Problem with character in interior scene with indirect sunlight

Hey guys,

perhaps you can help me from going totally insane. I have created a very simple scene - a room (quite small 4mx5m). The inside walls are made of single planes. The room also has outside walls (15cm - other mesh) and there are also thick meshes for ceiling and floor. Nothing intersects - everything is snapped together.

I only have a stationary sun light in the scene and I´m using baked lighting.

The inside of the room is completely black (as expected) - but the moveable character is very bright. Now, I´ve read that this has something to do with the indirect lighting baked into the mesh and the character picks up this lighting.

I think the problem is that the room is too small and the character picks up lighting from the outside. I don´t want ot use a massive shell around my room, because I need exterior and interior.

Would a Detail Indirect Volume help? Should I place this inside the room?

How can I prevent my character from picking up indirect lighting?

Thanks,
Michael

Maybe this helps?