Triple glazed window units consist of three glass layers and two gas layers. Compared to double glazing, this prevents even more heat from escaping your home. And, reduces noise transmission. There are other benefits which we‘ll discuss later.
But, what is the average cost of triple glazing in the UK, and are the benefits worth the extra expense?
Suppose you owned a typical semi–detached home and wanted nine triple glazed uPVC windows. They would cost about £3500 plus installation, or around £400 per window. Compare this with a standard double glazed window costing around £320.
Generally, window installation prices get cheaper if you buy more. But, the price of individual windows depends on the window‘s area. So, increases as the areas become larger.
How Much Does Triple Glazing Cost?
Although triple glazed windows cost roughly 33% to 50% more than double glazing, the benefits aren‘t correspondingly higher. However, glazing technology gets better every day. So, don‘t replace your modern double–glazed windows just yet as the extra cost doesn‘t justify the increased benefits. On the other hand, if you intend changing single glazed or old double glazed windows then choose triple glazed every time.
The following table gives you an idea of triple glazed window prices. We compiled them from multiple online sources as an approximate guide.
It‘s relatively simple to count the number of windows in your home and use this triple glazing cost calculator to provide an approximate purchase price from a typical installation company.
|House size||No. of windows||Estimated purchase cost|
|1 to 2 bedroom flat||4||£2000|
|2 bedroom terraced||5||£2500|
|3 bedroom semi-detached||9||£4400|
|4 bedroom detached||15||£7300|
Remember, prices include installation. But, exclude VAT. Also, they vary depending on whereabouts you live in the country. Triple glazing companies based in London and the Southeast increase their prices by up to 20%.
Triple Glazing Price Factors
As always, many factors affect a quotation. Windows can be made from different materials, have various styles and varying thickness of glass. Also, installation costs vary with the number of windows fitted in a property. So, let‘s consider these factors and others in more detail to gain a better understanding.
Triple glazing companies commonly make window frames from uPVC, because it‘s cheap, and versatile when compared with timber or aluminium. Unfortunately, it‘s a poor insulator when compared to wood. So, if you want to get the most benefits from triple glazed windows, use timber frames every time. The following table gives an idea of the range of prices for a typical sized window, depending on frame material. Once again, they are only an approximation. But, as you can see, like for like, wooden frames always cost more.
|Window frame material||900mm x 1200mm|
|uPVC||£400 to £600|
|Aluminium||£600 to £800|
|Timber||£1200 to £1400|
Window frames don‘t have to be only casement style, hinged on the side or top rails. Triple glazed sash windows are made as standard too. In fact, because of the increased weight of triple glazing, due to the extra pane of glass, they are much heavier than double glazing. Therefore, they need better support within the frame, so, they don‘t cause structural damage to the walls when opened on hinges. Mainly, for this reason, we often find triple glazed sliding sash windows contained within a sliding frame supported by springs, rather than as casement windows. However, unfortunately, triple glazed sash windows cost about 50% more than a casement window.
Typically, glass thickness ranges between 28mm and 44mm when used in triple glazing. Window glass can also be annealed, toughened, or laminated for safety. And, comes with a choice of obscure if you want privacy. Or, clear glass if you prefer natural light and a view. The following table shows how much triple glazed windows cost per m2 for different types and thicknesses of glass.
|Glass type||Triple glazing thickness of the glass||Price range per m2|
|Clear||Annealed||28mm to 44mm||£25 to £50|
|Toughened||£30 to £65|
|Laminated||£35 to £70|
|Obscure||Annealed||£30 to £60|
|Toughened||£35 to £70|
|Laminated||£60 to £100|
Triple glazed windows are a combination of three glass panes installed within an airtight surround, each separated by a spacer. The manufacturer fills the spaces between the panes with one of the following:
- A vacuum.
- Argon gas.
- Krypton gas.
- Xenon gas.
A vacuum doesn‘t allow any convected heat to cross the space between panes so would be ideal as an insulator. However, it’s very expensive to create a pure vacuum. And, the lack of gas pressure inside the triple glazed unit increases the chance of cracking caused by outside air pressure. So, it‘s much better to pump the spaces with dry noble gas instead.
These gases don’t contain water vapour. So, are dry and won’t transfer any moisture to the insides of the glass. Dense gases also transfer heat slower and improve the window‘s thermal insulation.
Usually, noble gases don‘t chemically combine with any other substance at the temperatures and pressures found in a domestic property. Their lack of reactivity reduces the risk of corrosion and the subsequent loss of seal between the panes.
Argon gas is the most popular gas used in double and triple glazing. It is about 35% less conductive than regular air so increases the insulating properties.
Krypton is denser than Argon and works better in triple glazing with smaller gaps between the panes. However, it is more expensive, and the small increase in performance doesn‘t make its use worthwhile.
Xenon gas is relatively modern filler gas. And, insulates even better than the other two gases. Unfortunately, it‘s also very much more expensive. And, the added benefits, at our present technological stage, just isn‘t worth the extra cost. Hopefully, in the future, this might change.
As you might expect, windows vary in price depending on their size. In the UK, the average triple glazed window costs per m2 can vary between £25 and £100, depending on the type of glass. However, this isn‘t a good way to get a quote from a supplier, as many other factors come into play when preparing a quotation. Generally, it‘s much better to ask the supplier for a quote, depending on your property, number of windows, size of window openings, accessibility and other factors.
A triple glazed unit comprises three panes of glass and two gas cavities. So, it‘s thicker than a double glazed unit and needs a deeper glazing rebate in the frame. Many people don‘t realise this and wonder why they can‘t always upgrade their double glazed units by simply replacing with triple glazing.
Perhaps you might not realise that ground floor windows cost less to install than those elsewhere in the house. This price variation is partly due to the extra time needed to carry an awkward, heavy and bulky triple glazed window up a scaffold. Partly because a heavy window needs an extra pair of hands to help lift it. And, partly to do with the hire cost for the scaffolding. Typically, scaffold hire costs add between £30 and £80 per window. This amount depends on the number of windows (more windows mean less money per window). And, the number of storeys (more than one storey adds a significant amount to the scaffold hire costs. So, the quote allocates a larger amount per window).
Benefits of triple glazing
Better insulation & increased efficiency
As we‘ve already determined, triple glazed windows have an extra pane of glass and another layer of gas. Both of which add to the insulation.
The British Fenestration Rating Council (BFRC) allocate a thermal efficiency to every type of window. The most efficient rating is ‘A+‘, but to be classed as ‘energy saving‘, the rating must be at least ‘C‘. To increase the rating of your windows, consider using low emissivity glass. These can be up to 40% more efficient than ordinary glass and certainly make a difference. Low emissivity glass (low-E) uses a metal coating on a plastic film, embedded between two glass laminates. It allows shortwave radiation (ultraviolet) from the sun to enter your home. But, it prevents longwave radiation (infrared) from leaving. I you look at a low-E glass window from the outside, it looks slightly mirrored. However, it’s hardly noticeable from the inside. If you look on the BFRC website, you can use their online tool to find manufacturers and suppliers of energy–efficient windows and doors in your area.
Condensation occurs when warm, moisture–laden air touches a cold surface. Probably, you already notice this on single glazing, but it’s also present on older double glazed units. As double glazing ages, it deteriorates. The airtight seal along the edge starts to break down and allows air and water vapour to enter the space between the glass panes. Even when there are no leaks, there is still a small difference in temperature between inside and outside. When this occurs, the moisture condenses against the cold, outside glass pane. We refer to the temperature difference causing the condensation as a ‘temperature gradient’. Because triple glazed units have two separate compartments, the temperature gradient is far less pronounced than double glazing. So, there is less condensation.
Usually, double and triple glazed units use toughened (also called tempered) or laminated glass. Specially treated tempered glass is safer because it’s less able to break. And, when it does break, the pieces are small and smooth rather than the sharp jagged pieces from annealed glass.
Laminated glass is also safer than annealed glass but is more expensive than tempered. A sheet of laminated glass comprises a PVB (polyvinyl butyral) later sandwiched in between two 3mm sheets of glass. The PVB layer prevents the glass from shattering and falling apart if it breaks. In effect, the PVB holds the glass together. So, it’s a major safety and security feature.
Furthermore, this feature makes laminated glass much more desirable in domestic situations, even though it is more expensive than toughened or annealed glass. Probably, you can also see that toughened or laminated glass helps keep your home secure.
The reasons for triple glazing being secure, mentioned in the previous section, also makes triple glazed windows safer. Because you have three glass layers, a window is harder to break. And if it does, it won‘t produce sharp pieces. Having no sharp pieces of glass means that the windows are safe if the kids are running around, slamming doors, and kicking footballs.
The UK Building Regulations now specify that we must use toughened or laminated glass in certain domestic situations. We‘ll talk more about this in the section dealing with Planning Permission and Building Regulations.
Adding extra material between indoors and outdoors provides another barrier to sound transmission. So, acoustic insulation using triple glazing is better than that from double glazing.
Even though it‘s more expensive than other types of glazing, modern triple glazed windows add value to your home, should you decide to sell. All the previously mentioned benefits combine to provide a more desirable home. And, the fact that you have new windows means the property has curb appeal as well.
As you‘d expect, triple glazing has disadvantages too. And it‘s up to you to decide which features you prefer.
Probably, by now, you have noticed that triple glazed windows cost more than double glazing. However, whether that is a problem, is up to you. Although triple glazing makes savings on your energy bill, the amount you save might not reimburse you for the money you’ve spent on the new windows. So, if you already have good quality double glazing that is in good condition. Don‘t replace them all just yet, as the added expense isn‘t worth it. Wait a few years for the technology to improve and for your windows to deteriorate before taking the plunge.
Because the light from outside has more glass to go through, you‘ll find that you have less natural light enter your home. Reduced light might not affect you very much. But, many people need the added vitamin D, especially during a UK winter.
That extra pane of glass and the thicker frame add to the overall weight. In turn, this exerts additional stress to your existing walls and might do some structural damage. New build houses, designed with triple glazing in mind, already has extra support included in the design.
Planning Permission & Building Regulation
Generally, you don‘t need to apply for Planning Permission if you intend replacing your windows with triple glazing of a similar appearance. However, there might be situations when you must comply with certain criteria:
- Do you live in a listed building? If so, you must do as the authorities say. If you‘re not sure, look on the Historic England website and use the search tool to check if yours is on the list. Alternatively, ask your local authority for advice.
- Maybe you live in a conservation area. If so, you must keep the area looking ‘historically pleasing’. Consult the local authority for advice.
- If you live on a fairly modern estate, your property might be subject to a ‘covenant‘. A covenant places certain restrictions on the property to keep the entire housing complex looking harmonious. One of these might be the type, colour or style of window. Check your deeds or ask for advice from the local authority.
If you fit into any of these three situations, don‘t despair! You might still be able to install triple glazing if you apply for permission. Once again, consult the local planning authority for advice on what to do.
External window installations come under the UK Building Regulations by being “controlled fittings“. This means that when you replace them, their manufacture and installation must meet certain standards. The Approved Documents relating to windows are as follows:
Part A deals with the safety of the structure. In this case, windows and the wall supporting them.
Part B ensures the structure comprises fire retardant materials, where necessary. It also ensures that windows allow for an escape route in the event of a fire.
Part C ensures the contractor uses damp proof membranes around the window frames to protect them from damp and rot. Or, uses window frames made of moisture–resistant material.
Part E ensures the windows provide insulation to reduce sound propagation. Although triple- glazing might not be designed for acoustic insulation, it does help.
Part F ensures the windows allow sufficient ventilation. If a window doesn’t open, then you need other ventilation methods.
Part K protects people from falling into or from contact with fragile glass. The document specifies where you can use glass, what size, and what type.
Part L deals with the installation of thermal insulation. In this case, the thermal performance of the window must comply with a specific Window Energy Rating (WER) and have a specific heat loss (U-rating).
Part Q ensures all external doors and windows have locks suitable for their purpose.
Regulation 7 ensures the window‘s materials are of satisfactory quality and comply with the appropriate British Standards. It also ensures that a professional installs the windows properly.
Local authorities ensure that triple glazed windows installations comply with these regulations, by using a competent person scheme. The register includes professionals trusted to self certify their work. If you don‘t use a ‘competent person‘, the Building Control office must certify the work instead.
Also, notice that all reputable window manufacturers and installers are FENSA registered. This registration scheme also ensures you use a ‘competent person‘. A FENSA registered person issues a certificate assuring that the installation complies with the Building Regulations. It’s also a way for the professional to register your windows with the local council. You need the certificate when you come to sell your home. It offers proof that the work was carried out professionally.
A FENSA certificate also means that the installer holds insurance to cover the installation, in case anything goes wrong.
We’ve only one last thing to mention on this topic. Installing triple glazed windows is too difficult to be a DIY project. The glass units are heavy, and we must handle them carefully. Likewise, we must install the frames properly to comply with the regulations. Finally, if you don‘t use a FENSA registered professional, you won‘t have the assurances that come with the certificate.
Triple Glazing Suppliers: Check List
Before choosing the installation company for your triple glazed windows, there are a few things to check.
- Make sure the installer is FENSA registered and appears on the ‘competent person‘ register. So, you can be sure the professional installs the windows correctly, complying with the Building Regulations. Then, he issues a FENSA certificate as proof. What‘s more, the certificate provides you with a warranty.
- Before any work starts, ensure you get a comprehensive quote on headed paper.
- Get three or four quotes from different companies and choose the best quote for your circumstances. Don‘t go for the lowest price. Instead, look at the overall package.
- Agree with the installation company, how you intend paying your bill. Sometimes, the company might ask you to pay a deposit before work starts. This is good practice as it proves to the installer that you are committed to the work. It also allows them to purchase the windows, without using the company’s capital.
- Ask the installer how long they expect the work to take.
- Ask for references from previous customers. And, follow up the references so you can see the quality of work.
Triple Glazing Cost FAQ
Is it worth getting triple glazing?
The cost of triple glazing is a lot more than double glazing. In contrast, the U-value associated with the triple glazing doesn’t increase in line with the price. So, don‘t rip out perfectly good double glazing and replace them with triple glazing. However, if you‘re current windows need replacing, or if you‘re building a new house, it is worthwhile.
Does triple glazing reduce noise?
Triple glazing is very good at noise control. And, it makes your home a much quieter place to live in. But, make sure you use different thicknesses, densities or types of glass so that sound waves don‘t amplify by resonance.
Why do triple glazed windows mist up?
Triple glazed window units mist up when the seal around the edge fails. The failure allows the noble gas filling the unit to leak away, allowing moisture–laden air to take its place. When this happens, water vapour condenses on the glass in contact with the cold outside air.
Is acoustic glass better than triple glazing?
If all you are concerned about is to soundproof your home, then yes it is. The acoustic glass reflects, absorbs and dampens sound energy. And, is designed to do this rather than providing thermal insulation. On the other hand, triple glazing primarily insulates against heat loss rather than sound. In certain circumstances, triple glazing can increase noise by each glass layer resonating with the others. If you specifically want thermal and acoustic insulation. Make sure the middle glass sheet is a different thickness or density to reduce the effects of resonance.
Can you put triple glazing in double glazing frames?
Theoretically, it is possible to replace double glazed units with triple glazing. However, there are certain things for which you must watch out.
- Make sure the glazing rebate on the frame is deep enough to accommodate the thicker triple glazed unit.
- Ensure the window frame is strong and sturdy enough to support the extra weight of the triple glazed unit.
- Make sure the opening casements have hinges, strong enough to support the additional weight.
- Check the wall is strong enough to support the extra weight.
- A Window Energy Rating (WER) is for the entire window, not just the glass. So by inserting triple glazed units into a double glazed frame, you might not have the WER you expect.
Does triple glazing keep heat out?
Triple glazing prevents heat from transferring from outside to inside as well as the other way around. Basically, it prevents all heat convection and conduction. However, it doesn‘t prevent heat radiation unless you use low emissivity glass (low-E). This type of glass contains a metal coating bonded to a plastic film, embedded between two glass laminates. It allows shortwave ultraviolet radiation from the sun to enter your home. But, it prevents longwave infrared radiation from leaving.
How long does triple glazing last?
Probably, good quality triple glazing has an average lifespan, of around 20 years. However, the range might run from 10 to 35 years, depending on maintenance and exposure to extreme weather. Generally, the appearance of the frames lasts a lot longer than the sealed units, which start to readily deteriorate and eventually leak. Thus, decreasing their energy efficiency as more gas escapes from the units.
Find Glazing Companies Near You
Suppose you intend replacing the windows on your house for new ones. It is worthwhile considering triple glazed units as an alternative to double glazed. But, even if you want to have a go, don‘t try installing the windows yourself. The job doesn‘t lend itself to a DIY project.
Instead, if you want to find out how much triple–glazed windows cost to install, complete the form on this page and you‘ll get 3 or 4 quotes from local registered window fitters.