I understand the method for point in time glare is different than annual glare(which takes the Ev as a calculated input and the image is rendered with -ab 0).

Nevertheless and since both methods use gendaylit to generate Perez sky(if I set the sky condition to Custom Sky(Perez) and correct Global horizontal irradiance in Point in Time glare) plus that the Ev should come similar either through rpict or any other method, I expected point in time glare should give same results for this specific hour to that in (.dgp file) annual glare. But I get different figures. 

The model is a simple south facing room with one glazing.

For point in time calc I also tried changing gendaylit command in the room_sky.rad file to match the .wea file entry for that hour but to no avail.

gendaylit 03 21 8.5 -W 675 95 -a 41 -o 74 -m 75

Can anyone suggest why the two methods give different values?

Tags: glare

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