DaylightAutonomy Extension

Introduction

Being autonomous in Daylighting means that the space does not need artificial light to perform the activities in that space.

Daylight Autonomy indicator is defined as the percentage of occupied time per year during which a sufficient level of illuminance can be maintained only with natural light.

This indicator is obtained by hour-by-hour calculation of the illuminance in a model using climatic data, taking into account the geographical position and annual weather data.

The indicator of daylight autonomy is used to describe on the one hand the performance in daylighting as it is defined by a minimum illuminance to maintain and secondly the electric energy consumption required to maintain this minimum.
The analysis of daylight autonomy is based on the assumption that when natural light is no longer sufficient, the artificial lighting is on. The calculation is done according to a minimum threshold of illuminance, usually 300 or 500 lux, measured on the work plane, and hours of building usage.

Daylight autonomy calculations affect thermal and lighting strategies:

• Evaluate if the model uses natural light in an appropriate manner,
• Evaluate if electric energy consumption will be within reasonable limits,
• Suggest if materials (internal and external) are appropriate to make the best use of natural light,
• Validate the positions of windows on the facades.

Calculation of the Daylight Autonomy or BREEAM indicator

The extension allows the calculation of the daylight autonomy according to three modes:

• a Daylight Autonomy mode, described below,
• a Useful Daylight Illuminance mode (UDI), described below,
• a BREEAM mode taking into account the BREEAM requirements for the daylight autonomy criteria detailed on DA BREEAM calculations.

How To Use DaylightAutonomy Extension

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

2. Open Daylight Autonomy dialog from toolbar or menu option Extensions -> De Luminae -> Daylight Autonomy -> Activate extension and enter the parameters of the calculation.

   "Daylight Autonomy" mode

   

   "UDI" mode

   

   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 da_output subdirectory.
     For SketchUp projects stored on network disk (Windows), see Work on a copy of the model.

   • Mode - Calculation mode selection:

     • Choose "Daylight Autonomy" or "UDI" (Useful Daylight Illuminance),
     • For the "BREEAM" mode, read: DA BREEAM calculation.

   • Illuminance - Illuminance threshold in lux:

     • In "Daylight Autonomy" mode, enter the minimum illumination threshold. A check box allows to also enter a maximum threshold.
     • In "UDI" mode, two fixed thresholds are used. Their value can be modified in the preferences of the extension.

   • Profile - Occupancy profile:

     • In "Daylight Autonomy" mode, select an occupancy profile in the list or create a new custom profile. Custom profile allows you to define occupation day by day, see Occupancy profiles.
     • The "UDI" mode always uses the profile: 7 days a week, sunrise to sunset.
     
     

   • Details - Models may require different density of sensors. Level of details definition is directly connected to number of sensors or their density on surfaces. Big unobstructed surfaces may need lower level of details with few sensors only, while smaller surfaces or surfaces with complex obstructions may require very high level of details. Level of details determines number of sensors for calculation, and has a major influence on calculation time and results accuracy.

     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.

   • Units - Results unit:

     • Percent [0-100%] - ratio of hours of occupation respecting the thresholds in relation to the total hours of occupation.
     • Total [hours] - Number of hours of occupancy during which the illuminance meets the thresholds.

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

     
     

   • Location - Building location coordinates. This info is used in combination with weather data to generate correct sky distribution. 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 by 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.

   • Period - Period of analysis. The daylight autonomy indicator is normally calculated over the year, but for specific analyzes a period can be chosen:

     • Season, year - select one of seasons or complete year. Results will be summarized for selected season.

       Default seasons are defined for northern hemisphere. Advanced parameters allow to use different definition of seasons. Read season definition.

     • Custom - Define the period by starting and ending dates.

       Full days - occupancy range from 0h00 to 23h59 on the day range (end date included). Click on the input box and choose the date in the calendar, or enter it directly.

       

     In trial version of the extension only 'summer' and 'winter' periods are supported. For more details read License information.

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 solar reflectance and transmittance.

   The tab of choice of materials:

   

   Materials panel consists of two main parts:

   • SketchUp layers table contains list of all layers defined in the SketchUp model. Each row contains SketchUp layer name and attached material name if exists. If text in a row is grayed, corresponding layer is not visible in the model. The table is updated in real time, as 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 required 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:

   
   • Automatic palette is generated during calculation and is based on calculated results for selected surfaces. This is the best option for first calculations, when user doesn't have idea about possible resulting values
   • Gradient palette enables global palette manipulations - definition of minimal and maximal palette values, number of colors and start and end color. It is very useful once user have idea of resulting values, but want to experiment with colors.
   • Custom palette gives full freedom to add/delete/modify each color separately. Good for creation of final results for representation, when some surface areas should be highlighted for example.

5. After all data are entered in DA dialog, select surfaces and press Render Selection or button.

   

   Calculation time depends on the 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 will is opened.

   

7. Results analysis.

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

     

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

     

8. For further calculations on the same model:

   • To run calculation on any surface simply select it 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, to change the period... 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).

   For example if a calculation has just been made for the "summer" season, then the season is changed to "winter" for a recalculation, and finally recalculated for "summer":

   • the system will redo the calculation of all the surfaces for the "winter" season, avoiding some steps: calculating the location of the sensors, preparing the weather file.
   • When the "summer" season is requested again, all the data can be restored from the cache, the "calculation" does not take more than a few seconds.

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.

   • 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.

10. 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 licence information).