Directional light baking goes trough interiors

Hey,

I have a static directional light to have a night light effect. When I bake the lighting, some meshes which are normally “closed” still receive lighting.

In the following picture, I have a rect light illuminating the room. However, there is also a bluewish reflection. The directional light used for exteriors has this blue color, but I dont understand why it gets through the ceiling.

It has to have tickness and normals must be outside. What modeling program do you use.