May not be true of what passes for slums in the US, but in other countries the next house in a slum begins where the current one ends. With hardly any windows t

May not be true of what passes for slums in the US, but in other countries the next house in a slum begins where the current one ends. With hardly any windows to let natural light in, the indoors are quite dark even during the day. So yes, while it might not work at night unless there is a strong source of light such as streetlights nearby, it certainly does offer visual comfort during the day.