Replacement Glass (Glazing) in Londonderry

You can only repair blown double glazed windows in the sense that you can replace the sealed unit (the glass part of the window) instead of having to replace the entire window.

When a double glazed window is blown, it means that the seal around the window has failed and is now letting air in and out. Often the first sign that the sealed unit has blown is condensation on the inside of the window, which is annoying since there’s no way to get rid of it! When your sealed unit has blown, you’ll be losing heat out of the window, meaning you could be spending more on your energy bills.

As a temporary fix, you could see if you can buy a misting repair kit online, but the condensation will eventually occur again as the air gets in. The best thing to do is ask a window installer or glazier to replace the sealed unit for you.

It's simple to replace the glass in a window – the specialist will remove the beading around the window, remove the blown glass from your window frame and set it to one side. They will then clean up around the frame before adding spacers in, then fitting the new sealed unit into the frame. They’ll make sure it’s a snug fit before replacing the beading back around the window to secure it.

There's no reason to put off repairing a blown double glazed window since the cost is generally much less than replacing the entire thing. A sealed unit with installation costs an average of £100, whereas a completely new window will cost around £400. You’ll soon notice that it’s less draughty and will be able see out of your window once you’ve had the blown glass replaced.

• The glass has smashed from an impact such as a stone hitting it from a lawnmower
• You have been broken into and suspects used the window to gain entry
• The glass has blown (lost its airtightness) from constant water build-up around the seals, which is common in bathrooms
• Extreme weather or pressure changes have caused a crack

1. Including the beading (the plastic and rubber seals around the windows that can be removed), measure the width of the window frame.
2. Do the same for the height of the window, making sure you include the beading.
3. Then, take 10mm off each measurement, and you have the approximate size of your glass.

Whether you need toughened glass in your windows depends on where the windows are in your home or business. Toughened glass is sometimes referred to as tempered or safety glass, and it just means it’s stronger than the standard glass that’s usually offered with double glazed windows. So how do you know if you need it?

Toughened glass is useful in areas of your home where you might come into contact with the windows if you were to trip and fall. If you put your hands out to steady yourself on standard glass the chances are it would break into large sharp pieces with jagged edges. Of course, this means that you could seriously cut yourself if this were to happen. With toughened glass, the structure of the glass is changed so that if it breaks it shatters into lots of tiny pieces, minimising the risk to you if you were to fall on it.

You might want to use toughened glass in patio doors, low windows or frames next to doors. It just means that you will be safer if the unlikely happens and you or a family member falls through the glass. There are certain requirements through Building Regulations with windows at a certain level, but any reputable window installer should be able to go through these with you if you need to replace your windows with toughened glass. The regulations will only apply to new windows – there's no need to switch your windows to toughened glass early, but when you do come to replace them you’ll need to make sure they meet the standard.

• Impact from a stone or other object smashing the glass in a ‘bullseye’ effect
• The result of a break-in
• Extreme weather or changes in pressure causing a crack
• The sealed unit being ‘blown’, meaning that it’s no longer energy efficient due to air leaking out