When it comes to specifying windows, the embodied impact has a small overall bearing on the building. The main consideration for specifiers is heat loss through them. Here we take a look at three high-performing alternatives. The Ecocontract range from the Green Building Store is aimed specifically at larger residential and commercial projects in which developers are trying to meet the criteria for BREEAM and the Code for Sustainable Homes. The windows are manufactured entirely from laminated Forest Stewardship Council European redwood, oak or mixed Accoya - a timber product made using a non-toxic wood acetylization process. But it's the U-values that we're most interested in. The double-glazed, 24mm argon-filled unit achieves an overall U-value of 1.4W/m~2k, with a light transmission of 79. While the triple-glazed, 44mm argon-filled unit achieves a U-value of 0.9 W/m~2k with the aid of a warm-edge spacer, and has a light transmittance of 72.
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