Top Causes Of Misted-Up Double Glazing Units

Double glazing creates high performance window units, which significantly improve a property’s insulation and energy efficiency.  

Furthermore, they are built to be secure, and to achieve a long lifespan with minimal maintenance requirements. 

But, in some rare instances, errors can start to crop up, which need to be addressed. Windows misting up between the two panes of double glazing glass is one of the most common issues to affect these windows. 

If left, not only can these faulty windows look visually unpleasant, but they will also compromise the energy efficiency of your property. 

Below, we’ve shared a quick guide to understanding misting in double glazing windows. This includes explaining why misting happens in the first place, and how you can fix or prevent the issue.

Why does condensation occur in double glazing?

Condensation naturally arises when warm, moist air comes into contact with a cold surface. When this occurs, the air condenses onto the surface, and water droplets form from the moisture present in the air. 

For example, in a standard home window, if humid air from a bathroom hits a cold window surface, then water droplets will form. 

Double glazing units are actually designed to reduce the amount of condensation created in this way. 

In these units, the two panes of glass are separated by a spacer. This gap is then filled with air, to create an insulating barrier. As a result, the inner pane of the window is kept much warmer, thereby reducing the rate at which condensation can occur.

However, when double glazing is faulty or fails (e.g. the seal on the unit fails) moisture can start to seep into this space. This results in a layer of condensation that cannot be wiped away (because it sits in between the two glass panes). 

Where can you find condensation?

Condensation can occur in multiple different points of a window. 

By identifying where the condensation is located, you can determine whether or not the unit is at fault.

Internal condensation

• This occurs on the inside surface of the window, and is caused by excess humidity inside the room. This does not indicate a fault with the window, and can be resolved by improving indoor ventilation. 

External condensation

• This occurs on the outside surface of the window, and it is actually a great indicator that your windows are working well. It tells you that your double glazing is energy efficient, and prevents heat loss from within the property. 

Condensation between the window panes

• This occurs inside the sealed double glazing unit, and is caused by a failure in the window’s seals. This indicates that the unit has failed, and needs to be repaired or replaced.

Why do double glazing window seals fail?

Double glazing window seals can deteriorate, and ultimately fail, as a result of: 

• Natural ageing – Causing the seals to weaken and break down.
• Poor installation – Resulting in pressure build-ups or weak spots.
• Weather fluctuations – If the temperature regularly flits between extremes, then this can cause the seals to repeatedly expand and contract. Over time, this can cause damage to the seals.
• Insufficient sealing – If the unit was not correctly sealed or dried during the manufacturing process, then, this can cause moisture to build-up and get stuck in the unit.

Please note, it is not common for high quality double glazing window units, which have been installed by professional installers, to fail. 

How to fix and prevent misted-up double glazing

Unfortunately, if condensation forms between the glass panes, then the double glazing unit has failed.

For the best results, the recommended course of action is to replace the faulty unit with a new double glazing unit. To keep costs down, you can just replace the sealed unit, but keep the original frames in place. 

Then, to minimise the risk of seal failure occurring, you can take these steps:

• Keep your home well-ventilated 
• Avoid using any harsh cleaning chemicals
• Select high quality double glazing 
• Work with trusted, accredited installers, like Stevenage Glass

At Stevenage Glass, we are double glazing specialists, offering dependable repair, replacement and installation services. 

To receive expert advice, or to arrange an installation with our skilled team of professional glaziers, don’t hesitate to get in touch.