Acoustic glass is the latest in noise reduction technology for box sash windows that brings some quiet back in to a home invaded by the sound of traffic, aircraft, trains or other nuisances.
Constant background noise is not easy to live with and can affect moods as well as sleeping, so any innovation that can shut out sound is bound to make everyone living in the house feel better.
Fitting the glass instead of standard double-glazing when replacing a sash wood window cuts down noise. A single pane reduces sound by around five decibels, while a window with two sets of acoustic glass can double that.
The principle is simple - two sheets of glass are bonded together with a transparent membrane that absorbs sound. They neatly fit in to most frames, including new sash windows - even if they are period.
One important factor to remember is weight - acoustic glass is up to 6.8mm thick and although increasing the thickness will cut out even more noise, the weight also increases to make sliding sash windows difficult to open and close.
The big question is how much noise reduction will including soundproofing glass in a sash wood window give?
The answer depends on how close you live to the nuisance and whether your box sash windows are soundproofed.
Noise reduction measured at 10 - 25 per cent is not unusual. Although that sounds a disappointingly low result, technically most acoustics experts would rate a five decibel drop in noise a noticeable difference, while a 10 per cent drop would rate as a real improvement.
Soundproofing is not the only benefit acoustic glass gives to sliding sash windows.
Security is increased because the windows are more difficult to break; the inside of a room is protected from more UV rays from the sun and the amount of heat that escapes is reduced considerably.
That last feature is important - the independent Energy Trust reckons double glazing can knock £135 a year off energy bills in a home with gas central heating, and as upgrading to stop noise cuts heat loss, that extra cash saving will let the installation quickly pay for itself.
Fitting new replacement box sash windows with acoustic glass really does offer a permanent solution to noise problems, without spoiling the look of period windows, and while saving money through better energy efficiency.