In this thesis the sphere of assuring visual comfort is discussed with the focus on how to best use daily or natural light. With the help of technical literature, standards and criteria in the theoretical part all the necessary demands to assure enough and modified lighting of spaces for different purposes are described. The empirical research focuses on the example of the high school Domžale, for which the measurements and simulations with the programming equipment DIALux 18.104.22.168 and VELUX Daylight Visualizer 2.6.7 are performed. The procedures of measurement and programming equipment for analysis of lighting of spaces are shown in detail. Further on different measures to improve visual comfort with the help of daily light for each analized space are sistematically presented. The results are shown in tables, graphs, pictures and descriptions, and are critically evaluated regarding the recommended values of minimal lighting of such spaces (300lx). The use of light shelves in the spaces of the first floor helps most in improving the situation, partially also white walls in all spaces aid in the improvement. Where this is possible – from the point of construction and design - there are additional window openings arranged. With the implementation of the roof windows in combination with appropriate shades it is possible to create almost ideal conditions of visual comfort in the attic. At the same time this sort of change does not hurt the existing architectural plan.