Let’s start with the basics:

  • Double glazed (or 2-layered) (2g) windows and doors function by trapping a layer of air between two panes of glass to provide extra insulation.
  • Triple glazed (or 3-layered) (3g) products feature a third sheet of glass in the middle that acts as an additional barrier, resulting in improved thermal performance.

Whether you’re undertaking a self-build or a renovation, it’s likely that creating a thermally efficient shell is high on your list of project goals. While high-quality 2g windows achieve good enough thermal performance for some builds if reduced heat loss is one of your key objectives, why not go to the next level by installing 3g?

Cutting down heat loss by fitting 3g windows and doors will allow you to slash future energy bills, which will help to offset the initial outlay for the glazing, too.

Here, we outline exactly how triple-glazing can benefit your project:

Thermal advantages

The thermal performance of your windows is measured in U-values – a measure of heat loss, where lower numbers indicate superior thermal performance. Typically, modern double-glazed units can achieve U-values around 1.3-1.5 W/m2K. Old-fashioned double-glazed products, on the other hand, offer U-values closer to 3.0 W/m2K.

At the other end of the scale, triple-glazed windows will likely score a U-value closer to 0.8 W/m2K. If your key goal is to create a high-performance structural shell – particularly if you’re building a Passivhaus – triple-glazed units are a smart choice.

Klarwindows triple glazed windows offer excellent thermal performance, capable of achieving U-values as low as 0.7 W/m2K – among the lowest levels on the market.

Klarwindows u-values:

Double glazed windows: 1.3 W/m2K
Triple glazed windows: 0.8 W/m2K
These are values for a standard EU test size of 123x148cm

It’s also worth considering just how much glazing your home will have; broad swathes of glass that let sunshine stream inside are a must-have addition for many projects. However, such large areas of glass are weak spots for letting warmth leak out of the thermal envelope.

Installing triple-glazed windows or doors, especially in areas of floor-to-ceiling glazing, can therefore make a huge impact on the overall thermal performance of the house.



Comfortable living environment

In addition to drastically reducing heat loss, triple-glazing windows can help facilitate a more consistent internal temperature throughout the home. Even though modern windows can deliver excellent thermal performance, they can’t match the level of thermal efficiency provided by solid, well-insulated walls.

The fluctuations in heat loss across solid walls and areas of glass are significantly cut down when you install triple glazing, resulting in a more consistent temperature throughout the property. Ultimately, you’re eliminating cold, draughty spots and establishing a more comfortable living environment as a result.


Other routes to thermal efficiency

It’s not just the glazing that has an impact on the thermal performance of your windows and doors; frame material, special coatings, and gas fillings all play a part, too.

The inner and outer layers of Klarwindows triple-glazing windows and doors feature a low-emission coating. This significantly reduces heat radiation on the surface and simultaneously reflects warmth back into the room.

Another way to boost the spec of your windows is to choose a product with an inert gas filling. Klarwindows triple-glazed units feature an argon filling between each of the glass panes. Argon is heavier than air, which means that the air circulation between the panes is reduced when it is cold on one side and warm on the other.

Last but by no means least, there’s frame material to consider, too:

High-quality wood or composite units (with wood on the inside and an aluminium face on the outside) are less conductive of heat, which means they will retain more warmth inside the home than frames made of just aluminium or PVCu.

All Klarwindows' timber windows are made from wood sourced from FSC-certified forests.


Efficient thermal envelope

Before splashing out on your new windows, it’s worth giving some thought to whether upgrades are needed to the structural fabric of the house, too. Essentially, there is little point in investing in high-spec triple glazed windows if precious heat is going to be lost anyway, via a poorly insulated roof or wall.

Taking a holistic approach to the build by paying attention to the entirety of the structural shell (rather than just the windows) will yield the best results.


Mix and match

If you’re building a new house from scratch, work with your architect to position the house on the plot in such a way that it makes the most of the sun’s free heat.

Depending on which way the house faces, you might also be able to incorporate different types of glazing on each side. One possible concern related to triple glazing is the risk of overheating in the summer. To combat this, you can design your home with a mix of 2-layered and 3 layered glass.

For instance, on the sunny southern elevation of your house, you might choose to incorporate double glazing. On the cooler, northern side of the property, you could have triple glazing to keep the heat in.

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