New Windows and Doors: Your Guide to Frames, Glass and Glazing

Replacing single​-​glazed windows with double glazing can save you money

Triple glazing is even more effective ​–​ and more expensive

Complete the form above to get free quotes from trusted specialists

A warmer, quieter, more secure and nicer-looking home that’s less expensive to heat… there are many benefits to be gained from investing in new, better windows if your old ones are getting a bit past it.

We’re here to help you work out the best choice for you and your home – and find trusted, skilled installers to help you get the best results.

To get free quotes from those experts, just fill in this form.

In This Guide to New Windows:

Head straight to a specific section by clicking the links below

Why Replace your Home’s Windows?

Around a fifth of the heat your home loses is lost through your windows. So some of the benefits of replacing your property’s windows are:

Comfort​. The less heat your home loses through its windows, the warmer it will be. This doesn’t just apply to single glazing; older double glazing is significantly less efficient than modern double glazing. Heat is lost around twice as quickly through single glazing as through standard double glazing. You should get less condensation, too, and less mould resulting therefrom.

Lower energy bills​. The better your home retains heat, the less money you’ll have to spend warming it up.

Peace and quiet​. As well as keeping more heat in, double glazing and secondary glazing keep more noise out.

Did You Know?

93% of UK homes have double glazing installed – though not necessarily in all their windows.

Security​. 2 panes of glass are harder and riskier to break than 1 – especially if the glass is toughened or laminated. More modern windows also tend to have more sophisticated locks. This doesn’t just mean it’s harder for a burglar to get in – a window that’s harder to break in general is always a good thing. The extra security could also save you money on your insurance.

Environmental impact​. The less fuel you burn to heat your home, the less you’re contributing to carbon dioxide emissions and use of the earth’s resources.

Less maintenance​. Old windows can be prone to problems, from leaks and draughts to sticking and rotting. New windows should come with a long guarantee. They won’t last forever, though.

Appearance​: New windows and frames will certainly make your home look prettier, probably both outside and in. Double glazing might also help reduce the fading of fabrics and furniture that prolonged exposure to sunlight can cause.

Adding value​: Double glazing can also be an advantage when it comes to selling your home, as it means the new owners don’t have to pay for the improvements themselves.


  • Comfort
  • Lower energy bills
  • Peace and quiet
  • Security
  • Environmental impact
  • Less maintenance
  • Appearance
  • Adding value

X Cons:

  • The initial cost

What Kinds of Glazing Are Available?

At the start of the decade, 93% of UK homes had double glazing installed, though not necessarily throughout the whole house. What makes it so popular?

Double Glazing

Double glazed windows have 2 panes of glass with air in between them, as opposed to single-glazed windows, which just have 1 pane of glass. Heat can get out through a single pane of glass quite well, but it’s much harder for it to get past 2 panes of glass and a layer of air. It’s actually that gap which really has the insulating effect – sometimes it’s filled with gases like argon, xenon or krypton instead of air to make it even more effective, as these gases are denser than air, so it’s harder for heat to get through them.

According to the Energy Saving Trust, replacing all the single-glazed windows in a 3-bedroom semi-detached house with B or A-rated glass (we’ll come to that in a minute) should save you between​ £75 and £110 a year​. Double glazing should last for at least 20 years; over time, the gas between the panes will very gradually leak out, rendering the window less efficient.

Do I need planning permission to have double glazing?

You don’t usually need planning permission for double glazing unless you live in a listed building or a conservation area, or your home is subject to what’s known as an article 4 direction. In these cases, you will need to check with your district or borough council. If you can’t have double glazing for the above reasons, secondary glazing might be an option.

Secondary Glazing

Secondary glazing is an alternative to double glazing where instead of the whole window being replaced, a second framed pane of glass is fitted inside your existing windows.

If you live in a listed building or conservation area where you can’t install double glazing, secondary glazing might be an option for you. It isn’t as effective as double-glazing, as it isn’t as well sealed, but it does have most of the same benefits: increased warmth, reduced energy bills, reduced noise and increased security. Some people actually say it is better at reducing noise, as there is a larger space between the 2 panes of glass. And because the window isn’t being replaced, it’s quicker and less disruptive to install.

Triple Glazing

As the name suggests, triple glazed windows have 3 sheets of glass, making them even more efficient at keeping in heat, reducing noise and increasing security. But it’s also more expensive, and experts are divided over whether it delivers big enough improvements over modern energy-efficient double glazing to make it worth the investment. We’ve more on the costs of the different types of window below.

Triple glazing may let slightly less sunlight into your home because of the extra pane of glass. It is also heavier than double glazing so your installer will need to consider whether the extra weight could damage your walls.

Window Frame Materials


uPVC, or to give it its full name, unplasticised polyvinyl chloride, is the most common type of frame for double-glazed windows in the UK.

This is because it’s usually cheaper than traditional wooden frames both to buy and install. It’s durable, sturdy and low-maintenance, meaning it’s weather and damp-resistant and won’t rot, corrode or swell. It’s easy to keep clean, too – all it needs is a wipe it with a damp cloth and maybe a bit of detergent. uPVC frames should last for 35 years, and they are recyclable.

uPVC frames and uPVC doors are available in different colours and finishes, including woodgrain finishes if you want to give them a more traditional look.

Wooden Frames

Wooden window frames look more traditional, which might be particularly important if your home is older or in a conservation area. Some people also prefer the fact that wood is a natural material.

Timber frames are usually more expensive than uPVC and need more maintenance – they can rot, swell, and crack and even be damaged by termites. They need to be looked after properly and closely, and regularly painted as a protective measure.

Aluminium Frames

Aluminium window frames are durable, secure, recyclable and low-maintenance – aluminium can’t rot, swell or rust, and can be cleaned with soapy water and a bit of wax to keep it looking shiny. Because it is so strong and lightweight, it makes for slim frames which allow more light into your home and better views from the outside. Whereas timber is a more traditional material, aluminium has a more sleek, contemporary look – particularly if you have large windows where the frame might otherwise look quite bulky.

Again, it is more expensive than uPVC – but it should also last longer.

Composite Frames

Composite frames​ are made from a timber core with cladding, usually made from aluminium, on the outside. This protects the wood from the weather and makes them much easier to maintain, but allows to enjoy the traditional timber look inside your home at least.

window frame materials

Window Frame Designs and Styles

Casement Windows

Traditional British casement windows are very popular – they are energy efficient, look contemporary, and are good at draught excluding as they are tightly sealed.

They work on hinges so can be designed to open sideways, downwards or upwards (handy for keeping out rain). The handle which locks them can also lock the window in place when it’s open, so it doesn’t get blown around by the wind and is more secure. The way the lock is embedded into the frame also make them difficult to break into.

Sash Windows

Sash windows are very common in Georgian and Victorian housing and on new houses designed to look traditional. They are made of 2 framed panes of glass, 1 or both of which slides over the other to open the window – usually vertically, though you can get horizontal
sash windows.

Traditional sash windows are single-glazed and the panes need to have a very slight gap between them to allow them to slide over each other, so a fair amount of heat can be lost through them. That said, they are usually large enough to let in lots of sunlight. Nowadays
you can get double-glazed sash windows.

You push upwards or downwards, rather than outwards, to open sash windows so they are easier to open if you can’t get right up to the window – for example, if your kitchen window is behind the sink.

Tilt and Turn Windows

Continental-style tilt and turn windows have hinges at the side and the bottom, so can be opened in 2 ways. You either tilt the window inwards from the top using the bottom hinge, or open it inwards using the side hinge (like a casement window, but opening into the house
rather than outwards). The windows will only tilt so far, which is excellent for safety and security – pets and children can’t fall out, and intruders can’t conceivably get in.

Tilt and turn windows tend to be quite large and should open inwards at least 90 degrees, so you can clean them without having to go outside (and escape through them if there is a fire).

Bay Windows

Bay windows project outwards, ​making a room feel more spacious, letting more light in and giving you better views. They can either be fitted to a normal aperture – so only the window juts out – or be part of the house walls, so the bay shape runs the whole height of the room even if the window doesn’t.

Dual Turn Windows

Dual turn windows look like traditional sash windows, but the panes don’t slide over each other – you tilt one or both of them open. The panes can normally be completely rotated so you can clean them from inside the house and escape through them in a fire – but you can choose to only have 1 opening pane, or to have safety locks fitted so they don’t open all the way.

Cottage Windows

Cottage windows use thin bars to divide the window up into smaller panes, giving it a traditional appearance which looks appealing in both modern and older homes.

Roof Windows

As the name suggests, roof windows go in your roof to add light to your loftspace or conversion. One of the biggest manufacturers is Velux and you can read more about the different types of roof windows here.

Coloured Window Frames

Window frames don’t have to be white! You can choose a variety of colours and finishes for your frames – black, cream, grey or brown and even brighter shades like green and red.

Some people choose uPVC frames with a woodgrain finish to give the plastic a more traditional look. If you want to, you should be able to choose 1 colour for the outside window frame and another for the inside.

What Types of Glass Can You Get?

Toughened safety glass ​is up to 5 times as strong as ordinary glass, so it’s much harder for a would-be intruder to break. If it does break, it shatters into tiny, usually blunt-edged fragments which are less dangerous than great big shards.

Laminated glass​ is even harder to break as it has a piece of plastic between the 2 layers of glass. The glass is stuck to the plastic, which holds it in place even if it is smashed, making it extremely difficult to break through.

Low​-​emissivity​ or low​-​e glass ​has a very thin, invisible coating which reflects escaping heat back into your room so it stays warmer.

Sound reduction glass ​reduces the amount of noise coming into your home from outside by ​reflecting or absorbing incoming sound waves. Double, secondary and triple glazing will all reduce the noise coming into your house, and laminating the glass with plastic or filling the space between the panes with an inert gas will help further.

Anti-sun glass ​reflects some of the sun’s glare to keep your room from becoming uncomfortably bright or uncomfortably hot.

Self-cleaning glass​ has a transparent, dual-action coating of titanium dioxide on the outside which uses sunlight and rain to get rid of dirt. Titanium dioxide is both photocatalytic, meaning it reacts with sunlight to break down and loosen organic dirt, and hydrophilic, which means that when it rains, instead of forming droplets, the water spreads more evenly over the glass and washes the dirt away more effectively. The coating will work whenever the sun is in the sky and should last as long as the window does. This means there is less cleaning to do (so either less work for you or fewer visits from the window cleaner), which is particularly handy if some of your windows are hard to reach. But it will not mean you never have to clean your windows again – photocatalysis only works organic dirt, plus even in Britain we do get spells where it doesn’t rain for a while.

Choose From Different Styles of Glass

Clear glass ​means you see completely clearly through the window with no distortion of shapes or colours. It lets light flow into the room unimpeded, which helps rooms to be as warm and bright as possible and to look and feel spacious.

Frosted or obscure glass ​helps you have more privacy – it is translucent rather than transparent, meaning it allows light through but not detailed shapes, so people can’t see much through it. It’s perfect for bathrooms or cloakrooms.

Etched glass ​features decorative designs such as patterns, artwork or lettering. Etched glass was popular in the Victorian era and allows you to personalise your windows.

Brilliant cut glass ​is made by using diamonds to cut intricate designs into the glass – another opportunity to create a unique look for your home. Despite the intricacy of the designs, the glass shouldn’t require any special cleaning.

Leaded glass ​uses very thin strips of lead to hold small panes of glass, often stained glass, together, often to make a pattern or design. Bevelled glass ​is cut with sloping edges.

Stained glass ​is coloured glass ​– either a single-coloured pane, or different coloured panes arranged together to create a pattern or a picture.

house windows

How Much Money Will Double Glazing Save You?

The Energy Saving Trust has these figures for the annual savings it would expect you to make by installing double glazing in a completely single-glazed home:

In England, Scotland and Wales (in a gas central-heated home), you’ll save up to £35 if you live in a flat and up to £110 in a detached property.

If you’re based in Northern Ireland (with oil central heating), you can enjoy savings of up to £30 if you live in a flat and between a maximum of £90 and £95 for a detached house.

Some estimates are more optimistic: the Glass and Glazing Federation’s calculator gave us figures of £125.90 per year for a flat and £221.59 for a detached house, both with gas central heating and new A-rated windows.

Energy Efficiency Ratings for Windows

Just like for boilers and other gas and electrical appliances, there are energy efficiency ratings for windows too. The Window Energy Rating (WER) scale goes from A++ to G, with A++ being the highest and G being the lowest. The ratings are administered by the British Fenestration Rating Council and are for the whole window – the glass and the frame.

Obviously the higher the rating, the more effective the window will be at everything it is designed to do. B-rated windows will save you around 6.5 per cent on your energy bills compared with C-rated, and A-rated windows will save you another 6.5 per cent compared with B-rated. All new windows in the UK must be at least C-rated by law.

You may also see manufacturers talking about a window’s u-value. A u-value denotes how easily heat can pass through a material. So the lower the u-value, the better, as the less heat will escape through the window. All new windows in the UK need to have a u-value no higher than 1.6. To put this in context, traditional single-glazed windows may have a u-value of more than 5.

Another thing to look for is the Energy Saving Trust Recommended logo. You can find a list of windows endorsed by them on the Energy Saving Trust site.

How Much Will Your New Windows Cost?

The answer to this depends on quite a lot of things: how many windows you want to replace, how big they are, what kind of house you have, what kind of glazing you’re getting, what kind of window you’re getting, what the frame is made of and of course which company you use.

We can give you a rough idea in the sections below, but it’s not really possible to get accurate online window quotes – you need an installer to visit your home, measure up, discuss the options and see what would look and work best. We recommend getting different quotes to make sure you’re not only getting the best deal, but working with an installer who you’re comfortable with. We can put you in touch with some of our trusted suppliers – just fill in the form at the top of the page.

How Much Does Double Glazing Cost?

As a very rough guide, 1 uPVC casement window would be expected to cost around £500, including installation​. So for a 1-bedroom flat with 4 windows, you would be looking at around £2,000; for a 3-bedroom house with 8 windows, probably around £4,500.. Windows on the first floor and above will cost more as your installer will need to put up scaffolding; on the other hand, if you’re having lots of windows done your installer may be prepared to offer you a discount. However, these prices can vary a lot, and obviously the larger the window, the more you will pay.

A second-floor window will probably cost between £55 and £75 more than a ground-floor window, and wood-effect uPVC frames are likely to cost around 15-20% more than plain white frames. If you already have double glazing and you choose to keep your existing window frames, replacement should be cheaper than a new installation.

See our double glazing costs page for more information on double glazing prices.

How Much Does Triple Glazing Cost?

As with double glazing, the price depends on a number of factors but, obviously, triple glazing is more expensive than double glazing. As a rough guide, you can probably expect to pay about a third again – so a £350 double-glazed window would probably cost about £485 triple-glazed. That said, the more windows you have installed, the less the overall price per window should be.

How Much Does Secondary Glazing Cost?

Again, a difficult question to answer without getting a quote. Secondary glazing absolutely should be cheaper than double glazing – it isn’t anything like the same amount of work to install, and it isn’t as effective. Yet some prices tell a different story, so once again we
recommend getting a number of quotes from reliable installers.

The quotes we got for a large (1200mm x 800mm) pane plus adhesive tape were all under £200, excluding installation. Lightfoot, which offers advice on energy saving, gives figures of £20 to £40 per square metre for plastic secondary glazing held in place by screws or magnets, and £300 or more for glass secondary glazing in a wood or aluminium frame. If you’re really on a budget, you can use plastic film, which will be only a few pounds, if that, per square metre.

How to Find Trusted Installers

Double glazing doesn’t just involve sticking an extra pane of glass onto your window. You need a whole new window and frame (unless your frames are in very good condition, in which case your installer might be able to retrofit the panes). Either way, it’s not a DIY job. We work with some of the UK’s leading window installers who have many years of experience; all you need to do is complete the form at the top of this page and we’ll put you in touch.

In England and Wales, you should choose a double-glazing installer who is registered with one of the official Competent Person schemes, such as FENSA, the Fenestration Self-Assessment Scheme.

It’s not illegal per se to use an installer who isn’t registered (including yourself), but you must get permission from the building control department at your district or borough council, and they will have to come out and inspect the work. Which will cost you money anyway. You would also need to check whether using an unregistered installer would invalidate your guarantee. These rules don’t apply to secondary glazing.

In Scotland and Northern Ireland, you should contact the Glass and Glazing Federation. You’ll be pleased to know that all of our supplier partners are part of these recognised schemes.

Best Double Glazing and Window Companies


Founded: ​1966

FENSA member: ​Yes

GGF member: ​Yes

Type of window: ​uPVC, aluminium, wooden

Products manufactured in Britain? ​Yes

According to Anglia’s own figures from 2015, 95% of customers would recommend the firm, and 42% of sales are to repeat customers.

Trustpilot rating:


Founded​: 1965

FENSA member: ​Yes

GGF member: ​Yes

Type of window: ​uPVC, aluminium, wooden

Products manufactured in Britain? ​Yes

Trustpilot rating:

Safestyle UK

Founded​: 1992

FENSA member: ​Yes

GGF member: ​Yes

Type of window: ​uPVC only

Products manufactured in Britain? ​Yes

Trustpilot rating:


Founded: ​1969

FENSA member: ​Yes

GGF member: ​No

Type of window: ​uPVC only

Trustpilot rating:

Check our our ​best double glazing page to discover other big companies in the market, and complete this form to receive free quotes from these specialists.

Jonathan Whiting
Jonathan Whiting

An eco hero with a head for numbers, Jon’s data visualisation skills are legendary. Whether it’s determining what countries will survive climate change or the animals most at risk from it, he has the planet’s best interests at heart.

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