## 3 Results and Discussion
### Cattle Dairy Compost Barn Building Validation Tests  
In Figure 14, the behavior of the air velocity measurements in five real CBP barns with different roof types present in Kentucky was estimated in Table 4. Results showed that the empirical equation to determine V\({}_{\text{air}}\) was statistically significant (\(p\)-value \(<\) 0.0001) and it presented the lowest coefficient of determination of 0.8157 (Figure 14D), being subsequently validated via a \(t\) test (\(p\)-value \(>\) 0.05). The adjusted equations were statistically significant (F test, \(p\)-value \(<\) 0.0001), providing an average error of 0.38 m/s.  
The variability of the V\({}_{\text{air}}\) real measured and simulated was higher for the OVR (Figure 14D), which presented an average and standard deviation equal to 0.63 \(\pm\) 0.39 m/s and 0.58 \(\pm\) 0.42 m/s, respectably. In such a CBP, the area with the lowest V\({}_{\text{air}}\) was observed in the north face, over the bed area, due to the structure of the barn that blocks and redirecting the air flow.  
In the ELR (Figure 14C), the real and simulated air velocity values showed a lower average (0.56 and 0.52 m/s, respectably) and variation equal to 0.37 and 0.32 m/s, respectably. The region with the lowest V\({}_{\text{air}}\) occurred near the north face.  
\begin{table}
\begin{tabular}{c c c} \hline \hline  & **Treatments** & **Means Values (\%)** \\ \hline \multirow{4}{*}{CBP} & ORC & 45.292 \\  & OPR & 27.512 \\  & CLR & 24.462 \\  & OVR & 23.497 \\  & ELR & 19.457 \\ \hline \multirow{4}{*}{CBP} & West to east & 32.366 \\  & East to west & 32.176 \\ \cline{1-1}  & North to south & 27.922 \\ \cline{1-1}  & South to north & 19.712 \\ \hline \hline \end{tabular}
\end{table}
Table 6: Mean values of percentage of heated floor area for different types of ridge vents and wind direction.  
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**SV** & **DF** & **SS** & **MS** & **F\({}_{\text{cal}}\)-Value * & **Probability** \\ \hline Ridge & 4 & 1620.038 & 405.010 & 0.531 & 0.716 \\ Direction & 3 & 526.051 & 175.350 & 0.230 & 0.874 \\ Residual & 12 & 9155.593 & 762.966 & & \\ \hline Total & 19 & 11301.682 & & & \\ \hline \end{tabular} Source of variation (SV), degree of freedom (DF), sum of squares (SS), mean sum of squares (MS) and probability (P).  
*: Significant at 5%, by the F-test; ns: not significant by the F-test.  
\end{table}
Table 5: Analysis of variance to heated floor area in different types of ridge vents and wind direction for all CFD models tested.  
The worst situation was verified for the CBP with ORC (Figure 14E), where V\({}_{\rm air}\) was less than 0.60 m/s in 48.9% of the barn area. On the other hand, in CBP equipped with OVR (Figure 14D), V\({}_{\rm air}\) was greater than 1.0 m/s in 58.4% (real) and 42.1% (simulated) of areas respectively, showing that the systems used promoted the increase of such an attribute to levels close to adequate in most of the facilities.  
The minimum and maximum average airflow velocities were 0.05 and 1.1 m/s, respectively. In all case, natural ventilation on this face of the barn became reduced, reducing heat exchanges with the environment and making surface temperature of bed composting lower.  
In all CBP facilities evaluated, the V\({}_{\rm air}\) was lower than the recommended (Figure 14). According to [PERSON] et al. (2013), in CBP facilities, the ventilation should be provided such that the V\({}_{\rm air}\) is close to 1.8 m/s throughout the entire CBP, so that it can dry the bed, remove gases and favor the heat exchanges between the animal and the environment.  
The results also show that the use of mechanical ventilation in tropical conditions is necessary for the proper functioning of the system, since only the natural ventilation was not sufficient to promote V\({}_{\rm air}\) values according to the recommendation for CBP barns.