The Ultimate Guide to Double Glazing

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How do I know I’m getting the best price for my double glazed windows?

double glazed windows
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While everyone who gets double glazed windows installed expects a substantial investment. Absolutely nobody wants to pay more for their windows than they have to.

Even once you’ve scoured your local market to find the perfect quote, you can still find ways to make further savings on the cost of your windows.

That’s where we come in.

At Double Glazing Funding, we provide you with all the resources you need to see if you’re eligible for home improvement grants.

We work in partnership with the Help 2 Buy Windows scheme to ensure that you don’t have to sacrifice quality for the price.

We also offer a Best 4 Less guarantee to ensure that you find the best quality windows at the most affordable prices.

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Don’t feel the need to settle for low-cost, low-quality windows. Just check out our easy to use Grant Application Tool, and see what savings and grant assistance are yours for the taking.

Our mission is to help people all over the country find the perfect windows for their needs without having to spend a single penny more than they should.

The Swiss-French pioneer of modern architecture said that the history of architecture is also the history of the window.

While we may take the humble window for granted, its inception transformed architecture as we know it today.

It allowed people to actually see their interiors without the need for artificial light like candles or torches. Windows have existed in forms of architecture all over the world for centuries.

The Romans were among the first to use glass in their windows around 100AD, although earlier windows in countries like China and Japan used paper in a wooden frame.

Here in the UK, while stained glass had pride in churches across the country, most homes used animal horn in windows instead of glass right up until the 17th century.

Suffice to say, the technology behind windows has come a long leaps and bounds since then.

Yet, for all the problems that today’s glazing solutions have solved, the abundance of choice today has created a new problem of its own...

How do you know which windows are right for you?

Today, homeowners have more choice than ever when selecting the right windows for their homes. In fact, they have so much choice that it can be something of an embarrassment of riches.

With so much on offer, it can be hard to make an informed decision. Whether you’re looking for new double glazed windows to replace your existing inefficient single-glazed windows.

Or whether you’re replacing older double glazed windows for a more energy-efficient alternative, the sheer volume of choice out there can be baffling.

How do you know which frames will suit the style of your interior and exterior? How can you tell which kind of glass panes will afford you the best energy efficiency?

How do you know you’re getting a good price on your double glazed windows?

Do you qualify for assistance paying for your double glazed windows?

Will your windows stand the test of time, or will they need to be replaced all over again in a couple of years?

It’s enough to make anyone’s head spin!

That’s why we’ve compiled this comprehensive guide to tell you everything you’ve ever needed to know about double glazed windows.

Let’s start with the obvious…
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Why should you get double glazed windows?

modern double glazed windows
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While there’s some pretty huge variance in prices when it comes to double glazed windows. It’s safe to say that they represent a substantial investment.

As such, frugal homeowners may wonder whether it’s even worth committing to getting double glazed windows installed.

However, while installing any kinds of new windows may require some upfront costs, there’s a lot you can do to mitigate those costs (we’ll discuss that in greater detail later).

What’s more, the costs are offset by the wide range of benefits that you’ll enjoy once your new windows are installed.

Some of the many benefits of double glazed windows include;

Energy efficiency

One of the most attractive benefits of double glazed windows is that they can afford you significant savings on your energy bills.

They are designed not only to trap heat from your home inside, in the colder months. But they’re also designed to block heat rays from the sun to keep your home cooler in the summer.

This can save a great deal not just on heating costs but on the air conditioning on those stifling summer days.

Without double glazing, you’ll find that you’re paying a lot of money for heat that’s literally going out of the window.

How much could you save?

That depends on the type of windows you have installed (we’ll get to that- don’t worry) and your property's size.

A semi-detached home can expect to save £75-£110 a year on its heating bill with double glazed windows. A detached home could save as much as £120-£155 per year, while an apartment will typically save between £35 and £55 a year.

In fact, homes with double glazing can save up to 30% of their energy bills each year.

Plus, no more shivering cold winter mornings. No more stiflingly hot and sweaty summer afternoons.

modern conservatory with double glazed windows

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Unfortunately, single glazed windows can be a pretty big security risk. They are easy to break and can provide a point of ingress for burglars.

Even single layers of laminated or toughened glass can be breached. Double glazed windows. However, they provide you not only with twice the energy efficiency but twice the strength and security.

Increased soundproofing

Suppose you’re regularly bothered by noise from neighbours or passers-by. Maybe you struggle to sleep on a Friday night because of noise from tipsy revellers.

Or if you’re the first to hear about it when the next-door neighbour starts trimming their hedge, you’ll be delighted to hear that double glazed windows have another benefit.

They offer superior soundproofing when compared to their single glazed counterparts. Because double glazed windows are thicker.

They’re much more effective when it comes to blocking nearby noise from neighbours, pets and passers-by.

The right kind of double glazed windows can increase soundproofing by up to 35 decibels!

Reduced interior fading

Don’t you just hate it when your beloved armchair gets a pale patch on the arm from years of exposure to the sun? Or when your beloved rug or carpet sports a faded line straight down the middle?

Exposure to the sun can fade some dyes, inks and paints, and this can reduce the aesthetic value of your home’s furnishings.

Fortunately, the same technology that keeps the heat from the sun out of your home also blocks the UV rays that can cause this fading.
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Increase the value of your home

Double glazing is highly desirable in any home and will be extremely useful to you should you decide to sell up and move to a new property.

Not only can double glazing add to the appeal of your home, but it can also add as much as 10% to your property’s value.

As you can see, there are many significant benefits to double glazing, which, over time, more than mitigates the upfront costs.

How do they work?

Chartwell green double glazed windows with a purple front door
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The benefits of double glazed windows are undoubtedly impressive. But can one extra layer of glass accomplish so much?

It can seem hard to believe until you take the time to learn how double glazed windows work.

Double glazing reduces heat loss by limiting how much heat can escape from your property through two of the three processes by which heat is transferred; conduction and convection.

Conduction involves the transfer of heat through a material. When heat from your home’s interior hits the glass, it is then transferred through the panel of glass to the outside world.

Heat can be conductive through a single pane of glass fairly quickly, passing through the pane into the outside world.

Double glazing helps to prevent this process.

Not only are there twice as many panes (thereby making the process of conduction harder, the conducted heat is transferred into the air (or other inert gas) between the panels. This is where the process of convection comes in.

The process

Convection takes place when heat is transferred through a moving liquid or a gas. In the case of double glazed windows.

There is a space between the panes containing air (or in some cases another gas like argon), which inhibits conduction.

Air is a poor conductor of heat. So the vacuum in double glazed windows helps to prevent the conducted heat from convecting.

Because it addresses the issues of conduction and convention simultaneously. Double glazing can be extremely effective in limiting the transfer of heat through your windows.

How much should you expect to pay for double glazed windows?

This is a tricky one to answer because there are so many variables at play.

The amount you can expect to pay depends on the size and style of the windows you want to replace. It can also depend on what kind of glass you want to use (not all double glazed windows are created equal, as we’ll see later).

And of course, it can depend on your property's size and how many windows it has.

However, while your average may vary, we can provide you with a ballpark figure.

The average cost of double glazing is somewhere between £400 and £600 per window. So by the rule of thumb, it will cost you around £2,000 to install 4 double glazed windows in an apartment.

This makes it between £4,800 and £7,200 in an average-sized UK home.

However, as we’ll discuss towards the end of this article. There may be a lot you can do to ameliorate those costs by applying for relevant grant assistance.

What’s more, it’s important to remember that you are in the driving seat as a consumer. By arming yourself with knowledge of the different types of windows out there.

Then you can get a clear idea of what kind is best for your home and your family.

When you have a clear idea of what you want.

You’ll be able to get the best deals on the market, and you’ll be less likely to be swayed by pushy sales professionals trying to sell you a host of unnecessary extra features.
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What are the different types of double-glazed windows?

internal view of double glazed windows
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When it comes to the different types of windows, consumers need to consider two things.

They need to consider the window style that needs to be replaced, and they need to consider the kind of glass which will be used.

Broadly speaking, double glazing installations all work in fundamentally the same way.

Your old windows are removed, and a new self-contained, made-to-measure unit is fitted to replace them. This is then sealed in place to ensure that no heat escapes through the interstice between your wall and your window.

After all, it doesn’t matter how energy efficient your windows are if the seal around them is ruptured. This is why it’s a good idea to keep an eye on your sealant and top it up every few years.

Not all installations are the same.

While most installations are the same. The materials used in the frame and the kinds of glass vary per the consumer’s needs and budget.

Most double glazed windows that you see, particularly older windows, are made from Unplasticized Polyvinyl Chloride or UPVC.

These are popular for several reasons. They’re affordable, and they are cheap to produce.

They’re also highly durable, and they’re readily recyclable. However, if your home’s aesthetic ers on the side of tradition and the contemporary look and feel of UPVC could be alien to your property. You have other options.

Recent advances in double glazing technology have allowed frames to be constructed with wood and/or aluminium.

If there is a better fit for your home and it would work every bit as well as UPVC.

In some cases, the window frame itself is treated with an insulating layer to restrict heat loss through the frame. These are called “thermally broken” windows.

A layer of reinforced polyamide is sandwiched between the interior and exterior frame profiles to provide an extra layer of protection.

The great thing about double glazed windows is that they can be incorporated into window frames of any size in various styles.

When it comes to the glass itself, consumers have a choice of a few different options depending on their budget and energy savings/security/soundproofing needs.

Some of these include;

Float glass

Float glass is the most common technique used to create double glazed windows. Developed by British engineer Sir Alastair Pilkington.

In the 1950s, the method involves floating melted glass on top of a layer of molten metal. This produces a uniform and perfectly flat finish.

This is how most glass windows are made today, but because it sounds fancy, some less scrupulous salespeople may try to make it sound like a selling point.

Low Emissivity Glass

Also known as Low e Glass, or Thermally broken glass, this involves applying a thin metal ‘low e’ coating to one side of the pane, adding an extra layer of insulation.

This restricts the amount of heat that is transferred between either side of the glass, thereby increasing the installation's energy efficiency.

Laminated glass

Laminated glass is best suited to the extra security conscious. In some cases, they are known as hurricane windows as they are excellent at protecting in the event of extreme weather.

Although they can also keep even the most determined intruders at bay. All double glazed windows are inherently more secure than their single glazed counterparts.

Laminated glass provides an extra layer of security (quite literally, in fact).

Laminated glass panels are made from two sheets of glass that are bonded together by a laminate layer. Usually made of polyvinyl butyral (PVB) or ethylene-vinyl acetate (EVA), sandwiched between them.

This results in the pane holding itself together if it breaks, rather than exploding into small, jagged pieces.

Laminated glass is also one of the best kinds of glass for soundproofing.
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Toughened glass

Toughened glass does pretty much what it says on the tin. It is glass that has been strengthened using heat tempering processes.

Not only does this help glass to maintain its integrity when struck. But it also helps to ensure that even if it should break, the pane will crumble into small chunks.

Rather than exploding inwards in dangerously sharp jagged shards. This type of glass is commonly used in car windscreens and the country’s few telephone boxes.

Double glazing that uses toughened glass provides extra safety and security for your peace of mind.

As you can see, there are numerous common manufacturing methods when it comes to double glazing. All of them have their own inherent advantages.

Hopefully, this clears up any misconceptions you’ve held about double glazing and the science behind the bold claims you’ve seen made about its efficacy.

The more you know about the different ways in which double glazed windows are made, the easier it is to choose the right solution for your home.

What colours and styles do double glazed windows come in?

Internal view of double glazed bi fold doors
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Let’s be honest, the technology behind the glass and what goes into making the frame are important considerations.

But they mean nothing if your new window looks like an eyesore when it’s installed in your home.

Many homeowners want to know that when they replace their windows with new double glazed alternatives. That they won’t do so at the expense of their home’s aesthetic.

With that in mind, let’s look at some of the different styles of windows that can be double glazed for a seamless fit;

Single-hung windows

Single-hung windows look great in all kinds of properties. On a single hung window, the top sash is fixed in place.

Although the bottom sash can be opened to provide ventilation for your home.

Double-hung windows

Double-hung windows, on the other hand. Allow you to move both the top and the bottom sashes to provide greater ventilation for your home.

These are great for busy kitchens, for example, or bathrooms that need to let out hot air and steam.

Awning windows

Awning windows have a hinge at the top of the frame and open outwards from the bottom. They are great for getting lots of natural light in and work well in confined spaces.

Horizontal sliders

Slider windows use two sashes on a track that open and close horizontally. These are well suited to shorter, wider panoramic frames.

Bay and bow windows

Internal view of double glazing
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Bay and bow windows are projecting windows that sit in the alcoves of your rooms. They can add a wonderful focal while letting in lots of natural light.

They have three faces, including a wide front and two shorter sides.

Casement windows

Casement windows are attached via a hinge to one side of the frame and open outwards for a traditional look and feel.

Tilt & Turn windows

When these open, they can be tilted and turned on a central pivot, making them easy to clean on both sides.


These are the most expensive kinds of double glazed windows, but they can be truly spectacular. They run right across the length of a wall letting in lots of natural light and offering stunning views.


Front view of a house with chartwell green windows and a purple front door
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There was a time when all UPVC windows were white. But now, they come in a wide range of colours and textures to provide a woodgrain or coloured effect.

Thus, even if timber frames are out of your price range, you can still enjoy UPVC exteriors which look for all the world like oak, cherry, rosewood or mahogany at a glance.

You can also get UPVC frames in a range of solid colours, including black, grey, green, blue and red.

However, by the rule of thumb, you can expect to pay 10-15% more for coloured windows than you would pay for the same window in white.

Who are The British Fenestration Rating Council, and what are BFRC ratings?

Sometimes, no matter how much research you do into the right kind of windows for you. You just need a quick reference guide to determine how well your chosen windows will keep your home insulated.

Then how much they will drive your energy bills down. The British Fenestration Rating Council aim to do exactly that by implementing a traffic light system that provides consumers with quick and easy reference.

Their criteria for energy efficiency for a window is typically based on three factors;

  • If it stops heat from escaping your home.
  • How well it stops drafts from getting into your home.
  • How well it absorbs the free energy produced naturally by the sun.

To comply with BFRC regulations, new window installations must achieve a C rating, but ratings go as high as A++ and as low as E.

It’s worth noting, however, that there is no statutory requirement for manufacturers to display the energy ratings of their windows.

But if they are not keen to share this information with you, this should set alarm bells ringing.


When researching double glazing companies near you. It’s a good idea to check the BFRC ratings of windows that they offer you.

However, keep in mind that it’s completely up to you which kinds of double glazed windows you install. If you think that A++ rated windows would be surplus to requirements in your studio apartment. Don’t let yourself be pressured into choosing them.

The Glass and Glazing Federation actually has a useful calculator which can help you to get a good idea of how much you can expect to save with your new windows.

It’s up to you to balance that with how much you’re prepared to spend on your new installation, given your current energy usage and how long you expect to stay in the property.

While the BFRC rating system is by no means infallible and doesn’t necessarily take other important considerations like security and soundproofing into account.

It remains a useful quick reference guide that shows consumers how much energy efficiency they’re getting for their money.

How do I get a quote for double glazed windows?

As with anything else, the key to getting the best quote for double glazed windows is shopping around. There was a time before the internet had the ubiquitous presence that it has in today’s households.

Consumers were beholden to the prices available from local companies. They’d make calls, and then glazing companies would send a representative over to subject homeowners to a high-pressure sales pitch in their living rooms.

Thankfully, today’s consumers are far better positioned to get a great deal. The internet makes it much easier to find local double glazing companies.

Also, many will allow you to use a calculator on their website to get a zero-obligation quote without even having to converse with a sales representative.

However, it’s worth noting that someone will likely come to inspect the property to ensure that the quote you’ve gotten online is accurate and correct for your property.

Even if they don’t have the facilities to get a quote on their website, pretty much most companies will offer a free quote to anyone who requests them.

Just don’t make the mistake of assuming that the first quote you’re offered is the best. A sales rep may say they’re making you a “once in a lifetime offer”.

They may make a show of calling their boss to try and get you an additional discount if you book there and then. However, never forget that you’re in the driver’s seat.


Get as many quotes as you can from as many companies in your area as possible. You may find that there’s a surprising amount of difference between quotes, even for the same windows.

Check out Google reviews for local companies and resources like Trustpilot to ensure that the company you have in mind has a reputation for quality and good value for money.

Don’t forget that local companies know that they have a lot of competition and will likely take steps to ensure that you choose them instead of their nearest competitors.

If, for example, you like the online reputation of one company, but another can offer you the same windows at a lower price, they may be amenable to the idea of price matching.

Just make sure that they are definitely like-for-like quotes before asking a company for a price match.

How long do double glazed windows last?

One of the many great things about double glazed windows is that they’re a long term investment. Once installed, they can continue to provide you with energy savings, as well as a quieter, more temperate and more secure home for decades.

In fact, you can expect double glazed windows to last for an average of 20 years or even as long as 35 years. It all depends on the quality of the materials used as well as the proficiency of the installation.

Why don’t double glazed windows last forever? Over time the gas between the panes of glass can seep out, thereby diminishing their ability to impede conduction through the glass.

Once around 25% of the gas has escaped, you may start to see a noticeable difference in the window’s energy efficiency.

Don’t worry. You don’t necessarily have to replace your windows after this time. You may find that a secondary glazing measure like an extra layer of transparent film or a semi-permanent fixture can extend your windows’ lifespan even after the gas within them has depleted.

What’s more, most manufacturers will guarantee their windows for at least 10 years against any issues caused by manufacturing defects.
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