Condensation outside windows: The causes and solutions explained

condensation on windows
(Image credit: Getty)

Condensation outside windows is an issue that is on the rise — and we are here to explain why. 

Whatever window style you have decided upon for your home, there are all kinds of problems that can crop up. These include condensation on the inside of glass, windows that stick in their frames and foggy glass panes caused by moisture getting in between double glazing. 

However, a slightly newer phenomenon that seems to be affecting more and more homeowners is condensation outside windows — but just why do double glazed windows steam up on the outside?

Here, we explain what causes the issue and what you can do to put it right — plus we look at a few methods for preventing it from happening in the first place. 

What causes condensation outside windows?

Picture this, you've just spent thousands of pounds buying and installing new double glazed windows for your home, only to pull back the curtains in the morning to see nothing more than condensation running down the outside of them. Not an ideal scenario, admittedly, but a surprisingly common one. 

So what causes window condensation? There are several reasons why it happens and, thankfully, it is not because you have purchased substandard windows. In fact, it means just the opposite. 

Condensation occurs when gas changes into a liquid. It happens when water vapour in the air comes into contact with a surface (in this case the glass in a window) that is colder than it is. When there is excess moisture in the air, on meeting this colder surface, the air releases water droplets (or condensation) on the window.

Why do double glazed windows steam up on the outside?

They are not actually steaming up — this is condensation. As mentioned before, water will condense on the outside of glass when the temperature of the glass is lower than the external air temperature. 

But why is this a common problem with double or triple glazed windows in particular? 

The reason behind it is down to the fact that new double or triple glazing units usually have inner panes that are comprised of low emissivity (low-e) glass. This type of glass is specifically designed to stop the transfer of heat across the glazing unit, meaning that the outer pane of glass never gets warm — hence the warmer air outside condenses when coming into contact with it. 

Although annoying, this is actually a reassuring sign that your windows are working as they were intended to. Basically, the better the thermal insulation of your glazing, the lower the outer pane temperature will be meaning there is a greater chance of condensation forming on it. 

This type of condensation is most common in early autumn and spring and early in winter.  

How do you stop window condensation outside?

While the easiest way to get rid of condensation outside windows is simply to wipe it off, this is not necessarily particularly practical long-term. 

Sadly, there is not a huge amount that can be done to prevent this issue. Choosing self-cleaning glass could help a little as it is designed to stop moisture from beading on the glass.

If you have already had your windows installed, however, try to keep your windows as clean as possible because spotless windows are much harder for water droplet to hold onto. 

That aside, take comfort in the knowledge that as soon as the sun rises in the morning and the surface of the glass warms a little, the condensation should soon disappear.

Natasha Brinsmead

Natasha is Homebuilding & Renovating’s Associate Content Editor and has been a member of the team for over two decades. An experienced journalist and renovation expert, she has written for a number of homes titles. Over the years Natasha has renovated and carried out a side extension to a Victorian terrace. She is currently living in the rural Edwardian cottage she renovated and extended on a largely DIY basis, living on site for the duration of the project. She is now looking for her next project — something which is proving far harder than she thought it would be.