[pjerem]

I guess there is a cultural difference on the word here and I should have be more precise.

In France, shutters aren't like most American ones, here we mostly use either plain wood with no gap for light (old houses) or for most of the recent houses, we use rolling shutters that let 0% of light (and therefore, 0% of radiative energy from the sun) get to the window and will make the room entirely black. Also, most modern rolling shutters are white by default so they are pretty reflective.

In the current situation, it's the air temperature that fuck us by not getting down at night and so our (concrete) buildings accumulate the heat even at night.

[DanielHB]

An awning protrudes out of the window so airflow can still pass and light still gets into the room (just not direct light).

Even if the shutters are wood and white when sun hits them they will radiate some heat into the indoors. But of course shutters are still better than letting the sun hit your floor directly.