The term 'daylight factor', used in assessing adequacy of natural lighting in housing, is defined as:
- A The ratio of window glass area to total floor area of the room, expressed as a percentage
- B The number of hours per day the room receives direct sunlight
- C The ratio of illumination at a point inside the room to the illumination outside in the open, expressed as a percentage ✓
- D The intensity of light falling on the work surface, measured in lux
Correct answer: C. The ratio of illumination at a point inside the room to the illumination outside in the open, expressed as a percentage
Explanation
The daylight factor expresses indoor illumination at a given point as a percentage of simultaneous outdoor illumination under an overcast sky, allowing assessment independent of weather and time of day. Option A describes the window-to-floor area ratio, a separate building bylaw requirement, while option D is simply illuminance in absolute units. Conflating the daylight factor with glazing area is the expected error.
Reference: Park's Textbook of Preventive and Social Medicine, 27th ed.
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