Vent trap in the attic space?

I don’t understand what appears to be a trap just to the left of the ceiling fixture. The black part was a rubber connector with hose clamps, not a plug or cap, so it appears that this pipe will continue on up.

Home had a tankless heater… no kitchen below… high-end green home.

Need more info I am not seeing the big picture either.

Is there going to be anything up there that needs to drain condensation?

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.

To prevent sewer gas from entering the HRV? Just a guess. I am not familiar with them.

This is a very tight home. So tight that unless they provide outdoor air (makup air), a whole house fan will probably depressurize the house to the point at which it will suck the water out of the plumbing traps and start sucking sewer gas into the home.
That actually happened at this home (also in boulder)… The owner, whom I’ve known for ten years told me about it (he’s also the contractor).

The HRV is designed to remove the heat from exhaust air. Basically, the intake and exhaust are either next to each other, one is inside the other or the heat exchange takes place inside a kind of plenum (although the airstreams are kept seperate)… at any rate the warm exhaust air pre-heats the cold makeup air which saves on home space heating costs.

We always recommend opening windows if you use the whole house fan. You can suck in fumes from flues if you don’t. (It also seems kind of silly to use with closed windows anyway)

Except at -10 F.

Why would they use the whole house fan at that temp?

It’s probably low CFM. When you start getting onto these green-built homes which are so tightly built, they start coming up with all sorts of systems for maintaining indoor air quality. Most of us think of whole house fans as those big noisy fans used to keep the home cooler.

I’m guessing that yes, this is a whole house fan in that it exhausts air from the whole house, but probably does it slowly.

Today I exhibited at a green home symposium in Denver. Most of the other exhibitors were vendors of green systems like tankless water heaters, insulation, etc.

There are a lot of new systems out there. I probably learned more than I explained at this show.