This Information Paper summarises 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 Information Paper also explains how the weightings are applied to BRE's tools for assessing the environmental impact of construction products. This Information Paper provides: * a description of the methodology, * the weighting results, * an explanation of how these weightings are used. 8 pages.