Embodied carbon, or upfront carbon emissions, is the amount of CO2 or equivalent emitted during raw material sourcing and product manufacturing. Minimizing embodied carbon emissions is critical because of the time-value of emissions, since earlier emissions have the most impact on planetary warming. Operational carbon—the emissions from the operation of the building—can be reduced over time through improved efficiency and grid-decarbonization, but today’s embodied carbon emissions will be warming the planet for centuries to come.

Since its introduction, insulating glass units (IGUs) have provided significant reductions in operational carbon emissions from buildings—yet, they increase the embodied (upfront) carbon. 

That is not to say monolithic glass is a better choice than dual-pane IGUs on a life cycle carbon basis, and other factors such as occupant comfort and thermal resiliency need to be considered. Using dual-pane IGUs rather than single-pane glass typically results in lower total life cycle emissions, since the operational emissions saved outweigh the upfront emissions investment, given a sufficiently long service life.