Residential Building Inspector B1Building Planning and Life SafetyEasy
A residential building inspector is reviewing plans for a new single-family dwelling that includes a window in a bathroom. What is the minimum required amount of glazing area, as a percentage of the floor area, for natural light in this bathroom?
- A6 percent
- B4 percent
- C8 percent
- D10 percent
Show answer & explanationAnswer & explanation
Correct answer: C. 8 percent
IRC R303.1 states that every habitable space shall have not less than one exterior glazed opening for natural light, with the aggregate glazing area equal to not less than 8 percent of the floor area of such rooms. A bathroom is considered a habitable space for this requirement.
Why the other options are wrong
- A. This percentage is less than the minimum required for natural light.
- B. This percentage is for natural ventilation, not natural light.
- D. This percentage exceeds the minimum but is not the minimum.
Habitable Space Natural Light
Minimum area of exterior glazed openings required in habitable spaces to provide natural illumination.
- Applies to all habitable spaces.
- Based on a percentage of floor area.
- Can be windows or skylights.
Memory trick: For a room to feel bright and free, 8% of its floor should be for light to see.