If you’ve a cracked window, you need to take action immediately. Even if the crack is only on one pane of a two- or three-paned window, it needs to be fixed.
The answer why is simple: energy bills.
Glass by itself is an absolutely terrible insulator. Windows only become insulated by preventing the movement of air between panes.
In a tight space, air cannot transfer heat by convection (mixing of different-temperature air), only by direct conduction.
Since air is bad at conducting, it forms an insulated layer that keeps heat either out or in a house.
When one pane of a window is cracked, air can move between the house and the area between the panes through convection. All heat needs to do is transfer across the glass, and it’s free to go.
This means that a good double-paned window is only as insulated as a single-paned one if there is even a small crack. If both panes are cracked, you’d be better off with an intact 50-year-old pane.
The amount of money that can fly out a single cracked window is amazing. Substandard windows account for about 30% of house’s heating bill. Cracked windows can push that up to 50%. Cut your heating bill in half: that is how much your windows are costing you.
So, you need to fix cracked windows. What should you do about it?
You can try repairing your window yourself, but it’s not recommended. If enough damage had been done to a window to crack it, the window likely has other serious problems.
Impacts can often cause the seal to fail, letting a breeze in. The frame may have warped or shifted. It is best to call in an expert.
