Spatial Daylight Autonomy (sDA / ASE) Extension

Introduction

Spatial Daylight Autonomy (sDA) assesses whether a space receives sufficient daylight on a work plane during standard operating hours on an annual basis. The target is 300 lux for 50% of the occupied period.

This extension also calculates the associated indicator ASE (Annual Sunlight Exposure). ASE identifies surfaces receiving too much direct sunlight that may cause visual discomfort (glare) or additional cooling costs. ASE measures the percentage of the work plane exceeding the threshold of 1000 lux more than 250 occupied hours per year.

The sDA and ASE indicators are part of the LEED rating system. They are defined in the IES LM-83-12 standard:

Illuminating Engineering Society, Lighting Measurement 83: Approved Method: IES Spatial Daylight Autonomy (sDA) and Annual Sunlight Exposure (ASE)

This extension is designed to follow the recommendations of the standard:

• reference plane at 30 inches from the floor (0.762m),
• display of sDA results according to the "preferred" / "nominally accepted" / "low" classification,
• use of the sensor grid defined by the standard (24 inches),
• lighting thresholds defined by the standard (sDA: 300 lux for 50% of the period, ASE: 1000 lux for more than 250 occupied hours per year),
• materials' library "leed_lm83" with the default materials ​​proposed by the standard,
• 8am / 6pm range taking into account the Daylight Saving Time (auto detection of legal time zone based on climate data file),
• sensors with no light for the "sDA" indicator are discarded, in accordance with IES-LM-83, §2.2.5: "Analysis points that are found to have a yearly maximum value of less than 1 lux, and are adjacent to other points with higher values, can be dropped from the analysis".

The extension offers two modes for sDA:

• a "sDA 300,50% from 8am to 6pm over the year" mode, stricly compliant with the standard,
• a mode allowing to modify the various parameters.

For detailed analyzes, in both modes, you can display either the performance ("preferred", "nominally accepted", "low"), or the zone reaching the threshold "sDA300,50%", or the duration above the illuminance threshold.

By default, the calculations of sDA and ASE are performed simultaneously in order to garanty their consistency. The report presents the two indicators for each surface.

How To Use spatial Daylight Autonomy (sDA / ASE) Extension

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

2. Open sDA / ASE dialog from toolbar or menu option Extensions -> De Luminae -> sDA / ASE (spatial DA) -> Activate extension and enter the parameters of the calculation.

   

   Fields description:

   • Project name - The project name is used during export and for output filename generation. The SketchUp model name is used by default.

   • Results - The directory where model will be exported for calculation.
     When calculation is started the model geometry and the resulting files will be saved in sda_output subdirectory.
     For SketchUp projects stored on network disk (Windows), see Work on a copy of the model.

   • Mode - Calculation mode selection:

     • sDA standard: LM-83 reference parameters are used, "sDA 300,50% from 8am to 6pm over the year".
     • sDA custom:
       • the values ​​of the illuminance and duration thresholds can be modified:
         
       • the calculation period (at the bottom of the dialog) can be modified:
         

   • Analysis - Selection of the analysis to be performed, settings for the palette, the false color textures and the report:

     • sDA: display of sDA results following the classification "preferred" / "nominally accepted" / "low". According to LM-83, the "preferred" rating means that the surface meets the criterion "sDA300,50%" on 75% of its area (percentage of number of sensors), "accepted" corresponds to a ratio of 55%, and "low" corresponds to a ratio of less than 55%.
     • ASE: display of ASE results. The 1000 lux and 250 hours thresholds can be modified in the preferences.
     • sDA area: display of surface reaching 300 lux for 50% of the period. Areas of the surface reaching the "sDA300,50%" threshold are shown.
     • sDA duration: Display of the percentage of time above the 300 lux threshold. This corresponds to the indicator "sDA300", areas above 50% validate the criterion "sDA300,50%".
     Note: if custom mode is selected, replace in the description above the values ​​300 lux / 50% by the values ​​actually used.

   • Details - The default selection is the grid required by LM-83:

     • 24 inches (0.6096m) between sensors,
     • 12 inches (0.3048m) minimum between sensors and edges of surfaces.

     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 grids.

   • Ground albedo - Reflection factor of the ground. The value can be selected from the drop-down list or a custom value can be defined:

     
     

   • 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.

     

   • Weather - Select annual weather file for the building location in Energy Plus weather file format. The weather file can be selected in the list provided by DL-Light or downloaded from Internet. See page Weather data.

   • Time zone - Display of the time zone used for the calculations.

     The time zone is defined from the selected climate data file.
     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.

     Daylight saving time: LM-83 specifies that the 8am/6pm schedule must take summer time into account (it is possible to change this option in the preferences). The time zone and the location indicated by the weather file allow automatic deduction of the rules for daylight saving time. If multiple DST time zones are possible (or synonyms for the same rule), you can select in the list the rule to apply.

   • Period - Period of analysis. The sDA indicator is normally calculated for 8am/6pm over the year. If the custom sDA mode is selected it is possible to modify the start and end dates and the planned hours.

3. 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 light reflectance and transmittance.

   

   Materials panel consists of two main parts:

   • SketchUp layers table contains the list of all layers defined in the SketchUp model. Each row contains a SketchUp layer name and its attached material name if any. If a row is grayed, it means that the corresponding layer is not visible in the model and will not be taking into account in the calculation. The table is updated in real time, whence 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. Subtree 'Model materials' contains materials currently attached to SketchUp layers.
     The leed_lm83 library contains the default materials defined in LM-83.
     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.

4. The palette of false colors uses the defined thresholds. It is possible to change the various colors. The palettes for the analyzes sDA, ASE, sDA area and sDA duration:

   
   
   
   

5. After all data are entered, select one or more surfaces and press Render or button.

   As glazings are used 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 the number of selected surfaces, the level of sensors details and model complexity.

   The "Daylight Autonomy" type of calculation (often referred to as "3-phases" calculation) is the most time consuming. DL-Light uses a caching system to switch between sDA and ASE analyzes without triggering a full calculation.

   By default, the sDA calculation also performs the ASE calculation. It is possible to modify this option in the preferences. The sDA calculation is then slightly faster and the ASE calculation is only performed when its display is requested:

   

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

   Rendering of the sDA analysis:

   

   Rendering of the ASE analysis:

   

   Rendering for area and duration sDA analyzes:

   

7. Results analysis.

   • The Report dialog displays the distribution of results for current palette, and calculation parameters.

     Presentation of the report for sDA / ASE analysis:

     Note: the “LEED sDA points” column shows the LEED classification points for each surface for the sDA criterion alone, without taking into account the corrections to be made with respect to the ASE criterion.

     

     Presentation of the report for sDA area analysis:

     

     Presentation of the report for sDA duration analysis:

     

   • Show/Hide Sensors and Values explores results directly in the model for each sensor.

     • Nota: the option "View / Guides" of SketchUp must be activated.
     

8. For further calculations on the same model:

   • To run calculation on surfaces simply select them and click Render .
   • It is possible to modify the calculation parameters: 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 changes, use the Render button. Previously calculated surfaces will be updated with the new settings if needed.

   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, providing it is 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

10. Comparison of results

    The comparison of two archives is displayed in a special report:

    

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

11. 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).