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Last updated: 24 March 2022

Double Glazing in the UK: Your Guide for Grants, Costs & Prices

What Is Double Glazing and Why Should You Invest in It?

Double glazing is the glazing process whereby two layers of glass are fitted so that a small gap of air is created in between. The gap is usually 12 to 16 mm wide and is filled with either normal dry air or in some cases argon gas.

If your energy bill or the noise outside is setting your teeth on edge it might be time for you to invest in double glazing. The two sheets of glasses used for double glazing are separated by a thin air gap and efficiently trap heat indoors. Installing double glazed windows or double glazed doors can add significant value to your property.

Today, 6 out of 10 homes in the UK have double glazing. Double glazing is a popular choice for homeowners in the UK because it is designed to reduce heat loss and noise pollution. Unlike single glazing, double glazing could save you a lot of money on your energy bill and significantly reduces your carbon footprint. 

If you require more information about the installation and cost of double glazing you can get up to 4 quotes by filling out a short 1-minute form at the top of this page. GreenMatch's services are free and there are no further obligations involved.

DOUBLE GLAZING  - What is it and how does it work? │GreenMatch

How Does Double Glazing Work?

Double glazing is a modern way to insulate a building and to primarily prevent heat loss. Instead of having one layer of glass, double glazed windows and doors consist of two panes. The secret to double glazing being such a good insulator is a tiny gap between the two layers of glass, usually filled with argon, xenon, or krypton.

The gas inside double glazed windows and doors reduces the transfer of heat by convection. It basically lowers the rate at which the heat energy escapes from one side to the other. 

The air that is trapped between the two layers of glass creates a barrier that significantly reduces heat loss and noise. Double glazing slows the transfer of heat by a process called convection.

In other words, the air between the panes can’t circulate properly as the gap is too small, therefore the transmission of heat is slowed down a lot. This process gives double glazing its insulating properties.

Even though the process of heat transfer cannot be stopped entirely, it can help reduce your heat loss immensely and save you a significant amount of money.

Therefore, a building equipped with double glazed windows and doors can lead to a total temperature difference of up to 20 degrees between the inside and outside of the building.

1 1: Double glazed windows limit the amount of direct sunlight coming into your house thereby protecting your furniture and carpet, which can fade with direct sunlight. 2 2: Solar transmission is reduced significantly through double glazed windows. 3 3: Double glazed windows are highly energy efficient as they provide insulation to reduce heat transfer from inside the house to the cold air outside. Similarly, they keep the heat outside during hotter months. This is a great advantage in both summers and winters. 4 4: Double glazed windows significantly reduce external noise and disturbance to provide a calm environment inside the house.
Double Glazed Windows

What Are the Components?

There are six key components to double glazed units:

The glass, cavity, primary sealing, secondary sealing, and spacer bar.

Double glazing generally consists of two annealed, tempered or laminated glass sheets. You will also have a choice between coloured, tinted or reflective glass.

These sheets are then separated by a spacer bar creating a cavity which allows air to be trapped, giving double glazing it’s insulating properties. The spacer frame usually consists of a desiccant that absorbs all moisture to prevent condensation in between the panes.

To keep additional moisture from entering the double glazing and to efficiently trap heat, two seals are attached to the glass, the primary seal and the secondary seal. The primary seal is attached on the outside surrounding the glass panes while the secondary seal is attached to the back of the spacer frame.

Double Glazing Componets

Double Glazed Windows

There are several different aspects to consider when buying double glazed windows. The costs and types are two of the main factors.

Cost of Double Glazed Windows

The cost of double glazed windows for your home depends on many different factors. Obviously, the price depends on the size of the window and the amount you would like to purchase. The bigger the window or the more windows you need the more it will cost. Generally, most companies reduce the price per double glazed window if you buy multiple units.

The frame material also plays an important role. UPVC is the most popular option for double glazing as it is the cheapest option. Other framing materials such as aluminium and wood are costlier, but besides their preferred aesthetics there aren’t any benefits over uPVC.

As sash and casement uPVC windows are the preferred choice for many people in the UK we provided you with their estimated costs in a table below.

White Casement Window Prices
Number of
Number of White uPVC casement windows
(600mm x 900mm)
Average cost
2 4 windows from £1,000
3 9 windows from £2,250
4 15 windows from £3,750
White Sash Window Prices
Number of
Number of White uPVC sash windows
(600mm x 900mm)
Average cost
2 4 windows from £2,000
3 9 windows from £4500
4 15 windows from £7,500

Bear in mind, that double glazing costs can’t be summarised into one fixed price. Rather, most glazing companies offer you a free appointment so that a member of their team can inspect your house and evaluate double glazing prices specific to your needs and wants. Check here, If you want to compare the best prices of double glazing.

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Types of Double Glazed Windows

One factor that will additionally affect the costs of double glazing for your home is the type of window. Double glazing companies provide customers with a wide range of different shapes and styles. These are the most popular ones:

Casement Windows
Awning Windows
Palladian Windows
Fixed Windows
Round Windows
Dual Turn
Dual Turn Windows
Secondary Windows

Double Glazed Doors 

Similar to double glazed windows, double glazed doors have several factors that determine their price per unit. We provided you with some information about the pricing and types of double glazed doors below. 

Costs of Double Glazed Doors

For doors, the framing material and design will usually have the biggest impact on the pricing. UPVC doors are the cheapest option while timber and aluminium ones are more expensive.

In general, sliding patio doors are lower in price while folding doors will cost you more. Bi-fold doors are the most complex and therefore the most expensive out of the three.

Below we provided a table including the average pricing for the supply and fitting for these types of double glazed doors.

White uPVC Doors Cost
Type of Door Number doors Average cost
Sliding Patio 2 doors from £1,200
French 2 doors from £1,000
Bi-fold 2 doors from £1,500

The information above applies to standard sized doors. It is important to note that double glazing companies fit the doors specifically to your house. Therefore, sizings and pricings vary from home to home.

Types of Double Glazed Doors

Similar to double glazed windows, double glazing companies offer you a variety of different door styles and shapes. These are a few of those: 

Bi Fold
Bi-fold Doors

The Best Double Glazing Companies in the UK 

There’s a variety of companies and organisations in the UK that specialise in double glazing. It is important to inform yourself before choosing the fitter and manufacturer of your windows and doors. We selected a few of the best ones to make your decision a little easier.

Double Glazing Manufacturers

Some of the top double glazing manufacturers in the UK are Rehau, Crittal and Eurocell.

If you’re after uPVC windows and uPVC doors Eurocell and Rehau will provide you with high-quality uPVC products that are available in all kinds of shapes and colours. Both companies have won multiple awards and put their focus on producing energy efficient and recyclable doors and windows.

If you’re interested in steel windows, Crittal is the manufacturer for you. Their products go through an extensive process and are suited for older homes as well as for new ones due to their versatility.

Double Glazing Fitters

The largest and most experienced double glazing companies in the UK are Anglian Ltd, Everest and Safestyle UK.

They all have been in business for a while and customers value them for their expertise and great quality double glazing. Anglian and Everest give quotes only after one of their team members has inspected your home while Safestyle provides you with an online quote.

When choosing one of these double glazing fitters you will be given the choice to price match with other companies and to choose a finance plan. 

Double Glazing Industry Bodies

To ensure that your double glazing is correctly fitted it is important to find a competent and experienced double glazing organisation.

FENSA, which was implemented by the Glass and Glazing Federation and Certass are two government approved schemes that work hand-in-hand with a number of double glazing contractors. Their services protect your rights as you are given mandatory guarantees and warranties for the installation of your double glazing.

Another scheme that offers you additional protection is the Double Glazing & Conservatory Ombudsman Scheme or short DGCOS.

5 Advantages of Double Glazing

1. Savings on Your Energy Bill

One of the main benefits of using double glazing is the financial savings you will have. Unlike single glazing, double glazing is insulating which lowers the loss of indoor heat and significantly reduces your energy consumption costs at home.

2. Sustainability

Studies have shown that homes cause around 28% of all carbon dioxide emissions. Double glazing keeps your CO2 emissions low as it lessens heat loss. Hence, if you would like to reduce your carbon footprint double glazing is the solution for you.

3. Additional Security

Another advantage of double glazing is that it will increase the security of your home. Because double glazing is more durable, it will be harder for intruders to break-in, giving you and your family a higher level of protection.

4. Adds Value to Your Home

Double glazed windows and double glazed doors are a valuable asset to your home. Thanks to double glazing, if you decide to resell your property the value will increase due to the added style, security, and sustainability.

5. Noise Reduction

Double glazing can decrease noises from outside by 60%. This guarantees you a quiet and peaceful home atmosphere.

Double Glazing Advantages

4 Disadvantages of Double Glazing

1. Can Trap Heat in the Summer

Whilst double glazing keeps heat from escaping during the colder months and keeps heat from entering during summer, its one key weakness is sunlight. The heat from the sun’s rays will not be able to leave as easily as double glazing is very insulating. To prevent this, you can install tinted double glazed windows and double glazed doors which will cost you extra.

2. Difficult to Repair

Over time the sealing of double glazing might become damaged. While it is not impossible to repair this, most companies won’t recommend it. In most cases, the whole window will have to be replaced which can be quite costly.

3. Initial Cost

Double glazing can be initially costly depending on the frame and sizing of the double glazed windows and double glazed doors. However, keep in mind that double glazing is an investment. Once the units are installed they will pay for themselves in the long run as you will save money on your energy bill.

4. Difficult to Fit in Conservation Homes

If your home is in a conservation area, you may not be able to install double glazing. Instead, you can insulate your home better by adding secondary glazing to your existing single glazed windows.

Types of Frames and Double Glazed Glass

Many double glazing companies offer a wide range of frame materials and glasses to create the perfect fit for your home. Besides the frame material and glass, you can also customise the spacer bar and decide what gas the gap in between the panes will be filled with.

Double Glazing Types of Frames

Different Types of Frames 


Unplasticised polyvinyl chloride or short uPVC frames are the most popular window and door frame choice for double glazing. They generally cost less than other frame materials but are just as insulating. uPVC frames are available in many different colours. Do keep in mind that, because the colour might fade and the frame might expand under strong sunlight over time it is recommended to purchase uPVC frames with a warranty of at least 10 years. 


Wooden frames have a more traditional look than the other framing materials. They make double glazing 1800 times more insulating than aluminium frames and with proper care can last a lifetime. Nonetheless, timber frames are definitely costlier than uPVC frames and require more extensive treatments and care.


Aluminium frames have a very contemporary and modern look to them. they could last you a very long time because aluminium requires low maintenance and is very durable. However, it is not as insulating as uPVC and timber and therefore the most unpopular choice for double glazing out of the three.

Different Types of Glasses

As well as the frames you will also have the choice to modify the type of glass for your double glazing.


Low-emissivity or Low-E glass is one of the most popular glass choices as it makes double glazing more energy efficient. Low-e reduces the amount of harmful ultraviolet and infrared light passing through while allowing sunlight in. This retains the heat indoors during cold months. 

Tempered Glass

It is a type of safety glass. It is more durable than normal annealed glass and therefore reduces the risk of injuries and accidents if broken.

Laminated Glass 

Similar to tempered glass laminated glass is a popular choice for safety and security glass. It consists of two layers and is thus very difficult to break.

Tinted Glass

An added film to your double glazing that reduces the transmission of ultraviolet light through your doors and windows. It protects your furniture from sunlight, keeps your house cooler during summer and offers you a higher level of privacy.

Reflective Glass

A metallic finish which gives doors and windows a very modern look. It efficiently cools your home during summer while heating it during winter by reflecting radiation.

Coloured Glass

Many glass types are available in almost any colour. To create coloured glass different metals are added to melted glass which can later be used in the double glazing process.

Is Double Glazing Repair Easy? 

Many online forums suggest Do-It-Yourself tips on how to repair double glazed units but we don’t recommend to take matters into your own hands in this case.

If your double glazing is damaged there are many different reasons for how this could have occurred. A very common fault from the wear and tear over time is condensation. If you notice this fault in one of your double glazed windows or double glazed doors you should immediately inform your installer. If you’re still covered under warranty you should be able to get full coverage for the repair. However, if you aren’t you might have to invest in new double glazed units. 

Double Glazing Condensation

Are There Any Alternatives to Double Glazing? 

Secondary Glazing. Secondary glazing involves attaching a secondary internal window or door to an already existing unit. It is a cheaper option to double glazing mainly because it can be a Do-It-Yourself project.

Secondary glazing could save you up to 10% on your energy bill but it is not nearly as effective at trapping heat as double glazing is. Nonetheless, in terms of noise reduction, secondary glazing is the clear winner.

Overall, secondary glazing can be a good alternative to double glazing if you would like to save money and increase the level of acoustic insulation.     

Triple Glazing: as the name suggests, triple glazing involves three panes that are bound together in the same way double glazed units are. Compared to double glazing, triple glazing is the more energy-efficient option as it traps even more heat indoors. It is also more durable and noise cancelling.

However, triple glazing is more expensive and as the glass is very heavy it requires stronger materials for the framing which will add to the costs. Triple glazing would be most efficiently used in colder parts of the world. So depending on where you live in the UK triple glazing might be the solution for you. 

Quadruple Glazing: quadruple glazing has a total of four layers of glass. Unlike double glazing quadruple glazing is not a very established product in the UK, yet and not many windows and door fitters offer this product. It is more energy-efficient and acoustically insulating than triple and double glazing.

However, the extra layer comes at a cost. Quadruple glazing is estimated to cost around £1000 more per unit than triple glazing.

Find the Best Double Glazing Companies in the UK 

We at GreenMatch know that it can be a tough decision when it comes to deciding who should fit your double glazing. Finding the right supplier that can satisfy your needs and wants needs time and effort. We’re here to help.

If you would like to give your house more style, security and sustainability with double glazing, remember to fill out our form at the top of this page. You can get up to 4 quotes from trusted suppliers for free and with no further obligations.

Get Quotes Now

Fill in the form in just 1 minute

Ana Kukoska
Written by Ana Kukoska, Former Writer

Ana is a Content Coordinator at GreenMatch. With a background in journalism and digital marketing, she has several years of experience in research, analysis, and content creation. On top of this, her focus lies on SEO and digital PR in the following areas: geen sector, sustainability, business, innovation, and more. She and her content team have been published in reputable sites like The Odyssey Online, My News Desk, Zero Waste Home and more