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 the numbers show
Counted from the threads quoted below. How we count
- The most recent one is from October 2026.
- This comes up 15.3× more often in r/hvacadvice than across the site as a whole.
What people tried
Every workaround mentioned in the threads below. We haven’t tested any of them — and nobody here is claiming they worked.
Found another way around this?
Share your steps and trade-offs so fellow engineers don't have to reinvent the wheel. No account required.
Does the vent duct go inside or over the hood?
- 1Routing ductwork down to the basement and across floor joistsDid this help you?
- 2Using rectangular ducting to fit inside restricted joist spacesDid this help you?
- 3Routing the vent through the wall and out the side of the house instead of the roofDid this help you?
- 4Trying to turn the 90-degree elbow to fit over the fanDid this help you?
- 5Using metal tape to attach the oval outlet to the round ductDid this help you?
- 6Using 3 sheet metal screws to secure the connection in place.Did this help you?
In their words
Unedited, grouped by where they were said, most upvoted first within each place, each linked to the thread it came from.
“I just bought this house, and i was aware of the top of the t duct not being connected to the roof vent but when I went up there to fix that I moved insulation out of the way and noticed that no attempt was even made to connect this fan to the duct.”source ↗
“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 ↗
“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 ↗
“What kind of budget should I expect for a through the roof range hood vent??”source ↗
Where this came up
People with this problem also raised
- 2How do you install a roof vent with an attached collar?
- 2How to add a vent when you can't reach the stack
- 2How to route a plumbing vent offset around obstacles
- 3How to tie in a vent line and shower drain in tight spaces
- 4Exhaust vent hole doesn't line up with the new range hood
- 14Where do I run the vent for a washer installation?