"So much about selecting a good window comes down to the warranty,” says Chris Mathis, of MC Squared, a building-science consulting company based in Asheville, N.C. Mathis focuses on windows, doors, and skylights, serves on the ASHRAE and ASTM code committees as well as the International Energy Conservation Code Committee of the ICC, and was a founding board member and the former director of the National Fenestration Rating Council. He insists that regardless of window materials and features, the warranty should be one of the first window-selection criteria to consider. “If a window fails in a few years, it doesn't matter how good or strong or energy efficient it started out to be,” Mathis says. “About 30% of the replacement windows installed are replacing windows that are only about seven years old. This speaks to how poor many of the units out there are.”
The most common window failure is the seal on an insulated glass unit. Once the seal blows, the window fogs up between the panes. This can cause a drastic reduction in window R-value and may oxidize the low-E coating, turning it into a high-E coating that absorbs heat rather than reflecting it. In the worst cases, the pane actually deforms, bowing inward, as a gas fill, such as argon, escapes.
Mathis recommends choosing a window with a minimum 20-year warranty on the insulated glass, which most of the big window companies offer. “There's a reason some of the big companies have been in business a long time.
Click here to read full article from Remodeling