Ductwork from roof vent directly to living space

[dorourke2 (Daniel O'Rourke)]

I haven’t seen this before and I’m trying to wrap my head around it with some sort of sensible reasoning, am I trying too hard to figure this out or is it just wrong or am I missing something?

At an 11th month inspection I saw a vent at the roof connected to duct that goes directly to a grille at the ceiling. I didn’t see anything else connected to the duct in the attic space or behind the grille.
I can’t figure out it’s purpose. Especially since it get to 115-120 degrees here and its pretty much a straight shot from the outdoors to the indoors it just doesn’t make sense to me.

Am I thinking too hard to try to justify something that just ain’t right?

Here’s the duct going to the roof vent:

Here’s the duct going directly to the ceiling (the one on the left, the one on the right is the return to the air handler):

[ndegaris (Neil DeGaris, CMI KY License # 102167)]

Possible supply air for combustion, can you follow the duct? Or what is located just under the area where it goes into the ceiling?

[dorourke2 (Daniel O'Rourke)]

No combustion air needed here, no gas appliances at the home. And its above the hallway near the entryway. The duct is all of maybe 6 feet long, does not connect to any other duct or equipment and goes between the roof and the hallway.

[dandersen (David Andersen, TN HI# 40)]

Regardless what it is for, it should enter the house through the HVAC unit.

@dorourke2

Am I thinking too hard to try to justify something that just ain’t right?

I see not reason for it as well. If they need air in the house, just leave a window open, same thing going on!