R303.1

Section R303.1 is titled 'Habitable rooms' and covers light and ventilation requirements for habitable rooms. The purpose of this section is to prevent a habitable room from having uncontrollable, absolute darkness which poses a traversal safety and general well being risk; and to require air movement so occupants have fresh breathing air for their health and well being.

The model shows a habitable room with the floor area highlighted which is used to calculate the required 8% glazed area and 4% openable area. (The floor area inside the closet does not contribute to the room floor area.) The entire window on the exterior wall has an area of 8% of the floor, half of which is openable to the outdoors. Note that exceptions to this section allow for alternative means of light and ventilation.