Condensation on windows is an extremely common problem in UK homes, particularly during the colder months. For properties with traditional single glazing, waking up to misted windows or water running down the inside of the glass can become an almost daily occurrence throughout winter.
But why does it happen, and could upgrading to vacuum glass help?
Yes. Vacuum glass can significantly reduce the likelihood of condensation forming on the internal surface of windows by helping to keep the internal pane considerably warmer than traditional single glazing.
For older properties where cold glazing is a major contributor to condensation, this can make a noticeable difference.
The air inside our homes naturally contains moisture. Cooking, showering, drying clothes and even breathing all increase the amount of water vapour in the air.
Problems can arise when this warm, moisture-containing air comes into contact with a cold surface.
If the surface is cold enough, the air immediately next to it cools below its dew point and some of the water vapour turns into liquid water.
This is condensation.
Windows are particularly susceptible because glazing has traditionally been one of the coldest surfaces within a building.
Traditional single glazing provides relatively little resistance to heat transfer.
A typical single pane of glass has a U-value of approximately 5.2 W/m²K. During winter, when temperatures outside fall, the internal surface of single glazing can become extremely cold.
Warm indoor air then comes into contact with this cold glass and condensation can form.
This is why older single-glazed sash and casement windows can regularly become covered with moisture during colder weather.
And it isn’t simply inconvenient. Repeated moisture around windows can contribute to damp conditions, damage decorations and timber, and create conditions in which mould can develop.
The key difference is thermal performance.
LandVac Vacuum Glass uses two panes of glass separated by an extremely narrow vacuum cavity. By removing the air between the panes, heat transfer through the centre of the glass is dramatically reduced.
The result is exceptional insulation from an incredibly slim glazing unit.
LandVac can achieve centre-pane U-values as low as 0.34 W/m²K, compared with approximately 5.2 W/m²K for traditional single glazing.
That difference has an important effect when it comes to condensation:
The internal surface of the glass stays warmer.
Because significantly less heat is being lost through the glazing, the room-facing pane can remain at a much higher temperature than traditional single glass.
A warmer internal surface is less likely to reach the dew point at which condensation begins to form.
In simple terms:
Cold glass + warm, humid air = greater chance of condensation
Warmer glass + warm indoor air = reduced chance of condensation
This is why improving the thermal performance of a window can have such a noticeable impact on internal condensation.
[IMAGE – Thermal demonstration / thermal camera comparison between single glazing and LandVac] – whatsapp image
The difference can be particularly noticeable when upgrading from traditional single glazing.
LandVac isn’t simply a small improvement in thermal performance. Moving from approximately 5.2 W/m²K for single glazing to as low as 0.34 W/m²K represents a substantial reduction in heat transfer through the centre of the glass.
For properties where cold glazing is contributing to condensation, improving this thermal performance can therefore significantly reduce the conditions that allow moisture to form on the internal glass surface.
Of course, every building behaves differently. Factors including indoor humidity, ventilation, heating, outside temperature and the surrounding building fabric can all influence condensation.
However, vacuum glazing tackles one of the fundamental causes at the window itself: a cold internal glass surface.
Alongside reduced condensation, the improved thermal performance can also mean warmer internal glass temperatures, reduced heat loss and improved comfort around windows during colder weather.
Interestingly, highly efficient glazing can occasionally experience condensation on the outside of the window.
Although this might initially seem concerning, the reason is very different.
With poorly insulated glazing, heat from inside the building continually passes through the glass and helps warm its external surface.
With high-performance vacuum glass, significantly less heat escapes.
Under certain combinations of temperature and humidity, the outside surface can therefore remain cold enough for moisture from the external air to condense onto it.
In other words, external condensation can be a consequence of the glass doing its job and preventing heat from escaping from the property.
It will normally disappear naturally as external temperatures and weather conditions change.
[IMAGE – External condensation on LandVac / waffle effect] – 20250103 img
When external condensation occurs on vacuum glazing, you may occasionally notice a temporary pattern across the glass as it begins to clear.
LandVac contains tiny micro-pillars between the panes which support the glass against atmospheric pressure.
Small amounts of heat can transfer through these points slightly differently from the surrounding vacuum area. As external condensation begins to disappear, these areas can clear first, temporarily creating what is sometimes called a “waffle effect.”
This is completely normal and is not an indication that the vacuum glass has failed. The pattern disappears as the condensation clears.
One of the biggest advantages of vacuum glass is achieving this level of thermal performance without requiring an exceptionally thick glazing unit.
LandVac starts from just 6.3mm overall thickness, making it particularly suitable for traditional sash windows, timber windows and heritage projects where accommodating conventional double or triple glazing can be difficult.
Depending on the existing frames and rebates, this can allow traditional windows to be retained while dramatically improving the performance of the glazing.
For owners of older properties experiencing cold glass and regular winter condensation, this provides an opportunity to improve thermal performance without necessarily sacrificing the appearance and character of the original windows.
[IMAGE – LandVac installed into traditional timber/sash windows]
Condensation is closely linked to surface temperature.
Traditional single glazing can become extremely cold during winter, creating ideal conditions for moisture within warm indoor air to condense against the glass.
Vacuum glass changes this considerably.
By achieving U-values as low as 0.34 W/m²K, LandVac dramatically reduces heat transfer through the glazing and helps keep the internal surface of the window warmer.
For properties experiencing condensation on traditional glazing, upgrading to vacuum glass can therefore provide a significant improvement — alongside substantially reduced heat loss and improved comfort.
And with LandVac available from just 6.3mm thick, these benefits can be achieved in many traditional and heritage windows where much thicker glazing solutions may not be suitable.
Whether you’re a homeowner looking to improve existing windows, a joiner working with traditional timber frames, or an architect specifying glazing for a heritage project, we would be happy to discuss whether LandVac could be suitable.
LandVac offers:
For more information, samples or advice on an upcoming project, get in touch with our team and we’ll be more than happy to help.
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