AluK's 58BD window range is the first of its kind to meet this demanding specification. The 58BD Window suite corresponds to the BRE Global Green Guide online generic specification for windows and achieves a summary rating of A for non-domestic and a �B� rating domestic schemes.

The Green Guide to Specification is a specification tool providing guidance for specifiers, designers and their clients on the relative environmental impacts of over 250 elemental specifications for roofs, walls, floors and fenestration.

The main environmental impact of windows is from the heat loss through them. Attention is drawn to the large number of credits available in BREEAM, the Code for Sustainable Homes and EcoHomes for reducing fabric heat loss and improving operational CO2 emissions compared to the small number available for materials specification.

The guide operates on a rating system with A+ ratings having the lowest overall environmental impact, followed by A, then B, C, D and E; with E being the worst performance overall.

By evaluating the performance of materials and building systems against specific environmental impacts, which have also been ranked on an A+ to E basis, it is possible for the specifier to select specifications on the basis of personal or organisational preferences or priorities, or take decisions based on the performance of a material against a particular environmental impact.