Put in a range hood. It is so worth it. Downdraft and gas don't work well together. If it sucks enough to actually contravene the laws of physics by sucking all that rising hot air downward, then it sucks enough to pull the flame on the gas. 325 CFM is also beyond meager in dealing with the cooking byproducts that will coat your home.

You're building from scratch. If youc can't do it right from the beginning, when can you?

An induction cooktop because it does not heat the room air requires less ventilation. It would still benefit from a smaller hood, but probably could get by without makeup air.

Never seen a downdraft that did even an adequate job of removing grease, steam or odors from cooking.

Cut costs elsewhere but get a proper hood vent. Most important things in a kitchen are the cooktop and its venting. everything else is secondary...

I'm so tired of hearing that a downdraft doesn't work with a gas cooktop. I often wonder if the naysayers have ever used a good one for any amount of time. Of course an overhead hood is more efficient- but there are many reasons why it isn't suitable for every kitchen.

25 years ago we installed a Thermador downdraft and cooktop when we replaced an inoperable Jennair unit. 5 years ago we remodeled the kitchen and installed a Dacor downdraft with remote blower and a Dacor gas cooktop (17,000 BTU burners).

We stir fry occasionally, fry bacon on a griddle, sear steaks in a cast iron skillet, boil pasta, cook fish etc. Our ceiling hasn't discolored, nor is it coated in grease, our house doesn't have lingering odors, the flame isn't pulled away from the burner and we've been very happy with the arrangement.

Now if I had gas cooktop with 23,000 BTU's I would certainly reconsider the application.

Well, I'm a naysayer who actually owned a Jennair ceramic cooktop with a built-in downdraft, not too different than what the OP is considering. I can say unequivocally that cooktops with built-in downdraft units are inadequate for anything beyond boiling and simmering. To put it bluntly, they suck, and not in a good way. I had to tent with foil to channel the smoke to the vent whenever I stir-fried, browned or even attempted to blacken. Smoke detectors were constantly being tampered with. If it was terrible for a ceramic cooktop, I can only imagine how much worse it would be for gas.

Here's a picture of my POS taken the night before demo. So happy to see it go:

I believe the unit that marie_cat has might be a pop-up downdraft. That may be acceptable, because the vent at least sits above the pan. But that's an extra component and cost above and beyond the cooktop itself. Probably worth considering if a hood is not possible.

I'm also a naysayer with direct experience of a GE Monogram gas cooktop with GE Monogram downdraft. Even with the sadly underpowered cooktop, the downdraft was next to useless. The cabinets all around the cooktop up to the 10' ceiling had grease residue from years of cooking with this setup. It took a lot of effort to get this to an acceptable state of cleanliness. I used this for about 7 months and couldn't wait to get rid of it.

I see posters on this forum cheerily posting about their downdrafts, or even not having any ventilation and I wonder why their experiences are so different from mine. When I cooked on the Monogram, not only could I see visible deposits on the wall behind the cooktop and cabinets above but food smells drifted and lingered thoughout the house.

We went to considerable trouble and expense to install overhead ventilation. This meant going into the wall and installing ductwork up and through the new roof. We also chose induction over the Bluestar cooktop I had always wanted, because there was no easy way to vent from the high power of a gas cooktop. We put in a 720 cfm Kobe hood and I'm very, very glad we did.

Cheryl

Thank you all very much for your replies!

It's a national builder, so we can't consult another builder. For the lowest end one they want 3500. That seemed steep to me. They also want me to upgrade the cook top to a different one.

I've read that one reason for a kitchen remodel is to add a vent hood, and that's why I wanted to figure it out before hand!

National, nternational or local you are the purchaser. You may have to put in some extra effort to end up where you need to be. The long term use for this is worth it. Post a floor plan and this forum and the electrical can help you plan and price an option. You may then be able to delete that segment from your builders list of responsibilities and receive a credit for work not done and an appliance not supplied.

jscout is correct and I should have been more specific - both of my units were pop ups. I agree completely about the inadequacy of a downdraft without a pop up vent. That's one of the reasons we replaced the Jennair.

My downdraft was a popup and it was next to useless.

I have used a JennAir for 30 years. Both ranges were down-draft. I never ever had any problems. In my new home, I will have to put a down-draft into an island or cover a window with a range and overhead vent. I do not like the looks of overhead vents in islands in smaller kitchens. What to do?