My Windows Are All Misted Up on the Outside. What’s Wrong With Them?

The simple answer is — nothing is wrong with them!

In fact, external condensation can actually be a sign that your energy-efficient windows are working properly (see more below).

If Nothing Is Wrong, Why Is There Condensation?

The longer answer is that the modern windows fitted by FENSA Approved Installers today are far more thermally efficient than those installed in previous decades.

Because they retain heat so effectively, less warmth escapes to the outer pane. This means the outer pane stays cooler, and when its surface temperature drops below the dew point, moisture in the air condenses on it — creating that misted-up look.

Why Does Condensation Only Form at Certain Times of Year?

Window condensation is often more noticeable during Autumn and Spring mornings. That’s because during these seasons, glass surfaces can cool down rapidly overnight, while the dew point remains relatively high.

Interestingly, some windows or panes may mist up while others don’t — even if they’re side by side. Factors like orientation, exposure to wind, and shelter from nearby buildings or trees can all influence how each pane reacts.

What Can I Do to Stop External Condensation Forming?

Unfortunately, there’s not much you can do to completely stop this natural process.

The good news? It’s temporary and usually clears up on its own fairly quickly.

And better yet — it’s actually proof that your windows are doing their job: keeping the warmth inside your home, which can help lower your heating bills and reduce your carbon emissions.