Triple glazed windows are emerging as the gold standard as homeowners increasingly prioritise sustainability, comfort, and energy efficiency. Although these windows cost up to 20% more than double glazing, the money saved on heating bills means they can pay for themselves in the long term.
But are they really worth the investment in the UK?
Often installed as standard in Scandinavian countries, they are becoming increasingly popular in the UK, especially in Scotland and the colder, northern counties where the magnified insulation is more beneficial than in the milder southern regions. However, homeowners throughout the UK can enjoy the enhanced soundproofing, increased security, and elevated property value that triple glazing brings.
In this article, our experts delve deep into the world of triple glazed windows, exploring their benefits, the science behind them, and why they might be the perfect fit for your next home improvement.
How do triple glazed windows work?
Triple glazing builds upon the foundation set by double glazing, incorporating an additional glass pane and an extra sealed compartment to amplify heat retention.
The unit comprises two low-emissivity (low-E) glass panes treated with a metal oxide layer to balance reducing solar heat during summer and retaining warmth during winter. Sandwiched between these layers is a Low Iron pane, enhancing heat conservation and retaining warmth in living spaces.
To prevent heat leakage, the edges of each sealed section have a spacer bar. The construction material depends on the manufacturer, but typically, uPVC is used due to its thermal insulation properties and non-conductive nature.
The intervening spaces are filled with an inert gas, such as argon or krypton. This design enhances thermal efficiency, slowing down heat transfer more effectively than the singular cavity found in double glazed windows.
Combined, these elements create a remarkably energy-efficient design, effectively preserving indoor warmth and reducing your heating expenses.
Pros and cons of triple glazing
What are the benefits of triple glazing?
Adding an extra pane of glass to a window might seem inconsequential. However, this simple addition can profoundly impact your home’s comfort and efficiency.
Improved energy efficiency
Triple glazed windows provide superior thermal insulation compared with single or double glazed windows, often achieving an energy performance rating of A+ or A++ – the highest possible rating.
The superior performance of triple glazing can be attributed to its sealed construction, which prevents draughts and minimises cold spots in the home. Consequently, households can save on their heating bills, with some manufacturers claiming this can be as much as 50%.
U-values quantify the rate of heat transfer through a material and measure the insulation effectiveness of a building’s components – the lower the U-value, the better. Triple glazed windows boast a U-value close to 0.9W/m²k (watts per square metre kelvin), in contrast to double glazed units, which register around 1.2/1.4W/m²k. Several manufacturers claim that triple glazing is up to 40% more thermally efficient than standard A-rated double glazing and 60% more efficient than C-rated double glazing.
Enhanced temperature regulation
Another essential factor to consider is the G-value. Also known as Total Solar Energy Transmittance, the G-value measures the amount of solar heat passing through the windows with 0 as the lowest measurement and 1 as the highest. A higher G-value can result in an uncomfortably warm home during summer, especially in south- or west-facing rooms.
Double glazing typically has a G-value of up to 0.78. However, triple glazing enhances performance with a top G-value of just 0.46. This distinction is crucial for maintaining a comfortable temperature in the height of summer.
Improved sound insulation
The extra pane of glass in triple glazed windows can improve soundproofing, although this depends on the glass thickness and the width of the spaces between the panes. If you choose acoustic glass, the reduction, according to some suppliers, can be 40 dB.
Increased security
Triple glazed windows are not only advanced in terms of energy efficiency but also in safety. They often incorporate superior safety enhancements, such as the Secured by Design locking mechanisms. Including an extra pane of toughened glass fortifies their structure, making them significantly more robust and difficult to shatter.
Reduced environmental impact
The production of triple glazed windows has raised some concerns regarding its environmental impact and whether the CO2 emissions generated from producing the window unit and its increased transportation weight might eclipse the carbon savings the windows offer once installed.
However, the true environmental efficacy of triple glazing hinges on the installation location. Colder, northern countries, such as Norway and Sweden, will undoubtedly reap more pronounced CO2 savings compared to the milder climate in the UK.
A study by Glass for Europe, the trade association for Europe’s flat glass sector, revealed that the CO2 savings over a triple glazed window’s lifespan surpasses the increased emissions produced during manufacturing. In Europe, the carbon payback period spans between 35 to 76 months, with colder northern European regions skewing towards the shorter end of that spectrum.
What are the disadvantages of triple glazing?
Higher prices
Triple glazed windows come with a price tag typically 10% to 20% higher than their double glazed counterparts due to their more complex design and greater amount of materials used in their construction.
Increased weight
Glass carries considerable weight, so triple glazing is heavier than double and single glazing due to the third pane of glass. This increased weight necessitates frames and installation methods that can aptly support the added weight. However, well-designed windows will always be constructed to dimensions that can manage this extra weight effectively.
Installation issues
The added weight of triple glazed windows presents a marginally increased risk of causing wall damage during installation. However, with an accredited professional installer, such concerns should be minimal.
How much does triple glazing cost?
Triple glazed window prices are approximately 10% to 20% higher than double glazing prices. This is due to the added chamber and spacer bars increasing manufacturing costs, and the greater weight potentially raising transportation expenses.
The price also depends on the window style and frame materials chosen, with uPVC casement windows being the cheapest option and timber bow or bay designs being the most expensive.
While specific grants for triple glazed windows don’t exist, you can explore other schemes to boost energy efficiency, covering a range of home improvements, including replacement windows.
Installation costs are typically embedded in double glazing quotations. However, with triple glazing, some providers prefer to give custom quotations instead of double glazing, where standard-sized units are often available.
Due to the increased weight of triple glazing – up to 10kg more in some cases, another cost consideration could be structural support. However, your installer should explain if this is necessary.
Several double glazing companies offer free or discounted upgrades to triple glazing when considering a double glazed installation, so always ask if this is the case.
Double glazing vs triple glazing
Deciding between triple glazing and double hinges on factors such as your home’s geographical setting, desired energy efficiency, personal tastes, and budget constraints. Before settling on an option, comparing quotes from triple and double glazing providers is advisable.
Triple glazing surpasses its double glazed counterpart for thermal retention and energy efficiency. This translates to increased energy and CO2 savings over time. While the initial investment might be steeper, many find the long-term benefits of reduced carbon emissions and lower energy bills worth the extra expenditure.
For those prioritising noise insulation, triple glazing can offer superior results, providing the spaces between the panes is around 16mm. Some manufacturers incorporate acoustic glass or variants with a greater iron concentration, which further enhances sound insulation.
If you wish to increase your home’s energy efficiency further, consider investing in a new combi boiler or insulation for your walls or loft.
Is it worth installing triple glazing?
A home can lose up to 20% of its warmth through windows. If yours are due for an upgrade, even though its upfront cost is higher than double glazing, triple glazing can offer increased energy efficiency of up to 30%, reducing your heating bills.
Incorporating a mix of triple glazing for colder rooms and double glazing for sunnier, south-facing spaces can offer the best of both window options.
Homes in the colder parts of the UK, such as Scotland or northern England, could benefit from the increased warmth offered by triple glazing more than the milder southern counties.
Getting several like-for-like quotes is always recommended in order to assess your options.
Triple glazing frequently asked questions
Triple glazed windows provide superior insulation compared to their double glazed counterparts. In colder months, the warmth generated inside the house remains indoors, reducing the need for additional heating. As a result, homes with triple glazing tend to be warmer, and homeowners typically rely less on their heating systems, leading to lower energy consumption and, by extension, reduced heating bills.
For many homeowners, especially those living in colder counties, triple glazing is worth the additional cost, while for others, the further cost might not be worth the benefits.
Triple glazing can significantly reduce the likelihood of condensation forming on the inside of windows, or eliminate it altogether. By providing a better insulating barrier between the cold outside air and the warm interior air, the innermost pane of a triple glazed window remains warmer, making it harder for moisture from the room to condense on its surface.
Adding triple glazing to existing windows is more complex than just inserting an additional pane of glass into your current double glazed units.
In most cases, it requires a complete replacement of the window unit, including the frame, to ensure it can accommodate the added thickness and weight of the third pane of glass. Additionally, the existing frame might not be designed to support the weight of triple glazing, and the seals may need to be improved to create the airtight chambers necessary. For those considering upgrading to triple glazing, investing in new triple glazed window units is often more practical and efficient than trying to retrofit existing ones.
Katharine brings over a decade of writing and research expertise, collaborating with some of the UK’s top organisations, such as the Independent, the Federation of Master Builders, Architectural Digest, and Cuvva Car Insurance. Her areas of specialisation include renewable energy, advanced technologies, and various aspects of home improvement, like kitchen renovations, combi boilers, and double glazed windows.
