In the episode Diamond Jack, when the trio retreats to Jack's bedroom pretending to count the money for the diamond smugglers, they attempt to escape through the window by climbing down a bedsheet. Unfortunately, the end of the bedsheet that was tied to the bed comes loose and it falls out the window, leaving the trio no chance to escape through the second story window.

But if you consider other episodes, then the window couldn't possibly be too high to jump out of. Consider:

1. In "The Kleptomaniac", Jack falls down backwards from the ladder he was painting from after he sees Chrissy take money out of his drawer.

2. In "Breaking Up Is Hard To Do", Janet falls backwards from the ladder she was leaning against the kitchen window when she sees Terri's new boyfriend put what she thinks is poison in the salad.

In each of these cases, neither Jack nor Janet sustained any serious injury. So if a backwards fall from a second-story ladder did not cause any injury, then surely a regular jump wouldn't have cause any injury either.