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 assess how well daylight is distributed in a room.

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 the ratio of indoor to outdoor illuminance, multiplied by 100 to get a percentage value.

3. Importance of Daylight Factor

Details: Daylight Factor is crucial in architectural design for evaluating natural lighting conditions, energy efficiency, and occupant comfort. It helps determine if artificial lighting is needed during daytime.

4. Using the Calculator

Tips: Measure indoor and outdoor illuminance simultaneously using a lux meter. Enter both values in lux. For accurate results, take measurements on an overcast day when the sky is uniformly bright.

5. Frequently Asked Questions (FAQ)

Q1: What are typical Daylight Factor values?
A: DF values below 2% are considered poor, 2-5% is average, and above 5% is good daylighting. Spaces with DF > 10% may need shading to control glare.

Q2: When is the best time to measure for DF?
A: On an overcast day around noon, when the sky luminance is most uniform and stable.

Q3: How does window size affect DF?
A: Generally, larger windows increase DF, but the relationship isn't linear. Window placement, glazing type, and room geometry also significantly impact DF.

Q4: What's the difference between DF and daylight autonomy?
A: DF is a static measure under standard overcast conditions, while daylight autonomy considers annual daylight availability under varying sky conditions.

Q5: Can DF be used for code compliance?
A: Yes, some building codes and green building standards (like LEED) use DF as one of the metrics for daylighting requirements.