With the growing threat of climate change, there is a growing interest in quantifying a building's environmental impact within the building industry. Several states and municipalities have taken action to pass laws targeting greenhouse gas (GHG) emission reductions with financial penalties for enforcement. Where legislation action is absent, large institutions and individual building owners have begun to set their own carbon mitigation targets. With this interest to decarbonize the growing building stock, understanding the terminology and methodology behind quantifying carbon emissions and specifically operational carbon emissions has become critical to the building consulting profession.

In an effort to clarify the use of operational carbon emission factors (EFs), this paper examines the various carbon emission definitions, data sources, temporal resolutions, geographical resolutions, uses, and best practices. Based on this review, this paper provides recommendations on how and when certain carbon metrics should be used by building design professionals.