Is Triple Glazing Worth It?

There has been some negative press about how long it can take to pay back the investment and if triple glazing is worth the additional cost. Does the cost saving on energy bills justify the difference in price between double and triple glazing?

In the UK, triple glazing has been seen as a ‘luxury’ option for windows and not the standard install of Scandinavian and some European countries. However, triple glazing is not just about how long it takes to pay back the investment of installation.

There are several reasons why triple glazing is worth it (or isn’t).

Why U values are important

The Window Energy Rating (WER) was introduced to compare the energy efficiency of different windows.

WER uses G-values for solar gain and U-values for heat transmission as part of its calculation.

WER is generally a good rating system to compare like-for-like products from different manufacturers, but when you are considering different rooms with specific needs, then it’s better to look at individual values separately.

Windows are predominantly a means to allow natural light into a room whilst keeping the space dry with a consistent room temperature. In the UK, we don’t experience the same levels of cold in winter as Scandinavia, but the predominant need is still to reduce heat loss and the U-value is the metric of focus.

A U-value measures the heat transfer through a material – the lower the U-value, the greater the energy efficiency. Building Regulations require all replacement windows to be 1.4 W/m2K, or lower.

Single glazed windows can be 4.8 W/m2K or more. Double glazing ranges from 2.4 W/m2K for old windows to 1.3 W/m2K for modern Everest Double glazed windows with Argon gas and warm edge spacers.

Everest Triple glazed windows are rated at 1.0 W/m2K.

The benefit of houses built with low U-value components are:

• Increased room comfort
• Energy bill savings
• Less surface mould growth
• Improved building health

Triple glazing and energy efficiency

Upgrading from single to double glazing is a considerable jump in energy efficiency (see below) and cost savings for energy bills. Replacing single glazing with A++ double glazing can save up to £235 a year on energy costs. But, some people think that the 23% upgrade (based on U-values) from energy efficient double to triple glazing is not enough to make any significant difference.

However, triple glazing should be considered on the incremental improvements and how that contributes to energy efficiency and comfort of living.

Passivhaus standards represent superior energy efficiency and the potential future for housing design.

Passivhaus was developed as a set of criteria and standards for an ultra-low energy house that has a minimal carbon footprint and consumes 90% less energy than the standard house in the UK.

The Passivhaus house has no traditional heating systems as it is so well insulated and designed to be efficient using only solar gain, mechanical ventilation and heat recovery.

The key features of the Passivhaus design are:

• Fabric insulation
• Triple glazed windows - not exceeding 0.80 W/m2K
• Airtight
• Ventilation
• Solar gain
• Compact shape/design

Superior energy efficient windows are integral to maintain the integrity of the Passivhaus design. Although, currently, in the UK, the best windows are rated at 0.99 U-value.

To retro-apply the full Passivhaus standards to a house might be a challenge. Choosing to fit triple glazing is a choice towards creating a house that takes advantage of progressive technology to be the most efficient it can be.

Climate change and the need to improve housing stock

Triple glazed windows are recommended on all new builds by the CCC for homes of the future needed today. Decarbonising and adapting the UK’s housing stock is critical for meeting legally-binding emissions targets by 2050.

The government has pledged commitments to reduce carbon emissions in the UK and has a focus on making the housing stock more energy efficient to meet those targets.

The government wants all housing to have an EPC rating of C or higher – currently, only 40% of UK housing meets this standard.

Government policies aside, 22% of carbon emissions currently come from our homes and this is where every person can significantly contribute to tackling climate change.

Improving your home to be as energy efficient as possible is ensuring that we all do our bit for the future of the planet.

Incremental factors add up and this is where the upgrade from double to triple glazing does make a difference.

Triple glazing or double glazing?

The biggest difference between double and triple glazing is how much less heat escapes from triple glazed windows. The visual representation of a thermographic image shows clearly how much more energy efficient triple glazing windows are compared to double glazed fitted in identical adjacent houses.

Triple glazed and double glazed windows made from the same material and to the same quality standard then the triple glazing should be around 20-30% more energy efficient.

Based on U-values, Everest energy efficient triple glazing is 58% more energy efficient than old double glazing and 23% more efficient than our Everest energy saving double glazing.

If you are comparing the efficiency of double and triple glazing, there are a few variables that will compromise the comparison:

• The depth of the glazed unit and space between the panes (more space = more efficiency)
• The gas used between the pane - air, Argon or Xenon (air is less efficient)
• Glass coatings such as Low E (more efficient)
• Quality of the frame (more chambers and insulation in the frame)
• The spacer bars used between the panes (warm edge = more efficient)

Is triple glazing worth it?

The cost of triple glazing is only 10-20% more than new double glazed windows, yet it's just under two-and-a-half times more efficient than old double glazing.

Standard double glazing windows have a WER rating of A, with A+ being the best rating on offer. Triple glazed windows achieve A++ rating for their efficiency. Triple glazing is 23% more efficient with a Uw rating of 1.0 compared to 1.3 for the best double glazing. Upgrading from old double glazing to triple glazing can expect 58% more energy efficiency.

The superior efficiency of triple glazing can help to create a house that reduces carbon emissions and uses less energy to heat. As the Future Homes Standards and Building Standards are introduced, the U-value and energy efficiency of a window will become more important.

At Everest, we are committed to making energy efficient windows and striving towards more efficient homes. We see lowering U-values and triple glazing as the future for all windows in the UK.