Light floods through walls

[CorSair]

I don't know what causes it, but the light floods through walls for unknown reason.

And I use fast compile to do this. Maybe it's that what causes it, but what's your opinion?

First pic is outside of the vent...
...And second is the interior.

[Plague Bringer]

I don't know what causes it, but the light floods through walls for unknown reason.

And I use fast compile to do this. Maybe it's that what causes it, but what's your opinion?

First pic is outside of the vent...
...And second is the interior.

make sure your brushes meet at 45 degree angles.
         | |
         | |
______| |
         \ |
_______\|
the red and blue both indicate brushes and the purple is where they meet.
if that doesn't work use thicker brushes.

[CorSair]

Ack, then it means i need to redesing the vents.

I got them 45 degree angle, and brush is 4 GU thick (grid 3 to be specific.)