Manufacturers make modern windows as double- or triple-glazed panes with an inert insulating gas sandwiched in between. When energetic heat-transferring particles bump up against the glass, the insulation radiates them back into the environment instead of allowing them to pass through. This prevents warm air from escaping in the winter and penetrating in the summer.
However, this type of window relies on an energy-efficient seal – a component that stops insulating gases from flooding out into the environment. Sometimes these seals can fail. And that can lead to air leakage and greater reliance on climate control systems.
Why Do Window Seals Break Down?
There are specific reasons why seals or caulk can break down, but it is worth noting here that all seals have limited lifespans. Wood and aluminium seals last around twenty years while vinyl-framed windows will function anywhere from five to fifteen years, depending on the quality of the spacer.
Reason #1: High Atmospheric Moisture
Ideally, you should purchase windows suited to the climate in which you live. If you don’t, this can cause the seal to fail.
For instance, wooden windows are unsuitable for cold, wet environments. Swelling and warping of the underlying material can create gaps in the seal, allowing insulating gases (such as krypton and argon) to escape.
Reason #2: Solar Pumping
Another common cause of broken seals is a phenomenon called “solar pumping.” When sunlight enters glazed windows, it heats the insulating gases inside. As it expands, it pushes up against the seals and begins seeping out (even if they are in good condition). Then, on cold nights, the gas cools, reducing pressure in the window, causing it to suck in unwanted air over time.
As this process continues, it progressively fatigues the seal material, causing it to weaken and harden. Eventually, so much of the original insulating gas leaves the interior of the window that it loses performance altogether.
It’s worth noting that most modern windows come with a bead spacer that allows the glass to expand and contract without putting excessive strain on the seal. This component extends the life of windows exposed to highly variable light and heat conditions.
Reason #3: Condensation
When there is a large difference in temperature between the inside and outside of your home, the risk of condensation rises. Water vapor in the atmosphere passing close to cold panes condenses into water droplets that form on the surface.
Infrequently condensation buildup won’t adversely affect the seal. However, if moisture occurs more often, it can lead to mold. And this causes damage. As mold grows, it penetrates the seal material, fatiguing it over time.
Reason #4: Manufacturing Or Installation Defects
Lastly, you can have a broken window seal because of manufacturing or installation defects. These could include:
- Failing to properly clean the surface of the window before installing the seal
- Incorrectly applying the seal
- Puncturing the seal during installation
- Failing to allow the seal sufficient time to dry before installation
Window installation experts can confirm whether this is the source of your problem.
How To Tell If A Window Seal Has Failed
The clearest sign of seal failure is condensation buildup on the interior surfaces of your window panes. When seals first fail, the visible signs will be subtle (i.e. a very small patch of condensation). But over time, you may start noticing more significant moisture buildup between window panels. And, eventually, the entire window can become fogged.
How To Respond To A Failed Seal
When a window seal fails, you have several options for how to proceed.
- Do nothing: When you suspect a failed window seal, one option is to do nothing. If you believe the failure is in its early stages, you usually have a couple of years before it will start having a meaningful impact on your bills. The downside is the condensation buildup. You may find the window fogging unsightly.
- Replace the seal: Another option is to replace the seal and then re-gas the window. This process allows you to avoid replacing the entire window, but it isn’t usually economical.
Replace the window: The final – and probably best – option is to replace the entire window. Here, you have two options. You can either use insert replacements that preserve all of the existing interior and exterior trim – the more affordable approach. Or you can just go the whole way and replace everything in full replacement.