1. What is Daylight Factor?

Daylight Factor (DF) is a measure that quantifies how much natural light reaches a point inside a building compared to the light available outside. It's expressed as a percentage and helps architects evaluate daylighting performance in building design.

2. How Does the Calculator Work?

The calculator uses the Daylight Factor equation:

Where:

• \( DF \) — Daylight Factor (percentage)
• \( E_i \) — Indoor illuminance at measurement point (lux)
• \( E_o \) — Simultaneous outdoor illuminance on unobstructed horizontal plane (lux)

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

3. Importance of Daylight Factor

Details: Daylight Factor is crucial for sustainable building design, energy efficiency, occupant comfort, and meeting building regulations. Higher DF values indicate better daylight penetration.

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 adequate for most tasks. Below 2% is poor daylighting, while above 5% is excellent.

Q2: When should measurements be taken?
A: Under overcast sky conditions to eliminate direct sunlight effects. Midday measurements are most consistent.

Q3: Where should indoor measurements be taken?
A: At the work plane height (typically 0.75-0.85m above floor) in areas where daylight is important.

Q4: What affects daylight factor?
A: Window size/orientation, glazing type, room reflectance, external obstructions, and room depth.

Q5: How does DF relate to LEED certification?
A: LEED credits are available for achieving specific DF thresholds in regularly occupied spaces.