The hotel Thompson Nashville is a relatively new addition to the city’s skyline. Located in an area known as the Gulch, the 12-story building presents an intriguing use of glass envelope. The Thompson’s facade is curved to follow the severe curve of 11th Avenue, the street on which the hotel sits.
(Photo: Thompson Hotel, a curved skyscraper, in Nashville, TN. Credit: Albert Vecerka/Esto)
The curved glass window wall isn’t only visually enticing; it’s high performing. The 60,000 square feet of material used on the hotel’s envelope is solar control low-emissivity glass – ideal in a place like Nashville, where air-conditioning costs are often of concern.
“We’re moving toward as high-performance [glass] as possible and highest visible light as possible at the same time,” says Meghan Beach, architectural representative for AGC Glass North America, makers of the glass used at the Thompson Nashville.
This hotel is just one example of how architects, designers and fabricators are using glass to – pardon the pun – push the envelope in their work for exteriors. It’s becoming increasingly common to see large glass envelopes on buildings today. Modern designs, color and energy reduction technology are now infused in a building material that’s been used for centuries.
And today, there are almost endless possibilities when it comes to choosing a glass envelope.
“There is probably an infinite number of options in the glass world, which makes it really difficult and challenging to get the right glass for the building,” says Daniel Shields, vice president of planning and development at IWR North America, a building enclosure subcontractor. “We have several categories that we need to focus on. Performance is one of the bigger ones. … There’s also that visual aspect.”
Maintaining Existing Glass
Your building’s envelope surrounds your tenants every day, shelters them and keeps them safe from outside forces and the elements. When that envelope is made of glass, there are certain considerations to keep in mind.
Below are simple steps you can take to ensure failure doesn’t occur.
Commission an inspection of your glass.
As a facilities manager, you have a plan on how your building should perform correctly and at its highest ability – and failing glass can throw off that plan. Shields says he’s seeing more building owners commission a third party to inspect their glass and come up with a prescriptive plan to ensure it’s following performance criteria.
“There are tests and scans they can do to see if any units have any failures,” Shields says. “From there, you can replace them.”
Look for hazy spots and leaks.
Shields recommends doing regular checks yourself for any spots that look like they’re dirty or hazy on the inside. That likely means there’s a sealant failure occurring and air and water is getting inside the glass.
Also keep an eye out for adhesive failures, absence of sealant, punctures in sealant and sealant reversion (when sealant reverts to its prior form and begins to degrade as a result). Leaks will occur where glass meets the metal.
[Related: Top 5 Envelope Failures and Water Leaking Solutions]
“Sealant doesn’t last forever,” Shields says. “It will fail at some point in the future. If it’s maintained properly, you can get a lot more life out of the glass.”
Double-check your warranty.
Another thing Shields says to keep in mind is how long your glass warranty is.
“Some [companies] don’t extend through the construction process, let alone after completion,” he explains. “More reputable companies we work with have 10 years on glass and 20 years on metal. With that, you’re getting that peace of mind that they have a product they’re willing to stand behind.”
Current Trends in Glass
There are many design options when it comes to glass, and the material is so sought-after because of its longevity and elegance. “It doesn’t rust or change colors, and it will look the same 50 years from now,” says Said Elieh, director of technical design/product manager at Bendheim, one of the leading suppliers of architectural glass.
That said, technology is always evolving in the world of glass, and some applications of glass are more popular. Below are some of the current trends in glass today.
Larger pieces of glass.
In the last two decades, building designers are opting for more glass and less metal on the envelope.
(Photo: Glass envelope from IWR North America - Weil Hall: Washington University East End Enhancement project in St. Louis, MO.)
(Photo: Welcome Center: Washington University East End Enhancement project in St. Louis, MO.)
Elieh says Bendheim’s channel glass can go 18 feet in height without any midpoint support. Ryan Hoffman, client development manager at Viracon, adds that oversized glass is becoming more common. Some units can get up to more than 200 inches.
Fewer sight lines.
Because larger pieces of glass are becoming increasingly popular, that means the metal sight lines that often go with it are becoming less popular. “Architects don’t like to see aluminum and frames,” Elieh says. Shields explains that the fewest amount of sightlines as possible is a common request.
“We’re seeing point-supported glass, which is a really thin piece of structure holding a fitting for glass,” he says. “The trend really is to max out the structural capacity of the system to get more glass, fewer sightlines.”
[On topic: Space Needle Now Has World’s First Revolving Glass Floor]
Although abundant natural light is considered a benefit of a glass envelope, there’s such a thing as too much daylight or not the right kind of daylight. That’s where textured glass comes in.
“Adding some sort of diffuser such as a texture or pattern or design [to the glass] helps bring in high-quality daylight and minimize glare,” says Jen Miret, director of marketing for Bendheim. “One of the most trending patterns is linear.”
(Photo: The recently completed Pier 17 at South Street Seaport, NYC features two stacked rows of Benheim’s channel glass, each 20 feet tall. The light-diffusing textured glass envelopes the façade and creates light boxes that glow at night. Credit: C. Taylor Crothers Photography, courtesy of Bendheim)
Use in non-ventilated spaces.
Bendheim, is also seeing an uptick in the use of glass as the main envelope for non-ventilated spaces such as parking garages and stair towers, Miret says.
(Photo: The new Museum of the Bible (MOTB) uses Bendheim’s high-performance double-glazed exterior wall system with low-e coated channel glass for enhanced thermal performance. Credit: Alex Fradkin, courtesy of Bendheim)
“Those used to be applications that were completely exposed to the elements or enclosed in opaque walls,” she explains. “Now we’re seeing projects use ventilated glass systems as a way to bring in daylight and maintain that sense of openness and natural surveillance, while protecting occupants and the structure from water damage.”
Benefits of a Glass Envelope
When a building has a glass facade, the beauty of it is something that’s noticed first. But the glass is more than just a work of art. It serves functional purposes as well. Some types of glass are designed to withstand extreme weather or help regulate the building’s temperature.
“People work better in those environments. In healthcare, they help the healing process. People closer to windows tend to have a faster recovery time.” - Daniel Shields
Below are some of the benefits of having a glass envelope.
Laminated glass is one of the ways in which the material can protect occupants. If it breaks, an interlayer between the two plies of glass tends to keep it together.
Shields says hurricane-resistant glass is a big selling point right now.
(Photo: University of Innsbruck, Austria. Exterior stair and elevator tower is enclosed with clear laminated glass in a ventilated façade system. Credit: Bendheim)
“One of the biggest things that hurts people [during a hurricane] is flying debris,” he says. “If we can design a wall that can withstand that, that saves lives.”
Places like banks and police stations can opt for ballistic-resistant glass. And fire-resistant glass can withstand a fire for one to two hours without letting it spread to allow occupants to evacuate the building.
Good views and natural light are appealing to occupants. “People work better in those environments,” Shields says. “In healthcare, they help the healing process. People closer to windows tend to have a faster recovery time.”
“From an energy standpoint,” Hoffman explains, “you’re saving artificial light if you bring in natural light.”
Shields adds that allowing in visible light while providing a barrier for reducing the amount of UV that penetrates it can then increase the glass’s U-value to help the building perform better and reduce its energy usage.
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