There are various things to consider when choosing the type of glass for your double glazed sash windows – particularly around the final look and style of the window, as well as the thermal and acoustic insulation performance that the glass, and window, is able to provide for your home.
Double glazed sash windows on period properties
If the property is listed or conservation, the sash windows should be replaced with either exact-match sash windows which replicate the design of the originals, or if the window frames are in good condition, new replica sashes fitted to the existing frames to preserve more of the original architecture. In both of these situations, the sashes can be double glazed in such a way as to give the appearance of elegant, slim single glazing.
This is done by: –
- Using slimline double glazed units, which look just like single glazing. Although these double glazed units are thinner than regular double glazing, their insulation performance can be the same or better than regular double glazing as they are filled with extra dense gas such as Krypton or Xenon, which is more thermally efficient than the gas used in regular double glazing (Argon or air).
- Using ‘restoration glass’ on the outer pane of the double glazed units. Restoration glass is made to replicate the uneven surface of the original period Crown glass and has a similar uneven reflection.
- If the windows have glazing bars, using the traditional method of fitting smaller individual double glazed units joined together with solid glazing bars rather than ‘applied’ glazing bars, which are stuck on to the glass of
a larger unit, to give the appearance of individual units. This traditional
method gives the authentic variable reflections which aren’t apparent
when one larger unit is used with applied glazing bars.
If you want to retain the original window in its entirety, then the only other option is secondary glazing – which is an additional layer of glazing that sits behind the original window inside a framework of its own. The downside of this is that it can ruin the aesthetic of the room, and can create a deep double reflection, as well as making ventilation and escape in case of fire more difficult.
Thermal and acoustic insulation
Whether you’re in a period, listed or even new-build property, there are various options you can choose to ensure your double glazed sash windows have the optimum thermal and acoustic efficiency – to ensure your home is kept warm and free from noise pollution. These include:
- Using Softcoat ‘Low E’ glass on the inner pane of glass, which is more thermally efficient than traditional hardcoat glass, and also reduces the amount of UV rays that come in to your home, to reduce the amount of discolouration to your furniture.
- Using acoustic or laminated security glass on the outer pane of glass. This glass is thicker than regular glass and has a soft plastic ‘interlayer’ which absorbs sound waves and reduces the amount of noise that can pass through it.
- At Timbawood, we also use ‘warm edge’ spacer bars to improve thermal efficiency in our double glazed sash windows. The spacer bar sits between the two panes of glass in double glazing to hold them apart – and is often made of aluminium, which is highly conductive and therefore loses a lot of heat. Warm edge spacer bars, by contrast, are made of a pre-desiccated, structural foam, and can increase the internal edge temperature of the glass by up to 65% compared to aluminium spacers.
If you would like to find out more about the options available for double glazing your sash windows, then please get in touch to speak to one of our window specialists, or to arrange a free quote or survey.