Pressure to increase the energy efficiency of windows and glass curtain walls has inspired decades of innovation since the widespread introduction of double-glazing in the 1970s.
It hasn’t been an easy road for exterior glazing and windows. Numerous studies point to the health and comfort benefits for occupants resulting from interior natural light and outward views.
However, the reduction of window-to-wall ratios, sometimes even to zero, has been suggested as a solution for improving a building’s energy efficiency.
As a counterpoint, advances in double and triple glazing have been remarkable. Argon-filled air spaces, Low-E coatings and innovative reflective surfaces have opened the door to inspiring building designs that enhance natural light and create more comfortable places to live and work while controlling energy consumption.
Alongside this, the reduction of thermal conductivity through framing has become a focal point of development and is moving framing away from traditional aluminum toward the increased use of fibreglass.
The thermal conductivity of fibreglass is over 400 times less than aluminum (0.58 W/m K vs 237 W/mK). It is also strong and corrosion-resistant. Fibreglass framing is able to withstand the most extreme weather and temperatures without becoming brittle or soft. The result is long-term durability, well over 50 years by some estimates, far more than the average lifespan of aluminum frames.
Fibreglass framing has been championed for several years by Edmonton-based GlasCurtain. The company’s family of Thermaframe triple glazed exterior glazing offers energy efficiency right up to PassivHaus standards.
As important as energy efficiency is to the operational costs of buildings, both new and retrofitted, increased attention is being paid to embodied carbon (EC). Windows come under review once more due to the high heat required for the production of glass and metal framing and spacers typically associated with windows and façades. Here again, fibreglass offers substantial embodied carbon reductions versus aluminum or steel.
Independent research investigating the EC associated with windows determined the embodied carbon for aluminum framing was 70 per cent of the overall unit, versus 10 per cent for fibreglass. The smelting process used for aluminum is the main culprit.
EC is destined to become an important topic going forward. During a recent panel discussion sponsored by Glass Canada Magazine, Anton Van Dyk of glazing structural engineering firm Layton Consulting Ltd, said embodied carbon may soon be added to the estimated 15 separate areas of compliance that fenestration products need to address.
The combination of innovative glass coatings, gas-filled spaces between layers and low EC framing materials are increasing the choices for individual projects, based on overall performance and cost-effectiveness.
These developments have been so significant in terms of energy efficiency improvements that the near-automatic choice to use triple glazing over double glazing has become more nuanced, particularly in climates less extreme than Canada’s.
High performance manufacturers like GlasCurtain have responded. The company recently announced its first line of double-glazed, fibreglass-framed R4 curtain wall called Thermafame4. With 50 per cent less upfront EC than comparable aluminum-framed systems, it’s targeted to meet the growing demand for double-glazed solutions in more temperate climates, particularly for buildings targeting net-zero and zero-carbon certification.
Further EC reductions are possible using warm edge spacer systems, such the Ködispace 4SG offered by German-based Kömmerling Chemische Fabrik GmbHin. The metal-free system has an organic composition produced with environmentally-friendly raw materials that completely replaces the traditional edge system made of spacer, desiccant and primary seal.
“Warm edge spacers have a lower thermal conductivity than conventional aluminum spacers, resulting in a significant reduction of the thermal bridge in the border and minimized cooling of the insulating glass edge.”
Due to its ability to form a chemical bond with glass and silicone, this system is particularly suitable for structural glazing, the company says.
The blending of energy efficiency expectations and reduced embodied carbon content will continue to drive new ideas and products, providing an array of exciting choices for project designers and owners in the future.
John Bleasby is a freelance writer. Send comments and Inside Innovation column ideas to editor@dailycommercialnews.com.
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