Approved for Heritage Buildings and Grade II Listed Properties

The design of the windows in a heritage building are an important part of the character of the property and must be retained, but single glazed frames are a major source of heat loss, provide little protection against noise and offer minimal resistance to burglary. Using purpose made secondary glazing in listed buildings will improve the buildings environment and make it more attractive to end users by reducing air leakage and heat loss, dramatically improving noise insulation and providing an additional security barrier. Owners of listed buildings and heritage buildings can benefit from advice available in the guides produced by many heritage organisations which recognise that secondary glazing is a practical and acceptable way to improve insulation levels.

Improving Insulation, Reducing Heat Loss and Draughts

Improved thermal performance – by eradicating the draughts and significantly reducing the heat loss from your existing windows your house will be more comfortable and you will enjoy lower energy bills. The technical term to measure the heat loss through a window is called the U value, which is measured as watts per square metre, per degree Kelvin, (W/m2K). Basically, this is expressed as a number – the lower the number, the more energy efficient the window. For example, a standard single glazed window had a U value of around 4.8, a modern uPVC double glazed window is 2.0. Our secondary glazing has been independently tested to show that when fitted to a single glazed window we can achieve a U value of 1.87, making it comparable or better than a new uPVC window.

 Helping to keep the Peace and Quiet

Acoustically – installing secondary glazing will drastically reduce outside noise nuisance such as traffic or aircraft noise, or just a busy town street late at night. Sound levels are measured in decibels (dBA) – the Acoustic Performance table in the Fact Sheets downloads section shows just how effective our secondary glazing is in reducing outside noise levels. The 16mm cavity in most current double glazing units offers good thermal efficiency, but is not acoustically effective. With a spacing of 100mm between the external glazing and our secondary glazing units the reduction in sound levels of 45dBA brings the noise level of a busy street to that of a peaceful sitting room.

Our secondary glazing units are bespoke and manufactured to fit the existing window perfectly. With either horizontal or vertical sliding units, the splits align perfectly with those of the original window, we can also match any colour.

Once it’s installed you’ll hardly notice it’s there!

Making Puddles on your Windowsill a thing of the Past

Elimination of condensation – water streaming down the inside of your windows and puddles on your windowsill will be a thing of the past. Condensation occurs when warm, moist air inside a room meets a cold surface such as the glass in a single glazed window on a cool day. The moisture is caused by every day living like showering, cooking or just breathing! Because with secondary glazing the inside pane of glass will be at the temperature of the room, while the outside pane is at the temperature of the outside air, the possibility of condensation is virtually eliminated.

Security – your house will be much more difficult to break into. By giving a potential burglar an additional layer to break through, one that cannot easily be opened or removed from the outside, you will be reducing the risk of break-ins. If security is a real issue for you, the glass used in the secondary glazing can be laminated, toughened or even made bullet-proof!