How can I make it so that rooms without light are completely dark?

I have a major issue with the game lighting. Rooms with light bulbs (PointLight) are normal, but rooms without light bulbs also appear to be normal instead of being pitch black. Even when I move the dark room further away from the lighted room it still doesn't appear any darker than the usual.

The lighting technology is currently ShadowMap, the ClockTime is 0 and Brightness is also set to 0. So How can I make it so that rooms without light appear to be completely black?