Hello, I need some advice as I'm somewhat concerned. My cabin is almost complete, we have R20 insulation in the ceiling and R12 in the walls. The exterior walls are 4x4 tongue & grove. I have a tin roof. As you can see by the enclosed pics there is condensation forming on the flue box. I also have condensation building up on the inside windows as well. The temperature today inside the cabin about 15-17c , heated only by a couple of space heaters at this point. The outside temp was around 0c, maybe +1 but was around -10c the night before. Why would condensation be forming on the flue box? is this a negative house pressure problem? I really have no idea, any ideas. The stove has not been used recently.