Vacuum glazing explained: is vacuum double glazing worth it compared to other window types?

Independent

2 days ago

In a nutshell, vacuum glazing — also called vacuum double glazing — works by placing a vacuum between two panes of glass, rather than filling the gap with gas as in regular double glazing.
This is advantageous because, as your school physics teacher would tell you, a vacuum is an excellent insulator because there is no matter – solid, liquid or gas – through which heat can be conducted.
It works the same way a vacuum flask keeps a drink hot all day long. This means that vacuum glazing is very good at keeping the heat in, or the cold air in summer.
Another upside is that vacuum glazing can be thinner. Regular double glazing gets its insulating properties from the inert gas placed between the glass sheets — often the noble gas argon.
But with a vacuum, you don't need that much of a gap. So where space is a premium, perhaps with an older building, this can be a plus.
How long does vacuum glazing last?
Like double glazing, vacuum glazing typically lasts between 10 and 25 years, depending on the quality of the unit and how well it's maintained.
Is vacuum glazing more expensive?
You may well have guessed the major downside – cost. It's harder to create a vacuum, especially in a bespoke window with a unique size, than it is to fill it with gas.
But in some circumstances, perhaps where the choice might be single glazing or vacuumed double glazing, it may be the only sensible choice if you have the money, because of how much heat single glazing can lose.
Vacuum glazing is a popular choice for sash windows because of its relative expense, no matter which glass you choose.
How much does vacuum glazing cost?
A new bay window can cost £1,000 to £3,000 or even more. If you are paying that much, the cost of the glass itself can be dwarfed by the cost of making the frames and fitting them.
Vacuum glazing costs between £340 and £390 per square metre, excluding VAT and delivery, according to specialist fitter Six Over Six. Their units are made in the EU and can attract an extra fee if energy prices are particularly high.
Meanwhile, regular double glazing with a low-e coating to reduce heat loss costs from £30 to £70 per square metre, according to Eco Happy, a fitter.
So you can see there's a big difference. But this figure isn't much use without knowing how much the frames and labour costs are, and those depend heavily on your choices from the cheapest uPVC options to handmade timber frames.
A uPVC double-glazed window including VAT, fitting, frames and everything else can cost under £600, by comparison. So going for a vacuum unit could easily add 50 per cent to the cost, and that would be for the cheapest frames.
Is vacuum glazing better than double glazing?
The two types of glazing last from 10-25 years, depending on how they are looked after and the warranty the manufacturer applies.
The expense today of vacuum double glazing means that it is unlikely to be a popular choice outside of specialist applications because of its cost.
It is technically superior, but it is also a lot more expensive, and it is likely that most buyers will get similar performance from triple glazing, which is only about 15 per cent more expensive than double glazing.
In a door, it is likely you will have more room to play with to install cheaper glass.
Is vacuum glazing a good investment?
So, is vacuum glazing worth it? That depends on several factors. Whether vacuum glazing is a good investment depends on a number of factors. For it to make sense, you will need to recoup the extra cost – the cost beyond regular double or triple glazing – in reduced heating bills.
This will depend on the size of the windows, the size of your home and other energy efficiency measures you have already put in place.
It won't be much use having super-efficient windows if you have a draughty home with no loft insulation, for instance. The heat will simply escape elsewhere.