it would be easier to test with the scene file but some general stuff, is that a real object or 3D? (hard to tell with that small a picture)
Either way, try and emulate the reality. The house should have thickness to the walls, the light should be a luminant object that’s very bright, the windows should probably have portals (check the help) to pass light outward correctly (portals are usually used in reverse – for light coming in – but here it might help too). The inside surface of the house should be pretty white by the looks of it.
The GI bounces will have to be high enough to get light up the towers (if your house is like that) – unless there are more than one light in there – I’ve seen similar stuff that use a string of white LEDs.