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To install one small double glazed window, it will take anywhere between two hours and half a day. It will depend on whether one installer is fitting your window or two. And if you’re doing it yourself and don’t have any professional experience, it will take even longer.

When the window fitters arrive, they will make sure they’ve got safe access to the window and move any heavy furniture if they need to. Any good installer will lay down a dust sheet, but it’s a good idea to check that they’ve got one laid down before they start.

The first step any window installer will take is to double check the measurements of the new frame against your existing one. Hopefully it should match up, so then they’ll take the old window out. Then, they’ll insert the new frame into the aperture and bolt it into the concrete. They'll check it with a spirit level to ensure it’s even before moving onto the glass sealed unit.

The installer will place the glass into the aperture, then fit the beads to secure the glass in the frame. They’ll then use silicone and trim on the inside and outside to ensure the window looks perfect. You won’t be able to see where they’ve used sealants or trims because they’ll colour match them so it’s not noticeable. Then, they’ll tidy up all of their tools and the working area and let you know what needs to be done in terms of proving that the window meets building regulations. Most good installers are registered with a self-certification scheme, so will be able to issue a certification once the work is complete.

How long your aluminium windows will last depends on their quality. They should last 20 -30 years at least, but have been known to stay in good condition for up to 45 years. This is considerably longer than uPVC and wooden double glazing.

Double glazed windows are better than single glazed generally because they are more energy efficient. The clue’s in the name – double glazed windows have two panes of glass while single glazed windows only have one. In double glazed windows, there is a space between the two glass panes. This space is filled with inert gas or a tight vacuum, which helps to provide an extra level of insulation. That means that heat won’t escape your home easily, nor will it creep in, so you can keep your home at a more comfortable temperature.

The extra pane of glass also helps to increase your home’s security. Single glazing is pretty easy to smash through, whereas it will take much more effort to smash double glazing and will create more noise, so burglars might be put off.

Another reason why double glazed windows are better than single glazed ones is that they help to reduce noise. Of course, if you live by a busy road you’ll still hear some traffic noise, but it can be significantly reduced buy double glazing. In the same way that the inert gas in the middle of the two panes keeps heat in and the cold out, it also helps keep noise out.

With double glazing, you’ll also notice much less condensation. With single glazing, it’s common to see condensation on the inside of the windows, especially when the heating is on. This is because the outside of the window is cold, but the inside is warm. With double glazing, the insulation between the two panes stops there being such a difference in temperature between the inside and outside of the window.

• Thick gloves
• A hammer
• A broom
• A vacuum cleaner
• Thick-soled shoes
• Safety goggles

1. Put your gloves on and use the hammer to remove the rest of the glass. Make sure you hit the glass away from you.
2. Using the broom, sweep away any loose glass from the area, making sure you do both inside and outside.
3. Use your vacuum cleaner to remove any small pieces of glass that you might not have been able to see.

Accidents happen, and sometimes windows get broken. And that will lead to you wanting to replace just the glass in your window, rather than the whole frame. Also, as windows get older they can mist up on the inside, which means that the unit has ‘blown’ - so you’ll also need to replace the glass. But how much is it to replace the glass in a window? Luckily, if the frame of your window is in good condition, there’s no need to replace it, and this will reduce the cost. For an installer to fit a new pane of glass in a single glazed window, the average cost is £100, while a replacement double glazed sealed unit will cost an average of £110. Of course, as this is an average, if your window is very large you may spend more, and if your window is very small the price may be less. That's why it’s important to get a range of quotes so you can compare costs and get the best price. If you’re good at DIY, you may feel confident enough to have a go at replacing the glass in your window yourself. In that case, the cost of sealed unit and any other materials you need will cost an average of £57. It’s a significant saving, and if you think you can do it, then give it a try. However, if you’re in any way unsure, it’s best to leave it to the professionals. A window installer will be able to replace the glass in your window in less than an hour. Even though it costs more for a professional to do it, if you get it wrong and have to start over it will cost you more in the long run.

If a window is double glazed, it has two panes of glass that have a space between them containing argon gas. The gas works as an insulator, keeping heat inside the house as well as reducing noise. It also strengthens the window.

• 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

As well as keeping your home warmer and reducing noise, you’ll notice a saving on your energy bills from installing double glazing. If you install A++ rated windows in your home after having single glazing, you could save up to £120 year on your energy bills. The Energy Saving Trust has more information.