The development of green building rating systems (GBRS) and sustainability metrics for buildings, including building products, is reviewed from a North American perspective. The Leadership in Energy and Environmental Design (LEED) system and the Living Building Challenge (LBC) are highlighted as primary examples of different levels of GBRS. Life cycle assessment (LCA) is introduced as a preferred method of quantifying sustainability, and its integration into current GBRS is examined a prominent building example. Two example applications of LCA to building products associated with GBRS - carpet and roof membranes - are provided. In the first example, conventional carpet was compared with carpet meeting the standards of the LBC's materials exclusion criteria (Red List, via the Declare product labeling system). In the second example, LCA was applied to both the manufacture and use phases of roof membrane alternatives for a building retrofit project, one of which would have aided in achieving LEED certification. The Declare-listed products did not perform better in every LCA impact category, and the GBRS-preferred roof system performed more poorly in all LCA impact categories, while suggesting the need for additional LCA categories. Both examples help to illustrate the complexity and tradeoffs encountered while integrating the quantitative perspective of LCA and the qualitative perspective of GBRS.
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