Said It Here

Does the vent duct go inside or over the hood?

Non-standard exhaust hood diameters, like 6.5 inches, rarely match standard vent pipes, leaving it unclear whether the duct should fit inside or over the collar. This sizing mismatch prevents a secure connection and forces awkward turns that make the system inefficient and loud.

What people tried

Every workaround mentioned in the threads below. We haven’t tested any of them — and nobody here is claiming they worked.

  1. 1
    Routing ductwork down to the basement and across floor joists
  2. 2
    Using rectangular ducting to fit inside restricted joist spaces

In their words

Unedited, grouped by where they were said, most upvoted first within each place, each linked to the thread it came from.

r/hvacadvice2 people · September 2026

It’s a quality range hood - Zephyr with rated 650cfm - but the fact that the duct has an immediate 90 degree turn, combined with having to push hot air down - means it isn’t very efficient. And it’s unbearably LOUD.source ↗

bdrlgionnnnn · r/hvacadvice · 1 upvotes

I'm wondering if a pipe is supposed to fit over the top of the vent hood or if a vent goes \*inside\* the vent hood.source ↗

Lastly, I've measured the exhaust vent hood diameter and it seems like it's 6.5" and no vent I've found can fit it inside it or over it.source ↗

LengthinessFamiliar5 · r/hvacadvice

Where this came up

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