Not to be confused with a window sill, window seals refer to the seals that modern windows use 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, causing issues with 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 likely had a failed seal.
Why Window Seals Fail
One of the main reasons window seals eventually fail is a process called solar pumping. As the sun shines 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.
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, and normal age and wear.
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, causing window fog. And while the fog may eventually clear with weather changes, now that the seal has failed, the problem will keep returning.
In windows with inert gases such as argon or krypton, these gases enhance insulation. If you lose your seal, that gas is essentially gone, and your window isn’t performing as well as it should.
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.
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 well before north-facing windows.
Climate affects longevity. In the Mid-Atlantic region, windows face particular challenges. Hot, humid summers followed by cold winters create 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 well 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.
Window seals cannot be repaired, only replaced. Unlike weatherstripping 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 permanently remove the trapped moisture.
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 a more targeted solution if your window frames are in good condition.
Full window replacement makes sense when frames are damaged, the window is quite old, or you want to upgrade to more energy-efficient windows with better features. 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, and only the seal has failed.
When full replacement is better: multiple windows need attention, frames show rot, warping, or damage, the windows are quite old, you want meaningful energy efficiency upgrades, or operational issues exist beyond the seal.
The best way to fix a foggy or fogged window is to replace the insulated glass unit. The work should be done by someone experienced who understands how windows are properly disassembled so the old unit can be removed and the new one installed correctly.
Planning Seal Repair or Window Replacement
Because IGU replacement and full window replacement costs vary widely based on window size, glass type, accessibility, and the number of windows involved, general pricing isn’t a reliable way to plan your specific project. Thompson Creek offers a free, no-obligation assessment to give you an accurate picture based on your home’s actual windows.
Insurance coverage considerations: Standard homeowners insurance typically doesn’t cover seal failure due to age or wear, since 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, a few habits can help maximize seal lifespan and delay premature failure.
Avoid power washing window seals directly. 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 lets you 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.
Climate considerations matter. In the Mid-Atlantic, extreme temperature cycles are unavoidable. 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 No-Hassle Warranty recognizes this reality and protects homeowners when seal failure occurs.
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, since 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, so it can’t be completely prevented. However, choosing quality windows with durable seals, proper installation, and windows rated for your climate zone can meaningfully extend seal life despite solar pumping stress.
What’s the difference between window seals and weatherstripping?
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. Weatherstripping is the flexible material around the window frame that prevents air and water from entering around the operable parts of the window, and 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, since 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.
Why Choose Thompson Creek
Experiencing foggy windows from failed seals? Whether you have a failed seal or you’d simply like to explore your options for new windows, we can help. We’ve served the Mid-Atlantic area with custom windows, doors, gutters, siding, and roofing for more than 40 years, and we pride ourselves in the work we do.
If your seal failure has you weighing repair versus a broader upgrade, our guide on insert vs. full frame window replacement and our overview of what to expect during window replacement are useful next reads.
Ready to address failed window seals? Contact Thompson Creek today for a free, no-obligation consultation. Our team will assess your specific windows and recommend IGU replacement or full window replacement based on what makes the most sense for your home.
