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Daylight Factor Equation:
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Daylight Factor (DF) is a measure that quantifies the amount of natural light available inside a building compared to the light available outside. It is expressed as a percentage and helps in assessing the daylighting performance of architectural spaces.
The calculator uses the Daylight Factor equation:
Where:
Explanation: The equation calculates the ratio of internal to external illuminance, multiplied by 100 to express it as a percentage. Location is considered via sun path for design purposes.
Details: Daylight Factor calculation is crucial for sustainable building design, energy efficiency optimization, occupant comfort assessment, and compliance with building regulations and green building certifications.
Tips: Enter internal lux (measured inside the building), external lux (horizontal outside measurement). Both values must be positive numbers. Consider location and sun path for accurate design calculations.
Q1: What is a good Daylight Factor value?
A: Generally, 2-5% is considered adequate for most spaces, with 2% being the minimum for tasks requiring good daylighting and 5% providing excellent daylight availability.
Q2: How should external lux be measured?
A: External lux should be measured on a horizontal plane outside, unobstructed by buildings or trees, ideally under overcast sky conditions for consistent results.
Q3: When is the best time to take measurements?
A: Measurements should be taken under overcast sky conditions to eliminate direct sunlight variations, or at consistent times for comparative analysis.
Q4: Are there limitations to Daylight Factor calculation?
A: DF doesn't account for direct sunlight, seasonal variations, or specific geographical locations. It's best used as a comparative tool rather than absolute measure.
Q5: How does location affect Daylight Factor?
A: Location affects sun path, climate, and available daylight hours, which should be considered in the design phase for accurate daylighting predictions.