Double-glazed windows have been the standard for windows for the past 40+ years, with the structure of the window preventing heat loss and condensation, and even promoting noise reduction. Beforehand, it was hard for single-paned windows to be beaten as the frames themselves reduced all the energy efficiency efforts of double-glazing units. However, that changed when uPVC was introduced into the market – offering high insulation properties whilst also being loved for its cost-effectiveness. This popularised double-glazed windows, and they took their place as one of the top home improvement investments in the market.
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However, there has been talk of triple-glazed windows someday soon taking over as the standard – leading many to question what the difference between double and triple-glazed windows is. With 93% of homes in the UK having double-glazed windows already installed, buyers need a justification to spare the expense.
However, there has been talk of triple-glazed windows someday soon taking over as the standard – leading many to question what the difference between double and triple-glazed windows is. With 93% of homes in the UK having double-glazed windows already installed, buyers need a justification to spare the expense.
Improving the overall energy efficiency of your home is important to keep running costs low. Prices of gas spiked to unbelievable levels as a result of the geopolitical turmoil caused by Russia’s invasion of Ukraine and cemented in the minds of many that controlling some expenses is impossible.
So, double and triple glazing – what are the differences? In this article, we’ll answer exactly that.
Triple glazing has recently come to the market as the next reasonable step for UK homes to take. Triple glazing incorporates three panes of glass instead of just two, creating two insulating gaps between the glass as opposed to double glazing’s one. Logically, it makes perfect sense that our homes should start to incorporate three panes of glass to improve our thermal efficiency as the technology becomes available, but what are the main differences between double glazing and triple glazing, and are they substantial enough to warrant the upgrade?
Table of Contents
What can double glazing do?
Between 10% – 20% of heat loss occurs through windows, and single-glazed windows offer next to no protection. Because the glass is in contact with the cold air outside, heat transmission increases. However, double-glazed units have two panes with insulating gas or air separating them. This gap slows down heat loss by a huge amount. Upgrading from single to double can increase heat retention by 50% plus. How much exactly depends on the window’s grade.
Double-glazed windows are graded via the energy performance scale, from G – A+. The difference in efficacy between them is detailed in the table below:
| Rating | U-Value (W/m²K) | Heat Loss Reduction vs. Single Glazing |
| A++ | ≤ 0.8 | Up to 80% reduction |
| A+ | 0.9 – 1.2 | 70–75% reduction |
| A | 1.3 – 1.5 | 65–70% reduction |
| B | 1.6 – 1.8 | 55–65% reduction |
| C | 1.9 – 2.0 | 50–55% reduction |
| D | 2.1 – 2.2 | 40–50% reduction |
| E | 2.3 – 2.7 | 20 – 40% reduction |
| F-G | ≥ 2.8 | Exceedingly poor (single pane window level) |
The difference between the grades lies in their construction elements. Such as:
- Glass type – Glass can be anything from basic to low-emissivity variants, further changing how slow heat transfers through.
- Coating – Double-glazed units can be coated with material designed to reflect heat inside.
- Gas fill – Whilst air is a perfectly good insulator, there are more advanced alternatives, such as argon, krypton or xenon.
- Spacer bars – Spacer bars maintain the air gap between panes, but they also have their level of heat retention ability. Aluminium is less conductive, whereas warm-edge spacer bars are designed to reduce heat transmission.
- Frame material – uPVC is a great material that offers great levels of insulation for the price, but not only are there different qualities of uPVC, but there are also premium alternatives such as composite.
All these are combined to increase the energy efficiency of your home. By having two panes of glass instead of one, the same pressures are not placed on the glass.
Triple Glazing
You may have noticed that we claimed that double-glazing windows are rated from G to A+. But if you see the table above, you can find that there is one more grade – A++.
| A++ | ≤ 0.8 | Up to 80% reduction |
A++ is unattainable via double-glazing windows – they are the sole domain of the highest quality of triple-glazed windows. Does this mean all triple-glazed windows are A++? No. Double and triple-glazing windows can both fall in the E – A+ ranks. The A++ rank simply denotes that all the highest standards of improvements are in place, with the addition of triple glazing.
So it’s possible for double glazing to have better heat retention than triple glazing due to the many small improvements made to its construction. That being said, on average, triple-glazed windows are typically better. Plus, they have other enhanced benefits.
The benefits of triple-glazed windows versus double-glazing are as follows:
- Better insulation – Explained above.
- Improve noise reduction – The third glass pane adds another layer to acoustic insulation, typically blocking between 30 – 40% more outside noise.
- Improved security – Double-glazed units are already strong due to the enhanced frame and glass construction, but triple-glazed windows add a third pane, making it that much more effective.
- Condensation prevention – Triple-glazed windows’ additional pane of glass further separates the cold surface of the outside from the warm surface of the inside, making the glass more resistant to condensation.
- Property value – Triple and double glazing both increase energy efficiency, therefore lowering running costs. Should these efforts result in EPC increases, you can see your home increase in property value.
How much does either window cost on average?
Three factors determine the cost of either window:
- Energy performance scale – The grade of your windows mirrors how much work has gone into the construction to improve insulation ability, incurring higher costs.
- Window frame material – The materials your windows are made of add to the price. Composite frames, for example, are multiple layers of materials bonded together to get the best of all of them. The manufacturing costs go into how much you’ll spend.
- Window type – Finally, the type of window. This doesn’t include what the window is made of, but rather the style. For example, casement windows that open up at the sides are standard, whereas bay windows, which create an alcove protruding outwards (allowing more window panes due to angle) cost far more due to their premium construction.
That being said, triple-glazing can be 20%+ more expensive than double-glazing units. Whether or not the cost is worth it depends on the window it’s replacing, as well as its age.
Still, for averages by grade:
| Grade | Double Glazing (£ per window) | Triple Glazing (£ per window) | Energy Efficiency |
| A++ | N/A | £1,200 – £1,800 | 80-85% |
| A+ | £700 – £1,100 | £1,000 – £1,500 | 75-80% |
| A | £600 – £1,000 | £900 – £1,350 | 70-75% |
| B | £500 – £900 | £750 – £1,200 | 65-70% |
| C | £400 – £800 | £650 – £1,050 | 60-65% |
Conclusion
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FAQs
What is the main distinction between double and triple glazing?
When considering double glazing vs triple, double glazing has two panes of glass with one insulating gap among them, whilst triple glazing features three panes of glass with two insulating gaps, giving advanced thermal insulation. Beyond that, the extra pane provides extra security, as well as increased levels of noise reduction.
However, it’s worth pointing out that this doesn’t mean that triple-glazed windows are automatically better than double-glazing. If heat insulation is what you’re after, you should always check to see the window energy rating.
Triple glazing has been continuously tested to be around 30 – 40% more thermally efficient than double glazing, significantly improving the energy efficiency of a home, with U-values as low as zero.
Are triple-glazed windows worth the cost of double-glazing?
When deciding between double or triple glazing, homeowners ought to weigh the advantages in opposition to the charges based on their particular wishes and budget. While triple glazing offers improved thermal efficiency, it costs around 20% more than double glazing.
Whether or not it’s worth the cost entirely depends on if you’re replacing existing windows. What window energy rating is your window versus the triple glazing? Also, there are the added benefits besides insulation – such as the extra sound reduction or increased resistance to condensation.
