Our inspector told us that they look for the same diameter of duct from your hood, to the one that MUA uses to bring fresh air in. So your toe kick idea might not work...not sure, I would call your city.

We should be able to meet the same duct area in the toe kicks, the plan would be to split the flow to the left and right, 4 inch tall by 20 inch long (or two 10 inch long in our case) rectangular duct would have the same duct area.

I hope it works and passes! In our case he just said that the diameter match, and a flap in both ends is how they check it.

MUA should be in your utility area or hallway. Not in the kitchen. That increases turbulenc.

Yes, a forum member within the past two years reported that using the toe kick area under the cooktop led to air being reflected from the opposite cabinets and reaching the plume area in a turbulent state, degrading capture. The solution is to either introduce the MUA such that it flows away from the hood zone from a ceiling diffuser and then returns in a more laminar and spread out area, or is introduced over a large toe kick zone that is directed away from the cooktop area, or is introduced in a hallway or other more distant location and flows toward the hood, filling the hall sectional area by the time it reaches the kitchen.

There is also the question of whether the nominal cook will be well enough protected from cold toe kick air to tolerate it without a negative reaction. Duct heaters for this purpose are available from Fantech, I understand. Or, the MUA can be introduced to a basement that has sufficiently high powered on-call heating, and the basement tempered air introduced into the kitchen area. Certain constraints on basement condition might apply. Alternatively, introduction into an on-call heated mud room, for example, might work.

We have hydronic heating and only an indirectly heated cellar, so no great options for discharging into an alternate space.

The vent area on the opposing side of the peninsula could be an option which would reduce the turbulence. Our cellar is also not internally accessible from inside the home nor connected by ducting, so would discharging into the cellar even provide adequate pressure stabilization? It may need to be somewhere in our living envelope.

We are considering building an alternative system using a hydronic air to water heat exchanger in the ducting to temper the mua with an added zone on the furnace using thermostatically and vent power controlled flow switch, but I would prefer to skip heating if possible.

Why would anybody install a stove that requires sucking freezing cold air in the winter and sweltering air in the summer into an already drafty house just to make dinner? Given the location and conditions, wouldn't a plain old stove like one installed in 99.9% of American homes make a lot more sense?

Need for hood air flow rate and hence MUA hood flow rate is driven by the cooking plume velocity, and while this may be larger for the most powerful cooktops, it can be demanding even from a more modest range, depending on cooking temperature, grease production, and odor removal importance.

When I included discharging into a cellar as an option, I expected that a means, duct or otherwise, would bring that air to the kitchen with low pressure loss.

Even with a blown air oil burner heating a boiler for hydronic heating, there is an upper limit on the pressure drop at the furnace that will avoid back-drafting carbon monoxide (~0.08 inches, w.c.). The cellar should have some MUA, or direct MUA ducting to a kit at the furnace should be used.

If the cellar is well vented, then the hydronic heater could be used in the path from the cellar to the kitchen. Otherwise, you may want to consider heating air brought from the roof to the attic and hence past the heater to a ceiling diffuser.

Electric heating may be easier to adapt into an MUA path, but has its own requirements w.r.t. connection to the electric supply.

wdccruise, why do folks add marble/granite or other materials when laminate would be fine. I love to cook and want the best I can afford. It wasn't a question of my range selection, I'm looking to understand better the ins and outs of appropriate mua.

kaseki, I truly appreciate your responses. Our cellar and hydronic furnace do by natural consequences have appropriate mua and I do want to get this right as I don't wish to bachdraft the furnace nor our supplemental wood stove.

I was taken back by the costs associated with the electric heated units for the amount of temperature rise necessary in worst case January weather.

I was looking to understand how critical tempering the air is, and whether it was possible to work an air curtain style system, by bringing the majority of the makeup air in as close to the range as possible. The hope was that heating would be unnecessary as the majority of the MUA would makeup air would end up as part of the effluent stream. Thank you for addressing those concerns.

Although we can pull MUA in from either from external to the attic above the kitchen space or external to the cellar. With including a water to air heat exchanger in the duct run to temper the air, the cellar made more sense, I just wonder whether it's possible. The style hx I'm referring is the same as used for converting hydronic to forced hot air. It would allow me to use our current heat system to temper the air directly rather than relying on a secondary system. It seemed straight forward, but maybe mildly unconventional. I could exhaust a heated MUA into an adjoining space, like the pantry/mudroom with a set of floor registers. How far from the hood is the minimum distance to prevent disruption of the laminar flow?

My heat exchanger looks like a Chevy radiator, but came from a source supplying such devices to wood burning boiler affectionados. (I can look up the source when time allows.) One wants to choose a size that can exchange the needed BTU/h at the air flow CFM that will be available to do so at the temperature difference between the cold air and the hot water. Mine is about 2 ft x 2 ft in area with fine fins. I don't recall the pressure loss at the design CFM, but in contexts where there are weakly or passively vented combustion appliances, a blower would be needed.

Because mine is in an attic, I have a sensor on the plumbing to run the loop if the temp gets below some plumbing risk temperature (40F maybe, forget my setting), and a sensor below the fins sampling the air fed to the house interior (65F, I think) to warm the air enough. These are configured in an OR logic, originally for running the loop circulator with my previous standard boiler, now for the loop controller in a single circulator System 2000 furnace. (Be sure your circulator can handle the pressure loss of the loop and radiator (equivalent head for hydronics) at the flow rate needed.

I have my exchanger in the attic above a larger framed opening covered underneath by a 3 x 3 foot one-directional diffuser down the hall from the kitchen.

Presently, the blower part of this project is unfinished, but a furnace filter above the heat exchanger, along with the exchanger itself, seems to completely block warm air from rising through the exchanger into the attic. In a finished system, a larger filter and dampers will be a more positive block.

The answer to how far is not an easy one and I haven't seen a formula for it. Some commercial systems run the MUA down a duct next to the exhaust duct and, at the ceiling interface of the hood assembly, force the air horizontally across the kitchen from a long narrow slot area. Others put it down the back of the cooking appliance via a wide duct and send it out in all directions across the floor. (Commercial cooking appliances have legs so the area underneath can be routinely cleaned.) Some air curtain designs exist, but I think you would have trouble achieving the desired effect without a truly custom sheet metal scheme.

A floor register won't be able to act like a laminar flow aiding diffuser, so the output will be somewhat turbulent. I would want to keep it about 10 times its largest dimension from the hood -- not as the crow flies, but along the dominant air path considering how the air will move from mud room floor to ceiling and out to hood via the kitchen layout and any intermediate partially blocking objects such as islands. You are just trying to weaken the turbulence by spreading the flow; true laminar MUA only exists in test kitchens where a wall opposite the cooking device (sans cook) is perforated to feed calibrated MUA into the test zone from a large wall area.

it sounds like what you have is very similar to what I was invisioning. I think we may be able to achieve a reduced turbulent solution by exhausting the mua from the peninsula in the opposite direction. There is a wide area of floor space in this area which would allow for mixing without significant turbulance, well, any more turbulation than my current system of toe kick heaters already contributes.

thank you for your help. I do appreciate the educated response.

What did you end up doing?

We are still midway through our project, we will be making a hydronic mua system later in the spring when we finally get all the ducting run.