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Failed Window Seals

At property inspections I come across failed window seals quite often.For many first time home buyers this can be a completely new topic that they don't know much about, so I thought I would gather some information together here as a resource. This is what a failed window seal looks like.
Failed Window Seal

Failed Window Seal

The window will appear foggy, sometimes injust a corner andnomatter how much you clean it or what the temperature is, the fog remains. What is a seal anyway? The window seal refers to any part of the window installation that blocks out the exterior environment. Most often, the term seal is used for weatherization and energy efficiency applications, and usually refers to the sashes (in sliding windows) and lites (window panes). Why do window seals fail? Sometimes they fail for these reasons:
  • Pressure building between the two panes of glass during hot days (referred to as heat pumping)
  • Contracting/shrinking inthe colder months
  • Expansion and contraction of the sealant material itself
Seals fail most frequently on windows facing south or west due to longer exposure to the sun. Too much direct sunlight deteriorates the original sealing material more quickly than windows facing in other directions. When considering new windows, always opt for solid, long-term, transferable warranties (20-year warrantiesare preferred) because the windows will not only perform better for longer, but the transferable warranty also adds resale value. What do you do about it? First you would need to figure out where the seal is compromised or leaking. In some instances, a nice amount of caulking can do the trick but will look unsightly. The other option is to just replace the panes. Lastly, in some cases the window framing is the cause, possibly due to poor installation, and a new window might be the answer. In a majority of cases I see, a window's broken seal is due to old age, and therefore replacing the window for a more efficient one is the best option. As with any home repair, if you are not a DIYerconsultyour qualified inspector or ageneral contractor for guidance!