You’ve had your insulating glazing (IG) units for years. Recently, however, you noticed that they are fairly clouded most of the time. Now, you’re wondering why they are misted up when these units are supposed to prevent this very dilemma.

Here’s the thing: Like any kind of window, IG units get old. And when they get old, their seals become fragile, resulting in failure.

What exactly causes IG units to fail?

Typically, an IG unit is formed from two glass panels that are separated by an air or gas pocket. This creates an insulating barrier that prevents it from misting up. It is only when the unit’s seal is broken that condensation gets in between the sheets of glass, resulting in a misted window.

There are a number of reasons why the seal breaks (or fails as it is known in the glass industry). Generally, though, it is mainly due to the following factors:

As mentioned, it could simply mean that your IG unit have been serving you for too long and, therefore, need a replacement. Over time, these glazing units, lose air or gas, which leaves the space between the panes at a negative pressure. This leads to increased heat transfer, further leading to condensation. This kind of failure is normal.

What isn’t, however, is when the unit fails too soon because of poor fitting and installation. Make sure to hire only the experienced and insured installer so you are assured that your new insulating glazing units won’t be easily compromised.

What you use to clean the IG units may also cause damage to the seal. When used frequently, certain chemical cleaning materials can weaken the seal over time, so make sure to ask the manufacturer or your supplier what cleaning material you can use.

Another reason why IGUs fail may have something to do with blocked drainage. To put it simply, if the window’s drainage is blocked, it causes dirt and water build up, potentially leading to a broken seal and fogged-up glass panes.

Is replacing the IGU the only way to remedy the issue?

If the unit suffers from condensation and misting on the inside, then you really have to replace it to maintain an energy-efficient home.

Sure, there are quick fixes on the market and you can always consider repairing the unit yourself. But then again, none of these efforts will matter if the seal is already broken. If you purchase replacement IGUs from a reputable company, you should be able to get a guarantee of workmanship. So if they do break again within the span of the warranty, you can have it replaced for free.

While there may be no other choice but to replace your IGUs when the seal fails, there sure is a way for their replacements to not suffer the same fate in the near future: keep them dry. Remember, IGUs loathe sitting in water. So before you conclude that your IGU’s seal is the problem, make sure you’ve looked at the unit’s drainage section.