1. What is Daylight Factor?

Daylight Factor (DF) is a measure that quantifies the amount of natural light available in an interior space compared to the light available outside. It's expressed as a percentage and helps architects and designers evaluate daylighting performance in buildings.

2. How Does the Calculator Work?

The calculator uses the Daylight Factor equation:

Where:

• \( DF \) — Daylight factor (%)
• \( E_i \) — Indoor illuminance (lux)
• \( E_o \) — Outdoor illuminance (lux)

Explanation: The equation calculates what percentage of outdoor daylight is available at a specific point indoors.

3. Importance of Daylight Factor

Details: Daylight Factor is crucial for sustainable building design, energy efficiency, and occupant well-being. It helps ensure adequate natural lighting while minimizing glare and excessive heat gain.

4. Using the Calculator

Tips: Measure indoor illuminance at the point of interest and simultaneous outdoor illuminance under overcast sky conditions. Both values must be positive numbers.

5. Frequently Asked Questions (FAQ)

Q1: What are typical DF values?
A: 2-5% is considered good daylighting. Below 2% may require artificial lighting, while above 5% may cause glare.

Q2: When should measurements be taken?
A: Under overcast sky conditions for consistent results, as direct sunlight creates highly variable conditions.

Q3: What affects Daylight Factor?
A: Window size/orientation, glazing type, room geometry, surface reflectances, and external obstructions.

Q4: How does DF relate to building standards?
A: Many green building certifications (LEED, BREEAM) have DF requirements for daylighting credits.

Q5: Can DF predict actual light levels?
A: Only indirectly - it's a ratio, not an absolute measure. Actual light levels depend on outdoor conditions.