Over the several months that I've been collecting information on installation of a range hood vent, I've learned quite a bit here. So I thought I would pass on this "best practices" info that has been very helpful to me about the ductwork. It's for a Ventahood ( I think) but seems pretty generic to me. It doesn't answer questions about induction vs gas but it did help me determine exactly what size ductwork to use, etc. It also mentions at the end : "Since smoke also expands as it rises, the hoods sides and front edge should extend 3" to 6" beyond the front and sides of the cooking surface" I knew the recommendation was to increase size on the sides but I didn't know about doing that in front. Well, don't think this is required by code so we will pass on this requirement but if we had problems, we might consider moving the vent away from the wall (and extending the ductwork.) So much to think about. I don't have a G.C. to pass this task onto so appreciate all the tips here. Hope this stuff I'm posting here may help someone else. Best Practices - vent hood

Can't really give any info without knowing what is this going to be over? Gas or electric? Also, which blower where you choosing? Just how did consummer reports rate this? In comparison to what? This design is noisy and not efficient for extraxtion but these are relative terms. Also, my experience is that they are 1/16 of an inch less wide than the specs. I think 1/8 would be real tight.

I am in the process of hanging a chimney island hood so I have been planning my install steps and working with an HVAC guy. To answer your questions, your DH is correct. The crimped end is inserted in the duct and the straight end goes on the outside of the collar since the air is moving in that direction. Your DH needs to make sure that the hood is the correct distance for the 6" pipe. If it is correct, I would plan on only lowering the hood far enough to get the pipe on the collar of the hood. I plan on using saw horses to support mine (make sure you put a towel or something on the saw horses so as not to scratch the hood). Put the pipe on the collar and tape (the shiny foil tape is better than duct tape) to seal so air cannot leak (less air leakage, less noise). The tape will also stabilize the pipe. At this point raise the hood and insert crimped end into the duct and attach the hood to the wall. Again tape the pipe to the duct to seal. Hope this helps.

Others may have more of a basis to disagree, but my guess is that the closer elbow will have more of an effect on noise than on effectiveness. You're interrupting the airflow closer to your ear, but either way you are turning the air. Even if someone says there's an airflow issue, I doubt anyone could get as specific as +/- 10%. And doubt even more if you'd notice any practical difference even if you actually tested it both ways, which you won't. Either way, I'd recommend asking the mfr. That said, straight up is always preferred from both a noise and effectiveness perspective. That would be my choice as long as the layout is feasible. Only negative that I can think of is you'll hear rain more on a roof cap.