Recirculating range hood with air scrubber
Like many people on here, I’m trying to
find an alternative to a vented range hood. There is an attractive option out of Vancouver (I forget the name), but it doesn’t seem to be out yet.
I’m wondering if a Plain Jane hood with a grease trap (or welded 304 stainless box with brackets for grease filters and a duct welded on the back) could exhaust out to a powerful air scrubber located elsewhere in the house. My workshop scrubbers pull between 750 and 2000 CFM and have three stage filtration (hog hair, carbon filter, and hepa filter). The scrubber could be located in the basement to cut down on noise, and the hog hair could be replaced with wool to cut down on odors and residual grease in the air. Air scrubbers are fairly affordable and mechanically simple. It seems like it would certainly be an improvement upon a recirculating hood.
Our house will have an ERV and dedicated dehumidifier. Our cooking appliances are all electric and our basement is in the conditioned envelope.
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Replies
Vent the hood outdoors properly and don’t worry about it. Don’t prioritize air sealing over indoor air quality here. Hoods vented outdoors are always, and in every case, superior at performing their intended function, which is to exhaust contaminants out of the cooking area.
Bill
User...704,
It does seem like a lot of gymnastics just to avoid venting outside. On the other hand, considering the average household only uses their range-hood 13% of the time, if this makes you more likely to do that, then it may be a good solution.
The problem with these unusual set-ups, especially those that require regular maintenance to work, is that they don't appeal to many other people, so the next owner of your house will probably have to run a vent anyway.
You’re right, I’m getting a little far afield. The air scrubbers are simple to maintain, but thinking about the next owner is a valid point. I’ll just have to get creative with ducting a rangehood. Our house has thick brick walls and a lot of windows to work around.
We have a falmec hood with charcoal filters over an induction cooktop. It works well for a family of six that cooks 2-3 meals daily. I wouldn't deep fry or sear steaks with it but we do stir fry with a wok sometimes. We replace the filters every 8-10 months.
I can't remember who said "Recirculating hoods are as effective as recirculating toilets". I can see why though.😁
Armando,
"You’d never settle for a recirculating toilet, would you? Press the lever and everything in the bowl just swirls around and around. Never leaving, just recirculating. That’s the image Professor John Straube painted for us last week in his talk at the Building Science Experts’ Session. He was discussing range hoods and indoor air quality (IAQ)."
Allison Bailes
To be a little more direct, a lot of the pollutants in stove combustion products are things that can't be filtered out, they can only be exhausted.
In case anyone is interested, this is the product I was thinking of:
https://www.activeaq.com/the-product
User ...704,
Thanks for the link. It will be interesting to see how they do.
I suspect the IAQ in kitchens (without gas ranges) is almost entirely reliant on occupant behavior. Some people don't grill or stir fry regularly. Most people with hoods don't use them. Ventilation rates in houses vary wildly. Your set up might yield really good results for many users. Like much advice given here, the suggestion to vent outside comes from the average experience.
@Malcolm - That's precisely the issue. As Designers, Builders and ventilation professionals, we don't know who's going to accupy the building in the future. We also don't know who will be the following owners, therefore is up to the building professionals and the original owner to do the right thing and as the codes mandates.
Armando,
I agree with you entirely. For related reasons I try and talk my clients out of overly customizing their houses to suit their unique needs, of too closely following current architectural fashions.
Much like bathroom fans in the past, I think the main impediment to the use of range-hoods is the noise they make. All the worries about flow and capture area don't mean much if people won't turn them on.
They're noisy, and they don't work that well. Or at least they don't seem to work that well. The capture rate is low enough that they don't seem worth using.
My testing with respect to VOC and PM2.5 points to a minimum of ~15 lbs of activated carbon, 1.8" thick, over 900 square inches of surface area at 100 CFM if you're trying to "scrub" just 100 CFM of air flow. This is specific to wild fire smoke, but your challenge is similar. Manufacturers of activated carbon suggest keeping humidity as low as possible to avoid clumping the media which is going to be pretty difficult for a kitchen exhaust. It's far easier to vent (and likely a lot cheaper) to vent as required vs building an effective scrubber.
Dennis,
I hadn't even considered the humidity.
Years ago we had odor issues with a plumbing vent on one of the cabin roofs at a resort I did a lot of work for. We bought a cap for the stack which was supposed to eliminate the problem by passing the air through activated charcoal. It worked for about three days before it became saturated. I bet the filter medium on a kitchen exhaust would be similarly short lived.