Just this swamp cooler on the roof. That shouldn’t have anything to do with it, though. What little attic space there is is chock full of icynene, there isn’t really much room for anything up there.
The draw inspection specs called out for a whole house fan and I couldn’t see one. Also called out for a Heat Recovery Ventilator (HRV) and I couldn’t see one of those, either.
I was in a hurry when I did the draw inspection, but I think now, after looking at these photos more closely that the fixture we see (which is over the stairwell) *is *the whole house fan because you can see it vent to the outside.
In that case the HRV may be part of this piping. They aren’t that big. If the system is designed to recover heat from exhaust air (which will carry moisture from the home interior), when the moist interior air meets cold makup air, the exhaust air will drop in temperature as it loses heat to the makeup air.
At some point it will drop below the dewpoint and condensation will be formed. That would require a drain, but why would it require a trap? I’ll stop by there tomorrow and try to get answers.