This Report gives the results of a BRE study conducted in 2006 to update weightings for a range of environmental issues first established in 1999. An international panel of 10 experts was set up to judge the importance of 13 parameters and their individual responses have been aggregated to create a single set of weightings. The Report also explains how the weightings are applied to BRE's tools for assessing the environmental impact of construction products. The Report: * describes the methodology, * analyses the statistical techniques employed and the statistical robustness of the weightings obtained, and * explains how the weightings contribute to the Environmental Profiles methodology for measuring the environmental performance of construction products. 22 pages.