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Daylight Factor Equation:
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Daylight Factor (DF) is a metric that quantifies the percentage of external daylight available inside a space. It represents the ratio of internal illuminance to external horizontal illuminance, expressed as a percentage.
The calculator uses the Daylight Factor equation:
Where:
Explanation: The equation calculates the percentage of available external daylight that reaches the interior space, providing a standardized measure of daylight availability.
Details: Daylight Factor is crucial for architectural design, building performance assessment, and ensuring adequate natural lighting in indoor spaces. It helps optimize building orientation, window design, and energy efficiency.
Tips: Enter internal illuminance and external horizontal illuminance in lux units. Both values must be positive numbers greater than zero for accurate calculation.
Q1: What Is Considered A Good Daylight Factor?
A: Generally, DF ≥ 2% indicates adequate daylighting for most tasks. DF ≥ 5% is considered well-daylit, while DF < 2% may require artificial lighting supplementation.
Q2: How Is Illuminance Measured?
A: Illuminance is measured using a lux meter or light meter. Internal measurements are taken at the working plane height, while external measurements are taken on a horizontal surface.
Q3: What Factors Affect Daylight Factor?
A: Window size and orientation, glazing properties, external obstructions, room geometry, surface reflectances, and geographical location all influence daylight factor values.
Q4: When Should Daylight Factor Be Calculated?
A: During building design phase, daylighting analysis, sustainability certifications (LEED, BREEAM), and post-occupancy evaluations to assess building performance.
Q5: Are There Limitations To This Calculation?
A: This simplified calculation provides average values. For detailed analysis, consider point-in-time simulations, climate-based daylight modeling, and seasonal variations.