## 4 Discussion
Calculated numerical results created the platform for discussion about the effect of microclimate changes in the animal production building on the animal heat stress. From the presented experimental results, it is evident that the installation of a PV system on the cowshed decreases the indoor temperature on average by 1.2 \({}^{\circ}\)C. The average ambient temperature during the measurements was 23.6 \({}^{\circ}\)C. For identification of the PV system installation effect on the THI, the interior temperature for ambient temperature in the range (20-40) \({}^{\circ}\)C (see Figure 20) was calculated. Then the THI was calculated by Equation (1). The calculation was done for humidity value 65%. Results are presented in Figure 16. From the mentioned figure, it is clear that the PV system installation has a positive impact on the THI. In the graph are three important points. At ambient temperature 25 \({}^{\circ}\)C, which is THI for the cowshed without an installed PV system 73.29, it represents mild stress. The THI for the cowshed with an installed PV system is 71.4, and it represents no stress. At ambient temperature 29 \({}^{\circ}\)C, which was cowshed without PV system THI 79.09, which means severe stress. If the ambient temperature in the cowshed with an installed PV system was 29 \({}^{\circ}\)C, the THI had value 76.9, which represents mild stress for animals. The THI 89.24 was found for the cowshed without an installed PV system at ambient temperature 36 \({}^{\circ}\)C. This value of the THI represents very severe stress for animals. This condition was identified for the cowshed with an installed PV system at the ambient temperature 38 \({}^{\circ}\)C.  
At the end of the discussion, we can state that all presented results are also in agreement with thermal theory, where the U thermal transmittance coefficient is defined as the measurement unit for determining the loss of heat in a building element. It expresses the quantity of heat which crosses a square meter of a building element per second for a temperature difference of 1 \({}^{\circ}\)C between internal and external air. The lower U value represents the higher thermal insulation. For example, the polycrystalline photovoltaic module with insulated glazing has, according to the standard EN 673 (Glass in building--Determination of thermal transmittance U value--Calculation method), the U value 1.1 W\(\cdot\)m\({}^{-2}\cdot\)K\({}^{-1}\)[53]. The same U value applies to a double insulated glazing window with argon filling [54] and approximately the same U value also applies to the PV module. The commercial PV modules have the U value from range (0.8-2.5) W\(\cdot\)m\({}^{-2}\cdot\)K\({}^{-1}\), in our experiments we used PV modules with a U value ca. 1.5 W\(\cdot\)m\({}^{-2}\cdot\)K\({}^{-1}\). The next problem which can be discussed is the type of installation. There were performed measurements in the frame of bilateral cooperation between SUA in Nitra and Mendel University in Brno. The research was focused on the comparison of PV system energy for two ways of the PV modules installation. At first, the PV modules were installed on the roof, and the same PV system was installed on the wall of the same building. The research results showed fact that better results were obtained for the PV modules placed on the facade of the building, but only in the winter season. In other seasons, the vertical installation had a negative effect on the PV system energy balance. This result was found only for the conditions of Central Europe. The comprehensive summary of study results has not been published yet.