We already know that on average 21% of a home’s heat is lost through windows and doors. Both double and secondary glazing over single can mitigate these loses by reducing thermal bridging and draughts. However triple and quaternary glazing is becoming increasingly common on the domestic market.
What is it?
Put simply, triple or quaternary glazing is 3 or 4 panes of glass rather than the traditional 2 with double glazing. The space between each pane is filled with inert argon gas to minimize heat exchange through the window and increase soundproofing characteristics. The increase in number of panes gives superior R-values and sound insulation over other forms of glazing.
Comparatively, how much is lost?
Single Glazing has a U-value of around 5, and older double-glazing about 3. The latest double glazing is now up to around U-1.6 due to refinements in construction methods.
So where does this leave high quality triple and quaternary glazing, if modern double glazing has come on so much? Well, properly insulated walls have a value of around 0.3, meaning windows are still a significant weak point in the efficiency of the building.
It is not just glass that requires consideration for windows, as the frame also constitutes a major heat loss area. Frame insulation is therefore key for high quality windows. Aluminium is often favoured over uPVC in modern triple and quaternary glazing for its increased thermal performance. Timber is also popular, as fewer CO2 emissions are expended during production, and it can more readily be used in conservation areas.
Lots of new homes are now being built with triple glazing and it is generally acknowledged as being better, but compared to top double glazing, the payback period is very similar.
Triple glazing offers a significant reduction in noise pollution, and is often installed in selected windows like the fronts of houses which face onto busy streets.
Double glazing can sometimes create cold patches in the house, due to the higher U-value of walls over windows and doors. This problem is often exacerbated by modern insulation, as better and thicker wall insulation means windows become much colder compared to the rest of the house. As a result the colder window units begin to collect condensation on the inside as they come into contact with moist air. Triple glazing can go some way to reducing this problem by leveling the difference in U-value between the windows and the rest of the building.
If you are planning to replace whole windows, or are undertaking a new build it is worth considering higher quality glazing. However if double glazing is already installed, it may not be a top priority.