Flat glass is an essential part of our daily lives. We use it throughout our homes, office buildings, and it is integral in all modes of transport and our interactive technologies. In the EU the use of flat glass amounts to a 15 Billion Euros of annual turnover, that continues to grow year-on-year. Even though the production of flat glass, the float process, is a high temperature industrial process, the total emissions of the industry in the EU is only 1% of the total EU industrial emissions. In general, the use of glass, in its many innovative forms, provides the means to reduce carbon emissions. Nevertheless, the value-added process of thermally toughening flat glass is a high temperature process. The open question is to the level of equivalent carbon emissions due to the thermal process and finally that of the thermally toughened glass. In this work a top-down hybrid life cycle analysis was used to determine the energy embodiment of the process and the product, as an equivalent carbon emission. Results indicating the potential processing changes that would decrease the overall embodiment are also presented.