Ceiling of room part is not lighted

[Vooker525]

Ceiling of rooms is always dark when switching light intensity. It can be lighted only by sunlight or self illumination.
Btw. How ceiling of room part is defined? For example i will make upside down room and group upside down room void with it. How it should behave?

[Deantwo]

You might need to give an example of this one. As I think I have seen it work before, so it sounds weird it doesn't work for you.