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Q&A Spotlight

Can a Kitchen Downdraft Fan Be Connected To an HRV?

Heat recovery ventilators bring fresh air into a house while exhausting stale air. Builders pull stale bathroom air through HRVs all the time — but what about greasy kitchen air?

A powerful downdraft exhaust fan. Downdraft exhaust fans, like this 600-cfm model from Siemens, can easily depressurize a house.
Image Credit: Siemens

Powerful kitchen exhaust fans do a good job of removing cooking odors and smoke. They also have the potential to depressurize a house, causing water heaters to backdraft and pulling ashes out of the fireplace and onto the hearth.

Our ‘question of the week’ comes from Kevin, who explains that he will be installing a 600-cfm downdraft exhaust fan in the kitchen of a new Passivhaus residence. “Our HRV installer said that he has heard of people tying in their cooktop ventilation to their HRVs,” Kevin wrote. “However, I am concerned that this would invalidate the warranty and greatly shorten the lifespan of the unit.”

John Brooks warned Kevin that the stovetop exhaust fan should not be tied in to an HRV.

Andrew Henry suggested ventilating the kitchen differently — through a ceiling grille located a suitable distance away from the range.

Martin Holladay explained that a house with a 600-cfm downdraft exhaust fan needs a makeup air unit.

Derek Vander Hoop noted that in Passivhaus building, the “perfect solution” is to connect the downdraft fan to a grease filter rather than exhausting the air directly outdoors. An HRV can then handle the moisture and odors.

Robert Riversong advised that gas stoves should always be vented to the outdoors.

What do you think?

Should an energy-efficient home include a powerful exhaust fan?

Must cooking odors always be vented outdoors?

Should an HRV pull air from a kitchen?

Read Kevin’s original question, and all of the responses it generated, here.


If you’re interested in more information, check out these resources:

“HVAC Equipment Can Overpower Wind and Stack Effect”

“Exhaust Ventilation”

“Designing a Good Ventilation System”

“HRV or ERV?”

6 Comments

  1. Interested Onlooker | | #1

    If I remember correctly, the
    If I remember correctly, the favoured solution in Europe is to use a recirculating cooker hood which traps the grease locally. You have to clean the hood filters every six months or so, depending on how often you cook. The odours, moisture and by-products of combustion are then removed through the HRV.

  2. Anonymous | | #2

    Leave the kitchen hood on,
    Leave the kitchen hood on, but open a window near by if the fireplace is on... Simple easy and low cost.

  3. Baltimore Green Construction | | #3

    Don't leave the range unducted
    I disagree with Derek's advice. Ranges should be ducted to the exterior.

    Filters will remove some small fraction of smoke, if something starts to burn. But they won't remove water vapor from a boiling pot, and they certainly won't remove combustion byproducts if you have a gas range (which is very common in many parts of the country).

    I think it's reasonable to expect that air will leave your house when you cook, because for health and moisture reasons it really needs to.

  4. Derek Vander Hoop | | #4

    Baltimore Green
    Baltimore Green Construction,

    I was misquoted in that I never "advised" anyone to use a recirculating filter. I did post a photo of what I thought was a perfect solution and offered it to Kevin and the Green Building Advisor community. Having said that, if I was building a Passive House today, I would use this method.

    If you have a PassivHaus, it makes sense to remove the grease and smoke while cooking and then gently exhaust the odors, moisture and stale air through an ERV and HRV (which Kevin is using), recovering the heat in the process. To me, this is a far better solution than forcibly exhausting 600 CFM of air, losing heat energy in the process and throwing pressure balances out of whack.

    I wouldn't use a gas stove in a Passive House, and I'd do my grilling outdoors, for obvious reasons.

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

    Thanks for your clarification
    Derek,
    Thanks for your helpful post. I've edited the section that summarized your views, in light of your clarification.

  6. Whetstone Green | | #6

    high CFM exhaust bad idea in super efficient homes
    First off, I agree with others that connecting a cooktop exhaust system to an HRV is a bad idea. Aside from other arguments presented, 600 CFM would overwhelm the capacity of virtually all residential HRV's, thus greatly reducing the efficiency (heat recovery fraction). And any dirt that accumulates on the heat exchange substrate will drop efficiency even further. Since a cooktop fan only operates a fraction of the time, I can't imagine a scenario where a dedicated HRV would be cost justified.

    I agree with Derek that a gas range has no place in a PassiveHaus or any other super high performance home. Electric ranges are perfectly happy with a 200 to 300 CFM hood. Downdraft fans require more airflow to overcome gravity, and should be avoided. Of course, this all requires customer education (Don't tell my wife she can't have her gas cooktop on an island!).

    Here in the US, commercial style 6-burner gas ranges have become very popular in high-end homes. Having long given up on convincing clients to go electric, I at least advise against installing one of those ridiculous commercial range hoods that pull up to 1200 CFM. These are required in commercial kitchens to meet OSHA requirements but have no place in the home. 300 to 400 CFM is plenty for a oversized cooktop. Unfortunately, 5-Star, Viking and other manufacturers haven't got that message. If you want your hood to match the range, you may not have a choice. These obviously require local make-up air. The best I can do is tell clients to only turn them up as far as necessary to draw in the steam/smoke, and to avoid using the highest speed when it's particular hot, humid, or cold outside.

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