Daylight Factor Calculator Uk

Daylight Factor Equation:

\[ DF = \frac{E_{in}}{E_{out}} \times 100 \]

Daylight Factor (DF):

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1. What is the Daylight Factor Equation?

The Daylight Factor (DF) equation calculates the ratio of indoor illuminance to outdoor illuminance, expressed as a percentage. It is a key metric in architectural design for assessing natural lighting levels in buildings, particularly in UK building regulations.

2. How Does the Calculator Work?

The calculator uses the Daylight Factor equation:

\[ DF = \frac{E_{in}}{E_{out}} \times 100 \]

Where:

\( E_{in} \) — Indoor illuminance (lux)
\( E_{out} \) — Outdoor illuminance (lux)

Explanation: The equation provides a standardized measure of how much natural light reaches a point inside a building compared to the available light outside.

3. Importance of Daylight Factor Calculation

Details: Daylight Factor calculation is essential for ensuring adequate natural lighting in buildings, improving energy efficiency, and meeting UK building regulations and sustainability standards.

4. Using the Calculator

Tips: Enter both indoor and outdoor illuminance values in lux. Both values must be positive numbers to calculate a valid Daylight Factor percentage.

5. Frequently Asked Questions (FAQ)

Q1: What is a good Daylight Factor value?
A: In the UK, a DF of 2% is generally considered the minimum for adequate daylighting, with 5% or higher providing excellent natural lighting.

Q2: How is Daylight Factor measured in practice?
A: Typically measured using lux meters at the work plane height, with simultaneous indoor and outdoor readings under overcast sky conditions for consistency.

Q3: Why is Daylight Factor important in UK building regulations?
A: It helps ensure buildings provide sufficient natural light, reducing reliance on artificial lighting and improving occupant wellbeing and energy efficiency.

Q4: Are there limitations to Daylight Factor calculations?
A: DF doesn't account for direct sunlight, glare, or seasonal variations, and assumes overcast sky conditions for standardized comparison.

Q5: How does Daylight Factor relate to window design?
A: Window size, placement, glazing type, and external obstructions all significantly impact the Daylight Factor in a space.