This is just a wild guess, but since it's only happening at night, could it somehow be related to the fact that lights are on (vs. during daytime)? I'm no electrician, but it seems that the difference between night and day might be the clue here. I wonder if the house wiring is somehow acting as an antenna/repeater (from the renovation you mention) is causing the issue, but only when the circuit is closed such as when lights are on.
Again, a wild-assed guess at best but logic dictates ruling it out as a cause.
Again, a wild-assed guess at best but logic dictates ruling it out as a cause.