Means of Egress
For safety purposes, every bedroom or room used for sleeping purposes in a home is required to have an emergency escape route. This is called an egress window—egress meaning the action of going out or leaving a place. Another function of the egress window is to provide easy access into a house for firefighters. Therefore, depending on the code where you live, minimum egress window size requirements are specified. For example, here are the minimum sizes required based on various authorities:
22 inches by 40 inches
20 inches by 41 inches
24 inches by 34 inches
18 inches by 32 inches
15 inches by 36 inches
In Ames specifically, the net clear openable area is 5.7 square feet with a minimum clear height of 24 inches and a minimum clear width of 20 inches. Note that using the minimum height and width requirement doesn't achieve the 5.7 square foot requirement. It is also important that a person is able to easily reach and climb out the window based on the height of the bottom sill. The maximum sill height can range from 40 to 44 inches. In Ames, code indicates a maximum height of 44 inches.
The following, for example, shows a window too small and even the kind of window would make it difficult for exiting the room. We recommend replacing them with proper windows for safety.