The Truth About Broken Window Seals

Broken Seals

Birds are chirpin’ and there’s fresh dew on the grass. Summer is here and spring cleaning is finished. You walk to your bedroom window to open it and take in the fresh air, only to notice the glass is fogged over. You quickly grab a microfiber towel and wipe the glass, but the condensation isn’t on the inside. So you raise the window and wipe the outside…nothing. Now the frustrating truth begins to sink in. Your windows have a broken seal.

You might be asking yourself “how did this happen?” or “what is a broken seal?” There is no such thing as a fail-proof thermal pane window. If they are properly maintained, wood and aluminum windows have a life span of around two decades. Vinyl framed windows can make it 15 years if they have standard box spacers. Most newer vinyl framed windows have a low-quality spacer and these windows begin failing in 5 to 8 years. Sunshine is the biggest cause of window failure, which is why your south and west facing windows usually fail first. Sunshine causes both a process known as “solar pumping” and the hardening of the sealant that forms the seals of the window. When sunshine hits a double pane window, the air inside heats causing the sealed window unit to expand and pushing air out through the semi-permeable seals. In the evening, the window cools and contracts, drawing air and humidity. Day after day, year after year, this cyclical expansion and contraction occurs, stressing the window seals and filling the air space with moisture.

Insulated or double pane glass was developed to save homeowners on energy costs. Glass is horrible as an insulator. Insulated glass is simply two panes of glass bonded together with a spacer. The space between the glass is filled with inert gases like argon, xenon, and krypton. Argon is the most popular gas used because it has a 34% lower thermal conductivity rate than our standard atmosphere. Window manufacturers expect and plan for a lot of abuse. From wind, rain, snow, baseballs, birds, and solar pumping, windows face a lot of different foes.

Out of all of the enemies, solar pumping is perhaps the least obvious. Built into every thermal pane window frame is a silica desiccant to absorb the small amounts of moisture inevitably drawn into the window. The desiccant, however, has a limited capacity and lifespan. At some point the desiccant will have absorbed all the moisture it can hold and that is the day a hazy, misty, bluish fog clouds your glass window pane. From this point on the window begins deteriorating rapidly. If left untreated, the trapped moisture quickly corrodes the inner window glass surfaces, eventually leaving mineral deposits and a permanent white silica haze.

When windows fog and fail, the only viable option might be replacement. Even if repair is possible, it is extremely difficult, expensive, and the glass might have been damaged by the minerals in the moist air. The best way to prevent a broken seal is proper maintenance. Every two years the exterior seam where the glass and wood meet should be caulked. Wood frames should receive a fresh coat of paint. But the best way to prevent a broken seal is to purchase a quality window from the start. Make sure the window has a long and comprehensive warranty. If you’re unsure whether your windows have broken seals or are just simply dirty, request a free estimate from your local Window Genie – they can assess the condition of your windows and offer guidance.

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