Embodied Carbon in Glazing Materials: What It Means and Why It Matters
Sustainable building design has spent the last two decades focused almost entirely on operational carbon: the energy a building consumes once it’s in use. Embodied carbon, the emissions locked into a building’s materials before it ever opens its doors, has received far less attention until recently. For glazing specifically, that’s starting to change, and the numbers involved are larger than most specifiers assume.
What embodied carbon actually covers
Embodied carbon includes the emissions from extracting raw materials, manufacturing components, transporting them to site, and eventually disposing of or recycling them at end of life. For facades, this typically covers life cycle stages A1 through A5 (materials and construction), B4 (replacement), and C1 through C4 (end of life), the standard scope used in whole-life carbon assessments, as outlined in a life cycle carbon study of facade systems across different climate zones.
Facades are not a minor line item in this calculation. Facades can account for up to 30% of a building’s total embodied carbon, according to CIBSE Journal’s coverage of facade carbon assessment, and glass specifically has been identified as contributing between 26% and 60% of facade-related embodied carbon, depending on the design configuration, per the facade life cycle study referenced above.
Why glass is a disproportionate contributor
Two factors make glass a bigger embodied carbon issue than its material volume alone would suggest.
The first is manufacturing intensity. Flat glass production is energy intensive, dominated by high-temperature furnace processes typically fueled by natural gas, as detailed in research on embodied carbon in building envelopes published by the Facade Tectonics Institute. This means the upfront carbon cost of the raw material itself is high before it’s even fabricated into an insulating glass unit (IGU).
The second, and often overlooked, factor is service life. Insulating glass units typically last around 25 to 30 years, well short of the 60-year design life often assumed for the rest of a building’s structure, as noted in both the facade life cycle study and CIBSE Journal’s analysis. That mismatch means most buildings will need to replace their glazing at least once during their operational life, effectively doubling the embodied carbon attributable to the glass alone. As the same Facade Tectonics Institute research puts it, single-pane glass that could theoretically last for centuries has, through modern IGU construction, been converted into a component with a service life measured in decades, with added recycling complexity at end of life.
Why this changes how glazing should be evaluated
This has a direct implication for how glazing decisions get made: durability isn’t just an operational or maintenance consideration, it’s a carbon consideration. A widely used metric in facade design is embodied carbon per year of service life, which allows components with different lifespans to be compared on an equal footing, as recommended in embodied carbon guidance from the Facade Tectonics Institute. Extending a glazing unit’s service life doesn’t just delay a cost, it directly reduces its annualized carbon footprint, since the upfront manufacturing emissions are spread across more years of use before replacement is needed.
This is also why policy is starting to catch up. A growing number of jurisdictions are introducing requirements for Type III Environmental Product Declarations (EPDs) and setting embodied carbon limits for common facade materials, including glass, according to research on unlocking embodied carbon reductions in facade systems. For projects in the Netherlands, this sits alongside existing MPG (milieuprestatie gebouwen) requirements, which already factor material-level environmental impact into building performance scoring, see RVO’s guidance on milieuprestatie gebouwen.
What this means for glazing specification
Reducing the embodied carbon impact of glazing comes down to a few concrete levers: minimizing unnecessary material layering (decorative rainscreens and shadow-box assemblies increase embodied carbon without improving performance), designing for a longer functional service life so replacement cycles are less frequent, and specifying materials and interlayers that are compatible with existing recycling streams rather than requiring specialized end-of-life processing.
None of this replaces the importance of operational energy savings, solar heat gain reduction, and HVAC load reduction remain some of the most effective levers a building has for reducing its total carbon footprint over its lifetime. But embodied carbon is no longer a rounding error next to operational carbon, and glazing decisions increasingly need to account for both sides of that equation rather than just one. For more on how eLstar approaches this from a manufacturing perspective, see our related piece, “Manufacturing Without Building New Factories: eLstar’s Approach”.