Embodied Carbon and Glass
As architects and glaziers work to design and construct building projects in a more sustainable manner, the consideration of embodied carbon has become a bigger factor in understanding the overall impact of a project’s carbon footprint.
Designers are working to balance the reduction of emissions from a building’s operations, known as operational carbon, with emissions caused by the manufacturing and installation of construction materials, known as embodied carbon.
Sustainability advocates are working to introduce initiatives, such as the Buy Clean California Act, aimed at reducing carbon emissions associated with the production of architectural products, including glass. In order to understand the impact these initiatives will have on the architectural glass industry and how Vitro Glass is working to meet these standards, it is important to first understand the role embodied carbon plays in glass production.
Carbon and Architectural Glass Production
Perhaps the most comprehensive metric to consider as it relates to embodied carbon in glass (or any building product) is Global Warming Potential (GWP). This measure takes all the energy used to create a product and converts it into kilograms of equivalent carbon dioxide, expressed as the term “CO2-eq.” The purpose of calculating GWP is to help stakeholders and sustainability programs more effectively gauge the environmental performance of glass and other products manufactured for buildings.
Most of the embodied carbon in glass originates with the energy-intensive process of heating the melting furnace to 3,000 degrees Fahrenheit to convert a blend of silica, soda ash, dolomite, metal compounds and recycled cullet glass to flat glass.
The processes of adding energy-efficient low-e coatings, tempering, laminating and fabricating flat glass into insulating glass units also contributes to the glass’s GWP – but to a lesser degree.
In fact, approximately 75% of the embodied carbon in an insulating glass unit (IGU) can be credited to the manufacturing of the flat glass lites. It is estimated that of an IGU’s remaining embodied carbon, 13% comes from heat strengthening or tempering the glass, 10% comes from the IGU fabrication process itself, and just 2% comes from the process of adding low-e coatings.
Reducing Embodied Carbon
To further reduce embodied carbon in architectural IGUs, Vitro is taking the following steps to reduce overall energy consumption in glass production:
- Developing expertise in furnace control systems to reduce variability of melting temperatures and fuel consumption
- Adding new low-NOx burners in our plants
- Using variable frequency drives on cooling fans to reduce energy use
- Utilizing recycled cullet (both pre- and post-industrial) to reduce fuel consumption
- Converting all facility lighting to LED, which reduces electric consumption by as much as 80% vs. incandescent lighting
- Using oxy-fuel technology at three plant locations in the U.S., which can reduce energy consumption in glass melting furnaces by as much as 20% and cut greenhouse gas emissions in half
It also is important to note the return on carbon that 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 each and every year of their very long lifespan.
Evaluating Embodied Carbon
Vitro Glass is the first North American manufacturer to publish third-party verified Environmental Products Declarations (EPDs) for flat glass and processed glass products. These documents provide detailed data about the life-cycle impacts of Vitro Glass products on the environment and may be used as credentialing for LEED® and other green building certification programs.
It is important to understand how to properly read, interpret and utilize data that is published in EPDs, which should generally be used to inform and indicate compliance with the requirements of green building rating systems and legislative actions. The purpose of an EPD is to provide information on the environmental impact of the product over the life cycle, and they typically rely on estimations of impacts and can therefore differ across product lines and reported impact. In the context of evaluating embodied carbon, EPDs will likely offer the most value in interpreting how a given product was manufactured and what steps manufacturers are taking to reduce energy expenditures. For more information, review the National Glass Association’s General EPD Education document.
Developing the EC3 Tool
Along with being the first North American glass manufacturer to publish third-party verified EPDs, Vitro Glass is participating in the development of the EC3 tool for architectural glass. Envisioned by the non-profit Building Transparency, this calculator is being created to help architects and other stakeholders benchmark, assess and reduce the amount of embodied carbon used among all the building products (including glass) specified for their construction projects.