Triple Glazing is still a comparatively new innovation, while we’re all much more familiar with double glazing that has been around for many years now, there’s still some uncertainty surrounding triple glazing and the true benefits.
How good is it, and is it really worth it?! …..
The typical U-value of a modern double glazed window is now around 1.6W/m²K. This has improved drastically from previous generation windows (see U-values for more information on these).
Modern thermally efficient, well sealed window frames, when glazed with triple glazed units (filled with Krypton rather than Argon) can now achieve U-values around 0.8W/m²K – this is significantly lower than a standard double glazed window!
However, this improvement comes at a cost – the glass costs over 50% more, as you have an extra pane of glass, and also an extra cavity, which needs extra spacer bars to fix the panes together, and extra gas filling.
The window and door frames also need to be larger to accommodate the wider units, and sometimes you may need upgraded mechanisms (e.g. hinges, running gear) to take the additional weight of glass. Transport costs increase too, with the extra size and weight of the products, as does the installation cost with extra labour needed on site to manhandle the frames into place.
But it’s not just about energy saving….
Triple glazing has another big benefit – acoustic control.
3 panes of glass will keep sound out more effectively than just 2 panes, making it a popular choice near busy roads, on aeroplane flight paths etc.
When looking for sound reduction, it’s also very important to have a quality window / door system. Sound will travel much more through a poorly sealed window frame with a single seal, compared to a well designed frame with multiple seals all the way around the opening panes. The installation must also be completed to a high standard, to ensure there are not air gaps around the outside of the frame, which again will help the sound to travel!
Will we get condensation? …
Triple glazing does reduce the potential to get condensation on the inside pane of glass.
It’s a slight misconception that you won’t get any condensation on modern windows and doors, as if there is sufficient humidity in any room (especially a kitchen or bathroom), you will get condensation! However with triple glazing, this is reduced – as the temperature of the internal pane will be closer to the air temperature inside the room.
So, why do other Countries use so much triple glazing?….
When you have a small temperature differential between the inside and outside areas, the amount of heat lost through the window or door is smaller.
When you have a greater temperature difference between inside and outside, for every extra 1° difference, the heat loss increases significantly. This is why Scandinavian Countries almost exclusively use triple glazing in their doors and windows. They have prolonged periods of it being very cold outside in the Winter months, which gives them significant savings on their energy bills with triple glazing, compared to the bills with just double glazing.
In the UK the savings would not be so great, as the differences are smaller between typical inside and outside temperatures. After a particularly cold Winter the savings should be noticeable, but after a mild Winter, they would not be as significant.
How much more does it cost? ….
There are different types of triple glazing available, which vary in price a fair amount. A fairly standard triple glazed unit with argon gas filling will cost a bit more than a double glazed unit, and will give you a modest improvement in the U-value.
To gain the maximum benefit, and get down to the low U-values we hear about (e.g. round the 1.0W/m²K mark), you have to use a high performance triple glazing, with Krypton gas in the cavities rather than Argon, which comes at quite a significant premium!
What should we do? …
If you are building an Eco House, you may have the glazing specification strictly stipulated, but usually the choice of glazing for your project will come down to you!
We will be happy to advise you of the options available for your particular project, and the cost implications of each of these, to help you make an informed choice!