You touch the pane. It’s smooth. The crack is on the inside—but between the two sheets of glass.
You don’t usually hear it happen. There’s no smash of baseball-bat glass, no howl of wind, no obvious intruder. You simply glance at the living room window one morning and see it: a thin, silvery line, or perhaps a web of fractures, snaking across the inner surface of the glass. double glazed window cracked inside
Consider it a gentle, visible reminder: every high-tech system, no matter how well sealed, has a lifespan. When the line appears, it’s time to give your window a second life—one clean, warm, crack-free unit at a time. If the crack is on the room-facing side (i.e., you can feel it) and the window is still fog-free, that is likely impact damage. You can temporarily cover with clear packing tape to prevent shards from falling. But if it’s between the panes, as described above, see Part 5—repair is not an option. You touch the pane
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. You don’t usually hear it happen
