DaylightFactor (EN 17037) Extension

Introduction

The EN 17037 standard (in UK: BS EN 17037:2018 Daylight in buildings) proposes to use the daylight factor to assess the natural light supply in a space. For the UK variant using the "UK National Annex", see DaylightFactor (EN 17037/UK). This extension is designed to follow the recommendations of the original standard:

reference plane at 0.85m from the ground,
display of results for the median target, the minimum target or the synthesis,
use of the sensor grid defined by the standard,
selection of the lighting thresholds according to the values listed in the standard,
palette of 4 colors corresponding to the high / medium / minimum criteria defined in the standard,
taking into account the criteria related to the supply of natural light by vertical, inclined and horizontal openings.
Display of thresholds in lux or foot-candles for compatibility with the WELL standard.

As this computation is based on the same process as classic DF calculation, we recommend that you get familiar with DF: Daylight Factor calculation.

DL-Light extension FLJ daylight factor en17037 Sketchup model snapshot image

How To Use DaylightFactor (EN 17037) Extension

Note: the WELL standard translates thresholds in lux of the standard EN 17037 in foot-candles. To display the various thresholds (palettes, reports) in foot-candles, use the option "Display in lux or foot-candle" in the preferences. Only the display is modified, the calculations are identical regardless of the option selected.

Open SketchUp model. Follow recommendations to prepare your model for DL-Light calculations.
Open DaylightFactor dialog from toolbar or menu option Extensions -> De Luminae -> Daylight Factor (EN 17037) -> Activate extension and enter the parameters of the calculation.

Fields description:
- Project name - Project name is used during export and for output filename generation. The SketchUp model name is used by default.
- Results - Directory where model will be exported for calculation.
  When calculation is started model geometry and resulting files will be saved in daylightfactor_17037_output subdirectory.
  For SketchUp projects stored on network disk (Windows), see Work on a copy of the model.
- Mode - Calculation mode selection:
  - Synthesis: the surface validates the high, medium or minimum level if it meets the criteria for this level for both the median and minimum target thresholds.
  - Target: the surface validates the high, medium or minimum level if:
    - for lighting by a vertical source, 50% of the reference plane receives the corresponding illuminance (750 lux / 500 lux / 300 lux) ,
    - for lighting by a horizontal source (opening in the ceiling), 95% of the reference plane receives the corresponding illuminance (750 lux / 500 lux / 300 lux).
  - Minimum target: the surface validates the high, medium or minimum level if 95% of the reference plane receives the corresponding illuminance (500 lux / 300 lux / 100 lux). The minimum target is only applicable for illumination by a vertical / inclined source.
  - DF levels: classic display of daylight factor values. The palette uses the 4 thresholds 100 / 300 / 500 / 750 lux corresponding to a vertical light source.
  Nota: To determine the percentage of surface reaching a threshold, the default setting is to consider that each sensor represents the same portion of the surface. The surface ratio is therefore the ratio of the number of sensors, this is the strict interpretation of the standard. Conversely, the standard DF calculation assigns to each sensor a weight proportional to its coverage area. See "Coverage area of sensors" in preferences.
- Horizontal source - Selection of surfaces whose illumination is mainly due to a horizontal light source. The "Surfaces" button opens a window displaying the list of horizontally lit surfaces. Click on a surface of the model to add it to the list, click on the red cross to remove it.
  
  Only the surfaces of this list have the horizontal lighting criterion. The surfaces selected for the calculation and not listed in this group are considered as lit by a vertical light source (general case).
- Details - The default selection is the EN 17037 grid required by the standard:
  - distance between sensors of 0.5 × 5^log10(d) meters, where d is the longest dimension of space if the length / width ratio is between 0.5 and 2, otherwise the smallest dimension,
  - The surface of the mesh excludes a strip of 0.50m along the walls, the grid is calculated on this reduced surface.
  The EN 17037 grid is very sparse compared to the usual sensor grids. For example, the density of sensors is more than 6 times lower than the density of the EN 12464-1 grid. The selection of a different grid is possible to allow a more detailed study of the daylight factor values on the surface.
  DL-Light allows to choose:
  - the sensor grid applicable by default to all calculated surfaces,
  - different sensor grids for some surfaces ("exceptions" button).
  See sensors selection for more information on the choices of proposed sensors.
- Ground albedo - Reflection factor of the ground. Value can be selected from drop-down list or defined custom value in next dialog.
- Illuminance - Selection of daylight factor thresholds according to the location of the project. The EN 17037 standard provides a list of locations (European capitals) and the corresponding median diffuse illuminance values. This list is used to determine the daylight factor threshold corresponding to the lux criteria depending on the location.
  
  Note: it is possible to add custom illuminances values for locations not listed by the standard. These new values can be entered in the extension preferences (expert tuning tab).
- Location - Building location coordinates. Location can be based on SketchUp model location, current Weather file location or be Custom. Below is dialog for Custom location definition.
  
  A weather file can be selected to facilitate the model location and détermination of time zone. See page Weather data.
  Important : For this calculation, the weather file is only used for location and time zone selection.
- Time zone - Display of the time zone used for the calculations.
  
  If a weather file is used, the time zone is defined by this file. Otherwise, a selection list allows you to choose the time zone.
  Nota: when a model is located in SketchUp, SketchUp proposes a time zone based on the longitude of the place. This value is sometimes wrong, especially for European or Asian countries.
Define materials characheristics.

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:

Materials panel consists of two main parts:
- SketchUp layers table contains the list of all layers defined in the SketchUp model. Each row contains SketchUp layer name and attached material name if any. If text in a row is grayed, it means that the corresponding layer is not visible in the model. The table is updated in real time, as the SketchUp model is modified.
- Materials tree contains all materials libraries available for DL-Light extension. Some of them are provided when extension is installed and others can be imported or created by user. Subtree 'Model materials' contains materials currently attached to SketchUp layers.
  To explore available libraries and add new ones, see Materials libraries dialog.
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.
The palette of false colors uses the thresholds of the standard. It is possible to change the different colors.
After all data are entered in DF dialog, select one or few surfaces and press Render or button.

As the glazing is kept for this calculation, it may be practical to use the DL-Light select by layer dialog to select the areas to be calculated.

Calculation time depends on number of selected surfaces, level of sensors details and model complexity.
When results are imported, selected surface will have appropriate false colors and Palette is opened.

Surfaces illuminated primarily by a horizontal light source receive this watermark:
Results analysis.
- The Report dialog displays the distribution of results over current palette, and calculation input parameters.
  
  Presentation of the report for the modes synthesis, target and minimum target:
  
  Presentation of the report for DF levels mode:
- Show/Hide Sensors and Values explores results directly in the model for each sensor.
  - Nota: the option "View / Guides" of SketchUp must be activated.
For further calculations in the same model:
- To run calculation on surfaces simply select them and Render .
- It is possible to modify the parameters of the calculation: to change the density of sensors to improve the visualization of the results (for all the model or a specific surface), to modify the palette of colors... Whatever the change, use the Render button. Previously calculated surfaces will be updated with the new settings.
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).
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.
- To archive the calculation results, click on the button Archive.
- To load the results of a previous calculation, click on the button Load
See the page Comparison of results for more informations about comparison of archives.
Snapshots:

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