Anything but an overhead hood with significant CFM would be a foolish choice with a grill. Remember your first apartment where you were trying to brown some pork chops and the smoke alarm would go off because it had a lousy recirculating vent? (Or, like my first apartment, no vent at all) You'll have a 10x worse smoke production situation with a grill. You've got to have good capture area, and you've got to have enough fan to move all of the smoke that's captured out of the home. None of that would work at all with a downdraft---not even if your were just grilling veggies. Your smoke alarm would be continuous. As would the grease deposits throughout your home.

And, don't forget that with a ventilation unit there comes the responsibility of makeup air to ensure that you don't suck the exhaust from the water heater back down from it's chimney and poison or kill your family.

If you live anywhere in the US where you can grill out 8-9+ months of the year, then a grill is usually wasted money for a kitchen redo. Especially considering the expense of the ventilation and makeup air required to compensate for a grill.

An overhead hood is what I really want. But you an read Gaggenau's "Planning Notes" that recommend against it except with a griddle plate on top here. I'll probably ignore it because it makes no sense, but I'm not usually comfortable ignoring manufacturer recomendations.

I'm near Washington DC where the whether is temperate only a few months a year, so indoor grilling is preferable.

Yes, I have a gas water heater and furnace (in the level below the kitchen), so make-up air is an issue. There is an openable window, but is there a better, built-in way to provide makeup air other than expensive commercial gear?

> Remember your first apartment where you were trying to brown some pork chops and the smoke alarm would go off because it had a lousy recirculating vent?

Actually, my current apartment (that I'm about to move out of) is like that. There is a real exhaust fan, but it's in the living room (!) ten feet away from the stove. Astonishingly, it works quite well; leave it on for five minutes and any cooking odors are gone.

If the gas water heater and furnace are in a separate closed room, you may be able to put a passive or active damper controlled port in that room connected to the outside that opens if the pressure in the room relative ot outside is less than some value, such as 0.03 inches. Or it opens whenever the furnace OR the water heater run. This MUA source would solve the combustion appliance safety problem.

You would then need to depend on opening a window to provide air to the hood or provide kitchen MUA through another duct system that could be passive or active. Some examples may be found on this site given rigorous searching.

Otherwise, an active MUA system is needed that keeps the negative pressure low enough to avoid back-drafting.

kas

The water heater and furnace are in the basement one level below the kitchen, but that's a large room. The intakes for the fan-forced heat are in the living room which is open to the kitchen.

Is this only an issue for high-CFM exhaust hoods needed for grills or mega-BTU burners? Because I see gas heat in houses all the time without any sort of dampers.

The exhaust fan in my apartment does cause the rest of the apartment to become hot in the summertime, as MUA from poorly-sealed doors and such fills the other rooms.

The grill itself is electric by the way - in the picture I used it's placed next to a gas cooktop, but I'm using electric for both units.

The flow of combustion air into the furnace heating chamber and thence out throught the chimney should be isolated from the recirculating house air, although it may not be. As the furnace is forced, the pressure needed to cause backdrafting may be negative enough that with the present kitchen fan and various sources of air leakage, combustion products do not leak into the house. However, the furnace might be expected to be running at a different combustion efficiency than it was tuned for.

Usually, the reason for high cfm hoods is not removing CO traces from megaburner combustion. It is to remove grease, smoke, odor and water vapor produced while cooking, particularly while wokking or grilling or frying. Hence, the need for high cfm is personal -- if one doesn't mind odor or grease on everything, electric grilling without good capture and containment is certainly permissible.

kas