Specular reflection (a mirror) would be ideal for sending energy back out into space most of the time but would occasionally death-ray your neighbors. White pai

Specular reflection (a mirror) would be ideal for sending energy back out into space most of the time but would occasionally death-ray your neighbors. White paint isn't quite as good (some of the diffuse reflection will hit non-reflective things) but it also won't incinerate anything. Feels like a good compromise.