Average Daylight Factor Formula

Average Daylight Factor Formula:

\[ ADF = \frac{\text{Total Daylight Illuminance}}{\text{External Illuminance}} \times 100 \]

Average Daylight Factor (ADF):

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1. What is the Average Daylight Factor Formula?

The Average Daylight Factor (ADF) is a key metric in building lighting design that quantifies the amount of natural daylight available in an interior space relative to the external daylight conditions. It helps architects and designers optimize building orientation and window placement.

2. How Does the Calculator Work?

The calculator uses the Average Daylight Factor formula:

\[ ADF = \frac{\text{Total Daylight Illuminance}}{\text{External Illuminance}} \times 100 \]

Where:

\( \text{Total Daylight Illuminance} \) — The total illuminance from daylight inside the building (lux)
\( \text{External Illuminance} \) — The illuminance from daylight outside the building (lux)
\( ADF \) — Average Daylight Factor expressed as a percentage (%)

Explanation: The formula calculates the ratio of internal daylight illuminance to external daylight illuminance, multiplied by 100 to express it as a percentage.

3. Importance of ADF Calculation

Details: ADF is crucial for sustainable building design, energy efficiency optimization, occupant comfort assessment, and compliance with building regulations and green building certifications.

4. Using the Calculator

Tips: Enter total daylight illuminance and external illuminance in lux units. Both values must be positive numbers greater than zero for accurate calculation.

5. Frequently Asked Questions (FAQ)

Q1: What is considered a good ADF value?
A: Generally, ADF values of 2-5% are considered adequate for most spaces, with higher values (5%+) providing excellent daylighting.

Q2: How is daylight illuminance measured?
A: Daylight illuminance is typically measured using lux meters at various points within the space and averaged to get the total daylight illuminance.

Q3: What factors affect ADF?
A: Window size and orientation, glazing type, room geometry, external obstructions, and surface reflectance all influence ADF values.

Q4: Can ADF be used for all building types?
A: While applicable to most building types, ADF is most commonly used for residential, office, and educational buildings where daylight quality is important.

Q5: How does ADF relate to energy efficiency?
A: Higher ADF values can reduce the need for artificial lighting during daylight hours, leading to significant energy savings and reduced carbon emissions.