09/11/2026
The OSI System: How We Seal a Window Against Water, Air, and Noise
The window itself is only one part of a good installation. Just as important is what happens around it, especially in the small spaces and joints that will eventually disappear behind the trim.
At Windura, we use the OSI system to help manage water and air around the windows we install. It involves three primary layers: flashing at the opening, low-expansion foam around the window frame, and exterior sealant at the finished perimeter.
Each has a different job. Together, they help create a properly sealed installation from the rough opening all the way to the exterior of your home. And once the trim goes back on, much of this work will never be visible again.
Watch video at: https://www.windura.com/the-osi-system-how-we-seal-a-window-against-water-air-noise-kansas-city/