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Does Double Glazing have a Vacuum?

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Does double glazing have a vacuum

Does Double Glazing have a Vacuum?

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Published on: April 7th, 2022

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Is there a Vacuum in Double Glazed Windows?

Does double glazing have a vacuum? What is in the space between the glass in your windows? If you want to know more about how double glazing works and what the best options are, read this article.

Most double glazing consists of two panes of glass separated by a cavity. Some people think that the gap in the windows is a vacuum, but that is not true. The cavity is usually filled with a noble gas, such as Argon. This gas slows down the heat that’s trying to escape your room – this is called thermal transfer.

Each Noble gas has a peak cavity width for maximum effectiveness; the higher the atomic number, the thinner the ideal cavity width. Argon gas performs best at 14-16mm and forms a bell curve as the cavity increases or reduces from this peak.

Disadvantages of Standard Double Glazing

One of the problems with standard double glazing is that, while it’s a significant improvement on single glazing, it’s still not terribly efficient by modern standards. It also has a Butyl seal around the edge, which allows some transfer of gas and moisture. Over time the dissipation of the Argon gas causes a drop off in the unit performance. Also, the gradual passage of moisture is initially absorbed by the desiccant in the perimeter seal, but eventually it becomes overwhelmed, and the unit suffers with internal condensation. The speed at which these phenomena occur can be affected by the quality of the window frame and the glazing process.

Another problem with standard double glazing is that it’s just not very pretty, particularly in heritage type properties. The wide cavity exposes the spacer bars and sealant to full view. You also get a double reflection on the two panes of glass. This is generally not acceptable on heritage windows, when the local planning officer will require you to maintain the original aspect of an older property as much as possible. Older properties that are classified as Listed would have been built with single glazed windows. Installing double glazed units with modern frames and double reflection would typically not get planning permission.

Alternatives to standard double glazing

Slim Double Glazing

Slim double glazing is similar to standard double-glazed windows, only narrower. It can look better in heritage projects and was seen as a significant step forward when it was originally introduced.

However, slim double glazing often needs to fit within small glazing rebates and suppliers forego some critical protective features of double glazing perimeter seals to achieve this. So called, low-sightline slim double glazing chronically suffers from moisture penetration and gas dissipation at much higher rates than typical double glazing. 

As a result, slim double glazing often fails after only a short period of time and does not represent good value for money.

Vacuum Double Glazing

You may have heard of vacuum double glazing. It’s the latest technology helping to keep your house warm and make it more energy-efficient. It was originally developed in Japan as a way of making buildings safer in earthquake zones, but it’s use has now blossomed to deal with heritage projects and Passiv-Haus applications alike.

How does vacuum double glazing work?

Vacuum glass still consists of two panes of glass – however in this case the gap has all the air extracted and is mechanically sealed.

Because heat and sound cannot cross a vacuum, these units are much more efficient than standard double glazing.

The gap in vacuum glazing is very narrow – less than 1mm. Despite the incredibly small gap, the windows are still more efficient than standard glass. This is because heat and sound cannot cross a vacuum. It doesn’t matter if the distance across the vacuum is a fraction of a millimetre or the vastness of space, it still has the same effect (the rules of physics are pretty firm on this!). 

Double Glazing diagram comparing vacuum glass to standard and triple glazing

Benefits of vacuum double glazing

  • Keeps your house warmer in the winter and cooler in the summer
  • Also reduces the amount of energy used
  • Helps to keep your house cooler in the summer, warmer in the winter
  • A very narrow sightline improves the looks of your house

Good quality vacuum glass is much more energy-efficient than standard double glazing. Your home costs less to heat and is more comfortable. The vacuum also helps keep rooms cooler in the summer too.

In LandVac, which we see as the best product on the market for new windows, the gap between the two panes of glass is  0.3mm with the whole unit is only 8.3mm wide. To achieve the same energy efficiency performance in a more typical unit, you would like need a 40-48mm thick triple glazed unit!

Uses for Vacuum Glazing

  • Heritage windows for Listed buildings where single glazing is preferred
  • Passive house projects where energy efficiency is important
  • Homes that want to reduce their energy consumption

Final Words

​​As well as keeping your home warmer in winter and cooler in summer, vacuum double glazing also prevents internal condensation on your window glass. This avoids mould forming on your windows and potentially causing damage to your home and the health of the occupants. Of course, you will need a good ventilation plan to ensure that the moisture is removed and doesn’t just settle on a different cold surface in the home.

Vacuum double glazing is the latest technology in the field of energy-saving and it’s easy to see why so many people want it. If you’re looking for a way to keep your home more comfortable, reduce your energy bill and keep your house cooler in the summer, then vacuum double glazing is for you.