Interpretation of values coming from Annual Irradiance Calculation

Hi all,

I have questions about how to interpretate the values of the annual irradiance analysis.
My set-up is the following:
Some horizontal louvers in front of a surface

The resulted mesh optically indicates that the gh set-up seems correct, and the calculations are done properly:

I simulated the scene 2 times, one with shades, the other one without shades and no I am comparing the values :

So I expect the values going down when the sun is most perpenticular to the recieving surface( about hour 11,12), since it is less obstruated by the shades.

Strangely the opposite is happening.

Is there any explication? Could anybody give any hints about possible errors?
Thanks for everybody taking the time and reading!

In case someone wants it, here is the file: (207.5 KB)

When you run an analysis with an EPW-generated Wea, you are going to be accounting for all sorts of weather anomalies associated with changing cloud cover from one hour to the next. If you want to do a “purist” comparison of blocked solar irradiance, you should generate a clear sky Wea using either the Wea From Tau Clear Sky or the Wea From Clear Sky component. The former is a little more accurate if you have a .stat file containing the monthly optical data.