Indoor Apartment Lighting as a Source of Outdoor Light Pollution

Abstract

This paper presents the results of research on the impact of indoor lighting in apartments in a Kraków housing estate on increased outdoor light pollution. The study aimed to determine the scale of this type of light pollution in relation to street lighting and to identify the potential negative impact of illuminated interiors on the surrounding area. It was found that this lighting contributes negligibly to the increase in the brightness of the night sky glow, practically having no impact on this form of light pollution. However, it often impacts the quality of life of residents by illuminating neighbouring windows, balconies, and terraces. In the case of apartments located on lower floors, their lighting affects the vegetation of nearby trees and shrubs. It should be emphasised that in the vast majority of cases, apartment lighting is turned off before midnight, allowing for a restful sleep, even without curtains, blinds, etc. However, in the evening, brightly lit windows become a trap for nocturnal insects and, indirectly, for birds and bats that prey on them. By creating artificial constellations on the facades of apartment buildings, brightly lit windows disrupt the coordination of migratory and hunting birds at night. It should be noted that even this impact of indoor lighting on the environment can be significantly reduced by covering the windows at night.