I think what was said above is right. Since the temperature inside the zone is higher than the out door temperature naturally heat will be lost through the walls to the outside same as that lost through the roof. So you better check your results and see what went wrong.

Sorry for the late reply and thank you for answering this question. This is the simulation result and I have no idea what wen wrong but I think there is not just air temperature difference that decide the heat transfer but the sol-air temperature because the radiation also a great part to heat the roof or wall causing when the outside temperature is lower but the fabric temperature is higher than inside.

Firstly the methodology that used to analyze the room thermal performance should be defined.  From the figure I think there is some think going wrong, because of the following:

1.      The figure of the heat flow shows that the walls losses heat to the surrounding from 7 to 18 hr. and gain head for the reset hours.

2.      If the operating temperature in the figure means the indoor temperature, then it is clear that the indoor temperature follows the outdoor temperature, which means that the thermal mass of the building construction approach to zero, i.e. the construction store no heat,  

3.      .   Finally the indoor temperature does not give a clear indication on the heat flow to the room, you should define the type of the walls and roof, it could be the inside wall surface temperature is grater than both outdoor and indoor temperature due to the high thermal mass of the building construction. I think you should draw temperature distribution through the wall to get clear indication about the subject.

In my opinion, it is because of heat accumulations while you have a higher temperature indoor.