I think a better question is why are you getting a 36 inch range? You barely cook and you don’t use more than 2 burners. Seems like a bit of a waste.

Will this be a gas range, and if so how many BTUs will the burners and over use? Do you have a gas furnace, gas hot water heater, or gas fireplace? If you have none of these gas appliances, then you should not need to provide make up air. There is no danger of back drafting a gas appliance and causing carbon dioxide to be pulled back into your house.

If you do have any there gas appliance, then get a hood that has 400 CFM or less. If should be enough for the amount of cooking you do. Be aware that if you were to install a 600 CFM exhaust fan, then you would need a 12 inch diameter duct. If you install a smaller duct, then you will restrict the air flow and not be getting 600 CFM. You will have spent a lot of money on a range hood that can't perform to its rated air flow, and you might be forced to provide make up air when it is really not required.

I am not an expert in this area, and neither are most HVAC and general contractors. You will get a lot of opinions on this topic. Be prepared to be frustrated. The concept of make up air is a topic for new construction that is not well understood by many professionals.

@mike_home you are totally correct about the frustration 🤦🏻‍♀️. I’m so over this topic - I hate having to deal with things that try as I might I just cannot figure out. My house is already gas. Dryer, current range, hot water heater, fireplace and furnace. Thank you for the guidance on the ductwork. One of the things that makes me most anxious about all this (and bathroom tile too!) is the need to educate myself enough to be sure it is correctly done.

@Jar G - I meant to say something about that in my original post. I totally agree that I have no functional need for a 36”. However, I’m investing in the aesthetics of the space. The kitchen design is based on a feature range. I’ve done a ton of research of home comparables in my area, because I will sell not too far down the road. It is extremely clear from the comps that “wow” (not just remodels) in the kitchens and baths are what makes the difference. I am prepared to lose some of my investment in the remodel, but the way to minimize that is to invest up front in desirable features that are harder to find in my area. In my neighborhood alone, the ONLY house that sold for enough that I could recoup most of my investment is the one that had a really amazing kitchen. So for me it’s worth a few thousand extra dollars to hedge my bets. What I mind much more than the money is the hassle this thing is turning into. But I’m not prepared to give up yet :).

@mike_home I neglected to answer your question about the range. Right now I am leaning heavily toward a BlueStar with one simmer burner (either 5 or 6k, I’m seeing different info in different places) three 15k burners and two 21k burners. The one thing I don’t like about it is that it’s not self cleaning. And I’m concerned about service availability. But the more I research the less I worry about service, because this is the closest thing I can find to an old-fashioned non-computerized range.

You can calculate cfm needed for total BTUs for a gas range. You might be able to search for that on the appliance forum, or maybe kaseki or someone else will see your thread and volunteer. With that range, I'd go for a higher cfm hood, because of potential. You don't cook much now, but maybe you'll become interested in cooking in the new kitchen, and when you sell, buyers will expect the hood to match the output of the range. Since you're investing in a high end kitchen, invest in the MUA system.

Thank you mama goose. I have tried to calculate CFM, but from reading the extensive and much appreciated work of Kaseki and others on other strings. I understand it’s affected by more than just the btu. For example, I think I need to also factor in room size (cubic sf) and the overall pressure in my house. That’s what’s making me feel out of my league. I’m pretty sure I need at least 600 CFM, but if I’m calculating right it’s barely over 600 (I’m getting 607 based on cubic sf). But I don’t know if I’m using too high of a room size, because my kitchen will be opened up to what is now other rooms, and I’m not sure I should actually be counting all that extra space. The next jump up seems to be 1,000 in most hood lines - a big jump that I would think would have a significant impact on the airflow in the house.

All this is why I think I’m really in need of someone to come to my house and help figure this out, but I don’t know what profession I’m in need of.

What is commonly misunderstood is that the ventilation systems needed to deal with a powerful range may cost as much as the range itself.

Here are some simple* steps needed to proceed for nominal conditions that lead to good ventilation performance:

• Specify the size of the range.
• Add 6 inches and make this your hood width
• Maximize within the limits of available hoods the hood front to back depth
• Plan on setting the hood for good sight lines to rear pans and to avoid bumping one's head (given bending at the waist)
• Use a baffle filter hood
• Best to have the baffles somewhat up in the hood space so that there is a capture/containment reservoir
• Calculate the square footage of the aperture area of the selected hood
• Multiply by 90 ft/min to yield desired full power flow rate in cubic feet per minute X
• Using the value X, calculate the duct sectional area that establishes a flow velocity in the 1000 ft/min to 2000 ft/min range; use the lower region if the duct will be cold. Flow velocity (ft/min) equals CFM divided by the duct sectional area in square feet
• Note that ducts leading to roof blowers may be long enough and exist in a space where a silencer can be added to the path to reduce noise
• Multiply the full power flow rate X by 1.5 and use this to select the blower rating to be used Y
• Refine blower and duct and hood selection if necessary so that they are compatible
• Full power blower flow rate X is also the desirable flow rate of the MUA system, although it might be set a bit lower if one can depend on house leakage to supplement the deliberate part of the MUA
• MUA must be provided so that house pressure (relative to outside) does not fall below the level specified for any combustion appliances that may be present that are connected, air wise, to the kitchen
• MUA can be passive (no blower) or active (with blower). The choice depends on MUA filtering affecting the MUA path pressure loss and how closely the interior air pressure must match the exterior air pressure.
• In municipalities enforcing deliberate MUA above some threshold, such as 400 rated CFM (value Y), an open window may work but won't be acceptable. One needs, at a minimum, an external cap of some sort, a duct, optionally a filter if pressures allow, and a diffuser of some sort that lets the MUA reach the kitchen without cause drafts at the cooktop. Normal HVAC contractors should be able to handle this task
• At the other extreme, the MUA path is powered with a blower having a nominal flow rate similar to the hood system blower, a good filter, and a heater. This type of active system will likely need a control system so that it keeps the house pressure within a narrow tolerance of zero differential pressure relative to the outside. Such a system will require either close cooperation with the company supplying the MUA hardware, or a commercial HVAC contractor's support.

Notes:

MUA is intended to avoid back-drafting carbon monoxide (CO) not carbon dioxide (CO2). it is also needed so the blower can actually flow at level X given a blower specified to operate at level Y in free air.

A 10-inch duct is OK up to 1000 CFM (X) from a 1500 CFM (Y) blower. This is what I have. A 12-inch diameter duct is massive overkill for a 600 CFM blower (Y). Assuming adequate MUA, the dominating pressure loss affecting the hood system blower achieved flow rate will be the baffles, not the duct.

_____

*By simple I mean basic without the background information that leads to the assertions. A kitchen renovation is the most complex systems engineering project most people will ever have to deal with, without, in most cases, being systems engineers. Skilled craftsmen, kitchen designers, and knowledgeable trades people will be essential. One has to determine how well one can deal with immense complexity before deciding how much of the detail he or she will take responsibility for.

Thank you VERY much Kaseki. This is very helpful (and yes, “CO” not “CO2” - thanks for the correction). I don’t fully follow all of the calculations (I’m lost on the one that’s starts with “using the value X” bc I don’t know what “duct sectional area” means lol) but I definitely understand enough to point me in a direction.
I will get in touch with the contractor tomorrow and get a reputable HVAC company to come assess the house and help to figure this out. Hopefully my 36” range will survive this additional budget expense, but if not a design change will be in order. I can’t tell you how much I appreciate this response - I have no doubt I will refer to it repeatedly as I move through this process. You represent the best of Houzz :).

Sectional area in square feet is (for circular ducts) equal to (pi x d^2) / (4 x 144) where d is the diameter in inches and pi is the irrational number that starts with 3.14.

Have you looked at the Kitchenaid 36 inch ranges? They have self cleaning ovens. It would be disappointing to me that after spending all t his money the oven has to be cleaned by hand. You may also get better service from Whirlpool/Kitchenaid if you have problems in the future.

No, I haven’t looked at KA, although I think I’ve looked at everything but :). I do wish the Bluestar was self cleaning. But in the end I think the serviceability of the Bluestar is more important to me than the self clean feature, for the same reason I bought (and love) my Speed Queen washer. No smart components, touch screens, computer chips etc to go wrong and cost me a fortune. Just a sturdy, easily repaired, hopefully high performing product. And unlike most of the other brands I looked at, the warranty starts at installation, not at purchase, which is important since I will order soon but likely not install until December. I found out there is only one authorized dealer in my city, so I’m going to look at one there this week. We shall see :).