Triple glazed windows: Are they right for you?

Triple glazed windows are becoming increasingly popular as homeowners seek to reduce energy bills and improve thermal performance. Triple glazing offers superior insulation by adding a third pane of glass, which can make them up to 50 per cent more energy efficient than double glazing. However, triple glazed windows cost on average 10–20 per cent more than their double paned counterparts. Does this enhanced performance justify the additional expense?

Our experts present the triple glazing facts and figures, enabling you to make the right decision about your new windows. 

Triple glazed windows are a type of insulated glazing, similar to double glazing, but with three glass layers instead of two. 

In between the three glass panes there are sealed gaps filled with inert gas, usually argon. A typical triple glazed window unit will also feature an insulating structural component called warm edge spacer bars, where the glass meets the inside of the frame.  

The main purpose of triple glazing’s three-layered design is to provide up to 50 per cent better insulation than double glazing. Further benefits include better soundproofing and enhanced security. These advantages do come at a cost, as triple glazing installation prices typically exceed double glazing prices by over 20 per cent.

The practice of triple glazing windows was pioneered in early 1900s Scandinavia, where harsh winter temperatures created a need for effective insulation. Today, against a backdrop of rising energy bills and upcoming eco-friendly building regulations, triple glazing is becoming popular in other countries with cool or cold climates – including the UK.

Due to the higher manufacturing costs, triple glazed windows are more expensive than double glazing.

However, energy-efficient triple glazing is steadily becoming more popular in UK homes, and prices are becoming more accessible as the domestic triple glazing market matures. uPVC casement windows are generally the cheapest option for triple glazing, with prices ranging from around £575 to £1,575 per window.

Window styles that impact triple glazing costs

The size and style of your windows will significantly affect the overall cost of triple glazing. Triple glazed windows are available in most of the same styles as double glazing, including:

• Casement window: This is the most common and cost-effective type of window. Usually, casements are hinged at the side and open outwards like a door.
• Tilt and turn window: These windows either tilt inwards at the top for ventilation and swing inwards from the side for easy cleaning. The tilt and turn window is common in ground-floor flats, and in homes where casement windows would pose a safety risk to children or pets. You can find a wide selection of these windows in triple glazing, as they’re common in other parts of Europe where triple glazing is more frequently used in housebuilding. Given their elaborate, multifunctional design, tilt and turn windows are understandably more expensive than casement windows.
• Sash window: In this traditional window style, there are 1 or more panes that slide open vertically. Owing to their complicated mechanisms and up-market appeal, sash windows are considerably costlier than casement windows.
• Bay window: This design combines three or more windows that protrude from the property to form an additional interior space. Bay windows are usually expensive because of their complex design and material-intensive construction.

Frame material and the cost of triple glazed windows

The frame material also impacts the cost of triple glazed windows.

• uPVC: Unplasticised polyvinyl chloride is durable and low-maintenance. It’s usually the most cost-effective option for triple glazed window frames.
• Aluminium: Sleek, modern aluminium frames offer a slim profile and a contemporary aesthetic. They’re robust and have a longer lifespan than uPVC, but come at a premium.
• Timber: Timber has a traditional appearance that suits period properties particularly well. It’s one of the most expensive window frame materials for use with triple glazing.

Glass specifications that impact triple glazed window costs

Like other kinds of windows, triple glazed windows are made with many different specifications of glass. The properties and quality of the glazing affect the price you pay.

• Gas fillings: Most triple glazed windows are filled with argon. Higher-end examples sometimes use krypton or xenon gases, which tends to add cost. These gases are similar to argon but are heavier and denser, so they offer superior thermal and sound insulation.
• Low-emissivity (Low-E) glass: Low-E glass has a thin film of low-emissivity material that minimises the levels of infrared and ultraviolet light that pass through the window, without compromising visible light. This type of glass boosts energy efficiency by reflecting heat into a room during the winter and deflecting external heat in the summer. 
• Glass thickness: Often, the outer and inner panes of a triple glazed window are made thicker than the middle pane for enhanced security or soundproofing.
• Acoustic or soundproof window: Designed specifically to reduce external noise, these specialised windows might include extra-thick glass panes and a sound-dampening gas in their voids. While acoustic windows can be particularly expensive, they’re invaluable for homes near busy roads or in noisy areas.

Triple glazing benefits explained

Superior insulation

Triple glazed windows are more insulative than double glazing, and far more so than single glazing. As such, triple glazing transfers less heat from the building to the outer air.

Better insulation means you can keep your home at a comfortable temperature while using your heating system less during cold weather. You can therefore reduce your energy costs and carbon footprint through a triple glazing installation.  

A triple glazed window’s capacity to limit heat transfer can be almost three times greater than that of a B- or C-rated double glazed window, or 40 to 50 per cent better than A-rated double glazing.

Windows fitted with triple glazing are nearly always A+ or A++ rated for energy efficiency, while double glazed windows are more typically A-rated.

Energy savings

Triple glazed windows offer enhanced energy efficiency thanks to their low U-value, which can help reduce your heating bills. While fluctuating energy rates in the UK make precise savings difficult to calculate, we can estimate the potential cost benefits.

Windows typically account for around 20 per cent of a property’s heat loss. Triple glazed windows are approximately 40 per cent more energy-efficient than double glazing. Here’s an example to illustrate potential savings:

Average annual gas heating bill: £887.59¹

Estimated savings with triple glazing: £71.01 per year

This estimate is based on upgrading from high-quality double glazing to triple glazing. If you’re replacing less efficient windows, the savings could be even greater.

Noise reduction

Triple glazed windows are very good at insulating a building from external noise. When sound hits a single glazed window, it causes the glass to vibrate, transferring sound to the interior. With a triple glazed window, the vibration passes through two additional panes of glass and two gas-filled gaps before it enters the room itself. This reduces the noise you hear in the room.   

Compared to double glazed windows, triple glazing can limit external noise by an additional 10 decibels, which is equivalent to the difference in volume between listening to a conversation and the sound of rainfall. 

Given their noise-reducing quality, triple glazed windows are a good option for sound-sensitive spaces such as bedrooms and work-from-home offices.

Reduced condensation 

Triple glazed windows reduce the incidence of condensation by regulating the temperature gradient between inside and outside the property. 

Because the third pane of glass and the second gap between the panes limit heat transfer even further than a comparable double glazed unit would, they ensure the temperature of the interior pane stays closer to room temperature. As a result, condensation is less likely to form, and indoor humidity levels are lower. 

These benefits of triple glazing are especially valuable in buildings that have a history of condensation, damp or mould.

Temperature regulation 

The relatively low heat transfer of triple glazing doesn’t just keep warmth in during winter; it also provides a relatively moderate rate of ‘solar gain’ during hot weather, which means a lower proportion of the Sun’s warmth passes into the room. This limits the sort of overheating that often occurs in single or double glazed rooms during summer. 

Because triple glazing regulates heat better than a comparable double glazed window, and much better than a single glazed unit, it’s a great choice for highly glazed homes, south-facing rooms, or properties in hotter parts of the country.

The energy efficient upsides of triple glazing are clear, but there are also some potential disadvantages to consider before you go ahead with triple glazing installation. 

Cost

Triple glazing is an advancement in window technology. It sets a benchmark for superior insulation against external temperatures and noise; for this reason, you should always expect to pay more than you would for single or double glazed windows. The type of gas between the panes also plays a crucial role in the window’s performance and, consequently, its price.  

Standard triple glazed windows cost around 10–20 per cent more than double glazing when additional costs are factored in.

Environmental factors

Although triple glazed windows can contribute towards lower energy use and a reduced carbon footprint, they do carry some upfront carbon costs. 

The production of triple glazed window production is resource-intensive, and manufacturers must source additional raw materials, such as sand for the extra glass panes. Further, additional energy is used to mould, transport and install triple glazed units, which are thicker and heavier than double glazing. From the start of manufacturing till the completion of installation, triple glazing has a bigger environmental cost than double glazing.The good news is that triple glazed windows offer relative environmental benefits in the long term. A study from Glassonweb demonstrated that the CO2 savings accrued over a triple glazed window’s lifetime exceed the volume of CO2 produced during manufacturing.

Increased weight

A triple glazed window’s extra pane of glass and thicker frame increase its overall weight and thickness. This makes triple glazing unsuitable for some walls that are relatively thin or unsupported. 

Older walls that were designed to support single glazed windows might not be capable of supporting heavy triple glazed units – at least not without modifications or strengthening. Window apertures and walls can be adjusted to provide support for the extra weight of triple glazing, but getting that work done is another cost you’ll need to factor in.

Double and triple glazed windows are similar products based on the same technology. As a more premium form of insulated glazing, triple glazed windows objectively out-perform their double glazed counterparts on most technical measures. The question we would put to you is this: to what extent will these advantages benefit you and your property?

Energy efficiency at a glance

Triple glazing usually has a lower U-value than double glazing, meaning it permits less warmth to leave the building via heat transfer.

Double glazing usually has a higher G-value than triple glazing, so it allows more heat from the Sun to enter a room. In short, triple glazing is a better insulator year-round, while double glazing brings more heat into the building – but only when the Sun is shining.

What are U-values and G-values?

• U-value indicates the level of heat transfer through a window. The higher the U-value, the more heat escapes outwards. Correspondingly, a low U-value indicates a lower level of heat transfer, which would suggest the glazing is a good insulator. In simple terms, the lower your window’s U-value, the lower your heating bills and carbon footprint will be.
• G-value indicates the level of solar gain through a window. The higher the G-value, the more warmth the window allows into the building from the Sun. Lower G-value glazing is the better choice for thermal regulation, which is an important advantage in south-facing rooms that are prone to overheating during summer, or in locations with a warm climate.

For reference, the U-value of double glazing is around 1.6W/m²K, while triple glazing achieves a significantly lower U-value of around 0.6W/m²K. 

This improvement in insulation can translate to savings on your energy bills. Specifically, switching from double to triple glazing could reduce your heating expenses by 10 to 15 per cent annually.

Noise reduction

Double glazing provides adequate soundproofing for most households, as its second glass pane and gas-filled gap dampen sonic vibrations from outside. However, for properties that are subject to noisier conditions, triple glazing provides valuable additional insulation against external noise, thanks to the third pane of glass and the second gas-filled space.

Triple glazing is up to 30 per cent more effective at reducing sound than double glazing. It’s clearly the better choice for acoustic performance – unless you prefer to keep a closer ear on what’s happening outside your home.

Balancing cost and climate

There’s a complex relationship between the relative cost of triple glazing, its benefits, and the local climate at the site of installation. Put simply, people in certain parts of the UK have more to gain than others by choosing triple glazing instead of double glazing. 

Due to their relative intricacy, smaller-scale production and the extra resources needed to make and install them, triple glazed windows cost about 20 per cent more than double glazed ones. 

Triple glazing might be unnecessary in areas with milder climates. The colder the location, the greater the benefits. Triple glazed windows will be considerably more beneficial in the north of Scotland, for example, where temperatures are 4-5°C colder than in the south of the country.

Given its high up-front cost, you may be uncertain whether it would be worthwhile to install triple glazing in your property.

Some households will benefit more from upgrading to triple glazing than others. Thinking about the following considerations will help you decide whether this advanced form of thermal glazing is right for you. 

Duration of residence

While triple glazed windows come at a high up-front cost, they will gradually ‘pay for themselves’ through energy efficiency savings, year-by-year. 

The longer you stay in your property, the greater your return on energy savings will be. With that said, it’s difficult to assess whether your triple glazed windows would enable sufficient energy cost savings to equal the price difference between triple glazing and double glazing within their lifespan of around 20-35 years (with uPVC frames). 

To some extent, you can offset the cost of triple glazed windows against any increase in your home’s value. Having modern, high-performance glazing will help you to secure a good energy performance rating for the property, which will be an asset if you decide to sell the property.

Window replacement vs installation in a new builds or extension

The cost–benefit analysis of fitting triple glazing is more favourable if you are working on an extension or new build. In these cases, you won’t have any existing windows to replace and dispose of, and the labour costs for installation should be lower. 

Additionally, installing triple glazing in your development may help you to secure a better energy rating for the building, which will be advantageous if you decide to sell or rent the property. 

Replacing existing windows can enhance energy efficiency and quality of life, but you should weigh these benefits against the disruption and costs of removal and installation.  

Climate

The colder your local climate is, the more you’ll benefit from triple glazing’s insulative properties. Typically, triple glazing installations in the colder north of the UK will yield higher energy savings and quicker payback times than those in the warmer south of the country. 

With that said, the entirety of the British Isles can experience cold winter weather, making triple glazing a worthwhile investment for many.

Location

Households seeking to install triple glazing face additional challenges in certain parts of the UK. For instance, if you intend to install triple glazed windows in properties built on Article 2(3) land, such as Conservation Areas, you may need to obtain planning permission to do so. One Portsmouth landlord was ordered to uninstall his property’s new triple glazed windows, after installing them without permission in a conservation area.

Similar rules apply to areas where the local planning authorities have imposed an Article 4 direction that restricts development. Moreover, if you own a listed building, you’ll need Listed Building Consent to replace the existing windows. Obtaining permission to install double glazing is tricky enough for these properties, but doing so for triple glazing may be even more challenging.

With all that said, the location of your home could provide an argument in favour of installing triple glazed windows – especially if you live in a noisy area. Triple glazing can reduce the volume of external sounds by up to 10 decibels more than double glazing does. If you’re struggling with external noise from roads, railways, aircraft or busy areas, this enhancement in soundproofing could greatly improve your quality of life, and might also make the property more attractive to prospective buyers or tenants.

Obtaining high standards of energy efficiency

Property owners who are interested in building or renovating homes with exceptional levels of energy efficiency will typically need to invest in high-performance triple glazing. 

Triple glazing is essential for obtaining A-rated energy performance certificates and meeting the high specifications required for EnerPHit (for retrofitting) and Passivhaus (for new builds). 

The EnerPHit and Passivhaus standards were developed to acknowledge properties built to robust energy efficiency standards that maintain near-constant internal temperatures with minimal heating. The EnerPHit standard specifies that a property must have high-performance triple glazing to qualify. 

Triple glazing is not a perfect solution for energy efficiency, given the embodied energy required for its production. But in the long term, it’s an improvement over double glazing – and at the same time provides quality of life benefits such as noise reduction, better home insulation and temperature regulation during warm weather. 

Moving forwards, many more UK homes will ideally choose triple glazed windows, and there is some speculation that triple glazing will become a legal requirement for new builds within the current parliamentary term.

We would recommend triple glazing installation to households with sufficient budget – but only when existing windows are due for replacement. In most cases, prematurely replacing double glazed windows with triple glazing wouldn’t make financial or ecological sense. 

Overall, homeowners and builders should weigh the immediate costs and challenges of installing triple glazing against the quality-of-life benefits and long-term efficiencies. There’s little doubt that your next set of windows should be triple glazed. It’s just a question of timing.