The required volumetric flow rate is determined by the nature of hot cooking plumes and the design of residential hoods, and not purchase and installation convenience factors. Your 9 sq. ft. hood aperture (Wolf) requires 810 or so CFM to provide 90 ft/min air flow into the hood entry aperture.

The air velocity of this flow rate in an 8-inch duct (0.35 sq. ft.) would be 2320 ft/min. This is above the recommended range of 1000 to 2000 ft/min, so some increase in impingement grease collection may occur. (It is unlikely that this will be an all day condition, so this is a lifetime type of issue.)

How long is your 8-inch duct? What type of make-up air system are you including? We need to estimate pressure loss from cooktop to outside and back to the cooktop to determine what size blower is needed. You might be able to get 810 CFM with a 1500 CFM rated Wolf blower, or with some larger Fantech in-line blower.

Duct noise will be on the high side, but blade tip turbulence noise and baffle turbulence noise may still dominate. For best results, a silencer should be used between hood and blower, relatively close to the hood to filter much of the duct noise.

Thanks for your reply. Some of this stuff is going way above my head but very much appreciated. Wolf has a make up air damper. I assume that I'll need to get this additional piece? The duct length is short as it travels to the side of the house (less than 10 ft) but it is obviously curved. Will I be able to use an adapter to go from 8" to 10"? I think Wolf's internal blowers only go up to 1200 CFM? Is that enough?

If an adapter can be fitted you can use it. Unless you put an external blower on the outside wall, you will have to deal with increased noise.

I have a Wolf 1200 CFM internal blower fan curve provided to me by Wolf ca. 2008, part no. 804702. This blower, likely supplied by Broan/NuTone, shows duct losses for 8-inch duct. First, this suggests that one of the duct options for this blower is 8-inch. Second, the duct pressure loss is relatively small -- 0.1 inches, w.c. -- for 10 ft of duct. The blower fan curve is evidently based on assuming the installed condition, because the fan curve at zero static pressure is already reduced to about 910 CFM. With 10 feet of duct, the flow is reduced further to about 870 CFM. So it should work so long as you have only modest pressure loss in the MUA path. Modest means not more than 0.2 inches w.c. along the MUA path from outside to kitchen. A short MUA duct and some low loss filtering might achieve this.

Wolf may sell a plate that adapts 8-inch duct to the hood of choice. A tapered adapter, however, will be lower loss.

Strive to have a damper at the hood and at the outside wall for the outgoing duct.

Great. I will consult with the installation individuals. Thank you very much for your advice.

It occurs to me that there may be confusion between the Wolf MUA damper and the hood exhaust dampers, based on my re-reading the wording of the messages above. The MUA damper goes into an MUA duct, which brings outside air into the house where it can replace the kitchen air being exhausted. It does not go into the hood exhaust duct. The MUA system can often be very simple -- a mere damper and hole in the wall -- or quite complex, depending on household pressure drop restrictions due to presence (or lack thereof) of combustion appliances.

Thanks for clarifying. I will speak to hood installers.