I am almost finish with my first house mod and everything is going great although there is one last problem.
The rooms where there isn't any type of lighting aren't dark. What I am trying to get at is, how can I make the rooms dark in the creation kit because when I test the mod in game, the rooms that don't have lights aren't dark at all and you can see everything. I want them to be abit darker like in the dungeons and basemants in Skyrim. Please help me anyone

Locate the cell in your Cell View Dialog and right click on it and select "Edit". This will open the properties for your cell. Click on the Lighting Tab, and there are 3 options you can play with to make it darker. Ambient lighting has the most effect, but play with them until you find the balance you like. This is for the GECK, but it's still pretty similar:

http://geck.gamesas.com/index.php/Cell_Lighting

Doh, I found this too:

http://www.creationkit.com/Cell_Lighting

Thank you Balok, that fixed it. If only we could hand out Rep++