No lights in scene, still lighting up I am making a house in Blender Cycles. In rendered mode, all shaders are somehow visible, even though I don't use any lamps. I do have an environment texture, however it shouldn't light up the inside of the house. Especially when there are no windows. Even if I set the background strength to 0, it still lights up the inside and outside of the house.

So now, if I add any lamps, I has nearly no impact on shadows, shaders, reflections etc.
What could be wrong with my scene?

Let me know if you have any questions on my settings that might help you find the problem.

File: https://www.mediafire.com/?cs3dl1xx56ih60a

These are the world settings: 

For the Ambient occlusion I always use this node: 

It usually works fine.
Objects may appear illuminated, if ...

they are illuminated by lamp objects
they are illuminated by mesh lights with emission shaders
they are emitting light completely or partially, if they have an emission shader
the wrongheaded use of an Add Shader in a material
they are illuminated by the world (background shader)
ambient occlusion is activated

The Ambient Occlusion is activated in your scene.
Uncheck Ambient Occlusion to disable it.
It is found under the World section of the Properties Panel.
Also make sure no light emitting objects are hidden by pressing AltH to unhide all objects.