This course is part of the Glass in Architecture Academy

Photo by Charles F. Neuman; courtesy of Guardian Glass

With a sweeping glass facade above the entrance and matching fenestration throughout, the Kaiser Permanente San Marcos Medical Center in San Marcos, Calif., uses natural lighting to imbue the facility with biophilic elements.

Environmental Product Declarations

Environmental Product Declarations (EPDs) are a way for manufacturers to take comprehensive, third-party-verified LCAs, which are quite complex, and turn them into standardized declarations for their products.

According to the U.S. General Services Administration,⁷ EPDs are environmental declarations that communicate standardized environmental information about the life cycle impact of a product. EPDs are independently verified and registered documents based on industry standard product category rules.

EPDs report a specific set of environmental results, which can only be created after an LCA is conducted. Common categories include product carbon dioxide equivalent (CO2e), ozone depletion potential, potential of acidification of land and water sources, potential for eutrophication, smog formation potential, and primary energy use.⁸

EPDs are tools architects, builders, and other stakeholders in the construction industry can use to help them make informed decisions based on the environmental attributes of the materials and products they use. However, industry professionals utilizing EPDs should be cautious in drawing direct comparisons between reports, as there are still varying factors that could affect the data such as the timeframe used, regional differences in energy sources and regulatory standards, and general data consistency.

Growing awareness of environmental performance and the desire to make informed choices have driven the adoption of EPDs in the building sector. They’re often voluntary or encouraged through incentive programs, rather than required, though there are some exceptions.

EPDs can support various building certification systems, such as LEED (Leadership in Energy and Environmental Design) and BREEAM (Building Research Establishment Environmental Assessment Method). Some countries and regions are requiring the use of EPDs for certain products for regulatory reasons. Consumer demand has also inspired further use of the tool.

As EPDs become popularized, they are being incorporated into building standards and codes in different ways. For example, the International Green Construction Code (IgCC) is a type of construction code that has similar aims as LEED and Green Globes certifications but is implemented in a code that is legally mandated by some states, governmental agencies, and companies.

In a single project, the IgCC mandates EPDs for at least 20 different products covering more than 25% of building material costs. Requirements currently allow industry-wide EPDs in addition to company-specific EPDs, as long as they apply regionally to where the building is being constructed.

dditionally, the IgCC accepts EPDs submitted for components of assemblies, rather than the full assemblies themselves, if those components cover more than 80% of the product weight or cost. For example, a curtain wall assembly necessitates EPDs for the glass and framing, without the need for EPDs on fasteners, sealants, hardware, spacers, and any other elements of the assembly.

Read the sidebar to understand more challenges and answers to creating and procuring glass-specific EPDs.

APPLYING CARBON REDUCTION TO GLASS MANUFACTURERS

Manufacturers are working to improve resource efficiency and minimize the greenhouse gas emissions across the cradle-to-gate life cycle of their products and product families. This, in turn, reduces the embodied carbon associated with their products.

Glass Manufacturing–Embodied Carbon

Float glass production involves mixing and heating raw materials, including sand, soda ash, dolomite, limestone and cullet (scrap or broken glass) to a liquid state in furnaces at temperatures of between 2700 and 2900 degrees Fahrenheit (or approximately 1500 to 1600 degrees Celsius)⁹, and then floating the subsequent ribbon of glass atop a bath of molten tin. Once the ribbon has sufficiently cooled, it is transferred onto rollers and annealed to limit residual stresses. Its edges are trimmed and the ribbon is cut to the desired sizes.

The energy consumption and associated carbon emissions can be reduced at various stages of the process, including with the raw materials. For example, there are some raw material substitutions that can be considered.

Natural soda ash can replace synthetic soda ash in a batch, if economically and logistically viable. Natural soda ash, a mined material, typically has a lower embodied carbon than synthetic soda ash, a material produced through a chemical process known as the Solvay Process.

Another potential solution is replacing carbonate batch components with other raw materials. For example, manufacturers could use caustic soda, a non-carbonate material, instead of soda, a carbonate material, to help reduce the release of carbon emissions.

Using decarbonated raw materials such as calcinated lime and calcinated dolomite can help reduce the carbon emissions released during the glass melting process.

Increasing the iron content in the batch improves the glass melt’s ability to absorb heat radiation, which requires less energy for the melting process and reduces the associated energy consumption and carbon emissions.

Of course, there are trade-offs associated with switching raw materials. For example, although using higher iron content can reduce energy consumption and carbon emissions, it can also impact optical properties by reducing solar and light transmission. Similarly, before replacing carbonate batch components with other raw materials, manufacturers should evaluate the full life cycle impact of the materials and also their impacts on quality. Such trade-offs should be considered while making decisions about raw material sourcing.

The bottom line is that ensuring raw material extraction and processing is done in an ecologically and socially responsible manner can help lower the embodied carbon footprint of a product.

Better yet, increasing the use of scrap or broken glass, also referred to as cullet, in the manufacturing process reduces the energy required to melt the batch materials and the demand for new raw materials in the first place, helping conserve natural resources.