## 2 Materials and Methods
### Case Study-Hall Building
With the given lighting system, at the critical point of the functional place on the horizontal plane, the following values are required:  
minimum standard value of daylight factor \(\mathrm{DF_{min}}\) = 1.5-2%,  
average daylight factor \(\mathrm{DF_{average}}\) = 5.0-6.0%,  
uniformity of the illumination more than u = 0.2  
for the given visual task [61; 62]. In a hall environment where a visual task is performed, the brightness of the surfaces is important. It is determined based on the reflectivity and illuminance of surfaces. The recommended reflectivity of surfaces and the reflectivity of some colors are given in Table 2[63]. Figure 5 shows the floor plan and schematic section of the hall. A total of 60 points are marked in the floor plan 12 \(\times\) 5 (A, B, C, D, E). Measurements were made at these points and were considered for computational simulation for individual color change variants. Calculated values of the daylight factor DF (%) in the hall from measured values of interior illuminance-current state can be seen in Figure 6.  
Figure 5: (a) ground floor—measured control points. (b) cross-section of selected hall building. During the creation of the computational model of the hall, boundary conditions were created on the basis of measurements in the hall with a saddle skylight [64]. The light reflectance values and properties of the materials used in the calculations are given in Table 2. The individual measured material constants (surface reflection factors, contamination factors, and glazing permeability) were also taken into account. Different surface colors (walls and ceiling) were used in this study; the floor is the same in all cases in this hall building (see Table 3). To increase the adaptation levels and visual comfort of users, it is more suitable if the surfaces in such a large hall are bright. For this reason, shades of white, yellow, and light green were chosen for the simulation. Calculations were performed for a set of different color rendering variants. There were 15 variant calculations, t. j. actual state (the real state in reality) plus 14 calculation variants of simulations (see Table 3). The factual state was determined by a concrete measurement in the real state. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Structural Surface** & **Reflectance/Transmittance** & **Color of Surface** & **Reflectance** & **Structural Surface** & **Optical Properties Reflectance** \\ \hline Ceiling & 0.7–0.9 & White & 0.75–0.89 & Floor & 10\% \\ Walls & 0.5–0.8 & Yellow & 0.44–0.78 & Windows & 40\% \\ Floor & 0.2–0.4 & Brown & 0.12–0.45 & Skylight & 64\% \\ Furniture, facilities & 0.2–0.4 & Gray & 0.15–0.67 & Facilities & 20–50\% \\ Windows & /transmittance 0.6 & Black & 0.02–0.04 & Trusses & 30\% \\ Skylight & /transmittance 0.36 & & & & \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Recommended reflection factor of surfaces, recommended reflection factor of colors, building material, and optical properties of the interior surfaces of the test hall. Figure 6: Calculated values of the daylight factor DF (%) in hall from measured values of interior illuminance-current state.