Direct-Vented vs. Recirculating Range Hood Fan
Hi,
The ongoing debate about direct vented versus recirculating hood fan has come up as we’re about to pour the slab. The house is better than Pretty Good House but not quite Passive House with an all electric home that will have a small wood stove. We initially thought about doing a recirculating hood fan but after the HVAC contractor planted the seed about a direct vented, my wife is second guessing now because we do a lot of cooking.
My concern is the make up air from a 100-200 CFM hood fan and more so with having a woodstove in the house. I suspect the weakest point in our house will very likely be the chimney and the directly connected outdoor air kit where make up air will be pulled from. The concern is backdraft from the woodstove.
Anyone has direct experience with a similar situation and how they approached it? What were the results from that approach?
Thanks,
Arnold
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Replies
Arnold,
Recirculating h0od fans aren't worth installing. They do poor job of eliminating fine particulates, and don't remove the moisture from cooking.
A 100-200 CFM hood shouldn't affect your wood stove, but to be sure I would install a small make-up air inlet or operable window near the hood.
A GBA search of "range hoods" yields several very good articles.
Thanks Malcolm for your feedback. I'll be honest, the idea of installing a make up air inlet goes against everything we're trying to achieve with our build.
The VanEE 2400 ERV we're installing indicates that it is "electronic balancing". Does that mean it will adjust itself (up to a certain point) if the hood fan is turned on?
https://www.vanee.ca/en/products/residential-air-exchangers/67-g2400h-ecm-new.html
Thanks,
Arnold
Arnold,
I don't think you can rely on the ERV to balance the pressure quickly or effectively enough to compensate for sudden draws like the hood. But I think you will be fine without any dedicated air intake. In our semi-airtight house we only see occasional problems when lighting the wood stove. Once it is drawing neither the fan or the dryer affects it much. The cure is as simple as briefly cracking a nearby window.
Thanks for the reassurance Malcolm.
Arnold
If you have a DIRECT connected OAK, I'd think it'd be pretty isolated from the house. Not entirely airtight, but I'm thinking like Malcom said, a window cracked when needed sounds reasonable to me.
My 100 year old full time home has no range hood or bath fan (yet), so I know what it's like without one. I've stayed in and cooked in places with recirc fans. The cabin I'm building with no well or septic....it IS getting a direct vent range hood.
Allison Bailes calls recirculating hood fans as effective as recirculating toilets. I trust his thoughts implicitly. Take a look at this article: Recirculating Range Hoods.
Direct vent range hood is arguably more important than a wood stove. IIRC code doesn't require makeup air when CFMs are under 400.
Just make sure the hood is correctly sized as large capture area will go a long way.
Another vote for a direct vent hood. Recirculating hoods aren’t much different than using a fan to blow your cooking around your kitchen.
If your main concern is with makeup air, put a power damper in the makeup air inlet (power dampers tend to seal much better than spring dampers), then interlock the actuator with the range hood so that the damper opens automatically when the fan is activated. You can use a second power damper on the range Hood’s exhaust duct to be doubly sure you aren’t introducing any extra air leaks in your building envelope.
Bill
Bill, what brands are you using for this power damper set up?
I have used various brands, I haven't done this enough times to be able to definitively say any particular brand is superior to any others. I like to use dampers with 24v actuators when possible though, since it allows them to be wired with thermostat wire instead of NM cable (romex) which is required for 120v "line powered" damper actuators. It's easy to wire a 24v control transformer into a range hood to provide 24v power to operate a damper or two.
Bill
Thank you all for the feedback. Sounds like everyone is in favor of a vented hood fan so we'll proceed with it.
Thanks again,
Arnold
Arnold,
Probably the biggest reason range hoods don't get used is noise. Choose one carefully, or better still install one with a remote fan: https://www.hvacquick.com/products.php/residential/Kitchen-Exhaust/Kitchen-Exhaust-Kits/Fantech-Kitchen-Ventilation-Kits
I agree. We have a cheap one that came with the house (large development) and my wife hates it because of the noise.
Arnold
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We just renovated our kitchen and replaced the gas appliances with all electric. We also removed the vented hood and installed a recirculating hood with charcoal filters. So far it's been great. The induction boils water so quick, the cooking times are reduced. This cuts down on the amount of moisture. The odors have not been any more than when using the vented hood. If you do a lot of frying it might be an issue. Otherwise, I say go for it. Two less giant holes in your envelope.
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