When is three better than two?
Everyone knows that double glazing is better than single glazing. And we all know why - it loses less heat, so it’s better for the environment and better for your bank balance. And it keeps out more noise.
So does it follow that triple glazing is better than double glazing?
Admittedly, triple glazing is actually the most popular form in Germany and Scandinavia, so do they know something we don’t? Do they care more about the environment? Or are they just shrewder with their money and don’t want to see it going out through the window? Then again, is three panes really better than two? Is it worth paying for? Or does the law of diminishing returns come into play?
Well, first of all, let’s go back to basics: not all double glazing is the same. There’s efficient double glazing, and the stuff that’s not worth the sand it’s made of. And we use three ways of assessing how good it is:
1. How efficient is it at keeping out draughts?
2. How well does it keep in heat?
3. How much of the sun’s heat does it let in?
Now, on the first count, triple glazing would score no better than Anglian double glazing, which has a perfect seal. Which means it has a perfect, airtight score of 0.
Next, thermal efficiency – the ability to keep heat in. Well, it stands to reason that a third piece of glass would offer more insulation.
But then again, so would more heat-efficient coatings on each pane of glass, more energy-efficient gas between the panes (to prevent heat crossing the gap) and a more advanced spacer bar to separate the glass (which is where most heat loss occurs) – all of which come as standard with Anglian double glazing.
Which means the score so far is Anglian Double Glazing 2, Triple Glazing 0.
So that just leaves Solar Gain – how much of the sun’s (free) heat and light does a triple glazing window let in?
This comes down to iron content (you can tell how much iron a pane of glass contains by the green tinge at the edge).
The less iron there is in a piece of glass, the more sunlight it lets through. Now, Anglian only uses low iron glass, so amazingly, three panes of their low-iron glass could have a better solar gain score than two panes of the standard glass used by other manufacturers. All of which begs the question: if Anglian’s materials and production methods mean their double glazing outperforms ordinary triple glazing, why don’t Anglian just start producing triple glazing to their own high standards?
The answer, at the moment, is cost. If you were to buy triple glazing made to Anglian standards, it would cost you far more than you’d save in fuel bills. That’s because Anglian won’t sell it to you if we can’t guarantee it for 15 years. And we won’t sell you something that you won’t see any benefit from.
It’s a complex engineering challenge to produce a pane of glass that spends its life in the centre of an air-tight, gas-filled natural heating unit like one of our windows. It never gets cold, because it’s never in contact with the outside air. But it can get very hot - so it could crack if not properly toughened, which is expensive.
Triple glazing units are also much heavier than double ones; so we need more installers, stronger vans, more fuel to transport and even stronger (again, more expensive) hinges. It all adds up. So right at this moment, it actually makes more sense to fit A-rated Anglian double glazing. As things stand, we’ll save you more in heating bills than they cost to fit.
But obviously, if triple glazing could be made more cost-efficient, it would be an even better option.
So rest assured, we are working on it. It won’t be long before we find a way to improve technology, reduce manufacturing costs and create a window that saves you even more money.