Double Glazed Units: Complete 2021 Guide for Frames and Panels in the UK

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Last updated: 11 December 2020

What Are Double Glazed Units?

Double glazed units (double glazing), which fit within doors or window frames, consists of two or three glass panes separated by a space filled with air or gas to reduce heat transfer between your home and the outside. The thickness of the glass ranges from 3 to 10 mm, but special applications may require thicker layers.

Over the last few years, the number of double glazed unit companies in the UK grew rapidly and now vary from large chains to small family businesses. Double glazing has expanded to include a wide range of different types of glass and frames. But why have double glazed units grown in popularity so fast?

Double glazing tackles the problem of heat loss and noise pollution, and consequently, helps to save on bills, while at the same time reduces homeowners’ carbon footprint.

If you’re considering buying double glazed windows or doors but want to avoid a time-consuming process of researching the best suppliers, simply fill in the form at the top of this page. We will provide you with up to 4 quotes from reliable suppliers in your area. The service is free of charge and doesn’t require any further obligations.

Double Glazed Units 

Learn More about Double Glazing Units in Our Guide

What Is the Cost of Double Glazed Windows?
How Much Do Double Glazed Doors Cost?
What Are the Advantages of Double Glazed Units?
What Are the Downsides of Double Glazing?
Components of Double Glazed Units
What Are the Different Types of Double Glazed Units?
Find the Best Double Glazed Unit Suppliers in the UK

What Is the Cost of Double Glazed Windows?

The price depends on several factors you should take into consideration before making a final decision. These include the amount of double glazed windows and doors you need, glass type, the material of the frames, shape, and style of the products.

The most popular material used for double glazing frames is uPVC because of its low price and efficiency. On the other hand, aluminium and wooden frames are usually more expensive, although the functionality doesn’t necessarily exceed uPVC.

New Green Homes Grant

In July, the government announced the new Green Homes Grant, which provides homeowners and landlords with £5,000 - £10,000 vouchers for energy-saving renovations.

Double glazing is included under the secondary measures of the grant.

Applications are now open. Read our guide about the Green Homes Grant for full details and to help prepare your application.

Note: the Green Homes Grant is only available in England, and works can continue in all tiers under the current restrictions.

Regarding the style of the double glazed windows, casement and sash uPVC windows are the most popular options in the UK. The table below provides an estimated cost assessment of the following two types.

Number of bedrooms

Number of Windows

(600mm x 900mm)

Casement Windows Sash Windows
2 4 windows from £1000 from £2000
3 9 windows from £2250 from £4500
4 15 windows from £3750 from £7500

How Much Do Double Glazed Doors Cost?

Similarly to double glazed windows, uPVC frames are the cheapest choice, whereas timber and aluminium doors are commonly more pricey. When it comes to the shape and style, sliding double glazed patio doors are the most affordable option. Folding and bi-fold doors are more expensive due to their complexity. However, because these three styles are the most popular in the UK, we included them in the price guide table below.

Type of Door Number of White uPVC Doors Cost of White uPVC Doors
Sliding Patio 2 doors from £1200
French 2 doors from £1000
Bi-fold 2 doors from £1500

Remember that the costs depend on each individual case and numbers do not represent actual offers. They are merely for general reference.

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Double Glazed Units Advantages

What Are the Advantages of Double Glazed Units? 

Carbon Footprint Reduction

Double glazing can help you reduce your energy usage, and consequently, lower your CO2 emission, making your home more environmentally-friendly.

Energy Bill Savings

Up to 70% of household heat is lost due to poor insulation when installing single glazed windows. You can avoid this with the help of double glazed units because they significantly reduce your energy consumption and can help you save around £9,000 over 20 years.

Noise Reduction

They are able to reduce the noise coming from the outdoors by 60%. This is a great advantage for those who live in busy city areas and want to make their homes more peaceful and quiet.

Increased House Value

Installing double glazed units in your house will significantly increase its value, making it a great investment in case you would like to sell or rent your property in the future.

Increased Security

Due to the additional layer of durable glass, double glazing is a good way to protect your home from burglars.

What Are the Downsides of Double Glazing?

Initial Price

Double glazed units are produced with more material than regular doors and windows, thus the initial cost is higher. However, the amount of money you can save in a long run makes it a worthwhile investment.

Trapped Heat

While keeping the heat inside is what makes the units so functional during cold seasons, it can be a downside during summer. Adding reflective or tinted glass can fix the problem, however, it may also add to the overall cost.

Impossible Repair

If the seal of the double glazed unit is broken, condensation appears between the glass panes. In order to fix the problem, most companies recommend investing in a replacement.

Bad Fit with Older Houses

Double glazed doors and windows have a fairly modern look. The aesthetics of older houses don’t make the best fit with double glazing. However, there are double glazing companies that specialise in producing double glazed units for older properties.

Double Glazing Pros and Cons

How Does Double Glazing Work?

Double glazed units consist of two layers of glass that create a barrier, which reduces heat loss and noise heard from the outside. The layers are separated by a spacer bar and the gap between them is usually 9 to 12 mm wide. The trapped air between the panes doesn’t have enough space to circulate and acts as an insulator, therefore the transmission of heat is slowed down. The process is called a convection and gives double glazing its insulating properties.

Moreover, the units can be either transparent, tinted or covered with reflective film. The two latter options are useful for controlling how much UV light is allowed to enter your home.

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Double Glazed Units: Complete 2021 Guide for Frames and Panels in the UK

Components of Double Glazed Units

There are six main components of double glazed products:

  • Glass
  • Spacer bar: a frame that separates the two panels of glass
  • Primary seal: the main barrier to air migration
  • Secondary seal: the adhesive that holds all the elements together
  • Cavity: the void between the components
  • Desiccant: a silicon material between the panes that absorbs moisture
  • Gas: dehydrated air, argon, krypton or xenon 

Double Glazing Components

What Are the Different Types of Double Glazed Units?

Nowadays, many companies offer a wide range of materials and glass types so that you can customise the windows and doors in regards to your needs. You can choose from different types of frames, glass, shapes and spacer bars. 

Types of Frames

  • uPVC: unplasticised polyvinyl chloride frames are the most popular choice among homeowners in the UK. They are the cheapest option and also available in many different colours. The only disadvantage of uPVC frames is that they might expand under strong sunlight, therefore it’s recommended to find a supplier who offers at least a 10-year warranty.
  • Timber: although wooden frames are the most expensive and require more extensive care, they are the most insulating material that can last a lifetime. Besides, timber frames will give your home a more traditional look.
  • Aluminium: these frames are the least popular choice as they’re not as insulating as uPVC and timber double glazed frames. However, some people prefer aluminium framing due to its modern aesthetics, low maintenance, and durability.

Types of Glass

  • Low-emissivity (low-e) glass: as one of the most popular options, low-e glass makes double glazed units extremely energy-efficient. It’s recommended for homes in cold regions that require a lot of heating. Besides, it reduces the amount of harmful UV light passing through the glass.
  • Safety and security glass: to protect your house from burglary, vandalism and any type of infraction, there are many different kinds of safety and security glass that are less likely to break or pose threat when broken. The most common designs include laminated glass, toughened (tempered) glass, wire mesh glass, and engraved glass.
  • Tinted glass: thanks to an added film to a double glazed glass, tinted windows and doors can reduce the transmission of UV light, protect your furniture from sunlight and keep the house cooler during warm seasons.
  • Reflective glass: with its metallic finish, reflective glass gives your home a more modern look. The reflective film reduces the amount of sunlight and heat coming from outside.
  • Coloured (stained) glass: many companies offer a variety of different coloured glass so that you can customise the double glazed units according to your needs.
  • Acoustic glass: for people living in the busy and noisy parts of the city, acoustic glass is a great option. The extra noise reduction is obtained by an additional acoustic interlayer that weakens the sound waves coming from the outside.
  • Decorative glass: many double glazed units manufacturers offer a variety of different patterns, textures and opacity. Decorative glass can be combined with some of the above-mentioned types, giving your house a unique look.
  • Self-cleaning: nowadays, you can also buy uPVC windows that don’t require you to clean them. They’re pre-coated with a transparent layer that breaks down dirt and dust. 

Types of Double Glazed Windows

Sash Windows

Double Glazed Sash Windows

Casement Windows

Double Glazed Casement Windows

Awning Windows

Double Glazed Awning Windows

Bay Windows

Double Glazed Bay Windows

Palladian Windows

Double Glazed Palladian Windows

Fixed Windows

Double Glazed Fixed Windows

Round Windows

Double Glazed Round Windows

Tilt & Turn Windows

Double Glazed Tilt Windows

Dual Turn Windows

Double Glazed Dual-turn Windows

Secondary Windows

Secondary Glazed Windows


Types of Double Glazed Doors

Entrance Doors

Double Glazed Entrance

Bi-Fold Doors

Double Glazed Bifold Doors

Patio Doors

Double Glazed Patio Doors

French Doors

Double Glazed French Doors


Types of Door Handles

Lever on Backplate

Lever on Backplate

Lever on Rose

Lever on Rose

Mortice Door Knob

Mortice Door Knob

Rim Knob

Rim Knob

Find the Best Double Glazed Unit Suppliers in the UK

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Are you interested in buying double glazed doors and windows for your home? Don’t waste time on time-consuming research, simply fill in the contact form at the top of this page. We will provide you with up to 4 quotes from reliable suppliers in your area for free, without any further obligations.

Get Your Quotes Now! It only takes 1 minute
Written by Ana Kukoska Content Coordinator 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
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