How do I make my indoor lighting dark?

I’m trying to make a game where you can walk outside to the terrain and its bright outside but when you walk inside to the hallways its dark and you have to use a flashlight to see. The problem is my SkyLight is brightening the lighting inside my indoor hallways. It shines right through to the inside and brightens it and I can see everything without any additional lighting other than a directional light. I want to use my skylight to brighten the shadows outside but I want the inside to be completely dark to the point where I have to use a flashlight. How can I make this type of lighting effect? Thanks for any help.