- Council for Aluminium in Building (CAB) -

'What's in 'A' Rating'

With the expansion of rating systems in our sector there is a concern that architects, specifiers, contractors and industry representatives are becoming confused and do not necessarily understand what it is they are specifying.

Right now we have three schemes that contain references to ‘A’ ratings and which form part of most tender specifications. They are:

British Fenestration Rating Council (BFRC), Window Energy Rating (WER) scheme with Bands A to E, details can be found at www.bfrc.org

BRE Green Guide (GG) to specification, the environmental profiling system for building materials and components with Bands A+ to E, details can be found at www.thegreenguide.org.uk

BRE Environmental Assessment Method (BREEAM), range of products that use GG ratings as part of their building credits system, details can be found at www.breeam.org/index.jsp

The BFRC WER scheme is not related to the GG or BREEAM. WER’s are a way of measuring the thermal performance of a window assembly using its thermal transmittance (‘U’ value), its solar gain (‘g’ factor) and its air permeability. WER’s are listed in the ADL1B and ADL2B Approved Documents for Part ‘L’ Conservation of Fuel and Power as one means of demonstrating compliance for replacement windows.

The Green Guide, Launched in the 1990s, is based on life cycle analysis (LCA) criteria and uses a weighting methodology to allow direct comparison of the environmental performances of ranges of building materials and products. These comparisons are published as a series of tables and accompanying text. Their chosen LCA methodology does not favour metals, particularly aluminium, with its bias towards recycled content rather than recyclability. However, it is important to understand that the GG is limited in its effectiveness as a means of selecting either materials or products. For further information visit the CAB web site ( www.c-a-b.org.uk ) and look under ‘Information’ for the ‘Misunderstanding the Green Guide’ article and other relevant documents.

BREEAM is another BRE product that has been in existence for several years and is a method of assessing the environmental performance of a building using a scoring system. Points can be gained in many ways but for materials and products BREEAM uses GG ratings. For windows it only awards points for GG ‘A’ or ‘A+’ ratings but does not disallow the use of lower rated products. The contribution of an ‘A+’ rated window to the overall building score is 1%, and to achieve a BREEAM ‘Very Good’ classification at total of 55% is needed, which highlights that the window contribution is minor to minimalImportantly for our industry, aluminium windows can achieve BRFC band ‘A’ rating and some aluminium window systems for commercial use can achieve a GG ‘A’ rating.

There has never been a better time to specify aluminium - the Council for Aluminium in Building is here to help specifiers and fabricators utilise the best that aluminium can offer.

News title: -    'What's in 'A' Rating'
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