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Published on: July 19th, 2011
In the ongoing search for carbon neutrality and environmental sustainability; it is now required by law that your window and door manufacturer shows you calculated U-values on your new units. Building regulations also state that the final U-value for any new unit must not exceed 1.6 w/m2K; except is certain (typically historic) housing authorities. So what is a U-value?
A U-value is the rate of heat loss through a material. The lower the U-Value, the less heat will be lost and the more efficient (and money saving) the unit will be.
This value is always measured from the least efficient point, the centre of the pane.
– Single glazed window – 5.6 w/m2K.
– Double glazed window, with standard air cavity – 2.8 w/m2K.
– Double glazed window, with argon-filled cavity – 2.6 w/m2K.
– Double glazed window, (low E glass) with standard air cavity – 1.8 w/m2K.
– Double glazed window, (low E glass) with argon-filled cavity – 1.5 w/m2K.
<3>Beware of Cheap Alternatives:
The British Woodworking Federation (BWF) have issued this statement:
“We hear that many window manufacturers are still not meeting their obligation to demonstrate the thermal performance of their windows and external door-sets and may not be achieving the necessary levels.”
They continued with this warning to consumers; “This is seen as a competitive advantage as poorer thermal performance can mean lower costs but a customer would be accepting work which did not comply with the Building Regulations and a manufacturer would be supplying a product which was not fit for purpose.”
Our quotes accurately detail the U-values of each individual unit. We only use double glazing with low-e glass, argon-filled cavity and warm-edge spacer bars; except where restricted by local authority and housing associations. Our standard unit significantly out-performs the government regulations, with a glazing unit centre-pane value of approximately 1.1w/m2K.
If you have any questions regarding U-values, please post comments below this article, as your thoughts (and our responses) may be of interest to other readers.