In tropical interiors, daylight factor is defined as the ratio of interior to exterior daylight and is limited in usefulness by which factors unless shading and diffusion are used?

• A. It measures interior daylight relative to exterior; in the tropics, high sun angles and glare limit its usefulness without shading and diffusion.
• B. It measures interior daylight indefinitely and is unaffected by glare.
• C. It measures exterior daylight only.
• D. It is not used in tropical design.

Answer: (B)

Daylight factor is the ratio of interior daylight to exterior daylight, and it assumes diffused daylight from the sky. In tropical interiors, the sun is high, and direct sunlight and glare can overwhelm the interior lighting, making this ratio less useful unless shading and diffusion are used to control glare and distribute light more evenly. Shading reduces the intense direct beam, while diffusion helps create a more uniform interior illuminance, making the daylight factor a more meaningful measure. The other statements misrepresent what daylight factor measures (it's not an indefinite measure and is affected by glare) and its relevance to tropical design.