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Sash windows can be made energy efficient

Posted by Cathy Debenham on 4 November 2009 at 11:24 am

Traditional timber sash windows are often associated with howling draughts, and are under threat as people replace them with plastic double glazed units. But before you throw yours on the scrapheap, read English Heritage's research which shows that simple repairs and basic improvements can significantly reduce draughts and heat loss. It is even possible to upgrade them to meet building regs targets.

Just by mending cracks and eliminating gaps you can reduce air infiltration by a third. Add some draught proofing and you can get it down by as much as 86%. English Heritage did its studies using a sliding sash window dating from the 1880s which it rescued from a skip.

It seems like stating the obvious, but heat loss can also be reduced by having thick curtains, and closing them when it gets dark. That reduces heat loss by 41%; a roller blind by 38%.

If you want to meet the building regs target of a U value of 2 or less, then it will cost a bit more. Installing good quality secondary glazing can bring the U value down to 1.7 (as can well-fitted, closed shutters). Both together gives a U value of 1.6.

An executive summary or the full report can be downloaded from the English Heritage website.

Photo by Athena

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Comments

1 comments - read them below or add one

Secondary glazing works very well but is aesthetically very poor, one would do better to install a comprehensive draught proofing system into thier original windows. This is cheaper in most cases than thick heavy curtains and given some prefer shutters gives more choice.

If you were to invest in secondary glazing you would do much better to install double glazed sashes to match your originals within the existing frame and then service. Much better value for money.

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