Best all,

I am new to Radiance but I am using it as an executable from C++ in my thesis to evaluate rooms using the Daylight Factor (DF). I am trying to verify the DF however I haven’t succeeded.

In most cases, my ADF is +/- 1,3x too high.

I am not sure why my values vary so much.

If anybody knows what parameters or settings I should check, all the help is welcome.

Below I will present my results and process.

PS: I already tried more “accurate” rtrace settings, such as: -I -h -ab 5 -ad 2048 -as 512 -aa 0.1 -ar 256 -oov. However, this resulted in my computer running for almost 5 hours, instead of 20 seconds. The results remain comparable (0.05 difference of ADF).

Model setup:

First, I am creating materials with the corresponding reflectance values.

I am using polygons to create the 3D scene: scene.rad

my Gensky settings are:

. 3 21 12:00CET -a 52.2 -o -4.5 -c -B 55.865 -g 0.2 > sky.rad

. (55.865 = 10000/179)

with oconv I compile the scene:

. oconv sky.rad scene.rad > room.oct

my Rtrace settings are:

. -I -h -ab 4 -ad 256 -as 32 -aa 0.9 -ar 256 -oov < gridfile > results.txt

I calculate the illuminance values then with rcalc:

. -e ‘$1=179*(.265*$4+.670*$5+.065*$6)’ results.txt > lux.txt

. (resulting in Epoint, per point specified in the gridfile)

Then I calculate the DF: (Epoint/Eout)*100% = (Epoint/10000)*100%

Then I calculate the average of all points to derive the ADF.

I modelled the following rooms (vD) of: Compare effect of window placement

Room x: room name: ADF study : ADF my result : percentage difference

Room1: A4 : 7,2 : 11,69 : 162%

Room 2: A3 : 2,2 : 2,62 : 119%

Room 3: C2 : 2,9 : 4,4 : 152%

Room 4: B3 : 0,7 ; 0,54 : 77%

Furthermore, I am also comparing rooms from this paper (VK):

Salah Vaisi, Farzam Kharvari,

Evaluation of Daylight regulations in buildings using daylight factor analysis method by radiance

Room a = block 2, horizontal window

WFR: ADF study : ADF my result : percentage difference

WFR 12: 2,47 : 3,75 : 152%

WFR 15: 3,43 : 4,62 : 135%

WFR 18: 3,85 : 5,47 : 142%

WFR 24: 5,03 : 7,12 : 142%

And I also modelled a simple room in Velux Daylight Visualiser:

This allowed me to control more settings. Still with no correct result.

5x5x3 room, with window of 3x2 centrally placed in the wall.

ADF study : ADF my result : percentage difference

3,86 : 5,22 : 135%