Builders need guidance on Green Guide
A little knowledge is a dangerous thing, they say, and BRE is warning those in the building industry against using its Green Guide without fully understanding what the tool is for.
This is the fear of the BRE, and the Construction Products Association that helped it draw up the guide.
As sustainable building continues to gain public awareness and climb the political agenda, so the guide has become increasingly popular and more widely used.
A name-check in the Government's Code for Sustainable Homes (CSH) has also helped the guide rise in prominence.
While all this extra publicity for green building, and the guide itself, is welcome, it does raise concerns about its proper use.
Instead of being used to inform decisions alongside BREEAM guidance and the CSH itself, there are concerns it will be used as an at-a-glance, tick-box guide by those who don't fully understand its grading system.
The guide essentially uses two marking systems - one which awards 'eco points' for a product or material's performance and another which ranks them A to E against other categories in their class.
The confusion arises when those planning a green building compare the letter-based grading of goods from different classes, rather than the eco-points.
The gap between A+ and E varies widely depending on the class of product - in some areas, the gap is relatively small while in others there's a huge difference in performance between the best and worst.
According to a statement from BRE the system: "takes the overall impact of the best and the worst results for a particular element and building type, and divides the gap between them into six equal bands, E to A+.
" The other results are then fitted into these bands. This is why there can be uneven distributions of scores, with some elements having most in the A and A+ bands whereas other elements may have a more even spread.
"For some elements, such as separating walls, windows or commercial floor construction, the difference between the best and the worst is relatively small in absolute terms with an E rating having approximately two to three times the impact of an A+ rating and the range being about 0.5 EcoPoints/m².
"In other elements, such as roofing or surfacing for heavily trafficked areas, the range is more than 1.5 EcoPoints/m² and an E can be over four times worse than an A+."
BRE says it would like to see a move towards a system where the scores of each material and product are added up for the whole building, rather like energy performance, adding that this could be done using the EcoPoints system that underlies the Green Guide.