Triple glazed windows: Are they right for you?

Triple glazed windows are growing in popularity as homeowners look for ways to reduce their energy bills and boost their homes’ insulation performance. 

Renowned for their superior insulation properties, these windows build on the success of double glazed windows with the addition of a third pane of glass to increase efficiency, making them at least 30 per cent more energy-efficient than double glazing, often more like 40 to 50 per cent more efficient.

However, on average, triple glazed windows are 10–20 per cent costlier than their double glazed counterparts. Does their superior performance justify this premium? We look at the costs, efficiency and more in our guide.

Triple glazed windows originated in the harsh cold of Scandinavia, where warmth and comfort are paramount. Now, they’re showing their worth in other countries with colder climates – and much of the UK can benefit from them, too. 

Most homes in the UK have double glazed windows, but triple glazing goes a step further by adding a third pane of glass to the formation. In between these sheets are pockets of inert gas, usually argon but sometimes krypton or xenon. Triple glazed windows are also typically built with warm edge spacer bars that insulate the edges of the window. These are usually uPVC bars, although manufacturers can use other materials.

The result is a triple sandwich of insulation with capabilities that go beyond those of a double glazed window and this type of window offers superior insulation and soundproofing than double glazed windows. They are also more secure.

As homeowners in the UK have become more aware of energy-efficient measures, triple glazing has been pushed into the spotlight, but understanding the costs of these types of windows is essential. Let’s take a closer look at triple glazed windows costs. 

Size and style of window

The window’s size and style significantly affect the overall cost of triple glazing. 

• Standard casement window: This is the most common and cost-effective type of window. Usually, it’s hinged at the side and opens outwards.
• Tilt-and-turn window: This European-style window can tilt inwards at the top for ventilation and swing inwards from the side for easy cleaning. Its multifunctionality makes it slightly pricier than a casement window. The tilt-and-turn window is common in ground-floor flats. You might find a wider selection of these windows in triple glazing, as they’re common in Europe, where triple glazing is more frequently used in housebuilding. 
• Sash window: This is a classic design with one or more panels that slide open vertically. Due to their complex mechanisms and aesthetic appeal, sash windows will be more costly than casement windows.
• Bay window: This design combines three or more windows that protrude from the property to provide additional interior space. Bay windows are usually more expensive because of their complex design and the amount of material required to make them.
• Acoustic or soundproof window: This window is designed specifically to reduce external noise. These windows might be made of thicker glass panes or have different gas in their voids, such as krypton. While these windows can be pricier, they’re invaluable for homes near busy roads or in noisy urban areas. Triple glazed windows offer better sound performance than triple glazed windows, as standard, however.

Frame material

The frame material also impacts the cost of triple glazed windows, just as it does for other types of windows. 

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

Glazing specification

Like other kinds of windows, triple glazed windows are made with many different types of glass, which affects their price.

• Gas fillings: Most triple glazed windows are filled with argon. Higher-end options sometimes use krypton or xenon gases, and tend to be more expensive. 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 is designed to minimise the amount of infrared and ultraviolet light that passes through it 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. It’s applied as a thin film. 
• Glass thickness: Typically, the outer and inner panes might be thicker for increased security or soundproofing. And manufacturers can add special coatings, such as Low-E coatings, to reflect heat.
• Acoustic glass: Homeowners can use this for enhanced soundproofing. It dampens and absorbs sound waves, reducing noise intrusion and leakage.

Some of the benefits of triple glazing for windows include the following. 

Warmer house

The better your home’s insulation, the warmer your home, reducing your heating bills. Triple glazed windows offer excellent thermal efficiency, as their superior U-values show.

A lower U-value indicates a material’s enhanced ability to insulate. A standard double glazed window may feature a U-value of about 1.6 watts per metre square kelvin (W/m²K), but a triple glazed window’s U-value could be as low as 0.6W/m²K. 

This suggests that a triple glazed window’s ability to mitigate heat loss can be almost three times that of a B- or C-rated double glazed window. 

Triple glazed windows are between 40 and 50 per cent more efficient than A-rated double glazed windows with U-values of around 1.2W/m²K. Triple glazed windows are nearly always A+ or A++ rated, while double glazed windows are more typically A-rated.

Energy savings

Because triple glazed windows have a naturally low U-value, choosing them for your home will automatically improve its energy efficiency, meaning lower heating bills. The ever-changing energy rate in the UK makes it difficult to calculate precise energy savings from triple glazed windows, but we’ve given an estimated savings cost below.

• Consider that 20 per cent of a property’s heat is lost through the windows, and that triple glazed windows are 40 per cent more efficient than double-glazed ones.
• Imagine that you have an average gas heating bill of £853.30 annually.
• Assume that you’ve upgraded your windows from good-quality double glazing to triple glazing. 
• These triple glazed windows might save you around £68.01 per year.
• The savings will be considerably higher if you upgrade from less efficient windows.

The annual energy savings might not be enormous. But retrofitting your home with triple glazing and making other eco-friendly home improvements, such as insulating floors and walls, will offer you greater savings and make your home more comfortable all year round. 

What are U-values and G-values?

A high U-value indicates a high level of heat transfer, suggesting poor insulation. A low U-value indicates less heat transfer, meaning a higher energy efficiency. Higher energy efficiency results in lower energy bills and a reduced carbon footprint, benefitting the planet.

 

Meanwhile, a G-value relates to how much heat from the sun is being allowed into your home through the windows. A very high G-value would be used to describe windows that let all of the sun’s heat into the home, while a low G-value refers to windows that block some, or all of, the sun’s warmth, meaning the room will not overheat on sunnier days.

Noise reduction

The design of triple glazed windows takes sound insulation to a new level,using three separate panes of glass and multiple air- or gas-filled chambers. The inclusion of that extra pane and gas-filled chamber can reduce external noise by an additional 10 decibels.

Therefore, in a home with an 80-decibel outdoor noise level, which is about the level of bustling street traffic, this could be reduced to a 30-decibel level in a home with triple glazed windows.

Triple glazed windows are around 20–30 per cent more effective at sound insulation than A-rated double glazed windows. 

Reduced condensation 

Triple glazed windows’ enhanced thermal performance reduces the risk of condensation by lowering the temperature gradient between the property’s interior and exterior. 

The third pane of glass and the second gap between the panes bring the temperature of the interior pane of glass closer to room temperature. This means  there’s less condensation formation, and indoor humidity levels are lower. 

This is particularly beneficial in homes that suffer from condensation and dampness around the windows. And it lowers the risk of mould, including the notorious black mould.

Triple glazing offers plenty of benefits, but there are also some downsides. 

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 can be 10–20 per cent more expensive than double glazed ones when additional costs are factored in. 

Environmental factors

While it’s undeniable that these windows can substantially reduce a home’s carbon footprint over time due to decreased energy consumption, there are also upfront carbon costs to consider. 

Triple glazed window production is resource-intensive, and manufacturers must source additional raw materials, such as sand, for the extra glass panes. They use additional energy to mould, transport and install these units. The production of triple glazed windows also requires more embodied energy than double glazed units, as the manufacturing process uses more materials. So, the cumulative environmental impact of producing triple glazing is higher than it is for double glazing. 

In the long term, though, triple glazed windows do yield environmental returns. A study from Glassonweb demonstrated that the carbon dioxide (CO2) savings accrued over a triple glazed window’s lifetime is greater than the amount of CO2 produced during manufacturing.

Increased weight

A triple glazed window’s extra pane of glass and thicker frame increase its weight and thickness, making this type of window unsuitable for thinner or unsupported walls. 

Older walls designed to hold single glass panes also may not be able to support heavier triple glazed units without modifications and strengthening. This doesn’t mean fitting triple glazed units is impossible. There are ways of modifying the window aperture and the wall to secure the extra weight, but this will come at an additional cost. 

Double and triple glazed windows are similar in many ways. But triple glazed windows objectively outperform their counterparts in most technical categories. Let’s break this down in detail. 

Energy efficiency at a glance

To evaluate any sustainable technology, it is vital to examine its energy efficiency. As noted, double glazing has a U-value of around 1.6 W/m²K. But triple glazing can achieve a far superior 0.6 W/m²K. 

In practical terms, 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

For residents of loud areas, triple glazing can significantly reduce exterior noise thanks to the third pane of glass and the additional gas-filled space between the panes. 

Triple glazing is up to 30 per cent more effective for sound insulation than double glazing. This can make a huge difference for those living in noisy environments. 

Balancing cost and climate

Top-notch performance has cost implications. Because of their complex design and the extra materials manufacturers need to make them, triple glazed windows cost about 20 to 30 per cent more than double glazed ones. 

Triple glazing might be excessive in areas with milder climates. The colder it is, the greater their benefits. 

Triple glazing will be considerably more beneficial in the north of Scotland, where temperatures are some 5°C colder than in the south. 

It’s true that triple glazing also maintains cooler temperatures in the summer by keeping heat from solar radiation out of the home when the windows are closed. But in the UK, it’s cheaper and easier to cool a property than to heat it. 

Triple glazing and double glazing compared

Double and triple glazed windows are similar in many ways. But triple glazed windows objectively outperform their counterparts in most technical categories.

Energy efficiency at a glance

To evaluate any sustainable technology it is vital to examine its energy efficiency. As noted, double glazing has a U-value of around 1.6W/m²K. But triple glazing can achieve a far superior 0.6W/m²K. 

In practical terms, 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 10–15 per cent annually.

Noise reduction

For residents in particularly loud areas, triple glazing can significantly reduce exterior noise thanks to the third pane of glass and the additional gas-filled space between the panes. 

Triple glazing is up to 30 per cent more effective at insulating sound than double glazing. This can make a huge difference for those living in noisy environments. 

Balancing cost and climate

Top-notch performance has cost implications. Because of their complex design and the extra materials manufacturers need to make them, triple glazed windows cost about 20–30 per cent more than double glazed ones. 

Triple glazing might be unnecessary in areas with milder climates. The colder it is, the greater their benefits. Triple glazing 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. 

It’s true that triple glazing also maintains cooler temperatures in the summer, by keeping heat from the sun out of the home when the windows are closed. But in the UK, it’s cheaper and easier to cool a property than to heat it.

So, is triple glazing worth it? The answer depends on your personal circumstances. 

The primary considerations are how long you intend to remain in your property, how well your current windows perform and how much an upgrade will cost you. 

A long-term perspective

Looking at home improvements as long-term investments is essential for homeowners who are committed to their current residence for the long haul. While triple glazing is more expensive initially, these types of windows will pay for themselves over time. 

With annual savings of around £70, it might take as long as 34 to 51 years to break even from upgrading a three-bedroom property to triple glazing. 

However, this assumes that you already have double glazed windows. If you have single glazed windows or are considering an extension or new build, then the value of triple glazed windows is considerably higher. Upgrading to triple glazing from single glazing would make more sense. 

You can also offset the cost of the windows against any increase in your property’s value. Having modern, high-performance glazing is critical to obtaining energy certificates and boosting your home’s appeal to buyers. 

Sound insulation

Triple glazing can reduce external sounds by up to 10 decibels more than double glazing. If you’re struggling with external noise from roads, railways, aircraft or busy areas, triple glazing could make a substantial difference in your overall well-being. It might also make it easier to sell or rent a property in a loud area. 

New builds and extensions

The cost–benefit analysis of fitting triple glazing is more favourable for extensions or new builds because you won’t have any windows to replace and dispose of, and the labour costs will be lower. You may also obtain a better energy rating for the property, which will be beneficial if you decide to sell or rent the property. 

Location

The colder the environment, the more effective triple glazing is at heat insulation. Generally speaking, triple glazing in the colder north of the UK will yield higher energy savings and quicker payback times than in the warmer south of the country. However, there are still other advantages to consider, no matter the climate of your location. Triple glazed windows not only keep homes cooler in the summer, they also reduce condensation and enhance soundproofing. Moreover, virtually every part of the UK is vulnerable to cold winters, making triple glazing a worthwhile investment for many. 

The location of your property is another consideration. You might not be able to install triple glazed windows in properties built on Article 2(3) land, such as conservation areas, without planning permission.

This extends to areas where the local planning authorities have placed an Article 4 direction that restricts development. Moreover, if you own a listed building, you’ll need Listed Building Consent to replace the windows. Failure to obtain it is a criminal offence. Obtaining permission for double glazing is tricky enough for these properties, but doing so for triple glazing is even trickier.

That’s not to say you can’t upgrade your windows in these situations. But there’s more red tape, and you’ll need to obtain the necessary permissions.

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 objectively beats double glazing across virtually every performance metric. For energy efficiency, noise reduction or insulation capacity, triple glazing is the superior choice. 

However, this performance comes with trade-offs. The initial cost of installing triple glazed windows is notably higher, and the production of these windows requires more embodied energy. As such, it may take a few years of usage before the energy savings from triple glazing outweigh the initial environmental impact. 

Overall, homeowners and builders should weigh the immediate costs and environmental considerations against the long-term gains when deciding whether to fit triple glazed windows.