Double glazing is used in every new home that's built today. It's only really been popular in the UK since the 1970s, but homeowners have been reaping the rewards ever since. 

As such, if you have a home that was built 30 or 40 years ago, then there's every chance it wasn't constructed with double glazing. This can be a bit of an issue, particularly when it comes to energy efficiency and overall home comfort. 

So, if you're looking to learn more about double glazing and how it works, then we've put together an extensive guide to double glazing. Here, we will explore everything there is to know about these products and what they can do for your home. 

An Introduction To Double Glazing

It's not uncommon for the gap to be filled with a gas like Argon

Double glazing refers to when a window is fitted with two panes of glass. Between each pane, there is a gap in the middle. This gap varies in size depending on the construction, but it's typically no wider than 16mm and no narrower than 12mm. 

Now, here's where things get a little bit complicated. If you just installed two panes with a gap between them, then they would eventually close the gap. As time goes on, the gap would slowly decrease as the panes moved due to structural changes. 

To prevent this, all double glazing includes something called a profile. This is commonly referred to as a spacer bar, and it is basically a hollow frame that sits between each pane of glass.

With this in place, the two panes can't move towards each other, and the gap stays the same forever. Things aren't just left like that, this gap gets filled with air. However, it's not uncommon for the gap to be filled with a gas like Argon instead. This is because it helps improve the insulation of the window. If you're wondering why this gas isn't automatically used all the time, it's because it's more expensive. 

Summary & Key Terms

To summarise this introduction to double glazing; it's where you have two panes of glass with a hollow frame between them, creating an airtight space filled with gas or air. 

Some of the key terms you may want to remember are: 

  • Spacer bar/profile: the hollow frame used to separate the two window panes

  • Window panes: glass sheets that sit inside the window frame

  • Window frame: the structure outside the panes (we'll talk more about this in just a second)

How Does Double Glazing Work?

With double glazing, the window is instantly thicker because of two panes, but there's also the all-important gap between them

Double glazing serves three main purposes: 

  • It functions as a standard window and allows light into your home

  • It helps to insulate your home by stopping heat from escaping

  • It provides soundproofing for your home

This is where double glazing differs from a single glazed window. When a window only has single glazing, it doesn't offer very good insulation. The glass pane is relatively thin as its only job is to let light in while ensuring other things can't get inside your home. 

With double glazing, the window is instantly thicker because of two panes, but there's also the all-important gap between them. This gap is what acts as the primary source of insulation. Whenever heat moves from a warm space to a cold one, something called convection occurs. For this to happen, there needs to be an excellent heat conductor. 

As it happens, the air in this gap is a poor heat conductor because it can't move anywhere or circulate. Therefore, it basically traps heat inside your home. If it was a good conductor, then heat could easily transfer from in to out. Also, Argon gas is even worse at conducting heat, which is why it's a better insulator. 

Some people wonder why double glazing isn't just an extra thick pane of glass, and this is why. There needs to be an air gap for insulation! 

When it comes to the soundproofing qualities, this is thanks to the multiple layers. Sound has to travel through the first pane of glass, the air gap, then the second pane. As such, it's naturally muffled and you don't hear things as loudly from outside. 

Diagram of how double glazing worksDiagram of how double glazing works

How double glazing works

What Types Of Double Glazing Windows Are There?

Timber windows aren't as energy efficient or durable, but they are a more eco-friendly option

You can get lots of different types of double glazing windows. They come in a variety of styles and can be made out of different materials. 

Double Glazing Window Frame Materials

Traditionally, most double glazing windows are made with uPVC frames. You sometimes see this referred to as just 'PVC,' but they're both the same. It's a building material that was introduced to replace classic wooden window frames when double glazing started to be built in new homes. 

It's relatively low-cost and requires very little maintenance. uPVC also has the benefit of being incredibly durable and energy efficient - making it the perfect partner for double glazing.

Aside from uPVC, the other two types of materials used are: 

  • Wood (timber)

  • Aluminium

Timber windows aren't as energy efficient or durable, but they are a more eco-friendly option. Also, they provide a unique look that might go well with country homes or more traditional houses. However, there's a reason uPVC was introduced; timber windows require far more maintenance, cost more to install, and don't last as long.

Aluminium is very strong and long-lasting - as well as requiring almost zero maintenance. Perhaps the best thing about this type is that it's so versatile. You can have so many different colour choices, and it goes really well with contemporary homes. The downside is that it is considerably more expensive, which is why uPVC remains the most popular choice. 

Double Glazing Window Styles

When you're looking to buy double glazing windows, you will come across a plethora of styles. More often than not, there are five main styles available: 

  • Casement

  • Sash

  • Bay

  • Tilt & Turn

  • Dual Turn

Casement

This style is trendy and involves the double glazing windows being attached via hinges to the frame. The hinge allows the window to open inwards into your home. Think of them as working in the same way as a traditional door. Casement windows can stay in place when they're opened so you can allow lots of air into your home. 

Sash

The best way to envisage a sash window is to imagine a classic guillotine that was used to chop off people's heads in the old days. The windows work with the same sliding motion up and down. They slide up to be opened, then down to be closed. Usually, there are two double glazing panes - one at the top and one at the bottom. In traditional sash windows, the bottom one is the only one that moves. 

But, you can get dual ones where both panes can be slid down and up to create a more versatile window. 

Bay

Bay windows add some extra space to your home by protruding outwards in a curved fashion. You almost get a crescent shape that's filled with four or more windows. They tend to be quite large to allow lots of natural light in, and the ones on each end can be opened. Typically, the opening mechanism is in the casement style. 

Tilt & Turn

Next, we have the tilt & turn style. Here, the windows have multiple attachments that let them open in different ways. They can tilt inwards with the bottom of the window staying in place. Sometimes, you can alter how far they tilt, other times it only comes out to a specific angle then gets locked in place. 

Then, you can also open them by turning the windows inwards as well. Here, they open similar to the casement style, but you can sometimes alter if they open from the left or right - it depends on the handle placement.

Dual Turn

These are similar to tilt & turn. But feature two panes on top of one another, both with tilting and turning functions. 

We recommend that you consider all the options before installing your double glazing windows. There's no definitive winner out of the styles, but uPVC is definitely the most popular material to use. The double glazing costs vary depending on the type and style of your windows, and we'll dive deeper into the figures later on. 

Double Glazing Energy Ratings

While we discuss the different types of double glazing windows, it makes sense to talk about the energy ratings as well. 

These windows are given a rating based on how energy efficient they are. This works the same as household appliances; the more efficient the window is, the better the rating. As a general rule, the better the score, the more expensive the window is as well. 

Energy ratings for double glazing windows are as follows: 

A++
A+
A
B
C
D
E
F
G

In the UK, current regulations state that all new windows have to come with at least a C rating. The higher up the scale you go, the more money you tend to save on your annual energy bills. 

Alongside this, you have to pay attention to the U-Value as well. This is a number that shows you how well heat passes through a surface. Ideally, you want double glazing with a high U-Value as this means it's excellent at trapping heat and stopping it from escaping. 

It's suggested that you look at both the energy rating and U-Value if you want to get double glazing that's genuinely energy efficient and insulates your home. 

A cross section of double glazed window unitA cross section of double glazed window unitA cross section of double glazed window unitA cross section of double glazed window unit

You can see all the different elements that make up a double glazed unit

Why Have Double Glazing?

People who live near busy roads or on noisy streets need double glazing for the soundproofing abilities it can boast

You might question why you need to have double glazing in your home. Well, it's not technically a necessity, but it is vital if you want to improve energy efficiency. Effectively, you have a long-term form of insulation around your home, which helps you cut down on your energy bills. 

Furthermore, double glazing is a must if you live somewhere with a lot of outside noises. People who live near busy roads or on noisy streets need double glazing for the soundproofing abilities it can boast. 

When you're constantly bombarded with the sounds of traffic or loud people on the streets, then it impacts your wellbeing. You start to hate being in the house, and you can fall under increased stress as you simply can't relax!

As well as this, double glazing gives your home an added security boost. The double-paned windows stand up impacts a lot better than single glazing does. If you have kids who like to kick a football around in the garden, then you have less to worry about if they accidentally hit a double glazing window!

In total, there are many reasons you should consider installing double glazing in your home. But, to provide a more balanced view, we should look at the pros and cons. 

A close up of a double glazed window unitA close up of a double glazed window unitA close up of a double glazed window unitA close up of a double glazed window unit

Double glazed doors and windows are still an energy efficient option for your home

Pros and Cons Of Double Glazing

If you're thinking about selling your home in the future, then this can be a great home improvement to invest in

It wouldn't be honest or fair to act like double glazing is perfect. Yes, it has a few drawbacks, but you find that the pros tend to outweigh the cons - especially in the long term. 

Pros

  • Save Money On Energy Bills: As mentioned before, double glazing will save you a lot of money on your energy bills. When you insulate your home and stop heat from escaping, the interior temperature will be a lot warmer.

    As such, there's not as much demand on your central heating system. You won't have it turned on as much, and it won't be turned up as high. The result is that you continue to save money every single month.

  • A Quieter Home: Due to the sheer thickness of the windows, double glazing keeps a lot of sound out of your home. You're not going to experience total silence, but you will reduce the level of noise you hear from outside.

    This can change your whole experience of living at home and make life more comfortable. 

  • Boost Home Safety: Double glazing is far stronger and more durable than single glazing. Therefore, it's much tougher for things to break the windows. It would require excessive force to actually smash a double glazing window.

    So, they provide additional safety and security for your home. It's harder for someone to break in as they'd need heavy objects and a great deal of strength to smash a window. With single panes, you can crack them relatively easily, which doesn't make them very secure. 

  • Lowers Your Carbon Footprint: Yes, double glazing helps you save money on your energy bills. But, did you know this actually makes you more eco-friendly too? Think about it; if you're using up less energy, then your home burns up less gas.

    You reduce your carbon footprint quite dramatically over time. Especially if you think about how much more energy you'd use with single pane windows. Realistically, you don't need to turn the heating on during the spring or summer. Double glazing ensures you don't do this, and your impact on the environment decreases. 

    Increase The Market Value Of Your Home: When most people are looking to buy a home, double glazing is seen as essential. If a house doesn't have it, then the buyers will most likely install it anyway.

    So, a home with double glazing instantly gets a market value boost. It's a coveted feature, so your house becomes more worthwhile. If you're thinking about selling your home in the future, then this can be a great home improvement to invest in. 

    Make Your House Look Modern: Double glazing will instantly make your home look more contemporary. It has a very modern look to it, and you may want to install it if you're looking to improve your home design. 

    Prevent Sun Damage: Finally, double glazing windows can lessen the impact of the sun on your home. Have you ever left your curtains drawn and seen that parts of your furniture or carpet have become slightly damaged?

    The colours have faded, and it's because of the sun shining through the windows. Double glazing helps prevent this damage by restricting the light that comes into your home. This is arguably one of the most underrated features it has. 

Cons

  • Expensive To Install: The cost of double glazing is easily the biggest worry for a lot of people. There's no beating around the bush; it can be expensive to install. You're looking at a few thousand pounds at the very least.

    For some, this is simply too much. If you operate on a tight budget, it's easy to see how this can seem unattractive. But, think about the savings you make in the future. You cut your energy bills each month, so you eventually end up breaking even - or maybe even saving more than it cost over time! 

  • Difficult To Repair: A single glazing window is easy to repair. You just replace the pane, and the job is done. It doesn't cost much, and there's no hassle. Double glazing is different because of the way it's constructed.

    If a pane gets cracked, then you can't just replace it. Instead, you have to replace the entire window - which will cost a fair amount.

  • Makes Your Home Too Warm: So, one of the main benefits of double glazing is that it insulates your home and keeps it nice and warm. But, this becomes a problem from time to time. Most notably when the temperature outside gets very hot.

    The summer months can be an issue as you stop heat from escaping an already warm home. The result is that you feel like you're melting under the heat. Sure, you can open the windows, but you can't really do that at night. Plus, opening the windows usually leads to flies, bugs, and who knows what else flying into your house. 

  • Doesn't Go Well With Older Houses: While the appearance of double glazing looks brilliant on a modern house, it has the opposite effect on older ones.

    If you have a more traditional home that was built decades ago, then double glazing windows might not match the exterior. In turn, this can make your home look a bit silly. 

    All things considered, there are lots of advantages and a few disadvantages. The main issues are cost and repair related. With things like an overly warm home, you can find ways around this by opening the windows or buying fans for your rooms.

    As for the modern appearance, getting timber double glazing windows can sometimes help them fit in with the traditional home design. 

How to lock a double glazed window with a keyHow to lock a double glazed window with a keyHow to lock a double glazed window with a keyHow to lock a double glazed window with a key

Ensure you have security features built into any new doors and windows

How Much Does Double Glazing Cost?

Double glazing installation can be more expensive or cheaper depending on where you live in the UK

We've touched upon the cost before in this double glazing guide, but now it's time for a more detailed overview. Before we begin, it's worth noting that any prices quoted are rough guides.

It's hard to come up with a definitive cost because there are so many factors at play. It depends on your home, how complicated the installation job will be, the type of windows you want, and so on.

To make things easier to understand, we'll start by comparing the prices of uPVC double glazing - seeing as it's the most popular. 

  • The average cost PER WINDOW is between £250 and £600

  • The average cost for installation of 4 double glazing windows in a UK home is between £4,800 and £7,200

  • The average cost for installation of 4 double glazing windows in a flat is approximately £2,000

Remember, these figures are rough estimates and take into account all the different styles of uPVC windows. When we split things up into each style, you see a fluctuation in the average prices. For reference, the following figures are for a standard double glazing window with a pane that's 100cm x 100cm (unless otherwise stated). 

  • Casement window double glazing average cost: £325 to £420

  • Sash window double glazing average cost: £640 to £820

  • Tilt & Turn window double glazing average cost: £490 to £625

  • Dual Turn window double glazing average cost: £525 to £670

  • Bay window double glazing average cost: £1,000 (this is for 240cm x 120cm window)

One of the main factors that alter the cost is the window size. 100cm x 100cm is seen by many as standard, but you can get much smaller ones that cost almost half the price. Also, you can see how the window style changes the price as well; so, bear that in mind when you look to buy double glazing. 

When it comes to wooden and aluminium windows, the prices increase across the board. 

  • Aluminium casement windows average cost is between £540 to £960

  • Aluminium sash windows average cost is between £1,200 to £1,500

  • Wooden casement windows average cost is between £700 - £1,500

  • Wooden sash windows average cost is between £1,100 to £1,900

We're only going to look at casement and sash windows for these two materials as it's very rare to get any other styles in them. As a result, it's hard to find any figures for them. But, we can safely assume that they will be more expensive than uPVC ones. 

So, wooden double glazing windows are the most expensive and uPVC work out as the cheapest. Of course, you have to take into account other factors as well. Along with everything we've already mentioned, the height of the windows plays a significant role. 

Windows that are installed on the ground floor of a building always work out cheaper than ones on the first or second floors. If you're wondering why then it's just a matter of effort. It requires more effort and time to install on a higher level, and it's often slightly riskier. As such, professional double glazing installers have to charge more.

We appreciate there's a lot to take in, so allow us to list all the main factors that influence double glazing costs: 

  • Window size

  • Window style

  • Material used

  • Number of windows

  • The position of the windows

  • Property type

  • The energy rating of the windows

Naturally, there is one more factor; the company you've chosen to provide and install the windows. Costs can fluctuate from business to business depending on how they price their service. 

Like most other things in this world, double glazing installation can be more expensive or cheaper depending on where you live in the UK as well.

An opened double glazed window showing trees outsideAn opened double glazed window showing trees outsideAn opened double glazed window showing trees outsideAn opened double glazed window showing trees outside

New windows often offer various ways of opening, full and tilting

Maintenance Of Double Glazing 

With wooden windows, you need to make an effort to clean the frames every few months

Maintaining your double glazing is essential to keep it in the best condition for as long as possible. You'll be pleased to know that it is generally straightforward for you to look after. As you can imagine, maintenance does vary from material to material. So, here's a breakdown of what you should do 

For uPVC and Aluminium double glazing, you can get away with washing these two or three times a year. Try and do them at regular intervals - such as every six or four months. When cleaning, you only need warm and soapy water. 

Always use a soft sponge too - never anything abrasive. This ensures that the windows stay in great nick and don't get any buildup of moss or mould.

With wooden windows, you need to make an effort to clean the frames every few months - but ensure you dry them thoroughly to prevent rotting wood. The main difference here is that you also need to treat your wooden windows.

Insects and the elements can damage it if left untreated, so get your hands on a product that's designed to keep wooden windows in their best condition. Generally speaking, it's recommended you try out Chromated Copper Arsenate for this task.

Of course, you should wash the glass panes regularly as well. Once a month should do the trick, and remove any jewellery or wear protective gloves to prevent scratches! 

Wooden double glazed windows that are closedWooden double glazed windows that are closedWooden double glazed windows that are closedWooden double glazed windows that are closed

Double glazed windows are available in a variety of materials

Double Glazing Advice For Buyers

We also suggest you shop around and look at different providers to get quotes from all of them

Those of you that are interested in buying double glazing need to follow a few pieces of advice. In the final section of our double glazing guide, we'll briefly run through the key things to consider before you purchase some new windows for your home. 

Work Out The Costs

You have to know how much this will cost you before you buy. The figures we've shown in this guide give you a good indication of how much it could set you back. As a consequence, it's worth figuring out how you can afford double glazing if your budget doesn't allow it. Set up a fund to save up for this investment or consider getting a personal loan from your bank. 

We also suggest you shop around and look at different providers to get quotes from all of them. Quotes are a far more accurate way of calculating the costs as the company can take your demands into consideration and show you how much it will cost. This also lets you see different options and decide which company may offer the best value for money. 

Get Recommendations & Search For Reviews

Double glazing installation must be done by experienced and trained professionals. Never attempt it on your own as you'll probably end up causing damage to your home! Therefore, you need to find a professional company that will do the job for you. 

To guarantee you find a trustworthy and experienced installer, it helps if you get recommendations from friends/family. See if they've had experience working with local companies, so you know who's worth your time and who you should avoid. 

Likewise, always go through online company reviews for a more transparent view of the business. Again, it lets you see if they're trustworthy and worth the money they charge.

Think About The Style Of Your Home

Lastly, take into consideration the way your home looks. As we said in the pros and cons, double glazing looks best on modern homes. But, if you have an older one, then you might need to think about the style of the windows. Wooden ones can look more natural, and you can even get uPVC ones that have a more wooden look to them. 

In essence, you just need to make sure that the windows will actually look good on your home and won't stick out like a sore thumb. 

On that note, you've reached the end of this extensive guide to double glazing. We've given you an introduction to double glazing and the different window types. You've seen the double glazing costs, benefits, maintenance tips, and much more. 

Hopefully, this all comes together to help you understand double glazing and make a more informed decision when considering it for your property.