## 3 Results and Discussion  
Real data obtained from real size house modules were used to find the effect of different sky temperatures on the building internal air temperature using CFD simulation. For example the cavity brick module (CB) were analysed for one month in summer (14 January 2010 to 13 February 2010) using 8 \({}^{\circ}\)C, 1 \({}^{\circ}\)C, \(-6\) \({}^{\circ}\)C and \(-14\) \({}^{\circ}\)C sky temperatures as shown in Figure 7.  
Figure 7: Real and simulated internal air temperature for different sky temperatures for the CB module. This simulation indicates that higher sky temperature will result in higher internal air temperature where each 2 \({}^{\circ}\)C increases in the sky temperature will increase the average internal air temperature by almost 1 \({}^{\circ}\)C and decreases the sky temperature by 2 \({}^{\circ}\)C will decrease the average internal air temperature by 1 \({}^{\circ}\)C.  
The sky temperature of 8\({}^{\circ}\)C increases the internal air temperature of the building but the sky temperature of \(-\)6 \({}^{\circ}\)C and \(-\)14 \({}^{\circ}\)C decreases the internal air temperature as shown in Figure 7. Therefore, the closest simulated results to the real data occurred for the sky temperature of 1 \({}^{\circ}\)C.  
The temperature inside the building increases or decreases in faster rate for the first week before it is stabilized, so the trend in the first week is representative while the effect of the sky temperature is considered. A one-week period was used here to determine the building internal air temperature for various sky temperatures. This is shown in Figure 8 for the InsCB module as an example. The sky temperatures of 2 \({}^{\circ}\)C, 0 \({}^{\circ}\)C, \(-\)2 \({}^{\circ}\)C and \(-\)4 \({}^{\circ}\)C, (which is higher by 8, 6, 4 and 2 \({}^{\circ}\)C accordingly than the accurate sky temperature of \(-\)6 \({}^{\circ}\)C) increased the internal air temperature of the module for August 2009 (see Figure 9). However, the sky temperature of \(-\)8 \({}^{\circ}\)C, \(-\)10 \({}^{\circ}\)C, \(-\)12 \({}^{\circ}\)C, \(-\)14 \({}^{\circ}\)C, \(-\)16 \({}^{\circ}\)C and \(-\)18 \({}^{\circ}\)C (lower by \(-\)2, \(-\)4, \(-\)6, \(-\)8, \(-\)10 and \(-\)12 \({}^{\circ}\)C accordingly than exact sky temperature of \(-\)6 \({}^{\circ}\)C) decreased the internal air temperature of the module as is shown in Figure 10. The average errors of the internal air temperature for various sky temperatures for the InsCB module is shown in Figure 9; the smallest error of 6.2% occurred for the sky temperature of \(-\)6 \({}^{\circ}\)C (accurate sky temperature) with similar trend as the observed internal air temperature for the module. The most accurate (exact) sky temperature for August, calculated manually was \(-\)5.3 \({}^{\circ}\)C and \(-\)6 \({}^{\circ}\)C when simulated by CFD (i.e., the trend of the simulation line up with observed internal air temperature). The sky temperature higher or lower than 6 \({}^{\circ}\)C will increase/decrease module internal air temperature as shown in Figure 10.  
The smallest error of 6.2% occurred when the sky temperature used in the CFD simulation was close to the manually calculated sky temperature of \(-\)5.3 \({}^{\circ}\)C. However the sky temperature of \(+\)2 \({}^{\circ}\)C and \(-\)18 \({}^{\circ}\)C increased the error between observed and CFD internal air temperature to 13% and 22.9% respectively  
It should be noted that the sky temperature was supposed to be similar for all modules and this hypothesis was analysed for one summer week in January 2010 and presented in Figure 11. The most accurate sky temperature fell within 1 \({}^{\circ}\)C, 1 \({}^{\circ}\)C, \(-\)1 \({}^{\circ}\)C and 0 \({}^{\circ}\)C for the CB, InsCB, InsBV and InsRBV, respectively. The difference between the highest and the lowest sky temperature is less than 2 \({}^{\circ}\)C between the modules. Figure 8: Real internal air temperature and CFD analysis with different sky temperatures for the InsCB module (for one week in August).