Normally ducts are installed before drywall is installed, and if they are lucky before electrical and plumbing.

Thanks, the duct has already been installed. my question was how to connect the range hood to the duct when we have a narrow wooden canopy that has already been installed.

...and poor planning.

Consider crimping the sides of a fixed duct on the fan and pressure fitting it into the fixed duct to the exterior. A high temperature sealant around the end should prevent leakage at the joint.

"Will the building inspector be poking a flashlight through the fan to check the ductwork Consider placing a solid duct onto the the fan exhaust and then into a flex duct."

@worthy - flex duct anywhere along the path of a kitchen hood exhaust is a fire hazard. Crevices inside the flex collect grease and can easily catch fire. One of the main causes of kitchen fires. It needs to be a solid duct - not just to "fool the building inspector".

^^^

Correct. Post edited.

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Our recently purchased current home was empty for a year to repair damage from a dryer fire. The insurance company contractors connected the new dryer with a flex plastic pipe. Slow learners.

What specifications did the cabinetmaker use to build the canopy? That’s the range hood insert you need to use with the canopy. They aren’t all the same; typically you provide the cabinetmaker with the specific model you’re using (or better, with the actual insert) and they follow the specs from the manufacturer.

And agreed, no flex duct. There’s a reason it’s not to code.

Thank you all. I’m going to provide more context - We have a proper duct coming in from the ceiling, and the canopy has been installed. There is enough space to connect the hard pipe to the duct but the issue is connecting the range hood to the hard pipe, ie taping it up. The HVAC guy says he doesn’t have enough room to do this.

Did the cabinetmaker have the specs before building it? Can you measure to confirm that it was built to spec? If it wasn't, it goes back to the cabinetmaker to fix. If for some reason the cabinetmaker didn't have the specifications, that's unfortunately on the GC--they should have been provided. (Also a little on the cabinetmaker for not lifting that up as an issue, but mostly on the GC.) If they followed the specifications for the range hood and it still doesn't fit, call the manufacturer and ask for guidance. It may be a simple solution or a bigger issue depending on what's causing the problem--hard to know.

the issue is connecting the range hood to the hard pipe, ie taping it up.

Tape is not the only solution, as I mentioned above. But with no pics, hard to offer solutions.

We have a custom panel hood - not that different from yours.

My builder had it built/installed with screw on panels for access - for this exact reason and also to service the hood if needed. It is an appliance and needs access not just a hole you shove it in to and forget about.

If I was an inspector, I would not find it acceptable to use a flashlight to check duct connections. I would want to see the external connection of duct to hood. It might look alright until you heat the thing up a few hundred times because you shoved it in and then threw duct tape on it.

Your canopy has to be uninstalled. You put the cart before the horse and the venting has to be in place or accessible before the cover is installed.