Considerations for estimating operational greenhouse gas emissions in whole building life-cycle assessments

Building operations, which include the energy from electricity and natural gas, account for about 28% of global greenhouse gas (GHG) emissions. Stakeholders need accurate assessments of building operations in whole building life-cycle assessments (WBLCAs), at both the individual building and the building stock level, to inform mitigation strategy selection, policy development, and progress in tracking of building-sector GHG emission mitigation targets. This review provides an overview of building energy estimation methods (measured, building energy modeling, representative empirical and modeled databases) and electricity emission factors (average versus marginal, regional versus utility, direct combustion versus life-cycle values) for estimating operational GHG emissions in WBLCAs. An investigation of the most commonly used approaches in WBLCAs, especially in the context of emerging considerations including grid decarbonization, non-constant building and energy supply loads, and embodied and operational GHG trade-off decisions, reveals that there is no standard practice for justifying method or dataset selection. While many of the datasets and tools discussed in this study are developed for the United States, the overarching methods for quantifying building energy use and emissions are applicable for global audiences. Based upon a literature survey and the utility of each building energy estimation method and emission factor dataset, we identify recommended approaches for quantifying building operational GHG emissions in WBLCAs under various policy goals, including establishing benchmarks, choosing mitigation strategies, implementing on-site renewable generation, and forecasting emission reductions in the building sector.