by Abigail Schantz
Sangwon Suh, Shivira Tomar, Matthew Leighton, and Joshua Kneifel (2014) analyzed the environmental benefits to be gained from three major building certification systems: LEED, ASHRAE, and IgCC. The final analysis showed that GBCC-compliant buildings reduce environmental impacts in major categories by 15%–25%. But, because LEED permits consumers to selectively choose which measures to adopt rather than maintaining strict baseline requirements, it is possible for a LEED certified building to show no reduction. The estimates also assumed proper use of the buildings, whereas after construction, occupants’ behavior can significantly decrease the reduction potential. The authors concluded that overall, with 40% of US energy consumption stemming from buildings, a 15-25% reduction can have a major impact and, therefore, implementing these certification systems should be seriously considered.
It is currently estimated that 40% of United States energy consumption comes from residential and commercial buildings. Efforts to reduce the environmental effects of this consumption include making changes in materials, building structure, uses of insulation, and more. There are already numerous efforts to do this, as demonstrated by the 44,270 LEED-certified projects in the US as of August 2013. In this article, the authors did not attempt to determine the best system but rather used Green Building Code and Certification (GBCC) as a standard basis for reviewing the three. As a base model, the researchers used the life cycle assessment (LCA) developed by the National Institute of Standards and Technology (NIST) and a model building from the National Renewable Energy Laboratory (NREL). GBCC used both inputs (materials, services, etc.) and outputs (waste, emissions, pollutants, etc.) to quantify and generate life cycle inventories (LCIs) for all three systems, as well as for a baseline building. The baseline building, a 3-story office building, which is consistent with the national average for office buildings, was estimated to emit 9.9 tons of C02-equiv/per square meter. Bills of Materials (BoM), comprehensive inventories of all products needed in construction, were also generated for all four buildings (baseline, and three GBCCs). The three systems all involve similar requirements, with slight variations. LEED is a voluntary program that assigns points to various potential features, allowing consumers to choose any number of options for impact reduction so long as the total number of points meets certification requirements. ASHRAE and IgCC both use minimum requirements that all buildings must include, as well as supplemental options. These two systems can be either offered as voluntary opt-in strategies or adopted by local governments as building requirements. The quantifiable components used in the LCA do not encompass all benefits or faults of the buildings, but this study ignored these variations because they currently cannot be measured. The unmeasured factors include, though are not limited to, indoor pollutants, light pollution, and improvements in occupants’ productivity. The buildings were analyzed at three stages: preoccupancy (construction), occupancy (use), and post-occupancy (end-of-life, demolition). Results were analyzed for twelve categories: global warming; acidification; human health-criteria pollutants; eutrophication; ozone layer depletion; smog formation; ecological toxicity; human health-cancer (HHC), human health-noncancer, primary energy, land use, and water consumption. Due to the large number of assumptions made in order to analyze the data generally, the team conducted an analysis to determine how responsive each result was to slight alterations in the unmeasured variables. The authors noted that a small number of the inputs represent a large share of the LCI while the majority have negligible effects. For example, of the 380 inputs measured, 13 comprise 99% of the HHC impact.
Suh, S., Tomar, S., Leighton, M., Kneifel, J., 2014. Environmental Performance of Green Building Code and Certification Systems. Environmental Science & Technology. DOI:10.1021/es4040792