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On the grand scale of things there isn’t a huge difference between B-rated windows and A-rated windows. Consumer watchdog Which? have calculated an extra 6.5% would be saved on energy bills with A rather than B rated panes. Be aware that A rated windows are slightly more expensive, however.

Are you about to purchase a double glazed unit and wondering how to go about the replacement project? If yes, then you’re at the right place. Firstly, it’s advisable to hire the services of a reliable professional who can guarantee the best results for help especially if you lack proper training and experience in the field. However, we’ve put together this step by step guide to provide you with a detailed information about the double glazed unit replacement process. Let’s get started!

The tools and materials you require for the project includes tape measure, hammers, nail punch, scraper, spacing blocks, non-hardening butyl putty, high-security glazing tape rolls and beading tacks.

• Work out the glass size required. Simply use the tape measure to measure from frame edge to frame edge while also taking note of the thickness.

• When about to order, inform the glass merchant that the measurement provided are frame-tight. This will make him reduce the dimension a little bit, mostly by 5mm for clearance.

• Remove the beading and ensure to support the glass while doing so. If the glass units are fitted in wooden windows, you may need to cut the putty-based compound they’re normally sealed with to remove the glass.

• Lay out the beading in the window’s shape to make for easier refitting later on.

• If you’re working on wooden frames, wipe out all traces of excess installation compound using a scraper and clean the rebate with a soft brush.

• Trial fit the double glazed windows to ensure they’d slide into the frame without being forced.

• Plastic frame windows are usually in between a pair of gaskets, you should replace this with a hight security glazing tape. While for a wooden frame, simply apply strips of flexible non-setting butyl putty or high-security glazing tape on either sides of the glass.

• Install and centralize the glass in the frame.

• Press the nail wooden beading or plastic beading back into place.

Most window installers will be able to provide you with one double glazed window and fit it for you. If you’re replacing one double glazed window in your home, ask them to try and source the same windows that you already have or find one that’s very similar. Externally, you probably won’t be able to notice the difference, but if your existing windows are very old there may be some exterior discolouration and the locks and handles might look slightly different.

If you want one double glazed window so you can fit it yourself, there are lots of online companies that can supply you with one window. However, window fitting is a skilled trade and you might want to consider whether you have the right tools and experience to fit it yourself. Of course, you’ll save money on installation costs, but if something goes wrong, you might end up shelling out to get it fixed anyway.

The other thing to consider is that any replacement windows need to be certified that they meet Building Regulations. If you fit the double glazed window yourself, you’ll need to apply to your local council building control officer to get a certificate that confirms that you fitted the window within the regulations. You’ll have to pay a fee for this, and it will be even more expensive if Building Control say that the window hasn’t been fitted within the regulations and you have to start again.

The alternative is to ask a reputable window installer that is registered with a self-certification scheme, like FENSA, to install the window. That means that they can self-certify that the window meets building regulations once they’ve finished the installation.

Unfortunately, you can’t fix the glass on one side of a double glazed window. That’s because they’re sealed units – once one pane of glass is broken, that will break the seal and its thermal insulation properties will be lost.

The good news is that if your window frame is still looking great, there’s no need to replace that. You can simply replace the glass in the window, which will cost much less. You can look to spend around £250 on a sealed unit, whereas a whole replacement single window may cost up to £600.

When an installer comes to replace the glass in your double glazed window, they will survey the inside and outside of your home around the window, then move any furniture by the window so they’ve got access. They should then pop a dust sheet down to stop any debris from getting on your floor.

Then, the installer will carefully remove the beads from the frame. They will then lift the glass out of the frame and put it somewhere safe before cleaning out all of the dust and any debris that has found its way into the frame. Using spacers at the bottom of the frame, the installer will make sure that the sealed unit is square in the frame to get a good fit. Once they’re happy, they will replace the beading and make sure it looks perfect before cleaning up their tools.

You could have a go at replacing the glass on a double glazed window yourself, but it’s not recommended. Leave it to the professionals who will know exactly what to do and will be able to do it quickly and safely.

Removing a double glazed window can be quite labour intensive. If you decide to try it yourself, make sure you give yourself plenty of time, and wear gloves and goggles.

Begin by unscrewing all opening windows at the hinges and removing them. Then take away the beading and putty around any fixed panes and take them out too.

Once you’ve removed all the glass, use a saw to put angled cuts in the frame, and a bar and hammer to remove it in sections. You should remove the sill if you’re going to replace that too.

Finally, cut through any screws holding the frame into place with a hacksaw.

Did you just purchase a double glazed window and confused about how to have it installed? Fitting the window yourself can be quite easy with the help of this step by step guide. However, if you lack proper training or experience, we’d recommend you reach out to a trustworthy professional who can guarantee the best results for help. That said, now let’s take a look at the process.

• Remove the old windows by detaching the old beading and glass window safely. Then make some interval cuts using a hand saw before using a crowbar to pry it out.

• Cut the external double glazed window seal. Once done, take a measurement of the window area’s width once empty. Then transfer the measurement to the window sil to face outside and cut using a handsaw.

• Seal the window sil. Add a bead of clear silicone along both inside lip as well as the centre to seal the sil.

• Screw the double glazed window to the sil. Position the window on the top of the lipped section that was siliconed. Then pre-drill them together and screw in three places. You should make sure the screws do not go totally to the sil’s bottom.

• Install the double glazed window. After successfully screwing the double glazed window to the sil, you can now fit in the double glazing. Make use of packers to make sure it’s even in the slot.

• Screw the uPVC window to the wall. If you’re happy and satisfied with the position of the window, you can then pre-drill through the frame of the window and the brick wall. Once done, simply screw it in place using masonry screws or Spax screw as they do not require crawl plugs in bricks.

• Seal around the window. To do this, simply fill any gaps with expanding foam, wipe out the excess and seal with silicone.

By replacing the single glazed windows in your home you stand to make savings of around £170 each year. It’s not just the financial gain that makes double glazing attractive though and you can also save up to 680kg of carbon emissions annually. Over 20 years this is a saving of around £3,400 and 13,600kg of CO2.

• 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.