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What are the benefits of triple glazing?

Every penny counts when it comes to saving money on your heating bills. Foot for foot, you lose more heat through your windows than anywhere else in your home. Anywhere between 10% to 18% of your home’s warmth goes straight out of the windows, putting glazing right up there with roofs, walls and floors as the main contributor to heat loss.  

Because of this, the type of windows you have will be taken into account by an energy assessor to determine the energy rating of your home for its Energy Performance Certificate.

Triple glazing is installed as standard in new homes in colder climates, like Scandinavia and Canada. And now, many home-owners in the UK are considering triple glazing as an effective way to make their homes more energy efficient.  

Here’s what you need to know about triple glazing. 

What is triple glazing? 

It’s not one, not two, but three layers of glass within a sealed, airtight unit in your windows. The cavity between each pane is filled with air or an inert gas – most commonly argon or xenon – that acts as additional thermal insulation.  

What’s the difference between double and triple glazing?   

Quite simply, the number of panes. That extra third layer of glass, and the additional layer of air or gas, is the difference. Triple glazing is, in general, heavier, and more insulating than double glazing.  

Externally, there should be no visible difference between good quality double and triple glazing. Building regulations do not permit single glazing to be installed in the UK today, apart from in some listed properties. 

What does U-value and G-value mean ⁠— and why are these terms important? 

Here’s the science. You need to consider your windows U-value (thermal performance) and G-value (solar performance). The better a home is insulated, the lower the U-value will be. The more solar heat is allowed into a building – from the sun’s rays – the higher the G-value will be. In warmer climates, you want the G-value to be lower to prevent too much heat coming in. 

Triple glazing has a better U-value than double glazing because it’s more effective at retaining heat inside the house. However, double glazing is more effective than triple glazing at letting warmth from the sun into your house (the G-value). But in the UK, thanks to our climate, the difference in G-value between double and triple glazing is small. 

Consider also what direction your windows face. Triple glazing might be best on north facing windows where there is less potential benefit from G-value. And you might prefer to choose double glazing for south-facing windows and benefit from the heat of the sun. But it’s possible to have a mixture of double- and triple-glazed windows in your home. 

Are there any other rating systems to know? 

The British Fenestration Rating Council (BFRC) assesses the energy performance of windows and doors with ratings that go from A++ (the best) to E.  

A to A++ is considered to be energy positive.  

What are the benefits of triple glazing?    

Reduction of heat loss in your home 

The thermal insulation of triple glazing helps to keep warm air inside your house and prevent cold air coming in, which reduces heat loss through your windows and glazed doors. This improves a home’s carbon footprint and lowers heating bills. 

Home security 

Triple-glazed windows are far harder to smash, and because they’re a sealed unit, they’re more difficult to lever from the outside, making your house more secure. 

Noise reduction 

They’re also an effective noise dampener. Their good sound insulation will make your home quieter. And they lower condensation inside your home. 

Overall, these advantages could be good selling points to highlight to future buyers when it comes time for you to move. 

What are the disadvantages of triple glazing?   

The cost 

Triple glazing is more expensive – see below – and those three panes of glass are heavy, meaning that you might have to spend more on the window frame and hinges to support them. 

Triple glazing isn’t suitable for all homes 

They might not be suitable for your home if you live in a listed property, and you’ll probably need to get permission if you live in a conservation area. 

Triple-glazed windows are difficult to repair when damaged 

Triple-glazed units cannot be easily repaired. While they are robust, if they do become damaged and condensation forms between the layers, you’ll need to replace the entire unit.  

How much does it cost to triple glaze windows? 

Triple glazing is on average at least 20% more expensive than double glazing. For a ballpark figure, allow at least £2,000 to £2,500 for triple glazing four windows.  

Adding extra insulation can push the price up too. For example, invisible Low E glass, which has a metal oxide coating that reflects heat back into the room, or a more expensive and effective insulation gas in the gap between the panes, will add to the overall cost. 

Does triple glazing improve energy efficiency? 

Yes. On average, triple glazing is 40% to 50% more thermally efficient than older double glazing, especially with a well-insulated frame.  

The technical explanation is as follows: triple glazing has a U-value (measuring the thermal loss) of around 0.8 W/m2K (watts per square metre per degree Kelvin). Modern double glazing has around 1.1 W/m2K and older double glazing is closer to 3 W/m2K. For single glazing, this rises to 5.2 W/m2K.  

New building regulations introduced in June 2022 state that any new building in the UK must have windows with a U-value of 1.4 W/m2K or less. 

Can I triple glaze existing windows? 

In theory, yes, but the additional weight that triple glazing carries may require changes to existing window frames. 

How long do triple glazed windows last? 

Most manufacturers say their triple glazing should last for 20 years. After that time, the energy efficiency is often not as effective. 

How much warmer is triple glazing? 

There’s a reason why triple glazing has been used so extensively in northern Europe for years. However, significant improvements to the U-value of double glazing in recent years has lowered the gap between double and triple glazing. Upgrading to triple glazing accounts for a 5% improvement in the overall energy performance of a new house, according to figures from  

Is triple glazing right for my home?   

It could be, if you’re replacing single-glazed windows, or windows with older double glazing. Or if you have an issue with noise outside your house, or you live in an especially cold area. 

The improvement in heat retention and energy efficiency, and the money you can save, can be significant. If you’re replacing relatively new double glazing, it might not prove worthwhile. However, like underfloor heating compared with conventional heating, triple glazing is undoubtedly “better” for energy efficiency and for lowering the carbon footprint of your home. 

Want to check your home’s energy rating? Find out how to check your Energy Performance Certificate.

READ MORE: How do solar panels work and how much do they cost?

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