Not to be confused with a window sill, window seals refer to the seals that modern windows have to hold in the air between multiple panes of glass. Unlike older windows with only a single pane of glass, modern windows come with two or sometimes three panes separated by layers of air or inert gas and sealed with an elastic sealant. Referred to as insulated glass units, they’re also sometimes called double-pane or thermopane windows.
A failed seal allows moisture and humidity to seep into the air separating the glass panes in your window and causes issues with window visibility. If you’ve ever gone to admire the view from one of your home’s windows and were instead greeted by fogged glass, you probably had a failed seal.
Why Window Seals Fail
One of the main reasons window seals eventually fail is through a process called solar pumping. As the sun shines down on your windows, the glass expands and puts pressure on the seal. Overnight, the glass cools and shrinks. Day after day, this process repeats, and, over time, the seal may fail. Windows on the south and west sides often fail before others since they receive the most sunshine.
Of course, there are other reasons seals fail too. Anything that causes damage to the elastic sealant can cause the seal to fail, including:
- Physical damage during installation
- Extreme temperature fluctuations
- Poor installation techniques
- Manufacturing defects
- Age and normal wear
As mentioned, fogged windows are a sure sign of window seal failure. When a window seal fails, moist air seeps in between the glass panes and condenses on your windows, causing window fog. And while the fog may eventually go away with weather changes, now that the seal has failed, the problem will keep coming back.
In windows with inert gasses, such as argon or krypton, these gasses serve to enhance insulation. If you lose your seal, those gasses are as good as gone, and your window isn’t doing its job as well as it could.
How Long Do Window Seals Last?
Understanding the expected lifespan of window seals helps you plan for eventual replacement and recognize when seal failure is due to quality issues versus normal aging.
Average lifespan: Quality window seals typically last 10-20 years, though some premium windows with superior seals and proper installation can last 25-30 years or more. The wide range depends heavily on several factors that accelerate or slow seal degradation.
Sun exposure matters most. Windows facing south and west receive the most direct sunlight, experiencing more dramatic temperature swings that stress the seal through constant expansion and contraction. These windows often fail 5-10 years earlier than north-facing windows.
Climate affects longevity. In the Mid-Atlantic region, windows face particular challenges. Hot, humid summers followed by cold winters create extreme temperature cycles that accelerate seal breakdown. Coastal areas experience even faster degradation due to salt air exposure.
Installation quality is crucial. Even the best window seal won’t last if the window isn’t installed correctly. Improper installation puts stress on seals from day one. Windows that are forced into openings, inadequately supported, or installed without proper flashing often experience premature seal failure. Learn more about signs of bad window installation that can lead to early seal problems.
Thompson Creek windows are backed by our 50-year No-Hassle warranty, which covers seal failure and other window defects. This comprehensive coverage provides peace of mind that your investment is protected far beyond the typical seal lifespan.
Can Window Seals Be Repaired or Must They Be Replaced?
This is one of the most common questions homeowners ask when they discover foggy windows, and the answer might disappoint you.
Window seals cannot be repaired—only replaced. Unlike weather stripping or caulk around the window frame, the seal between glass panes in an insulated glass unit is hermetically sealed during manufacturing. Once moisture penetrates this seal, there’s no way to re-seal it or remove the trapped moisture permanently.
Understanding your replacement options:
Insulated Glass Unit (IGU) replacement involves removing the glass portion of the window while keeping the existing frame and hardware. A window professional removes the damaged glass unit and installs a new sealed unit in its place. This is often the most cost-effective solution if your window frames are in good condition.
Full window replacement makes sense when frames are damaged, the window is very old, or you want to upgrade to more energy-efficient windows with better features. While more expensive initially, full replacement provides a fresh start with modern energy efficiency and often includes updated hardware and operation.
When IGU replacement is best:
- Window frames are structurally sound
- Hardware operates smoothly
- The window is relatively new (less than 15 years old)
- Only the seal has failed
When full replacement is better:
- Multiple windows need attention
- Frames show rot, warping, or damage
- Windows are more than 20 years old
- You want significant energy efficiency upgrades
- Operational issues exist beyond the seal
Unfortunately, you can’t simply replace failed seals. The best way to fix your foggy or warped window is to replace the insulated glass unit. The work should be done by someone knowledgeable who understands how windows are properly disassembled so that the old unit can be removed and the new one installed.
Window Seal Replacement Cost: What to Expect
Understanding the financial aspects of seal failure helps you make informed decisions about repair versus replacement.
IGU replacement costs typically range from $150 to $400 per window, depending on several factors. This includes the new insulated glass unit and professional labor to remove the old unit and install the new one.
Cost factors for IGU replacement:
Window size is the primary cost driver. A small bathroom window might cost $150-200 to replace, while a large picture window could run $300-400 or more. Standard-size windows are generally less expensive than custom dimensions.
Glass type affects pricing. Basic dual-pane clear glass is least expensive. Adding Low-E coatings increases cost by $30-50 per window but significantly improves energy efficiency. Argon or krypton gas fills add another $20-40 but enhance insulation value.
Accessibility impacts labor costs. First-floor windows are straightforward to service. Second and third-floor windows require ladders or scaffolding, increasing labor costs by 25-50%. Some window designs make IGU replacement more complex and time-consuming.
Full window replacement costs range from $400 to $1,000+ per window installed, depending on window type, size, materials, and installation complexity. While more expensive than IGU replacement alone, full replacement provides updated energy efficiency and often makes sense when multiple windows need attention or the existing windows are older. Learn more about comprehensive window replacement costs to help plan your project budget.
Labor costs in the Mid-Atlantic typically run $75-150 per hour for professional window services. IGU replacement usually takes 1-2 hours per window, while full window replacement takes 2-4 hours depending on complexity.
Insurance coverage considerations: Standard homeowners insurance typically doesn’t cover seal failure due to age or wear, as it’s considered normal maintenance. However, if seal failure results from storm damage, impact, or a covered peril, your insurance might cover replacement. Check your specific policy and document any damage thoroughly.
How to Prevent Window Seal Failure
While seal failure is eventually inevitable for all windows, you can take steps to maximize seal lifespan and delay premature failure.
Avoid power washing window seals directly. The high pressure can damage the seal between the glass and frame. When cleaning windows, use gentler methods and avoid directing high-pressure water at the edges where seals are located.
Keep window frames clean and well-maintained. Dirt, debris, and moisture buildup around frames can accelerate seal deterioration. Clean frames regularly and ensure proper drainage so water doesn’t pool around windows.
Monitor for early warning signs. Catching seal failure early prevents secondary damage. Check windows periodically for slight haze between panes, small amounts of condensation, or changes in how windows operate. Early detection allows you to plan replacement on your schedule rather than in an emergency.
Ensure proper installation from the start. Quality installation is the single biggest factor in seal longevity. Windows that are correctly sized, properly supported, adequately flashed, and installed without stress on the frame will have seals that last their full expected lifespan. This is why choosing experienced professionals for window installation is crucial.
Climate considerations matter. In the Mid-Atlantic, extreme temperature cycles are unavoidable. However, properly installed windows with quality seals are designed to handle these conditions. Using windows specifically rated for your climate zone ensures the seals are engineered for local temperature ranges and humidity levels.
Set realistic expectations. Even with perfect care, seals will eventually fail. It’s a natural consequence of the thermal cycling that occurs with daily and seasonal temperature changes. Quality windows from reputable manufacturers simply take longer to reach that point. Thompson Creek’s 50-year warranty recognizes this reality and protects homeowners when seal failure occurs.
While replacing the insulated glass unit is the easiest way to fix failed window seals, it might be a good idea to replace the entire window if the window is warping or difficult to open due to its age.
Frequently Asked Questions About Window Seals
Does homeowners insurance cover failed window seals?
Most standard homeowners insurance policies don’t cover seal failure from age or normal wear and tear, as this is considered routine maintenance. However, if seals fail due to a covered event like storm damage or impact, your policy may provide coverage. Review your specific policy and contact your insurance agent for clarification.
Can I prevent solar pumping damage to window seals?
Solar pumping is a natural physical process that occurs with temperature changes—it can’t be completely prevented. However, choosing quality windows with durable seals, proper installation, and windows rated for your climate zone can significantly extend seal life despite solar pumping stress.
What’s the difference between window seals and weather stripping?
Window seals are the hermetic seals between glass panes in insulated glass units—they’re permanent and can’t be accessed or replaced without replacing the glass. Weather stripping is the flexible material around the window frame that prevents air and water from entering around the operable parts of the window—it can be replaced as needed.
How do I know if argon gas has leaked from my windows?
You can’t see or detect argon gas leakage directly, but fogging between panes indicates seal failure, which means any argon gas has escaped. Some newer windows have indicators that show gas presence, but most don’t. If your seal has failed, assume the argon is gone and the window has lost its enhanced insulation value.
Can new windows be guaranteed never to have seal failure?
No reputable window manufacturer can guarantee seals will never fail, as thermal cycling eventually affects all windows. However, quality manufacturers offer long warranties covering seal failure. Thompson Creek’s 50-year No-Hassle warranty provides extensive protection against seal failure and other window defects, giving you peace of mind about your investment.
Experiencing foggy windows from failed seals? Whether you have a failed seal and you’d like to find out what kind of options you have for new windows all around, we can help. We’ve provided the Mid-Atlantic area with custom windows, doors, gutters, siding, and roofing for over 40 years, and we pride ourselves in the work we do. Get in touch today for all your home needs.