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How to Repair a Broken Window Seal (2024 Guide)

Written by Joe Roberts , Edited by Gianna Cappuccio

Published on June 13, 2024


How to Repair a Broken Window Seal (2024 Guide)

Do you have drafts, high energy bills, or fogged window panes? Broken window seals might be to blame! Read our guide to learn how to fix these issues.

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If one of your home’s double- or triple-pane windows has become drafty or foggy, you might have a broken window seal on your hands. Window seals (as opposed to window sills) seal off the space between window panes to create an airtight gap between them. This gap is often filled with an inert gas to increase the window’s insulation and energy efficiency.

If a seal breaks, the window will become less energy efficient, more drafty, and more susceptible to moisture buildup. This can raise your energy bills, decrease your home’s comfort level, give your windows a dingy look, and even cause the damaged window frame to rot, so repairing leaky seals should be a priority. Professional fixes typically cost between $100 and $183, but some DIY fixes can be more affordable.

Keep reading, and we’ll teach you how to spot a window seal failure, what to do if you find one, and how to prevent leaky seals in the first place.

Hire a local window repair company to fix your double-pane windows

Key takeaways

  • A drafty or foggy window may be caused by a broken seal around one of the window’s glass panes. This issue can cause higher energy bills, water damage, and discomfort. 

  • Professionally fixing a failed window seal generally costs between $100 and $200, though it can cost significantly more to fully replace the entire window. 

  • Most window seal fixes are pretty complex, so they don’t make good DIY projects and should be left to professionals.

  • Window seals can last several decades, though things like pressure washing, removing paint with a heat gun, and extreme weather can cause them to fail early.

What is a window seal?

Windows with two or three panes of glass feature small open spaces between the panes. These spaces are sometimes filled with an inert gas like krypton or argon to prevent radiant heat from passing through the window. This design makes these types of windows—sometimes called thermopane windows or insulated glass units (IGUs)—much more energy efficient than traditional single-pane windows.

When paired with other efficiency features like low-e coatings, a gas-filled IGU can help your HVAC run more efficiently, keep your energy bills low, and ensure your home is more comfortable year-round. 

To lock the krypton or argon gas between the panes and prevent outside air from entering the window, airtight seals made with silicone sealant and rubber gaskets are installed around each panel of glass. Under ideal conditions, these seals can last decades, though improper usage or exceptional weather can deteriorate and rupture them.

If left unaddressed, a broken seal can result in high energy bills, HVAC strain, moisture damage, and uncomfortable temperatures in your home. Luckily, broken window seals are pretty easy to diagnose. 

How to spot a damaged window seal

Broken window seal on a home showing condensationCondensation trapped between a window’s panes of glass is a sure sign that the IGU’s seal is leaking. Image source: Reddit

While a leak in an IGU seal will start small and, therefore, be hard to see, these easy-to-spot symptoms of window seal failure make themselves obvious very quickly:

  • Fog between the window’s glass panes: When a window seal breaks, moisture from the air outside will start to accumulate between the panes, resulting in fog and beads of water on the glass.

  • High energy bills: A broken window seal will greatly decrease your home’s energy efficiency by requiring your HVAC system to work harder to maintain comfortable temperatures. If you’ve seen a recent spike in your power bills, a broken window seal might be the culprit.

  • Discolored spots on the glazing: The space between an IGU should be devoid of anything except air or an inert gas, so if you see spots of color on the inside of your glass panels, you’ve likely got a leak.

  • Drafts: A leaky window permits outside air to enter your home, so if you feel a draft near one of your IGUs, the seal may be leaking. However, you should also check the caulking around the window sash or other signs of damage in the frame, as these types of damage could be causing the drafts instead and require different repairs.

Once you’ve determined that you have a leaky window seal, you should get the problem rectified as soon as possible to prevent the problem from worsening or costing you more money on your power bills. 

Pro tip

Before you schedule your window repair or glass replacement, be sure to look over the warranties that came with your window. The window manufacturer or installer might cover the damage, so you could get your window defogged and resealed (or even replaced!) free of charge.

Window seal repair options

Defog the IGU

If your window is fogged up with condensation from outside air, you should get it defogged before fixing the seal. Otherwise, all that water will stay inside the window, looking unclean and causing moisture damage over time.

Professional foggy window repair starts with a technician drilling a tiny hole into the window’s glass. Through this hole, the technician removes the trapped moisture and excess air. They then apply an anti-fog chemical to keep the window from fogging again. After this, the technician seals up the hole they made in the window.

This typically costs around $100 per window, though it can cost more depending on the size of the window and how difficult it is to access. 

Replace the sealant

Once the fog has been removed, you can get the leaky seal repaired. This process is usually less complex than defogging a window, at least in theory. A technician will need to remove the old silicone sealant and gasket using a putty knife and then install new sealing materials around the window’s glazing. The average homeowner spends about $140 per window on this project, though size and location can affect prices. 

Replace the window

If you simply want to replace your leaky old window with something better, that is also an option. In fact, it’s recommended if your old window is showing significant signs of damage (mildew, cracks in the frame, etc.) in addition to its leaky seal.

Of course, this home improvement project will cost significantly more than just resealing the old window. The cost of window replacement can vary dramatically depending on factors like the type of window you get, the size you need, and where you live. Still, it can cost anywhere from a couple hundred dollars to over a thousand dollars per window.

Leave new window installation to the pros

DIY solutions

All the solutions we’ve listed so far involve fairly complicated procedures. To ensure high-quality results, you should leave them to professionals. But if you want something a little more budget-friendly or you’re a do-it-yourself purist, worry not! There are two ways to mitigate (though not really fix) the drafts caused by a leaky window seal without hiring a pro:

  • Use a draft stopper: Laying a draft stopper—sometimes also called a draft snake—along a drafty window can prevent air transfer between your home and the great outdoors.

  • Hang thermal curtains: Thick curtains draped over a leaky window can help prevent heat from leaking through the window, thereby keeping your home more energy efficient.

It should be noted that these fixes will only prevent drafts and help maintain your home’s energy efficiency, but they won’t do much to prevent a window from becoming foggy. To learn more, check out our guide to preventing window drafts

Why window seals fail (and how to avoid seal failures)

In general, window seals can last 20 years without a problem, though there’s a long list of things that will break them prematurely:

  • Pressure washing: Using a pressure washer to clean your home’s exterior may seem convenient, but a high-pressure water stream can quickly destroy the seals on your windows (and deteriorate your home’s siding). For safer cleaning methods, check out our guide to cleaning your home’s siding the right way

  • Improper maintenance: Maintenance needs vary from window to window, so carefully follow your manufacturer’s or installer’s care and cleaning instructions to ensure all of your windows’ seals, frames, and glass last as long as possible. 

  • Heat guns: Heat guns can quickly remove paint from a window frame but usually compromise the window’s seal as well. To avoid this, use sandpaper to clear old paint off a window frame instead. 

  • Extreme weather: High temperatures can result in “solar pumping,” a phenomenon where sunlight heats the air between window panes, causing the gas inside to expand so much that it ruptures the window’s seal. Similarly, high winds and heavy rainstorms can also break a window’s seal. The best way to avoid these outcomes is to only get windows that are designed for your climate’s temperatures and weather patterns. 

  • Improper installation: A window installed incorrectly is susceptible to problems like a cracked frame, jammed openings, and broken seals. This is why you should always hire pros to install your windows instead of trying to install them yourself.

How to find a professional to repair your window seal

Now that you know how to diagnose broken window seals, how to fix them, how much repairs cost, and how to maintain a new window seal, it’s time to meet with a contractor. Fill out the form below, and we’ll put you in touch with the best local window repair companies in your area.

Find local window repair contractors

Window seal repair FAQ

Can a window seal be repaired?

Yes, a window seal can be repaired by a qualified professional. A repair contractor will remove what’s left of the old seal and then install an entirely new seal to restore the window. On average, this will cost between $100 and $183, though it can cost more if the window needs to be defogged first. 

Can you replace window seals yourself?

While it’s possible to patch up a window seal with your own two hands, the new seal is more likely to fail again than one installed by an experienced pro. If your window has become fogged because of the broken seal, you should call in a professional since defogging a window wrong can result in greater damage. 

Do you need to replace a window if its seal is broken?

No, as long as the window is in good condition; otherwise, you can usually just replace the window’s seal instead of replacing the whole unit. However, if the window has other problems—like a cracked frame, mold growth, or a jammed latch—it may be better to replace the whole thing. 

Are weatherstripping and window seals the same things?

No, weatherstripping is a different type of sealant than an IGU seal. Weatherstripping is usually installed between a window sash and the window frame to make the window more airtight when closed, whereas a window seal wraps around the window’s glass panes within the frame. 

Do broken window seals cause mold?

A broken window seal will permit moisture into the space between a window’s panes, which can lead to mold and mildew if left unaddressed. This is part of the reason it’s so important to reseal a leaky window ASAP. Otherwise, you could add mold remediation to your list of necessary repairs, and your window could become unsalvageable.

Written by

Joe Roberts Content Specialist

Joe is a home improvement expert and content specialist for Fixr.com. He’s been writing home services content for over eight years, leveraging his research and composition skills to produce consumer-minded articles that demystify everything from moving to remodeling. His work has been sourced by various news sources and business journals, including Nasdaq.com and USA Today. When he isn’t writing about home improvement or climate issues, Joe can be found in bookstores and record shops.