Perfecting PerformanceAugust 12th, 2020 | Category: Architects' Guide to Glass and Metal
Energy Efficient Glass and Glazing Solutions Make Headway
by Jordan Scott
Compared to the U.S., the adoption of triple glazing insulating glass units (IGU) in commercial building is more prevalent in Europe and Canada where energy codes are stricter. Vancouver, B.C. has some of the most stringent codes in Canada, as the city moves toward net zero goals in the next decade.
565 Great Northern Way, an office space in Vancouver, achieved LEED Gold using triple IGUs. The project was designed by architecture firm Perkins+Will. The triple IGUs were fabricated by Garibaldi Glass in Burnaby, B.C., and installed by Flynn Canada.
The vision glass configuration includes a 6-mm lite of clear glass with Guardian SunGuard SuperNeutral 68 coating on surface number two over a 13-mm Technoform TGI warm edge spacer with an argon fill in a ½-inch air space, then a 6-mm lite of clear glass, a TGI spacer and argon fill, and a 6-mm lite of clear glass. The overall units were 44 mm thick and ranged from 62 inches by 28 inches to 62 inches by 108 inches, totaling approximately 40,000 square feet.
Architect Aaron Knorr of Perkins+Will says the owner wanted to maximize daylighting and views of the nearby mountains.
“Early on we developed an energy model to look at different cladding options. It became clear that we’d need to use triple glazing to achieve both a high performing envelope and aesthetics,” he says.
Energy performance and views weren’t the only deciding factors though. Knorr explains that the triple IGU also helps maintain acoustic comfort as the building is located along a busy street.
Knorr says that triple IGUs often are seen as a luxury product, but with energy codes becoming more progressive he’s seeing triples becoming more commonplace in the Vancouver market.
For architects who want to specify triple glazing, Knorr recommends approaching an owner or developer with a holistic approach, speaking to benefits such as energy and thermal performance, acoustical performance and occupant comfort.
One thing Otto Word, business development, sales for Garibaldi Glass, recommends keeping in mind is that though there are several glazing system options for triple IGUs in the commercial sector in Canada, there are fewer options on the residential side. As Vancouver moves toward its net zero goals, Knorr expects glazing systems manufacturers to be challenged to make their systems more efficient.
Vacuum Insulating Glass
When Walter Robbs Callahan & Pierce Architects sought to turn the historic Union Station in Winston-Salem, N.C., into a commercial office space, the plan was to reglaze the original steel casement windows with quarter-inch plate glass and use storm windows on the inside for energy efficiency. Th at was before the architect attended a lunch and learn with Pilkington North America and learned about VIG’s viability for historic retrofit due to its high energy performance and thin profile.
Kyle Sword, business development manager at Pilkington North America of Toledo, Ohio, says the storm windows would have had a tradeoff on aesthetics and only would have been able to achieve R 2 or R 2.5.
“Pilkington Spacia allowed them to reglaze the original windows without the aesthetic tradeoff s and losing sightlines. They won’t lose operability either and the overall window performance is higher. The center of glass performance is closer to R 4 or R 5,” he says. “It’s higher performing and aesthetically better.”
The project used approximately 3,000 lites of glass, around 16 by 20 inches in size. One challenge was ensuring that the historic review board approved the upgrades. Sword says it wasn’t a major issue but took time to complete the process.
“That’s one challenge with VIG as a retrofit solution. You have to do more upfront surveying to understand the size of the windows,” explains Sword. “You have to make sure the existing steel and wood are in good shape. There’s more prepping than just ripping every-thing out.”
VIG units have micro spacers and a cap to prevent the glass from collapsing in on itself due to the pressure of the vacuum. Sword says this creates a slight difference aesthetically and it can sometimes be a challenge to get people to understand how the system will look once installed.
“Once installed it looks like the original glass and you don’t see a difference,” he says. Sword adds that using VIG in retrofi t or historic applications allows the original design to be maintained, paying tribute to the original architect. In this case, Fellhimer & Wagner, which completed the building in 1926.
Sword expects to see VIG used for more historic adaptive reuse projects as cities and developers realize that it’s not always possible or sustainable to build new buildings.
“You need to have better strategies for how to deal with retrofitting an existing window that minimizes your operation and embedded carbon impact … VIG opens possibilities of how to find new life in old buildings and how to drive high performance without ripping everything out,” he says.
While VIG is finding a market in historic retrofit, the technology is also finding interest in new construction. Sword says new codes are exceeding what is capable using double glazed low-E windows. However, availability is one limiting factor.
Pilkington’s VIG product is made in Japan and it’s not readily available in the U.S., but he says it’s just a matter of time until that changes.
One consideration Sword recommends architects keep in mind when specifying VIG is that it can only be shipped using ocean freight due to the pressure differentials in the air, which leads to longer lead times.
Double-skin façades allow building operators to control the temperature of the building by exhausting heat in the summer or closing dampers to retain heat in the winter. Sunshades or blinds often are integrated within the system to block light and heat from passing into the occupiable space of a building. They allow architects to achieve a high level of energy efficiency while maintaining transparency. Coatings and performance features that might decrease the desired aesthetic can be placed on the inner layer of glass while the outer layer of glass can maintain the desired appearance of uncoated glass.
22 Bishopsgate in London has a closed-cavity façade designed by PLP Architecture. It’s similar to a double-skinned façade with all the energy efficiency and aesthetic benefits, but without the need for maintenance to the cavity, according to Johannes Schwenk, senior project manager with Josef Gartner, the Permasteelisa company responsible for the façade installation. Instead, he says, the cavity is sealed with clean, dry air.
The inner skin consists of insulating glass units with an outer heat strengthened glass and an inner laminated annealed glass unit with medium-low iron Clearlite. The exterior skin is a laminated glass unit consisting of annealed glass with low iron Clearvision, both manufactured by AGC Interpane.
The inner façade is a double IGU with a 3/16-inch monolithic outer lite, a 5/8-inch Argon space and a 7/16-inch annealed laminated lite with AGC Interpane’s low-E Iplus Advanced 1.0 coating for thermal comfort. The outer coating has Ipasol Bright White sun protection to reduce heat build-up in the cavity. The cavity depth is approximately 6.3 inches.
According to Alex Cox, Permasteelisa North America’s marketing communications manager, a closed cavity double-skinned façade was used to achieve high thermal performance while not consuming too much valuable floor space.
“A closed-cavity façade was chosen because it achieves the target U-value and solar heat gain coefficient by virtue of the blinds protected within the cavity,” says Cox.
While maintenance is reduced significantly due to the closed cavity design, occasional access to the cavity for blind replacement or other service is necessary. In order to allow for this, a “shuffle glazing” detail was added where the glass can be raised by 40 mm from the sill position.
This building was designed to be the tallest building worldwide with a closed-cavity façade system, according to Cox.
Jordan Scott is the editor of Architects’ Guide to Glass & Metal. She can be reached at firstname.lastname@example.org.
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