Making objects contribute to lightmass but not be seen

Essentially what I have is a small spacestation location, but this game is third person from a bit of a distance, and it’s not feasible to have my camera in the station itself. So far in order to achieve this my station basically has no roof so it can be seen into. Obviously though, this prevents light bouncing around in the room.

Is there a way I can have an object contribute to the lightmass bouncing but not see it.

Alternatively I could use a single layer wall, and have the normals facing inwards but that seems like a poor solution and I am not sure if it would even work