How does double glazing reduce energy loss?

Before the 1930s there was only single glazing, but by the 1950s it was quite popular in the United States to have double glazing. In 2013 over 80% of homes in the UK are now at least partially double glazed. Some even have triple glazing.

But why? Why would you want double glazing or triple glazing?

Pure and simple… you want to save energy, and regulate the temperature in your home.

Double glazed simply means that two panes of glass sit in the window frame rather than one. Factory units are sealed together, so you fit them as one unit. In some cases, people retain their original window and fit secondary glazing behind this original window. Sealed units tend to work better, but the principals involved are the same.

The layers of glass have an air gap between them. Contrary to popular belief, in sealed units the air inbetween is at a low pressure, NOT a vacuum. Although having a vacuum would be ideal (as we’ll learn) it would put too much strain on the glass. In sealed units the air is dried too, to prevent the glass misting up inside the unit. Secondary glazing is simply another pane of glass, so it’s usually designed to open easily to remove condensation.

So how does trapping air between two panes of glass reduce energy loss?

Air is a great insulator, especially if it can’t circulate properly. So, the gap is made deliberately small so that the air can’t move around. Removing some of the air to create a partial vacuum also helps. Less air means less conduction of heat out of the room. So, double glazing doesn’t stop heat loss, but it does slow it down quite a lot, which means your radiators can be on a lower setting, which in turn saves money on your heating bills.

Energy saving isn’t the only reason to install double glazing – there are other benefits;

• Most double glazing is fitted in PVCu frames – no more painting!

• Lower noise – that extra layer of glass and low pressure air reduces the noise coming into the room

• Newer windows are generally more secure with beefed up locking mechanisms

• Having your home fully double glazed can increase it’s value and reduce insurance quotes


If you’re considering double glazing for the first time, or you’d like to replace your tired old units, give us a call and we’ll give you some sound advice and great prices…