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Gas cooktop: OK with exhaust-only ventilation?

Gordon Taylor | Posted in Green Building Techniques on

First, I’m talking about a new house being planned for Zone 4 Marine climate. We’re just about there with the design. My wife wants a gas cooktop. I want a simple energy-efficient house. It will be around 1850 sf, 3 BR, 2 BA. I’m not planning on being obsessive with the air sealing: probably will be ~3ACH50. Posts by Martin Holladay, Riversong, and AJ Builder, all people I trust, convince me that an exhaust-only ventilation system with Panasonic fans can work. And, of course, there are the houses by Carter Scott, as written up in the latest FH. Now comes my wife’s beloved gas cooktop. Martin has written,

“Needless to say, any tight house with an exhaust-only ventilation system shouldn’t have any atmospherically vented combustion appliances. Any combustion appliances should be sealed-combustion units.”

Does this mean a gas cooktop? No one in his right mind would use it without a range hood, and that includes my wife. Where do we stand with this?

Now comes Dr. Lstiburek, who is certainly no slouch, telling us that we should not “suck” as Martin, Riversong, AJ, and Carter Scott have been doing. Evidently there is a toxic cloud in my garage threatening to engulf me courtesy of a couple of Panasonic fans. And there, on pp. 74-75 of Fine Homebuilding, I can see Carter Scott’s houses, all using exhaust-only ventilation, and all obviously with attached garages. What is a poor GBA reader supposed to think? Can I use a gas cooktop in our new house? Does the exhaust-only option still pass muster in the new age of Lstiburek Orthodoxy? Thanks for any comments.

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Replies

  1. Curt Kinder | | #1

    Great questions

    Have you considered Induction cooking? Same instant control as gas at about 4x the thermal efficiency and less ventilation needed.

    Regardless of cooking fuel a reasonably sized and operated range hood in a 3 ACH 50 House should be able to get along in slow speeds without overly depressurizing it. Ensure kitchen has operable window(s) and that visiting cooks know to use them.

  2. Dennis Heidner | | #2

    At 3ACH50 AND energy efficient -- you have some kind of make up air coming in either through an HRV, ERV, or a damper. The kitchen hoods do work much better when you crack a kitchen window to provide the a nearby source of fresh air. Or you could look at some of the Broan models that can remotely control a damper to allow in extra air.

    Even with induction cooking - you will still want to vent the VOC's that result when simmering, browning (or in my case blackening) the meals...

  3. Gordon Taylor | | #3

    Curt,
    Thanks for writing. Yes, we've considered induction. And we may yet go that route. If we end up making the house tighter, induction would be the preferred option.
    Dennis,
    I realize I'll have to use a range hood, no matter what. What I'm wondering is, could I use a gas cooktop without extraordinary measures, like cracking a window? People don't ordinarily crack windows while cooking. At least we don't. But if that's the price for not dying of asphyxiation, we'll pay it. Thanks for commenting.

  4. Curt Kinder | | #4

    I didn't mean to imply that an Induction cooktop needn't be ventilated, and don't for an instant consider the code-minimum nonsense of drawing cooking fumes through a screen filter and exhausting them back into the kitchen.

    I don't consider cracking a window during intense cooking to constitute an extraordinary measure, although YMMV.

    Unless the house is airtight to near PH standards, you should be able to operate a reasonably sized range hood in low gear without problems, and that should be adequate for most cooking. Frying, sauteing, blackening, etc do require stronger measures. If those are routine, consider a makeup system, IMO.

    My stance against gas is that at best it transfers about 20% of heat to cookware. The rest goes into the kitchen as substantial extra heat AND humidity, water vapor being a product of gas combustion. Induction operates inversely - 80+% of the heat stays with the cookware. Of course this is viewed through a Southern lens - extra heat and humidity are almost never welcome in a southern kitchen. Zone 4 marine likely has similar heat and humidity part of the year.

  5. User avatar GBA Editor
    Martin Holladay | | #5

    Gordon,
    Exhaust-only ventilation systems work best in small homes with an open floor plan. In larger homes, the problem of fresh air distribution arises. Exhaust-only ventilation systems don't do as good a job of providing fresh air to your bedrooms as a supply-only or balanced ventilation system.

    However, if you always sleep with the bedroom window open a crack, perhaps none of this matters.

    As you have correctly noted, you certainly want a range hood over your gas cooktop. I think it is possible to have a house with an exhaust-only ventilation system as well as a gas cooktop and a range hood, as long as you follow the recommendations in this article: Makeup Air for Range Hoods.

  6. Aj Builder, Upstate NY Zone 6a | | #6

    Gordon.... Thanks for the mention... As to your posting, I think Curt has it handled quite simply and straight forward. Riversong use to mention passive air inlets... A search will bring up past yaps.

    So add Curt to your list of trustees.... If you feel as I.

    And Dana Dorsett for sure.

  7. Gordon Taylor | | #7

    Good answers all. Thank you for replying. Curt, I wouldn't think of not ventilating, no matter what device we choose. You wrote:

    "My stance against gas is that at best it transfers about 20% of heat to cookware. The rest goes into the kitchen as substantial extra heat AND humidity, water vapor being a product of gas combustion. Induction operates inversely - 80+% of the heat stays with the cookware."

    Those are mind-boggling numbers, and I will certainly share them with my wife.

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