Triple-glazed Windows – Are They Worth It?
In this guide, we explain why triple-glazed windows are more energy-efficient, quiet and secure, and how to decide whether the added cost for a more sustainable option is worth it for your home.
Jump to a section
Window energy ratings and U-values
What are the benefits of triple-glazed windows?
Can you replace double-glazed panes with triple-glazed?
A look at the best triple-glazing available
Are triple-glazed windows worth it?
What is a triple-glazed window?
In 1970, over 90% of British homes had single glazing – just one pane of glass per window to keep out the cold. Then, to combat heat loss, mould, condensation and subpar security, double-glazing took off. By the year 2000, around three-in-four British homes had two panes per window instead of one.
Since then, researchers and designers have consistently improved the performance of double-glazed windows to make them even better at capturing heat from the sun and retaining it on cold days, without compromising on light transmission.
Today, triple-glazed glass – three panes instead of two – is used in the most energy-efficient windows. Like double-glazing, triple-glazing uses sealed cavities filled with inert gas between the panes to minimise heat loss. The most advanced triple-glazing also uses special invisible coatings (called ‘low-e’ glass) to increase thermal performance further.
All windows have ratings that sum-up their energy-efficiency. One rating is the U-value, which represents how much energy the window frame and glass lose and how quickly heat escapes. The lower the U-value, the better a window’s energy performance.
Old single glazed windows
Standard double-glazing with air between the glass
2.8 to 3 W/m²K
Modern double-glazing with inert gas and low-e coating
1.2 to 1.6 W/m²K
Latest triple-glazing with inert gas and low-e coating
0.8 W/m²K or lower
The other system is a letter-based rating from A++ (best) to E (worst). Since 2010, all new windows must be rated at least C, but to keep your bills down and help the environment, you should aim for A or B rated windows where possible. To learn more, check out our guide to energy-efficient windows.
Our most energy efficient triple glazed window
Triple-glazing offers the same types of benefits as double-glazing but with even higher performance. So if you’re interested in achieving the best heat and sound insulation possible, it’s worth considering three panes instead of two.
A warmer home and lower energy bills
The image above shows the dramatic difference triple-glazed windows can make to the energy performance of your home.
The red and white areas show where heat is being lost most significantly (e.g. the downstairs, single-glazed windows). The dark blue parts show where heat is prevented from escaping (e.g. the upstairs, energy-efficient glazing).
Naturally, the difference in energy performance between double- and triple-glazing isn’t always as dramatic as between single and triple. It all depends on the quality of the windows.
Low-E coated triple-glazing is up to twice as energy-efficient as standard double-glazing.
You don’t have to choose triple-glazing to achieve excellent energy efficiency. High-quality double-glazing, such as the glass found across our range of double-glazed timber windows, offers strong thermal performance in most settings.
Triple-glazing makes the most sense when you want maximum thermal performance, such as:
Superior sound insulation
Just because a window has three panes of glass instead of two doesn’t mean it will automatically offer better sound insulation. In combination with the glass type and spacers, the size of the gap between the panes is critical in deciding the acoustic performance of the window.
STC ratings sum-up a window’s ability to reduce sound. The higher the rating (ranging from 20 to 65), the better the acoustic insulation. A single-pane window usually has an STC rating of around 25, whereas double-glazing is typically 29-37, depending on whether ‘dissimilar glass’ (panes with different thicknesses) and lamination are added.
Triple-glazed windows, such as our Stormsure Energy+ window, can achieve incredible STC ratings of 40 or higher. It’s only when the STC rating reaches 40 that nearby train lines, passing lorries, road works, and other significant noise issues are solved.
In most cases, an extra pane of glass makes triple-glazed windows more resistant to shattering by an intruder than double-glazing. However, for extra peace of mind, it’s worth looking for laminated triple-glazed windows. This means the glass cracks instead of shatters, making forced entry significantly harder.
For an extra level of security, look for windows with Secured by Design accreditation. Read more about how we meet the highest security standards in our windows and doors.
Glass-only replacements are possible in some situations, but only if you have a suitable framing system. If your window frames can’t support triple-glazing's extra weight and thickness, you’ll need to replace the whole window unit.
If you go this route, you get the benefit of choosing your window frame material, which makes a big difference to energy-efficiency, not to mention the style and character of your windows.
Check out our article on timber vs uPVC windows to weigh up the two main window materials' pros and cons.
Benefits of the triple-glazing found in our Stormsure Energy+ windows:
Improved energy efficiency with our highest energy rating.
Reduces noise transmission to create a more comfortable home environment.
Improved security benefits for extra peace of mind.
- Choice of colours and design options to create the perfect aesthetic.
- Made from natural materials to reduce the environmental impact of carbon emissions.
To achieve the above benefits, triple-glazed windows typically cost 20-50% more than double-glazing. But remember that high-quality double-glazing windows could easily outperform lower-quality triple-glazing on thermal insulation and sound reduction.
Check the energy and sound ratings, low-e coatings, and window frame features (e.g. warm edge spacers), plus customer reviews, to make sure the extra money will make a worthwhile difference to your home.
On that point, it’s also worth considering whether your walls, doors, and roof are sufficiently insulated to make triple-glazing worth it. If they leak more heat than they should, the energy conserved by an extra pane of glass may not lower your energy bills by much.
Finally, if cost is a concern, you could consider triple-glazing for only the coldest areas of your home, such as north-facing windows.
Still curious whether double- or triple-glazing is the right choice?
Our window quote tool will give you a free bespoke price quote based on your choice of style, size and glazing type.