Other than natural sunlight, there are two artificial ways to bring light in from a window:
This first way is the classic technique of making the glass into an LEM. Light setting can be anything from 15-30. Disadvantage is now you cannot see through the window. But the light quality is gentle and it looks great!
This second way uses two omnis in the center of each window. Make a rectangle the exact size of each window, and group them. Give a light setting of 8-10. Move them back a little distance so they won't cast hotspots on the window frame. The light quality is more abrupt, not so gentle as the first one. But render speed was much faster.
Method 2 works okay as long as the window is not up against a surface like a floor, wall or ceiling. One bonus is that because omni lights are transparent, you can have both the omni and sunlight at the same time, which is something the window LEMs cannot do.
If you light the room from within, for example using an LEM you can get this result. The model is attached.