Double and Triple Glazing Information


It’s difficult to imagine that less than forty years ago many of us had single pane windows and had to suffer massive heat loss during the winter months. Fortunately, most of us nowadays have double or even triple glazing that not only increases our energy efficiency and keeps us warm, but also saves us plenty of money.

As a long term investment with a substantial initial outlay, double glazing is one of the first things home owners opt for in addition to better wall and loft insulation. Without these, introducing more economical heating systems and more energy efficient measures just don’t work. You might say that double and triple glazing are one of the foundations on which the rest of our eco-friendly strategies rest.

History of Double Glazing

You might be surprised that one of the first instances of double glazing being used was in Scotland. In the cold winter months those canny scots used to putty an extra layer of glass onto their windows. The double glazed windows that we know today were first formally invented in the 1930s in America by one C D Haven. The trouble was that these windows were initially very expensive to produce and so there wasn’t a rush for everyone in the country to get their windows fixed up.

Large scale manufacturing didn’t begin in earnest until after the Second World War and this was led by an Ohio based company who called their double glazed windows Thermopanes. It wasn’t really until the late 70s and early 80s that double glazing began to take on in the UK and became a standard in new builds by 1985.

Companies like Thermotech in Canada began making triple glazed windows and these have become more popular as the green revolution has taken hold. They are less common in the UK but are gaining in popularity as we seek better ways to insulate our homes.

How Double and Triple Glazing Works

For double glazing, two panes of glass are combined with a layer of air in between which acts as an insulator. Glass is actually quite a good conductor of heat, which is why there is so much loss when only single panes are used. Not only does a double glazed window act as a barrier to heat loss but it also keeps the noise level down as well. One of the important part of the window is the seal – if this is not complete then air can get into the gap and cause condensation.

Triple glazing utilises three layers of glass for extra insulation and is more popular in colder regions such as Canada and Scandinavia. For both double and triple glazing, the glass can be coated with a low emissivity metallic layer that reflects more heat back into the room where the window is situated. All windows produced in the UK must comply with European Union legislation which means they should be marked with the CE logo which ensures they are compliant. 

The energy efficiency of a particular window design is determined by the R Value. A single pane window may have an R value of around 0.15 whilst a uPVC window will have a level of 0.50 or more.

The Benefits of Double Glazing

  • Double or triple glazing greatly reduces the amount of heat lost through your windows.
  • It’s not only keeping you warm in winter that makes double glazing important. It also keeps your home cooler in hot summers.
  • Double glazing greatly reduces the amount of noise from outside, particularly important if you live near a busy road.
  • Double glazed windows also reduce condensation by keeping the temperature in your room relatively constant.
  • They are more difficult to break into with the double layer of strengthened glass and the addition of more secure locks.
  • They increase the resale value of your house – people are less likely to make a good offer if they know they have to spend money and time on installing double glazing.

Energy Efficiency and Double and Triple Glazing

There are a variety of choices for double glazing and it pays to shop around to find the one suited to your home. Energy savings are measured over A, B and C ratings, with A being the most efficient. This will all depend on how your windows are made up. Windows with such ratings will also have a U value that shows how much heat they let through – a lower U value suggests greater energy efficiency than a high one. 

The glass is important and if you want the best then you need something with low emissivity added – this is a coating of metal oxide that allows light to come in but then stops the heat escaping to the outside. The gas that is used between the glass panes can also vary. Heavy gases such as argon are less conductive and provide better insulation but are more expensive. The spacers which keep the panes separated contribute to efficiency and non-metallic ones are better than something like aluminium.

The material your window frames can be uPVC, wood, aluminium or steel or composite. There are pros and cons for each. For instance, uPVC lasts a lot longer and is recyclable whilst wood has a lower environmental impact but needs to be well maintained over the years.

Cost of Double Glazing

More than any other home installation, getting the right price for your double glazing means doing a fair amount of research and getting those quotes in. Prices can vary considerably across types of window and from supplier to supplier. They can also vary depending on whether you use a national company or a local one. For a 3 bedroom semi you should be expecting to pay between £3,000 and £5,000 and 4 bedroom detached might cost as much as £6,500.

Paying for Double and Triple Glazing

A number of the national companies will offer financing for the installation of double glazing but it’s a good idea to look around for alternatives such as using your own savings, taking out a bank loan or increasing your mortgage to find the best rate. The government has now closed down the Green Deal which was a loan scheme for homes that wanted to improve their energy efficiency and there are no plans to replace it with anything else (they cite low uptake as the prime reason for closing the scheme).

Combining Double Glazing with Other Insulation

Once you have had your double glazing installed you can expect to make at least £100 savings on your fuel bills over a year. It does not work in isolation though. Other measures such as proper lagging in the loft and wall insulation can also make a big difference.

Double Glazing Sales Tactics

The double glazing industry has suffered over the years with complaints about aggressive sales tactics and shoddy workmanship. Sales persons have often been accused of upping the price of installation when they first visit a property and then reducing it to make things seem like they are offering you a ‘good deal’. That could mean that your price drops by as much as 70% but all they are actually doing is guiding you to the price they want you to pay. Other less reputable companies will ask for a large deposit up front so that they can hang onto if it problems occur during the installation.

Homeowners should also be aware that the majority of double and triple glazed window installations are made to measure, in other words, fit your home properly. This means you rights are slightly different than if you purchased a standard size installation. You can find out more about your rights here.

Double and Triple Glazing Manufacturers and Suppliers

It’s a problem with the industry that there is such variation with installation costs and our advice is to follow some simple rules:

  • First of all, do your research so that you know what you are talking about. There are plenty of online sources available that can give you good advice and you should investigate these thoroughly
  • Whilst choosing a national installer might seem the best bet, check out local, smaller firms who may offer a better deal. It’s often the case that less well-known local outfits are more concerned about their reputation and will go that little further to make sure you are happy.
  • Always ask to see evidence of recent work and go and talk with the homeowners to see what their experience was. It’s one of the easiest ways to find out how your prospective company operates and whether they provide a good service.
  • Check how to contact the company – if they just have a mobile number and not a landline, think seriously about employing them.
  • Check for guarantees of work and after sales service that make the difference. Most reputable companies will offer a 10 year warranty on their work, though it is also a good idea to check what this actually covers.
  • Get at least four or five different quotes and don’t be side tracked by limited time offers and pressure sales techniques. Again, good companies will be willing to let you think about their offer and will not press you into making a decision.
  • Check if they are a member of a scheme such as Fensa, BM Trada or Certass which ensures that they have undertaken to follow a certain set of rules and be more likely to provide a competent service.
  • Above all don’t be in a rush to make a decision – it could cost you in the long run. Weigh up the different quotes and don’t be afraid to pick up the phone and ask additional questions if you need to.

You can search for manufacturers and suppliers in your local area through our dedicated data base.

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