Priority for School Buildings Programme

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1 Priority for School Buildings Programme Daylighting Criteria DA and UDI in RadianceIES Written and Prepared by Date Revision Rosemary McLafferty and Don Stearn August 2013 Rev 01

2 Contents Introduction to Dynamic Daylighting Simulation in Radiance... 3 Setting Environment Variable... 9 Step-by-step guide to running a Dynamic Daylighting Simulation in the VE page 2

Introduction to Dynamic Daylighting Simulation in Radiance In VE-Radiance we have used the ray-tracing capability of Radiance to generate images, luminance or illuminance, by using the module rpict.

3 Introduction to Dynamic Daylighting Simulation in Radiance In VE-Radiance we have used the ray-tracing capability of Radiance to generate images, luminance or illuminance, by using the module rpict. We have also generated illuminance data at given points in 3D space using the module rtrace, to generate illuminance over the WP or at sensor points. Both these approches can be expensive to get accurate results for daylighting simulation for even a single time-step. Luminance image In order to get results for multiple time-steps we have to use a relatively new Radiance module, rcontrib (which is an updated version of rtcontrib and based on the rtrace module). This module does a ray-tracing simulation to create the daylight coefficients for points in the scene, i.e. sensor points or grid points on the WP. These coefficients can then be used to calculate the illuminance at particular time-steps. This is much more efficient than running a ray-tracing simulation at each time-step. page 3

The underlying idea is to divide the celestial hemisphere into disjoint sky patches, this was first proposed by Tregenza who used 145 sub-divisions (see image below).

4 The underlying idea is to divide the celestial hemisphere into disjoint sky patches, this was first proposed by Tregenza who used 145 sub-divisions (see image below). Others (Reinhard author of DAYSIM) have divided these patches by 4 or even 16 to achieve greater accuracy at the cost of increased simulation time. The efficiency is that once the daylight coefficient has been calculated, any sky distribution can be pluggedin to generate the illuminance data. Because this is a simple and fast calculation we can do this across a full year to generate annual metrics or time-step by time-step to get a true dynamic simulation. Tregenza Sky Patches page 4

Reference - A STANDARD DAYLIGHT COEFFICIENT MODEL FOR DYNAMIC DAYLIGHTING SIMULATIONS http://www.stanford.

5 Reference - A STANDARD DAYLIGHT COEFFICIENT MODEL FOR DYNAMIC DAYLIGHTING SIMULATIONS page 5

6 We use this technique in two ways in VE-Radiance - 1. Dynamic Simulation for zone We create a grid of points across the zone and for a given design day (15th) of each month we do a simulation at each hour that the Sun is risen - we repeat this simulation for the Sunny Sky, Clear Sky and CIE Overcast Sky. Grid points across zone We can examine this data at each time-step Average Lux for CIE Overcast Sky page 6

We can interpolate the data against the "cloud cover" climate data to produce Daylight

7 We can process this data to get average values for each point for the given skies, and percentage within a given range (less than 100, , etc). We can interpolate the data against the "cloud cover" climate data to produce Daylight Autonomy results. Annual average Lux for CIE Overcast Sky % in range Lux for Daylight Autonomy page 7

8 2. Sensor data for Thermal Simulation We create sensors for each zone and run an annual simulation using the Sunny Sky, Clear Sky and CIE Overcast Sky (using same time series as before). Sensors on WP pointing up Annual Lux data for particular sensor page 8

Setting Environment Variable In order to activate the Dynamic Simulation tab in Radiance it is necessary to set an Environment variable. Please follow the steps below to set this up.

$Navigate through the registry to: HKEY_CURRENT_USER\Software\IES Applications\modx\RadianceIES In the right hand column, right click and select New > String Value.$

9 Setting Environment Variable In order to activate the Dynamic Simulation tab in Radiance it is necessary to set an Environment variable. Please follow the steps below to set this up. NOTE: Please ensure that you are comfortable working with the registry on your machine, if necessary, seek advice on making alternations to your registry from the IT department as you may not have admin privileges. To set the registry go Start > and type regedit into the search box Select Regedit.exe and allow the program to make changes to your machine. Navigate through the registry to: HKEY_CURRENT_USER\Software\IES Applications\modx\RadianceIES In the right hand column, right click and select New > String Value. Create a string called DDSFLAG and set the data value to 1 page 9

The images below show the new features that have been enabled in Radiance.

10 Now that the environment variable has been set the "Dynamic Simulation" options in Radiance are activated. The images below show the new features that have been enabled in Radiance. "Illuminance - WP dynamic" option in "Images" tab "Dynamic" button in "Sensor Settings" tab New "Dynamic Simulation" tab page 10

11 New "WP Grid" tab New "Area of Interest / AOI" tab (not currently in use for the PSBP tests) page 11

Step-by-step guide to running a Dynamic Daylighting Simulation in the VE I have created an easy to follow workflow for the new Dynamic simulation features in Radiance.

12 Step-by-step guide to running a Dynamic Daylighting Simulation in the VE I have created an easy to follow workflow for the new Dynamic simulation features in Radiance. The new features enables users to achieve the required Daylight Autonomy and Useful Daylight Index outputs for PSBP projects. I have also provided a test model for you to easily follow the steps in the document (test_model1.cab ). I would recommend saving the model on to you C:\VE-Projects\PSBP folder Step 1: Open the VE test model provided page 12

13 Step 2: Select Radiance from the Applications browser Step 3: Select the "Dynamic Simulation" tab The "Run Simulation" button will be inactive until at least one zone is selected - when clicked it will perform an annual simulation for each selected zone - initially we recommend that this is done for a single zone. The "Display Results" and "Process Results" buttons are inactive unless annual results have been calculated for a single zone. page 13

14 Step 4: Select a zone to simulate Step 5: Click on Run simulation - the simulation will start running A Stop simulation button will appear beside the progress bar page 14

Step 6: Display results When a single zone, for which annual results have been created, is selected the "Display Results" button is active - clicking this pops-up the results table The combo-box can

15 Step 6: Display results When a single zone, for which annual results have been created, is selected the "Display Results" button is active - clicking this pops-up the results table The combo-box can be changed to show results for - "CIE Overcast Sky" "Sunny Sky" "Clear Sky" "Daylight Autonomy". The combo-box can show results for - "Average Lux" "Minimum Lux" "Maximum Lux" "% less 100 Lux" "% range Lux" "% range Lux" "% greater 2500 Lux" The Lux values in the % range selections above are defined by the settings for the "Low", "Medium" and "High" threshold values (see below). Climate data is automatically read to generate the "Daylight Autonomy" data displayed on the grid - in this version of the software it uses a simple interpolation between the CIE Overcast Sky and the Sunny Sky by using the "Cloud Cover" climate variable. page 15

Change Threshold ranges Click on the "Thresholds" button - pops-up the

Thresholds" button in the "WP Grid" tab, with different functionality.

values is changed and the "Display" button applied the grid data will change.

Grid display of the data, here we have set to only a single threshold, "< 200"

16 Change Threshold ranges Click on the "Thresholds" button - pops-up the "Thesholds" dialog" - Note: this dialog is also activated by the "Display Thresholds" button in the "WP Grid" tab, with different functionality. The check-boxes can be used to switch the ranges ON/OFF - If any of these values is changed and the "Display" button applied the grid data will change. The colour buttons on this dialog will change the colours displayed in the Grid display of the data, here we have set to only a single threshold, "< 200" or "> 200" The threshold ranges also change the data that's collated in the "Post Processing" filters. page 16

17 Process Results When the "Process" button is clicked, the annual results data is processed into sets of data that can be displayed via the mechanism available in the "WP Grid" tab, see below. There are three options available as check-boxes - "Overwrite" "Use Climate data" "Use Occupancy profile" deletes the "wpd" file and write new data, otherwise any new data is appended to this file. generates data for "Daylight Autonomy" using algorithm as explained above. The simulation is run for the full year. filters the "Daylight Autonomy" data using a 9:00am to 17:00pm occupancy profile, in addition to the full year data. This data can be viewed by using the options on the "WP Grid" tab, see below. Note: this data is filtered by the settings of the thresholds page 17

18 Step 7: Select the "WP Grid" tab When a zone is selected all the data files that apply to this zone are displayed. NOTE: The data files are named using the "ZoneID" eight character label - if the data file has been created using the annual data then "_A" is appended to this label. When a results file is selected all the available simulations are displayed in the "Results" drop-down list. These results are displayed automatically - at the MODEL level this shows the grid points that define this simulation. page 18

19 When the zone is selected, click on the DOWN arrow which takes you to SURFACE level. At this level the data values are shown. Select PLAN view to display the results in coloured bands page 19

"Display Thresholds" This pops-up the "Thresholds" dialog - This has a combo-box with three selections "Lux", "Daylight Factor" or "Percentage", the default ranges for these are: low medium high

20 "Display Thresholds" This pops-up the "Thresholds" dialog - This has a combo-box with three selections "Lux", "Daylight Factor" or "Percentage", the default ranges for these are: low medium high "Lux" "Daylight Factor" "Percentage" These thresholds can be changed in value or switched off to either three or two ranges, independently of the other ranges. page 20

21 In this example the colour of the lower range has been changed and the high threshold has been set at 1000 Lux: page 21

Using Daylighting Performance to Optimise Façade Design. Colin Rees Consultancy Manager

Using Daylighting Performance to Optimise Façade Design Colin Rees Consultancy Manager About IES IES was founded over 20 years ago and headquartered in Glasgow is recognised as a world leader in 3D performance