I have a house built in 1983 with Seletex? sheeting and masonite horizontal siding. As soon as it gets cold outside, i also get that brown liquid coming out from the siding. it is the worst around the two bathrooms. To go with this, I have noticed the bottom 3 or 4 siding planks to have rusty nails, and you can see the siding bowing a bit higher up on the wall. The colder it gets (42 in the attic this morning) the higher the humidity which was 65%. No roof leaks, bathrooms vented, i put in a new ridge vent and increased the size of the soffit vents to increase flow. there are no water pipes or anything in the attic.. I will say that the house is constructed as follows: drywall, then sheet plastic, then the insulation &framing, seletex, and siding. I have already spent a ton of cash trying to figure this. also replaced all of the insulation in the attic as well. Al of the contractors around here give me a different answer...Oh yeah, the interior house humidity is never higher than 40-45% if that helps.