In a common roof with an attic and soffit and either gable or ridge vents it is common to use the
plastic baffles at the eves to prevent the vent system from being blocked by the ceiling insulation.

In that case the shoot is only a few feet long and does not have much effect on the overall system.

However, I was an episode of Hometime where they where building a new home with a vaulted
ceiling and it got me to thinking (always a danagerous thing).

The rafters where I-joist, 11+ inches. They had continous plastic chutes from eve to peak. High
density, unfaced FG insulation. They did not say what the R-value was, but that it meet code and I
believe that it was in MN. And a poly vapor retarder that was carefuly sealed at all boundries.

There are two reason that are given for attic ventilation. Reducing roof (and attic where there is an
attic) temperature. And getting rid of any moisture that finds it’s way into the roof.

Now the chutes only covered about 1/3 of the space between the rafters so I doubt that it would have
much cooling effect.

And what is the perm of the baffels. It seems to me that they would be a barrier to moisture anyway.
And even if they where affective again they only cover 1/3 of the area.

My guess is that with the careful attention to the details of the poly vapor barrier that this roof would
have performed just as well without the baffles and soffit/peak vents.

And even with all of the ventilation that if they had not used the poly and have a bunch of penitrations
for lights and the like without good sealing that they would have problems.