Solar exposure highest in winter?

Good morning,
I was running a model in the Southern hemisphere however I noticed my solar exposure intensity very high in the winter months. I have no shading and its a simple rectangle (longer orientations are the North and South facing facades) with the same glazing percentage across each façade , so I am unsure why this would be the case? What am I missing?

This is probably because of the low angle sun in winter. Then the radiation is higher than in summer where the sun is coming from a much higher angle. Of course this is true on vertical surfaces, which i understand this is what you are testing.

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Thanks Abraham, I always thought the sun exposure was higher in summer regardless, as the afternoon sun is very intense and at a angle. I’m just surprised that a building with no shades can provide that much internal shading. But thanks again, its always good to get another persons insight.

Hi @Shanice and @AbrahamYezioro ,

In the southern hemnisphere it is summertime in January, Februari, March.

Sure! That’s why on the facades you get higher radiation in winter than in summer.
On roofs, of course, summer rules.



An additional, but minor contributing factor to the higher low-angle solar radiation is the “horizon brightening” factor: for clear skies, the horizon has slightly higher diffuse radiation then the sky patches overhead (excluding patches containing actual sun position). image

But, at the same time, this is mitigated by the higher amount of atmospheric scattering and diffusing of direct solar at the horizon, as well as the fact that in the southern hemisphere, the maximum distance between the earth and sun occurs during the southern winter period. So thats why we would still expect a surface oriented directly to the summertime sun to have higher incidence radiation then an equivalent surface oriented directly to the wintertime sun, in the southern hemisphere.

Thanks @SaeranVasanthakumar, It is interesting to hear about the brightening factor. I based my assumption of a few things, like the distance of the earth and sun so I’m sure you can see why it was confusing that the windows have higher radiation in winter but I guess all the little things (along with sun angle) contribute to it.