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tel: 07831 194655 sales@supasash.com trade enquiries: mail@supasash.com
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More on u-values
Remember, the lower the u-value, the better the insulation.
It's clear that many manufacturers are, shall we say, stretching their claims over U-values they offer. It's important to distinguish between the value at the centre of the pane (where edge- and frame-losses are minimal) and the whole-frame value. This latter u-value will be a larger figure and therefore worse performance. With a centre-pane u-value of 1.2 or 1.3 it is possible to reach a calculated overall frame value of 1.5 or thereabouts for a tradition boxed sash with slender glazing profiles using 20mm or 24mm sealed units, although this level may not be achieved in practice if there is much in the way of glazing bar (astragal) which tends to increase the thermal losses. With centre pane values of around 1.9, no ultra-slim DGUs using conventional technology are going to get near meeting the current Building Regulations, although for a while (until they fail) they will be a significant improvement over single glazing.
Recent developments in glazing technology mean that U-Values as low as 0.8 can be obtained in a DGU light enough to be used in a sliding sash window. As with most new technology working at the limit, these DGUs are not cheap, although unlike the welded-edge vacuum units, they ARE affordable. Ask for details.
In the mean time, be sure to ask for a calculated value with your Energy Certificate.
Remember, the lower the u-value, the better the insulation.
It's clear that many manufacturers are, shall we say, stretching their claims over U-values they offer. It's important to distinguish between the value at the centre of the pane (where edge- and frame-losses are minimal) and the whole-frame value. This latter u-value will be a larger figure and therefore worse performance. With a centre-pane u-value of 1.2 or 1.3 it is possible to reach a calculated overall frame value of 1.5 or thereabouts for a tradition boxed sash with slender glazing profiles using 20mm or 24mm sealed units, although this level may not be achieved in practice if there is much in the way of glazing bar (astragal) which tends to increase the thermal losses. With centre pane values of around 1.9, no ultra-slim DGUs using conventional technology are going to get near meeting the current Building Regulations, although for a while (until they fail) they will be a significant improvement over single glazing.
Recent developments in glazing technology mean that U-Values as low as 0.8 can be obtained in a DGU light enough to be used in a sliding sash window. As with most new technology working at the limit, these DGUs are not cheap, although unlike the welded-edge vacuum units, they ARE affordable. Ask for details.
In the mean time, be sure to ask for a calculated value with your Energy Certificate.