Double - Glazed Window Crack !!link!!ed Inside

Your window frame expands and contracts at a different rate than the glass. If the installer used too little glazing tape or overtightened the retaining beads, the frame pinches the IGU. Over a few seasons of expansion, the inner pane, which has less flexibility than the outer (being further from the external buffer), gives way.

This is the "hot coffee in a cold mug" effect, scaled up. Imagine a bright winter morning: The outer pane is freezing. The inner pane, warmed by your central heating, wants to expand. But the outer glass holds the entire unit rigid via the spacer. The result? Tension builds in the inner pane until it yields. You’ll often see these cracks starting perpendicularly from the edge, then arcing. double glazed window cracked inside

On a sunny day, the gas between the panes heats up, expands, and presses outward on both glass sheets. At night, it cools, contracts, and pulls inward. This daily breathing is normal. But if the perimeter seal is old or poorly fitted, the pressure becomes uneven. Eventually, the inner glass—the side facing your conditioned home—shatters from fatigue. Your window frame expands and contracts at a