Daylighting Calculations

DesignBuilder provides 2 types of daylighting calculations:

1. Daylight illuminance contour plots and average daylight factor and uniformity are generated for each zone calculated using the Radiance ray-tracing simulation engine. Standard reports detailing eligibility for LEED EQ8.1, BREEAM HW1 and Green Star IEQ4 daylighting credits are provided. Click on the Daylighting screen tab to view these daylighting results.
   
   
2. Daylighting integrated within EnergyPlus simulations allowing savings in electric lighting to be calculated based hour-by-hour on daylight availability throughout the year.

The rest of this section covers the detailed Radiance ray-tracing calculation of daylight.

Radiance Daylight Simulation

The DesignBuilder Radiance simulation provides a detailed multi-zone physics-based calculation of illumination levels on the working plane of a building. The calculations allow light to be transmitted through exterior and interior windows and the shading and reflective effect of local shading devices and component/assembly blocks is included. Window shading options such as slatted and diffusing blinds are not included in Radiance calculations.

More information on Radiance daylighting calculations can be found in the Introduction to Daylighting Tutorial

Model Data Used

You can use DesignBuilder to generate data on distribution of illuminance levels and daylight factors within each zone for one or more zones in the building. To do this, DesignBuilder uses the following data provided in the model:

• Surface visible reflectance of the material on the innermost layer of constructions.
• Window glazing transmittance.
• Detailed geometry description including the 3-D surfaces as seen on the Visualisation screen.
• Daylighting calculation options.
• Site ground reflectance
• You can select which zones are regularly occupied with regard to daylighting calculations using the Include zone in daylighting calculations option on the Activity tab.

The above data is passed to the Radiance simulation engine which calculates the distribution of illuminance and daylight factors on the working plane using a ray-tracing method.

When the calculations have been carried out, the daylight data can be displayed.