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Daylight Factor Equation:
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The Daylight Factor (DF) is a measure that quantifies the amount of natural light available indoors relative to the light available outdoors. It is expressed as a percentage and helps in assessing the adequacy of daylighting in architectural design.
The calculator uses the Daylight Factor equation:
Where:
Explanation: The equation calculates the ratio of indoor to outdoor illuminance, multiplied by 100 to express it as a percentage.
Details: Calculating Daylight Factor is essential for evaluating natural lighting conditions in buildings, ensuring energy efficiency, and promoting occupant well-being by providing adequate daylight.
Tips: Enter both indoor and outdoor illuminance values in lux. Ensure that both values are positive and measured under similar sky conditions for accurate results.
Q1: What is a good Daylight Factor value?
A: Generally, a DF of 2-5% is considered adequate for most tasks, while values below 2% may require supplemental artificial lighting.
Q2: How is illuminance measured?
A: Illuminance is measured using a light meter (lux meter) placed at the point of interest, with the sensor facing upward to capture light from all directions.
Q3: Does weather affect Daylight Factor calculations?
A: Yes, outdoor illuminance can vary significantly with weather conditions. For consistent results, measurements should be taken under overcast sky conditions, which provide diffuse light.
Q4: Can Daylight Factor be used for all types of buildings?
A: While widely used, DF is most applicable in spaces with side lighting (windows). For top lighting (skylights), other metrics may be more appropriate.
Q5: Why is Daylight Factor important in sustainable design?
A: Maximizing natural light reduces the need for artificial lighting, lowering energy consumption and contributing to green building certifications like LEED and BREEAM.