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 RE: BRE Green Guide to Specification as it relates to the draft PVC report
Tom Lent, Healthy Building Network The Building Research Establishment (BRE) has produced "The Green Guide to Specification: an Environmental Profiling System for Building Materials and Components"[1]. Like the PVC Task Group, the authors of the Green Guide chose to base their environmental rankings of building materials based on Life Cycle Assessment studies of environmental impacts. Green Guide ratings are converted into a relative A, B, C ranking system with C representing the most environmental impact. The purpose of the Green Guide is much broader than the Task Group's assessment of PVC, evaluating composite building element specifications, however some useful patterns can be discerned to inform the Task Group's effort. The Green Guide evaluated three building specifications where at least one option in which a large percentage of elements of the assembly is PVC: rainscreen claddings (p. 32), hard floor finishes (p. 49) and windows and glazed curtain walling (p.54). Two other specifications also include PVC elements (Proprietary and demountable partitions, p. 58 and Suspended ceilings, p.60). The PVC component of those assemblies represents a rather small percentage of the whole so those cases are probably not particularly useful for comparison on a PVC/non-PVC basis. In each of the three cases where the proportion of PVC is significant, the "Human toxicity to Air and Water" and "Ecotoxicity" of the PVC element rated a "C" - the worst rating. In two of the three specifications the "Summary Rating" of all factors for the PVC based elements was also a "C". For rainscreen claddings, all five other options were rated better (four "A"s and just one "B"). For windows and glazed curtain walling, only glass block window rates as poorly as a PVC framed window. The other six rate better with two "A"s and four "B"s. Only in one specification did the PVC based element gain a "B" rating(hard floor finishes). This was only because one assembly element type was rated worse (synthetic rubber) and pushed the scale up higher than in any other specification category rated by the Green Guide. All nine other hard floor finish element types studied rated better that the PVC element type with "A"s. These specifications are three of the six highest impact specifications of the 14 areas that the BRE study covered. This study indicates that high PVC content of an assembly is generally associated with the highest impact category in the areas studied. Shifting specification to any of 20 of the 22 non PVC specifications studied would have resulted in an improvement in rating. Only one (glass block) would have resulted in no change and only one (synthetic rubber flooring) would have resulted in a decline in rating. In any scientific study, it is important to review relevant literature and understand what factors may have brought different studies to different conclusions. We trust that as the PVC task group works on its second draft, they will review this study and seek to understand why its conclusions are more definitive than those of the Task Group's initial draft study. [1] Jane Anderson and David Shiers with Mike Sinclair, 2002 by Consignia, Oxford Brookes University and the BRE, published by Blackwell Science Ltd, Oxford |
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