Daylight factor
This page describes the simulation settings and result outputs specific to the Daylight factor calculation. For general information about the Daylight tab, including how to define and edit Optical Properties and Measuring Planes, please refer to the generic Daylight tab documentation.
Daylight Factor (DF) is a ratio that expresses the amount of natural daylight available inside a space compared to the daylight available outside under an overcast sky. It is typically expressed as a percentage, and higher values indicate better daylight availability.
Daylight Factor is always calculated using the CIE Standard Overcast Sky, a theoretical sky model defined by the International Commission on Illumination (CIE). This sky represents a uniformly overcast sky with no direct sunlight, designed to simulate the worst-case scenario for daylight availability. The model is fixed and does not vary with time, date, or geographic location, making the Daylight Factor a static and climate-independent metric.
Calculation settings
Type of sky
By definition the sky used to calculate the daylight factor is set to CIE Overcast sky and cannot be changed.
Precision
Set the detail level of the Radiance calculation. Click the Precision link to view or edit specific Radiance parameters or to create custom precision settings. For more details see the page Radiance workflow and parameters.
Controllable shading
As a static metric, the Daylight Factor can only be calculated with internal shading devices set to either fully open or fully closed. This setting applies uniformly to all windows in the model and does not vary over time. Dynamic or time-based shading control is not supported in Daylight Factor calculations.
Optical properties
See Daylight tab > Optical properties.
Measuring planes
See Daylight tab > Measuring planes.
Daylight factor results
After the calculation is complete, Daylight Factor metrics are displayed in the results table for all selected zones and measuring planes. The following scalar values are calculated by aggregating the results over each measurement grid:
- Median daylight factor: The median daylight factor value across all grid points on the measuring plane.
- Avg daylight factor: The mean daylight factor value on the measuring plane.
- Min daylight factor: The lowest daylight factor value recorded on the measuring plane.
- Max daylight factor: The highest daylight factor value recorded on the measuring plane.
- Uniformity Ratio (UR): The ratio of the minimum to average daylight factor value, indicating the uniformity of daylight distribution.
In the results table, you can:
- Select and copy individual cells to paste into other applications,
- Sort the data by clicking on a column header,
- Export the entire table to Excel, and
- Visualize any daylight factor metric directly on the 3D model by clicking the box icon
in the corresponding column header (see illustration below)
You can also display a heatmap of daylight factor values for each measuring point directly in the 3D view. To do this, select Daylight Factor from the variable list in the 3D visualization interface:
