Are your windows a heat hazard?

Concave windows and how to find out if you are at risk.

We recently heard an interesting story from a homeowner, he was telling us that he kept getting dry/burnt spots on his grass and he couldn’t figure out where it was coming from. He was thinking it was coming from his exhaust pipes on his garage but couldn’t be sure. He knew that it was some sort of reflection from the sun because the issue continued, and anything placed in that spot of the yard would be affected. There was even patio furniture out in that area one summer and the reflection melted the patio cushion! Finally, one winter he was walking out in the yard and he felt a strong ray of sun on the side of his face, he looked up and there it was…a reflection of the sun from the picture window in the living room!

What would cause a window to directly reflect the sun in such a dangerous way?

Concave glass. This is a type of glass defect that can happen sometimes especially on larger picture windows. It’s when the two panes of glass bend in towards each other. Some cases are so extreme that the dual pane glass can touch in the center and even crack. Since glass is not a true solid material it can warp over time.

How to test your windows for a concave glass defect.


Tools you’ll need:

  • A yardstick, or some type of straight edge that spans the length of the window

How you test your window:

Hold the yardstick or straight edge diagonally across the window. You’ll be looking for a gap at the center of the straight edge against the glass. If you see a gap in the center you know that your window has a concave defect. We tested this out on a window we knew was concave and you can easily see the bow in the window (you’re looking for the red gap area highlighted in the second photo). If your windows are concave you might be at risk of melting your siding, your neighbors’ siding, your yard, or items in your yard.


How do you fix it?

One option is adding a screen to the window, this can help diffuse the sunlight enough to prevent damage.

You’ll also want to check with the original manufacturer to see if your window is protected by a warranty. If your window isn’t covered under a warranty, you might consider having it replaced so it can’t cause any more damage to its surroundings.

If you’re ready to replace your windows schedule a free in-home consultation with one of our design consultants today.

Want more information about window installation?

Click here to download our Installation Checklist.

Posted in: