Less Than Zero

Driving Down Carbon Emissions Needs More than High-Performance Glazing

By Ellen Rogers

Move over, carbon neutral. It’s time to talk about embodied carbon. For more than a decade, carbon neutral processes—balancing carbon dioxide (CO2 ) emissions with an equivalent amount removed—has been the buzz. Developers and builders became focused on reducing the carbon footprint of their projects, striving to reach net-zero emissions. Some cities and other jurisdictions enacted stringent building codes to improve energy performance. New York has been at the forefront with its Local Law 97, which set a goal to reduce the city’s largest buildings’ emissions by 40 percent by 2030 and by 80 percent by 2050. This is all good news for the glass industry and its high-performance products. However, there’s more to it than just running a net-zero building.

“Issues surrounding potential climate change through the accumulation of additional carbon in our natural environment may very well be the challenge of this generation,” says Tom Bougher, director, applied research for Oldcastle BuildingEnvelope® (OBE), headquartered in Dallas. “Considering the built environment consumes approximately two-thirds of all electricity, any stakeholder within this sector, including the architect, building products supplier, and their downstream supply chains, has an inherent responsibility to fi nd ways to reduce this demand. Of course, all sources of carbon generation are contributing to this problem, but there has been a recent shift that focuses on embodied carbon in particular.”

According to Architecture 2030, an organization focused on transforming the built environment from a major emitter of greenhouse gases (GHG) to a central solution to the climate crisis, buildings generate nearly 40% of annual global CO2 emissions. Those building operations are responsible for 28% annually, while materials and construction are responsible for an additional 11% annually. Moving toward carbon neutral does require reducing a building’s operational carbon—GHG emissions caused by the building’s energy consumption—but problems begin long before the building is operational. That’s where embodied carbon comes in. According to the Carbon Leadership Forum (CLF), embodied carbon refers to GHG emissions that come from manufacturing, transporting, installing, maintaining, and disposing of building materials in the building industry.

Three materials—concrete (11%), steel (10%) and aluminum (2%)—account for the majority of total global emissions in the construction industry, while heat and energy-intensive float glass production is also a concern. As a result, many glass and metal companies have turned their attention to embodied carbon and the upfront impact that their materials can have on the building industry’s carbon footprint.

According to Helen Sanders, who works in strategic business development with Technoform in Twinsburg, Ohio, this impacts the design and construction of buildings.

“The most sustainable building is the one that you don’t build because you haven’t expended anything in making it, and you haven’t expended anything in running it,” she says. “If you have to build, it’s better to retrofit an existing building.”

However, not building isn’t a likely option, and retrofitting, while increasing, isn’t taking over the mainstream. The façade industry has a big opportunity to improve its operations and educate architects and end-users about selecting materials wisely.

Embodied Carbon 101

Before addressing the issue of embodied carbon as it relates to the glazing industry, it’s important to understand its origins. To start, the manufacturing processes for both aluminum and float glass are heat and energy-intensive, emitting carbon even before a product is manufactured. After that, carbon emissions can come from additional fabrication operations, shipping and transportation, installation and end-of-life considerations, not to mention the emissions from sourcing raw materials needed, in some cases, to manufacture the materials.

“The farther you have to move things around, the worse it is for the climate,” says Bruce King, author of The New Carbon Architecture, and a registered structural engineer who has served as a green/clean tech advisor to numerous start-ups and other organizations. “You don’t want to move materials further than you have to. That becomes more and more important the bigger and bulkier the product.”

One metric to consider in understanding a building product’s carbon impact is its Global Warming Potential (GWP). The GWP considers all of the energy used to create a product and converts it into kilograms (kg) of equivalent carbon dioxide.

“Calculating GWP helps stakeholders and sustainability programs gauge more effectively the environmental performance of glass and other products manufactured for buildings,” says Paul Bush, vice president, technical services and government affairs for Vitro Architectural Glass in Carlisle, Pa. “Measuring GWP and carbon intensity in glass manufacturing involves many complex distinctions and calculations, such as the GWP differences between flat glass and processed glass.”

For architectural glass, most of the embodied carbon originates from converting sand and clay to glass. Approximately 75% of the embodied carbon in an IGU occurs as a result of flat glass manufacturing¹.

Adding low-E coatings, for example, also contributes to an IGU’s embodied carbon, but to a much lesser degree. Coating application is a room-temperature process, compared to the float process, which requires a significant amount of heat and energy. Estimates show that of an IGU’s remaining embodied carbon, roughly 13% comes from the heat treatment process, 10% comes from the IGU fabrication process itself, and just 2% comes from the process of adding low-E coatings.²

Aluminum production is also energy-intensive, though in the U.S. about 70% of electricity consumed in aluminum smelting facilities comes from hydroelectric sources, according to the Aluminum Association, which notes this helps reduce the environmental impact of the process.

In her blog for USGlass magazine³, Sanders adds that “worldwide, the average renewable energy use for aluminum manufacturing is only 26%⁴ and aluminum made in China uses 90% coal power, which is very carbon-intensive. In addition, nearly 40% of the North American aluminum supply involves recycling (secondary production), which is 92% more energy-efficient than primary production.”

Paul Walker, business development manager for Hydro Extrusion North America, says the global aluminum industry has been aware of the carbon footprint of its product for some time, as the process of mining and producing raw aluminum is energy-intensive.

“Smelting aluminum with coal-based power creates roughly four times more CO2 -equivalent emissions per kilogram than primary aluminum produced with renewable energy,” he says. “Due to the energy-intensive nature of the aluminum smelting process, the most significant reductions in embodied carbon can be achieved through the use of renewable energy and/or using less energy via recycling scrap aluminum.”

Inside The Plant

Companies across the industry are aware of the concerns surrounding embodied carbon and have taken measures to address the efficiencies of their operations.

“Vitro and its legacy company PPG, pioneered oxy-fuel technology in the early 1990s, which it operates at three plant locations in the United States,” says Roberto Cabrera, vice president of technology with Vitro Architectural Glass. “Oxy-fuel technology can reduce energy consumption in glass melting furnaces by as much as 20% and cut greenhouse gas emissions in half.”

He continues, “In addition to being used at our plants in Fresno, Calif., Wichita Falls, Texas, and Meadville, Pa., Vitro licenses oxy-fuel technology to other glass manufacturers around the world seeking to reduce their CO2 and other greenhouse gas emissions.”

Other float glass companies are also taking action. In a world-first trial, the NSG Group successfully manufactured glass at its facility in the U.K., using hydrogen power. During the three-week trial, the company transitioned between natural gas and hydrogen. According to the company, the results proved that hydrogen was as capable as natural gas in achieving excellent melting performance, adding it could be possible to operate the furnace with reduced carbon emissions. Switching from natural gas to hydrogen to power production means that float glass furnaces, which account for the majority of NSG’s overall carbon emissions, would be able to operate with significantly lower emissions, according to the company.

And according to King, this is a step in the right direction.

“To reduce the carbon footprint of any product … in the long run [you need to] switch to hydrogen. This is a good start.”

Aluminum companies are also addressing the issue.

“The use of clean hydroelectric power and cutting-edge smelting technologies have enabled Hydro to produce Reduxa, our primary aluminum product that has a third-party certified carbon footprint of maximum 4.0kg CO2/kg aluminum,” says Walker. “Hydro is also using a high percentage of post-consumer scrap in the production of Circal, our aluminum product that contains a minimum of 75% recycled post-consumer scrap. The process of recycling aluminum has a very low carbon footprint, requiring only 5% of the energy of the original primary production process.”

Walker adds that both Reduxa and Circal are produced by facilities in Europe and have been received well by that market. The company is in the process of developing a high-recycled content product for the North American market.

Examine Your Operations

Not every process requires drastic operational changes to improve production efficiencies. Sanders suggests companies can perform their own in-house life cycle assessments (LCA) to understand the biggest concerns. “We just did one in-house ourselves. You get your electricity bills, and figure out how much energy you use. Look at your gas bill, your water bill. Look at your raw materials coming in. Do some research on your annual supply chain,” she says. “Then you can get a mass balance and an emissions overview of your production operations, and you have a clear view of where the thickest impacts are coming from.”

Richard Braunstein, vice president of research and development with OBE adds, “Good policy begins with good data, which is why OBE began that journey with our first LCA. This has shed light on all the environmental impacts attributed to our manufacturing operations and material flows (largely our vendor-supplied materials),” he says. “With this information, we can see causal relationships and build a short- and long-term mitigation plan.”

Braunstein points to a three-prong approach for companies looking to build a plan: Supply chain, internal processes, and product design.

“For us, the majority of [supply chain] impacts come from the processing of our base materials, which we purchase from suppliers,” he says. “Evaluating our supplied materials by factoring in environmental attributes alongside the traditional cost and performance criteria is necessary. This will require you to choose and engage with suppliers like you would any partner aligning around a common goal.

“The second opportunity focuses on internal manufacturing and handling processes. With an LCA, you can pinpoint each step of your process and see measurable outcomes, both wanted and unwanted. With a long-term strategy, you will be able to identify, improve, or eventually replace those processes that are causing the greatest harm.”

He says the third opportunity involves product design.

“Most products in the market today were not designed with environmental considerations as a core driver in the design solution. When you add sustainability to the traditional four drivers in the design process—cost, aesthetics, performance and legal—a flood of new opportunities can be revealed.”

Choose Wisely

The move toward reducing embodied carbon also calls for educating architects and specifiers about product selection. Discussing Environmental Product Declarations (EPDs) is a good start. EPDs are independently verified and registered documents that communicate transparent and comparable information about the life-cycle environmental impact of products.

“Everyone will be using EPDs,” says King. “You’re not in the game until you have an EPD on your product. Once you have that, buyers will compare your products to other manufacturers. Having it will be you advantage or disadvantage. [If you don’t have one], get your EPD and start improving.”

EPDs are available for many products across the glass and metal industry and are becoming increasingly important. Regarding embodied carbon, Sanders says a fabricated glass EPD isn’t as important as one for float glass. That’s “because all the embodied carbon impacts are already baked into the system. The biggest impacts are due to the thickness of glass, how much you’re using, and so forth.”

She continues, “When I say ‘how much you’re using,’ it’s not in the context of the window or wall ratio because the wall has its own [carbon] impact to worry about. And, it’s not like in the energy realm where everyone’s worried about window-to-wall ratio, because then the wall is better than the window. That might not be the case in terms of embodied carbon. When I talk about how much glass, it’s more in the context of making a big building or a small building, or not building at all.

“If you have to build and you can’t reuse, then use materials wisely. Make the building as small as you can because if you’re using less to build it there should be fewer emissions when operating it.”

Walker says education is also needed when it comes to different types of aluminum.

“Not all scrap is created equal and we continue to work diligently to educate architects, fabricators and designers about this topic. Our goal is to educate, provide design assistance, and produce low-carbon products for our customers in order for them to meet the requirements of local, state, and federal building codes that are driving the change in today’s demanding building and construction industry.”

One of the challenges, Walker says, is that some companies in the aluminum industry take a “loose” approach to the definition of recycled and/or scrap aluminum, failing to make a distinction between post-consumer scrap and industrial scrap.

“When recycled aluminum is made from used beverage cans, windows, or car parts, the material starts another life. Previously used aluminum is referred to as post-consumer scrap, and its carbon footprint is close to zero. Recycled aluminum made from secondary production or pre-consumer scrap is different. This material has not yet completed its life and must retain the carbon footprint of its original material footprint,” he says. “If this isn’t done, there is a definitive risk that the material’s production emissions are not accounted for. If all scrap is accounted for equally, we lose visibility into this critical difference in emissions, and we undervalue the importance of post-consumer scrap and a product’s lifecycle.”

The Big Picture

According to Bougher, a holistic view of embodied and operational carbon will lead to the best design decisions. He compares a dual-pane IGU and a hybrid vacuum insulating glass (VIG) IGU as an example.

“The hybrid VIG will have higher embodied carbon compared to a dual-pane IGU, but it will also have an insulating rating approximately three times higher. In a cold climate and a building using carbon-intensive heating, the hybrid VIG will almost certainly have a lower impact on potential climate change over its lifetime,” he says. “An EPD from the manufacturer will report on the embodied carbon. On the other hand, a comprehensive LCA that includes the use and end-of-life phases is required to assess the product’s entire carbon impact. The LCA captures differences in the life span of different products enabling a more accurate comparison of wood, vinyl, and aluminum framing systems.”

Sanders says glass fabricators can educate the architects on where the impacts are and what they can do in the design process to help minimize carbon. Likewise, part of what architects can do is help the fabricator reduce scrap.

“One way they can help fabricators with this is to look at their designs and try to create better uniformity so every unit isn’t a different size. If you’ve got a hundred units on the project, try and make them all the same size or not so many different sizes so you can have an economical manufacturing process,” she says.

Braunstein says, though, having a straightforward and accurate method to
calculate lifetime GWP is critical for accelerating decarbonization.

“Currently, architects, engineers and materials suppliers have no agreed method of analysis capturing both operational and embodied carbon that is accurate, accessible, and complete. A whole building LCA with supplier-specific data and building-energy modeling can offer an accurate accounting of carbon, but is extremely time-intensive and often requires costly third-party studies. In contrast, manufacturer EPDs are based on cradle-to-gate LCA, which accurately estimates embodied carbon but does not account for operational carbon, limiting its value as the driver in environmental impact decision making. If key stakeholders can agree on a standard method of comparison that properly accounts for the most important contributions to environmental impact over the entire life of a fenestration product, it will help the industry make better decisions using better data and drive real carbon reductions in the built environment.”

In addition to LCAs and EPDs, there are other tools and resources available. For example, Building Transparency, an organization focused on providing open-access data and tools to help the building industry address embodied carbon’s role in climate change, is developing the EC3 tool for architectural glass. This free calculator allows benchmarking, assessment and reductions in embodied carbon, focused on construction materials’ upfront supply chain emissions.

What’s Next?

Opportunities exist for industry companies to improve their own embodied carbon emissions and contribute to the use of low-carbon materials in buildings. Speaking of products, Bush says it’s important to keep in mind the return on carbon energy-efficient glazings deliver.

“While the production of raw glass does carry embedded carbon, high-performing low-E coated glass reduces the negative environmental impact of the built environment. Between reducing solar heat gain and providing daylighting, modern architectural glass reduces carbon emissions for thousands of homes and buildings every year of their long life-span.”

Bougher adds, “The fenestration industry has generated a great amount of innovation over the past 50 years with the goal of reducing operational carbon. We should continue these efforts as we also consider the embodied carbon of our products.”

Ellen Rogers is the editor of USGlass magazine. Follow her on Twitter @USGlass and like USGlass on Facebook to receive updates.

1., 2. Vitro Architectural Glass, Understanding Embodied Carbon
3. Insights and Inspirations, September 6, 2019, https://www.usglassmag.com/insights/2019/09/carbon-counting-a-driver-for-u-s-sourced-aluminum-part-2/
4. https://international-aluminium.org/statistics/primary-aluminium-smelting-power-consumption/#histogram

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