## 2 Materials and Methods  
For measurements of microclimate changes in the interior space of the building after photovoltaic module installation was designed the model cowshed. The model cowshed is showed on (Figure 1a) and its dimensions were \(a=570\) mm, \(b=600\) mm, \(c=830\) mm, \(\mathrm{d=700\;mm}\), and the angle of the roof inclination was \(\alpha=43.5^{\circ}\). The model roof was covered with the same roofing material made of aluminum as a real object; the thickness of the aluminum sheet was 1 mm. The side walls of the model building were made of MDF boards. In terms of thermophysical properties, a material (MDF board) was chosen for the model object due to similar thermal properties as the thermal insulation tarpaulin used as a covering of the side walls of the cowshed in real conditions. The thermal conductivity of the MDF board used for model building was 0.073 W\(\cdot\)m\({}^{-1}\cdot\)K\({}^{-1}\). The thickness of MDF board was 25 mm, and the thermal resistance of 0.342 m\({}^{2}\cdot\)K\(\cdot\)W\({}^{-1}\). Thermal conductivity was measured in Thermophysical laboratory (Department of Physics, SUA in Nitra, Nitra Slovakia) by instrument Isomet 2104 (Applied Pecision Ltd., Bratislava, Slovakia). The thermal insulation tarpaulin used as a wall in a real cowshed has a thermal resistance 0.340 m\({}^{2}\cdot\)K\(\cdot\)W\({}^{-1}\). Diffusion resistance of the used material was the same. The realization of the model building took into account the fact that in the conditions of Central Europe, the natural ventilation of the building is used for at least 10 months a year in combination with ventilation equipment. It was the main reason for the installation of two computer fans with diameters of 80 mm that were used to simulate the cooling and air flow in the model building (Figure 1b). The fans were used to simulate the air flow that occurs in the cowshed. The main function of fans was blowing air out of the model. The fans work all the time, but the power of the fans was regulated continuously by potentiometer so that the speed of the air flow in the interior proportionally corresponded to the real conditions in a specific season. Air velocity in the model building and the real cowshed was measured throughout the whole experimental period by using dataloggers Comet S-3121 (COMET SYSTEM Ltd., Roznov pod Radhostem, Czech Republic) and instrument Testovent 06995100 (Testo SE & Co., Titisee-Neustadt, Germany). The ventilation system was used in full, especially in the summer months from June to August. Both external and internal conditions were taken into account in the experimental simulation. The average air flow velocity in a real cowshed in the summer period was in range (0.7-1.2) m\(\cdot\)s\({}^{-1}\), in the winter period the air flow velocity was from 0.2 to 0.25 m\(\cdot\)s\({}^{-1}\). During the spring season, the average value of the air flow velocity was 0.45 m\(\cdot\)s\({}^{-1}\), and in the autumn 0.56 m\(\cdot\)s\({}^{-1}\). In calculating the air flow rate, we used the information presented by [PERSON] et al. (2013), which states as an optimum 40 to 60 air changes per hour. During the measurements in the model building, fifty times air changes per hour were ensured. It means the volume flow, approximately 6 m\({}^{3}\cdot\)h\({}^{-1}\), corresponds to the average velocity of air 0.04 m\(\cdot\)s\({}^{-1}\) in the model building. [PERSON] et al. (2002) claim that the required air flow depends on the temperature, and for the temperature range (10-28) \({}^{\circ}\)C, they correspond to the air flow rates in the cowshed (0.1-1.3) m\(\cdot\)s\({}^{-1}\). The exterior air flow velocities were also taken into account for calculation. One of the most important microclimate parameters is the temperature. Temperatures were measured with a specially designed and constructed measuring device, which is  
Figure 1: (**a**) The model dimensions designation; (**b**) detail of model building with fan integrated on the facade; (**c**) the experimental equipment with photovoltaic (PV) module on the roof.