The model has two light openings but they are strange openings, unusual at least, that's why I asked for the scene to test. Based on my experience, Radiosity should lighten the interior, but not in an uniform way. There would still be darker areas. I agree with Bruno that the Skydome lighting won't have much of an effect in this situation, because of the settings. Gain and Bias should work though. But to balance the effect in a correct way, one should be able to work on the original scene. Every scene requires it's own settings and as I said, this one isn't your typical standard interiors with a wall and a window. But I certainly don't have the time to model a replica of this building just for testing-replying.