I don't have equipment to measure the pressure differences but I have done some qualitative tests to evaluate the velocity of air that comes through a known opening (small window) for H/M/L blower settings as well as the velocity of air exiting the blower exhaust. What I found is that the pressure difference between the kitchen/dinette/family room space is greatest on the LOW blower setting and less on HIGH and MED settings even though the volume of air exiting the house from the exhaust is H/M/L as you would expect. I attribute this to the lack of MUA on the LOW setting due to the closed MUA damper. The hood flow I am perfectly satisfied with although it bothers me that the low setting is lower than designed because of the lack of MUA. I believe replacing the airflow MUA switch with a simple current sensing switch will be a good solution. We live in the PNW with a fairly mild climate with low temperatures seldom below freezing and never below 0 degree F and our furnace does not seem to have any trouble keeping up with the colder MUA inflow so far (although we have not had many cold days yet). opaone: Our MUA damper is a Broan MD10TU with a motorized damper triggered by a remote flow sensor switch. Thanks for the input on interlocking the MUA with the blower - I had thought that would be a good idea for MUA performance but not considered the static buildup aspect. The 6" MUA damper originally installed with the furnace is interlocked with the blower so I guess I better research how that works. And thanks for the kitchen compliment.

Well, I can be long and rambly too, and suggest reviewing the many hood threads here to see that demonstrated. I can also suggest that if you, @Margaret Davis, do so, you will learn a lot more about both hood requirements and make-up air (MUA) requirements. I'll supplement the information on this site, first by noting my astonishment that whoever wrote that blurb for Proline seems to be missing the most fundamental concept -- no air leaves the kitchen that doesn't get replaced. No reports of imploded houses due to hood blowers pulling a vacuum have ever come to my notice. With respect to the requirement that outgoing air be matched by incoming air, the size of the kitchen is irrelevant. The blower size is irrelevant. How long you run your hood is irrelevant. There is always a balance such that the actual hood duct airflow matches what leaks into the house, or is allowed to flow into the house, or is deliberately blown into the house. Gag the MUA, and the house interior pressure drops until the hood blower volumetric flow rate matches what can leak in at that pressure drop. The controlling aspect is the 'fan curve' of the hood blower when MUA is passive (not blown) and the combination of fan curves when the MUA is active (blown). Example fan curve [click to enlarge] Broan 1200 CFM blower fan curve. The pressure that determines where one can operate on the fan curve is determined by pressure loss passing the hood baffles, the ducting, the exterior cap if not included in the fan curve, and the MUA pressure loss getting air back into the kitchen. With a large diameter passive MUA or imperfectly tuned active MUA, you are likely to see the actual hood air flow to be only 2/3 of the zero static pressure flow rate, that is, 2/3 of 1200 or 800 CFM. Modern codes require, as @Celedon noted, deliberate (active or passive) MUA when the hood rated blower size (not actual flow rate) exceeds 400 CFM. This is to ensure that any combustion appliances that are present, or may be present in the future, are not back-drafted by negative house pressure thereby introducing carbon monoxide into the house. Second, I won't go into hood requirements here as those should be easily found among the hood threads, and in any case you seem to have picked a hood or hood size. However, I will address the vertical duct question. Generally, the highest pressure losses will be the hood baffles and the MUA if passive, depending on duct size and filtering. So longer ducts will drop the overall flow, but perhaps not too much relative to these causes. This can be evaluated by plugging the duct parameters into on-line calculators that may be found by searching. Third, most ventilation noise is air turbulence noise, dominated by that at the blade tips of the blower. Duct turbulence will also contribute. Silencers reduce this, and may (as in the case for me) reduce the noise such that baffle turbulence (hiss) dominates. An advantage of running the duct into the attic would be that in the attic there may be room for a silencer to be inserted between the external blower and the hood. One can also angle the ducting there so that the external blower is at an advantageous point on the roof. No matter what tortuous path you choose, and the ducts you have sketched aren't really that long, be sure that the chase allows access to the ducting in case cleaning is needed (usually rare in residential cooking). In cold climates it is best to keep the duct warm over as much length as possible, so exterior ducting may want to be in a chase if very long. With a larger chase, a silencer can be put closer to the hood, which helps suppress duct noise. Fire protection in the chase may be an issue; discuss with your code enforcement officer. You should plan on using at least 10-inch ducting, but note that the Fantech 10-inch duct silencer is 14 inches in diameter by 3 ft long.

@opaone raises an important point that I'd like to expand upon. Commercial hood operation and its MUA support is one of the highest cost activities for commercial kitchens. The hoods run for long durations, and often require air conditioned make-up air, at least into any restaurant customer area where the pressure is set a tad higher to keep out kitchen odors. Commercial systems are thus designed for power efficiency. In residences, the hoods are operated for shorter periods of time, and typically (where MUA is nearly free) the cost of operation is small in the overall household power budget. Affordability then tends to be a matter of capital cost -- buying the hood, blower, ducting, and its MUA counterpart components and installing them. Striving for power efficiency through higher capital costs will take a very long time to pay off. Also, typical residential kitchens are ill suited aesthetically and space-wise for incorporating commercial hoods. The intermediate case is where the household is subject to stringent air quality requirements that cannot be met by just fresh air exchange. In such as case, treating MUA can be expensive, and the requirement for almost total cooking plume removal requires a large hood, high flow rate, and a lot of MUA. Here, commercial or quasi-commercial systems like opaone has incorporated may be optimal from an overall cost and performance point of view.

"Thank you, Kaseki! I’ve been reading your past posts-would you mind sharing again what cooking device/range hood/ makeup air system you chose and why?" You may find images of elements of my kitchen in various posts. I won't repeat them here. Also, some hood flow parameters may be found in FAQ I. Please note that my kitchen reno planning began in 2007, with most purchases of appliances made at the end of that year. Delivery was taken significantly later for most items, but well in time to confirm measurements and interface details. Explaining rationale would make this tediously long, take too much of my time, and jack this thread. I owe a kitchen photo to the FAQ II thread, and one or more should appear in the fullness of time. The cooktop: I have two induction cooktops, a 36-inch Frigidaire Gallery (replacing a 36-inch Electrolux clone Kenmore that failed after 5 years or so) and a Cooktek 3500W induction wok. These are set in soapstone over cabinets in which there is added stone support and wire racks for pans, providing maximum air volume for cooling. The hood system: Overspreading these is Wolf's largest Pro Island hood set at 34.5 inches above the counter. The hood connects to a damper, then a Fantech silencer, and then a Wolf (Broan) 1500 CFM roof blower (which has a damper). (As I have explained many times, once installed in a hood system blowers cannot flow their rated CFM due to pressure losses. I have measured, however, about 1000 CFM with presently passive MUA and no other household exhaust blowers operating.) Duct is 10-inch. The secondary hood system: There is a secondary system comprising a pair of ceiling registers (14 x 20 if I recall), 3M Filtrite filters in the register boxes, a damper, silencer, and roof mounted NuTone down-blast blower. I believe this blower is rated 600 CFM, but can't find my literature for it as it was originally bought to provide additional flow for a '70s cooking center with miniscule blower performance. The registers are ceiling mounted over a pair of Wolf wall ovens. The MUA: I have planned an active MUA system, but all parts have not yet been acquired. There seems to be no end to new "required" projects. The system as it presently exists is operated passive, and comprises a highly ventilated attic with an additional roof-mounted down-blast commercial blower housing for eventual ducted air intake, a one-inch pleat 24 x 24 furnace filter (to be replaced with a lower pressure loss 4-inch pleated canister version, a 30 x 30 heat exchanger connected to my oil-fired hydronic heating system, and a 36 x 36 diffuser at the end of a hall that connects to the kitchen. The control system for this is intended to keep the kitchen pressure equal to the outdoor pressure (which will be the attic pressure once the MUA is ducted). Some elements of this are place. A Fuji computer module in a DIN control array next to my furnace will attempt to adjust its natural frequencies (poles and zeros) such as to make a stable MUA system independent of the main hood flow rate, the wall oven vent flow rate, and bathroom blower flow rates. The differential pressure sensor upstream and motor downstream control loops are 20 mA current type. Separate sensors and controls are used to keep the heat exchanger from freezing when not in use and otherwise keeping the air passing it temperate. Blower will be the largest that can get into the attic that Fantech sells that incorporates the 10 Vdc control voltage motor. (I forget the part number.) This wasn't available back ca. 2010, nor did Fantech list a motor controller that could handle that size motor back then. If starting from scratch, I would investigate the present offerings of Electro and Fantech to minimize my work, but large flow rate in an assembled unit would likely not fit into the attic without removing the diffuser and heat exchanger for a one-time installation. While balanced air pressure is highly desirable for several reasons repeated often on this forum, I should note that my System 2000 oil furnace has its own MUA and a sealed exhaust stack installed within the original brick chimney that served the previous one- and two-generations-back Beckett boilers. The hot water storage is heated via a hydronic loop on the furnace, and the dryer is electric. Hence, back-drafting of combustion appliances is not an issue. To deal with the flow to the MUA heat exchanger (capable of 120k BTUh if necessary) as well as the longer reaches of my house hydronic plumbing, I use a larger (higher head vs. flow rate) Taco pump than is usual.