How the daylight analysis works for window and skylight?

Dear community!

I compared the daylight performance of two design scenario, one is only with skylight and the other one has skylight and west side vertical window as below model shows.

DA results show that the vertical glazing can improve the daylight performance of the area nearby the window, but it also reduced the daylight of other area.

What I expect is the window should improve the daylight performance of all area, but it seems not work like that.
May I know why this happen, maybe the daylight from skylight is bounced out from the room through the window?
Thanks for your help in advance.

Are you sure that you are looking at the Daylight Autonomy (DA) and not Useful Daylight Illuminance (UDI)? UDI will go down when you have too much light at certain hours, as I would expect from adding more windows.

Also, it looks like you should probably improve your Radiance parameters a bit if you don’t want the difference between the two options to be so splotchy.

I would also think that your Radiance parameters need more refinement. You can test if your parameters are good enough by comparing the results of 2 consecutive simulations of the same scene (e.g. run 2 simulations of your case 1 and see the difference).

Hi, @chris @IasonBournas
Thanks for your reply!
Yes, the results are DA metric and calculated with -ab 5
Please find attached gh file for your information.
skylight (124.5 KB)