Damaged Thermal Seals: Why Your Windows Are Cloudy

Date Published: November 9, 2022

We’ve all been there. Your window looks a little cloudy, so you grab a cloth and give it a wipe down. But despite the wiping, the cloudiness remains. So you open the window and give it a wipe on the other side – still no luck. What’s going on? The fact is that this cloudiness is actually on the inside of your window, and you most likely have a damaged thermal seal.

About Thermal Seals

Thermal seals are made of a rubber-like material and installed along the edges and in between glass panes. They are meant to improve the U-Factor, or energy efficiency, of a window. Most modern windows are double or triple-paned, with a layer of inert gas – usually argon or krypton – between the panes. Thermal seals are applied to the window in order to keep the panes airtight and to prevent the inert gas from escaping.

However, sometimes thermal seals will fail due to factory defects, improper installation, outside forces or just gradual deterioration. Once the seal fails, the inert gas will eventually seep out of the window, leaving space for air to enter into the panes. Unlike inert gases, the air in our atmosphere carries moisture and creates condensation when there are temperature fluctuations between the inside and outside of the home. The result – moisture on the inside of a multi-paned window.

This is a common occurrence, and we see it quite a bit during our home inspections. The level of moisture intrusion can vary in severity. You may see slight bit of droplets or fogginess along the (usually lower) edge of the window; or in extreme cases, the whole pane might become fogged up.

Fogged window due to broken thermal seal

Image sourced from: https://www.hgtv.com

This can cause obvious aesthetic issues. No one wants their crystal clear window panes to be obstructed by a cloudy mass.

But more importantly, a breach in the thermal seal can affect the energy efficiency of the window. With all the other components of the window intact, the overall performance of the window won’t decrease drastically. However, over time, damaged thermal seals could mean higher energy bills.

Fixing A Thermal Seal

When dealing with a defective thermal seal, there are a few routes you can take. First of all, check your warranty. The window(s) may still be covered by the manufacturer. In a lot of cases, windows will have 10-year, 20-year, or even lifetime warranties.

You may be able to get a full or partial replacement without spending a cent of your own cash. So make sure you do your research!

However, in many cases, the windows might not be covered or past their warranty life. So what else can you do? For starters, it’s a good idea to consult with a window specialist to find out the extent of the damage.

In many cases, with thermal seal damage, full window replacement is not necessary. The insulated glazing unit (IGU), which is just a fancy name for the glass panes and spacers between them, can be extracted from the window frame and replaced. This is a solid alternative to full window replacement, as it is less labor-intensive and cheaper.

double pane window cross section

Image sourced from: https://thearchitectsdiary.com

Then next question you may be asking is – can I do it myself? Well yes, you technically can. There are plenty of resources out there that can you give you a step-by-step tutorial on how to replace an IGU. And truthfully, it will likely save you quite a bit of money.

However, there is a lot of room for error. The last thing you want is to spend loads of time and energy, only to discover an installation error in the end. So unless you are very skilled with window working, hiring a professional is probably the way to go.

Another, less common remedy to the thermal seal issue is to hire a window defogging company. In this process, a window defogging specialist drills one (or multiple) hole(s) in the window, in order to clear out the moisture within the panes.

An anti-fogging solution is then applied within the window, and sealant is added to the bottom of the window to reinforce the damaged thermal seal. This process yields a great aesthetic improvement – no more foggy window. However, it does not improve the the U-factor of the window because inert gas is not added back into the IGU.

Inspecting Windows

During our standard home inspections, we are always examining the windows closely from the exterior and interior. And as stated above, we come across thermal seal issues quite commonly.

When our inspectors do identify a foggy window, they will generally mark it as a maintenance item. It is more of a cosmetic issue and is not a huge concern.

It is true that a window’s performance can be affected by this problem. But if only one or a few windows have these thermal seal issues, the effect will only be marginal. We will not make it a primary concern on a home inspection report.

home inspector inspecting a window

If you are in need of a Colorado home inspection, we hope that you will consider Scott Home Inspection. We have been providing inspection services to CO for over 10 years, and we look forward to helping you with all of your inspection needs! Learn more about all of the our inspection services or schedule your inspection today.

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About the Author: Chris Kimmel

Chris Kimmel worked as an Associate Home Inspector for two years, handling numerous services including sewer scope inspections, pest inspections, mold air sample testing, radon testing, and water quality testing. Chris now works with Scott Home Inspection as a Content Writing Specialist.

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