Using the Ratings
A user looking for a straightforward answer to which specifications within an element group have the lowest environmental impact, can review the Summary Ratings for the element group. The summary Rating takes account of the performance of the specification for each of the environmental impacts, and the fact that some impacts are assigned more importance than others. Those with A+ ratings will have the lowest overall environmental impact, followed by A, then B, C, D and E; with E being the worst performance overall.
Alternatively, users may compare the different specifications for a particular impact and can therefore effectively choose their own weighting.
When reviewing ratings, it is important to remember:
1. The A+ to E ratings are only relevant within a specific element group. An A+ rating in one group is not equivalent to an A+ rating in another group. Hence, if a user were interested in using cork as flooring, it would not be valid to try and assume the ratings for cork floor tiles would be the same as those given for corkboard in the Insulation materials section.
2. The A+ to E Summary Ratings for some elements span a much broader range of values than for other element groups. Hence, in some cases, e.g. Insulation, the difference between an A+ rated and an E rated specification may be relatively small, whereas for other elements the difference may be substantial.
Similarly, for impact ratings, the intensity of the impact and range can differ significantly. For example, for one impact category, the range may be small and close to zero, for another, small but all with higher impact, and for another, large, starting at zero.
3. The number of A+ to E ratings are not equal for each environmental impact or element. This arises because the spread of results for a range of specifications is rarely evenly distributed within the A+ to E rating sub-ranges.
4. For different environmental issues, the ratings simply indicate where each specification lies within the range of values found for each group.
5. Most buildings will last much longer than the assumed 60 year study period and hence the value of low maintenance and design for extended longevity are potentially under-estimated in the ratings. In the typical replacement column in each table a figure of 60+ years is used to identify those specifications and component that have service lives greater than 60 years.
6. The ratings are assigned at the time of writing using the best of known available information. It is recognised that our knowledge of these issues is still evolving and the ratings will continue to be updated.