Solarban Champane™ Glass at Vitro Architectural Glass, Glass Technology Center 

For example, a library, retail setting or university research lab seeking visibility to showcase the activities or merchandise inside is likely to choose more transparent glass. Whereas multi-family buildings or government and corporate spaces, where more  privacy is required, might opt for less visibility and more reflectivity.

The Type of Light Matters

To understand glass reflectivity, you first need to understand the solar energy spectrum and how visible light interacts with glass and coatings. Energy, heat and light constantly flow away from the sun into Earth’s atmosphere in the form of short-wave energy, including:

• Ultraviolet Light (UV) which represents 3% of the solar energy spectrum
• Visible Light which makes up 44% of the solar energy spectrum
• Infrared Light accounts for 53% of the solar energy spectrum

Energy efficient glazings, such as low-e glass, block a portion of the UV and infrared light while allowing a high percentage of visible light to come through. The result is less need for artificial lighting, increased comfort for building occupants and an overall reduction in energy usage.  

Understanding Exterior Reflectivity

Glass reflectivity refers to the measure of how much visible light bounces off the glass surface. The reflectance value indicates how the glass will interact with natural and artificial lighting and influences factors such as visibility and privacy.

In addition to providing privacy, glass reflectivity helps to control glare and impacts visible light transmittance (VLT) and solar heat gain coefficient (SHGC). As the glass’ reflective properties increase, light levels decrease and thermal performance increases as less solar heat comes into the building.

The higher the reflectance value, the more the glass will mirror its surroundings – especially during the day or when lighting conditions outside are brighter than those inside. The lower the percentage, the more transparent the glass will appear. 

As mentioned above, high exterior reflectivity is desirable for buildings that require high levels of privacy. Mid-reflective glass is ideal when there are no major privacy concerns, and a façade with a slightly less reflective appearance is desired.  

Mid-reflective glass provides some coverage of the building’s HVAC systems, presents a more harmonious façade appearance and blends well with spandrel glass, metal panels and extrusions. This glass category also helps control glare, thereby reducing the level of interior and exterior shading systems required.

Mid-reflective glasses such as Solarban^® R77 glass and Solarban Champane™ glass by Vitro deliver around 25% exterior reflectivity and strike a balance between allowing some visibility in, while still retaining a level of privacy and a vibrant crisp aesthetic.  

Where daylighting and mitigated heat gain is desired, which is often the case, mid-reflective glass can help strike that delicate balance. For example, Solarban^® R77 clear glass has a VLT of 47% and SHGC of 0.25. 

What About Interior Reflectivity?

Interior reflectivity is a measure of how much visible light is reflected off the inside surface of the glass. Low interior reflectivity is a key performance metric for optimizing views from inside the building. It is particularly important for applications where clear views are desired, such as in an office or home, because it reduces reflections from the inside, improves visibility of the outside and prevents a "mirror" effect that can make it hard to see through the window at night.  

Viewing Guidance

There are many factors that impact our perception of glass reflectivity. When it comes to privacy and reflectance, it’s important to consider both the interior and exterior lighting conditions because what we see when we look at glass depends on where the light is brightest.

If it’s night and you’re outdoors looking into a well-lit interior, you’ll be able to see into the building because you’ll get a transmitted view. The same applies when you’re inside a building looking out on a bright sunny day – you’ll get a clear, transmitted view of the outdoor scenery.

Conversely, if you’re outside on a bright, sunny day looking into a darkened building, you’ll see a reflected view of the outdoor scene, and if you’re inside with the lights on at night, you’ll see a reflection of the interior.

Design Trends

In the realm of aesthetics and color, the market offers a number of reflective glasses in crisp silver-blue hues in the cool color range. These offerings present a light appearance, enabling the glass to reflect the color of the sky.

At the same time, architectural and interior design trends have shifted toward more natural materials like timber and limestone. This, in turn, has created a need for reflective glass in warmer colors — like champagne, bronze and warm silver — to reflect and blend with these façade tones and interiors.

Responding to evolving market preferences, Vitro has added Solarban Champane™ glass — a crisp, warm-toned low-e glass — to its mid-reflective line. The new offering will better harmonize with wood, stone and biophilic materials while providing the benefits that the Solarban^® low-e glass line of products has become known for, like its excellent solar control and low-e properties.

The warm hue is created by manipulating magnetron-sputtered vacuum deposition (MSVD) coating stack layers used to produce the Solarban^® coating with reflective glass characteristics.

Prior to the development of MSVD technology, the industry relied on tinted glass to create a bronze-colored tint, but the drawback was a reduction in light transmittance. Now, with the MSVD-created warm-toned mid-reflective glass, daylighting is preserved. As a result, the interiors are enhanced with more natural light and the views outside are brighter.

Careful Evaluation is Key

When specifying mid-reflective glass, it’s important to carefully evaluate samples. Due to the nature of the glass, it is insufficient to lay the glass sample down on a conference table. Instead, the glass pane must be held up against a white background to view and evaluate the transmitted color and against a black background to accurately see the reflected color of the glass. For the most accurate evaluation, glass should be viewed at all angles and at multiple times throughout the day in natural light.

Like other glass and glazing products, mid-reflective glass can incorporate bird-friendly technology. To achieve this, a first surface treatment with a laser edge or frit is more effective. This helps birds perceive the glass as a barrier as opposed to an opening they can fly through.

Mid-reflective glass can also meet Sea Turtle Code requirements as mandated in locations like the Florida coast and other Gulf state municipalities as it meets the 45% VLT requirement. This prevents hatchling sea turtles from mistaking the light of the moon for artificial lighting and subsequently migrating away from the water where chances of survival are very low.

For more information about Vitro’s latest mid-reflective glass options, visit vitroglazings.com.