Glass Windows Happened Earlier Than You Had Thought.

Glassmaking was remarkably advanced during the Roman era, and many ancient homes had glass-paned windows. The earliest windows were panes of glassy pebbles laid on a wooden frame — these would let some light through, but probably weren't that transparent. Clear glass panes were first invented in the late 3rd century AD, when glass-makers would blow a cylindrical bubble of glass and then slice it lengthwise and flatten out the results. Wiki.