DaylightFactor Extension


Daylight Factor (DF) is used to study daylight illuminance levels under overcast sky conditions. It depends on space geometry, materials and external obstructions (environment buildings and relief), regardless of climate data for building location.

Daylight factor is defined as the ratio of the inside illuminance to the exterior diffuse horizontal illuminance on an unobstructued plane, for a standard CIE Overcast Sky luminance distribution.

The advantages of DF are its ease of apprehension, speed of calculation and independence of climate. But the fact that it does not take into account the direct radiation of the sun (weather, season and time) is a limitation.

DF is a good indicator of the behavior of the project in an unfavourable climatic situation (overcast sky).

DF indicator is part of environmental standards in many countries.

DL-Light DaylightFactor Extension DF Sketchup model snapshot

Daylight factor calculation affects lighting strategies:

Daylight factor simple or BREEAM

The extension allows calculation of the daylight factor according to two modes:

Calculation of the daylight factor for standard EN 17037

The EN 17037 standard provides a framework for calculating the daylight factor (criteria, specific sensor grid).

The extension Daylight Factor (EN 17037) is dedicated to this standard.

How To Use DaylightFactor Extension

  1. Open SketchUp model. Follow recommendations to prepare your model for DL-Light calculations.

  2. Open DaylightFactor dialog from toolbar df_dialog_icon or menu option Extensions -> De Luminae -> Daylight Factor -> Daylight Factor Calculation and enter the parameters of the calculation.

    DL-Light DaylightFactor Extension DF General tab

    Fields description:

  3. Define materials characheristics for energy calculation.

    Since calculation is done with validated Radiance tools it is necessary to 'attach' physically based material to each layer in SketchUp. Note that materials should be defined with their solar reflectance and transmittance.

    The tab to choose materials:

    DL-Light DaylightFactor Extension DF Materials tab

    Materials panel consists of two main parts:

    To attach a material, select in the table layer(s) and either double-click on the chosen material in the tree or select the material in the tree and press Attach/Detach button.
    To detach from the layer(s), select it and click Attach/Detach button.
    To revert all layers to previous state press Revert button.

  4. Palette of false colours can be defined with precision. 3 options for palette are given, Automatic, Gradient and Custom:

    DL-Light DaylightFactor Extension DF Panel tab
  5. After all data are entered in DF dialog, select one or few surfaces and press Render or run_selected button.

    DL-Light DaylightFactor Extension DF Sketchup selection

    Calculation time depends on number of selected surfaces, level of sensors details and model complexity.

  6. When results are imported, selected surface will have appropriate false colors and Palette is opened.

    DL-Light DaylightFactor Extension DF Sketchup result imported - automatic palette
    DL-Light DaylightFactor Extension DF Sketchup result imported - automatic palette
  7. Results analysis.

  8. For further calculations in the same model:

    Since version 8.0, DL-Light uses a calculation cache algorithm. It automatically detects if a surface requires recalculation or if a previous result can be reused. By default, the cache keeps the information of the last 10 calculations (value configurable in the preferences).

  9. Archiving results:

    DL-Light allows to archive all the results of a calculation: reports, textures and calculation steps (exported Radiance model, weather file, ...). This archive can be reloaded on the model, subject to using exactly the same model as during the calculation.

    See the page Archiving results for more informations about this feature.

    See the page Comparison of results for more informations about comparison of several archives.

  10. Snapshots:

    Current SketchUp model view with imported results can be exported with palette snapshot_with_palette_icon or without palette snapshot_icon to png format. To explore created images user can open folder where they are saved open_snapshot_folder_icon.
    This option is not supported in trial version of the extension (see license information).

    DL-Light DaylightFactor Extension DF Sketchup model snapshot image