Triple Glazing vs. Double Glazing - is it really worth upgrading?

June 27, 2018
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For years, double glazing has been the industry standard for noise reduction, thermal insulation, and security - in other words, everything you want from a window. But as the demand for energy efficiency in new buildings increases, and new legislation comes into place, a new contender has entered the arena: triple glazing.

For many, this is a slightly controversial issue. Due to the dodgy door-to-door dealings of a minority of salespeople in the fenestration industry, double glazing has developed a bit of a bad rep. The introduction of a new alternative - the name of which practically screams ‘unnecessary moneyspinner’ - is already raising some eyebrows.

But the evidence is in, and it’s a fact: triple glazing exceeds double glazing in performance in many areas. It is, however, inevitably more expensive. These are the two factors with which professionals need to become familiar, and weigh up to ensure they can recommend the right choice for each specific project.

Read on to discover the ways in which double and triple glazing differ, in order to decide if the upgrade is really worth it for you or your clients:

Comfort

Comfort is one of the most important factors when considering a glazing upgrade - and this contributes significantly to the allure of triple glazing. What’s interesting is the tapering of the potential impact an upgrade can have, with a significant leap between single and double glazing, but a less noticeable increase from double to triple.

The difference in insulation between single glazing and a modern double glazed window is notable: in cold weather, the internal surface temperature next to a single glazed window sits at around 1C. This is a far cry from the 21C average room temperature. Replace those windows with modern double glazing, however, and the surface temperature rockets up to 16C - a very noticeable difference.

If you were to replace those windows with triple glazing, however, the average surface temperature rises by only a couple of degrees, to 18C. This might not seem like a lot, but homeowners will feel the difference - 90% of those surveyed in the UK stated that their house feels warmer with new triple glazed windows installed.

It’s also worth thinking about aesthetics, as for many homeowners, this will play a large factor in their decision to upgrade. While both double and triple glazed windows can be constructed in a wide variety of styles, there are an increasing number of high-end products such as luxury triple glazed sliding doors that are appealing to the top end of the market. In the case of a high-end home renovation, the increasing scope for top-tier triple glazing is making the option more tempting for those looking for something truly unique.

Winner: Triple Glazing

Energy efficiency

One of the primary reasons for triple glazing to even exist relates directly to energy efficiency. Fundamentally, in adding a third layer of insulating glass, triple glazing presents an increased level of insulation - but is this high enough to justify its inclusion in a project, or a full replacement in a home? 

The metric used to measure the energy efficiency of windows is the same as the one used for walls and roofs: ‘U-value’. As building regulations are bolstered and minimum standards increase, windows with a low U-value as possible are increasingly required - and there’s no denying that triple glazing outperforms its lesser counterpart.

The U-values of double glazed windows have fallen in recent years, as production techniques and technology have improved. The vacuum between the panes of glass is now often filled with an inert gas such as argon, while low emissivity coatings and the use of wider cavities between panels (at least 16mm) are now prolific. The result is that modern double glazing windows offer a U-value of up to 1.6-1.8.

Triple glazing, on the other hand, performs even better. Using the same innovative technology, along with an additional pane of glass, triple glazed windows can reduce their U Value to as little as 0.5 to 0.7.

It’s also worth noting that as we become increasingly aware and conscious of the impact our buildings have on the environment, the more insulative and energy efficient a solution is, the ‘greener’ a home can become. This is likely to be an important factor for many clients, particularly as we place increasing emphasis on the importance of being eco-friendly.

Winner: Triple glazing

Heat absorption

Windows don’t just impact on insulation: they absorb heat from the sun too, and in certain cases can even act as net contributors to the heating of a home. Yet while this is true for high-end double glazing units, the same can’t be said for triple glazing.

The additional layer in a triple glazed window acts as a greater barrier to heat transference, and the result is that these windows don’t always absorb as much as they lose. This can be tricky to measure, but some steps are being taken to demystify the issue. In the UK for example, windows are rated on the comparison between how much heat they lose and how much they contribute, with a rating between ‘A’ and ‘G’ provided to qualify this measurement.

What this means is that in some situations, and in certain climates (particularly those that don’t suffer from extreme cold), triple glazing is less effective. The overall contribution to the warmth in a home offered by double glazing can outweigh the insulation offered by triple glazing, and so many would argue an upgrade simple isn’t warranted.

Winner: Double glazing

Noise reduction

While many clients will prioritise energy efficiency, the comfort of a warm home and the savings from better insulation, noise reduction is another area in which double and triple glazed windows differ. While it might be easy to assume that the additional thickness of triple glazing would simply block out more noise, this isn’t always the case.

The noise-reducing potential of a window is slightly more complex than simply how thick the window is. The two primary elements are the thickness of the glass panes,and the size of the gaps between the panes. It’s also important to understand that sound travels more effectively through a solid than it does a gas.

In a double glazed window, if the panes of glass are of two different thicknesses, then as sound passes through it the wave will be changed by the first (thicker) pane, before passing inefficiently through the gas in the center, and being further distorted by the second pane of glass. The result is a significant drop in audible noise.

In a triple glazed window with similarly sized panels (which is often the case), the noise from outdoors meets less resistance in the form of gas, and remains undistorted due to the uniform thickness of the panels, ultimately presenting less of a barrier to sound.

The result of this is that when comparing two double and triple-glazed windows of the same thickness, the double glazed option will often outperform the triple-glazed version in terms of decibel reduction.

Winner: Double Glazing

Cost

This is the factor that, for many clients and contractors, will be the most relevant and important. At the heart of every project lies a budget, and the inevitably higher cost of triple glazing is a variable that will need to be weighed by both parties, and compared with potential savings as a result of energy efficiency.

The biggest question for many home and property owners is whether triple glazing will offer enough of a reduction in heating bills to eventually pay for itself. The honest answer is that it doesn’t actually differ as much as you might think from double glazing. Over the long term, however, even this small difference could be enough to justify the purchase.

It’s difficult to put a specific price on how much more it will cost to install triple glazing in a project, but the increased shipping costs due to weight, a need for more precise installation, and a greater material cost all contribute to triple glazing being a more expensive option.

As a rough ballpark, in the average UK home it would cost around £5000 to install double glazing (from single), whereas an upgrade to triple glazing would cost over £7000.

Compare this with the potential savings to be made, and it’s clear that if a homeowner is hoping to save extra money by upgrading to either double or triple glazing, they’re in it for the long haul - but that haul could be slightly more achievable with triple glazing.

These figures are admittedly painted with a broad brush, but based on a saving of around 10% annually on an average heating bill in the UK, double glazing would take approximately 77 years to pay for itself. Triple glazing on the other hand, with its increased insulative powers (and greater initial cost taken into account) could be repaid in closer to 45 or 50.

While this might seem like a win for triple glazing, ultimately, context needs to be considered. With the average first-time homeowner aged 25-35, many of your potential clients will only really be able to reap the benefits of a triple-glazed upgrade by the time they’re 70 - and that’s in a best-case scenario.

Winner: It depends!

Conclusions

If you want to look at it in the most reductive way possible, that’s two victories to both double and triple glazing, with one tie. But the situation clearly isn’t that simple, and there are a lot of variables for your clients to consider.

Ultimately, if a building is equipped with poor quality double or single glazing, then the potential benefits of an upgrade are self-explanatory. In these situations it can be sensible to adopt a ‘may as well’ attitude, and opt for a triple-glazed solution - particularly when you consider that the impetus for buildings to reduce their energy consumption is only likely to increase. If budgets are tight however, double glazing remains the industry standard for a reason, and offers a reliable and tested solution.


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