Impact of Direct Lighting Luminaires' Luminous Intensity Distribution on Lighting Quality in Interiors

Luminous intensity distribution of luminaires influences the qualitative metrics of lighting. Direct lighting is the most common way of illumination in public interiors. Thus, its application should be carefully considered. For defined luminous intensity distributions of direct lighting luminaires and their layouts, in rooms with various sizes and reflectances, the ceiling and wall illuminance ratios, and UGR values were calculated and analysed in detail. Meeting the recommendations for ceiling and wall illumination, and discomfort glare were checked. Impact of luminous intensity distribution of the direct lighting luminaires on ceiling and wall illumination, and discomfort glare was assessed. Impact of room size and reflectances on ceiling and wall illumination, and discomfort glare was also observed. Substantial limitation of the direct lighting luminaires for general illumination in interiors was demonstrated and it should be regarded with great concern if visual comfort for people in interiors is to be provided.