How efficient are recirculating kitchen range hoods with carbon filters at removing air pollutants from cooking?
dvaut
| Posted in Mechanicals on
I looked at a few of these filters for the recirculating range hoods and they didn’t look all that impressive, but maybe I am looking at the wrong hoods. If passive houses are using recirculating hoods how well are the hoods actually working. Clearly there is a tradeoff for energy efficiency and range hood function. Is there any specific data on this? Are there certain types of carbon filters that work better than others? I am not talking about removing moisture or CO from gas ranges but more grease and other pollutants produced when cooking with electric ranges and ovens.
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Replies
Dillon,
There is no doubt that a range hood fan that is exhausted to the outdoors is more effective than a recirculating range hood with a charcoal filter.
People who are happy with a recirculating range hood are usually vegetarians or people who cook rarely. If you cook a lot, and you like to cook meat, a range hood fan ducted to the outdoors is what you want.
Dillion,
Martin recently did the math on make up ventilation air (following up on math done by John Rockwell of Zender) here: https://www.greenbuildingadvisor.com/blogs/dept/guest-blogs/siding-and-interior-finish-work-new-hampshire#post_comments . With a reasonably sized range hood your energy cost would be under $1 a day and well under that most days. My take on that is get a reasonably sized stovetop, and an appropriately sized exterior vented range hood for it.
We have a recirculating hood, cook substantial meals every day, and although we do make lots of vegetarian meals, we also cook the occasional steak. For us the recirculating hood works just fine. I especially like not having a big hole in my wall for the exhaust and another for the make-up air.
What we don't do is deep fry stuff or generate much smoke. Typically we saute in a little oil or bake. When we do generate a little smoke or lots of water vapor, boosting the hrv seems to handle it fine.
The giant restaurant style cooktops that need massive fans are, for most home cooks, overkill.
Dillon,
You may find this article useful:
https://www.greenbuildingadvisor.com/blogs/dept/green-building-news/hazards-cooking-gas
As someone who just cooked dinner under a recirculating carbon filtered hood (installed by the previous owner) with an electric stove, I can confirm that they are much more energy efficient. With a brand new carbon filter, the recirculating hoods are so effective at removing smoke that most of the time we do not have to turn on the fan, which saves lots of electricity vs. vented hoods. A few design items for a successful installation:
1) make sure your town fire marshal is ok with you installing heat detectors instead of smoke detectors throughout your house
2) make sure you have lots of operable windows throughout your kitchen, and that your kitchen can be closed off / isolated from the rest of your house -- better still, you put your kitchen outside of the rest of your house (note this has the added benefit of decreasing the temperature in your kitchen, increasing the efficiency of your refrigerator, saving even more electricity)
3) pre-run ducting so that the second time you cook you can use your newly purchased and installed vented hood while you curse the person who decided to save $100 on a non-ducted hood
Of course, given all the appliances making kitchens are the most expensive room in the house, you may save money (and lots of heating efficiency) forgoing a kitchen altogether and doing takeout
Recirculating hoods are probably okay if you have an induction range (electro-magnetic) because the 'burners' on an induction range do not emit heat that needs to be evacuated along with the smoke and moisture. The only caveat to induction is that your cookware must be cast iron or stainless steel (hold a magnet).
http://www.prolinerangehoods.com/1-801-973-3959/support/what-size-range-hood-do-i-need/#ducted
@Stephen. Which recirculating hood are you using?
We are planning for the next house and considering a recirculating exhaust for the electric oven. (The house will be all-electric like the current one.) We are not big-time foodies, so I don't imagine creating too much smoke or moisture while cooking. It's also likely we will install a Zender or similar air system.
Steve- I just checked and there is no label on it, so I don't know what the brand is.
We cook every night, but don't generate much smoke. Frankly, we a lmost never use the hood, relying instead on the HRV boost. We h ave an induction cooktop.
Thanks, Stephen. I have some time to weigh the options, but it is good to know that ductless will probably work if properly implemented.
I kind of second what Steve wrote. We have electric cook top, and a recirc. If something burns a bit and we have a tad bit of smoke. We turn on the bath fan to assist in the downstairs bathroom and we crack a window on the other side of the stove. It clears out in five minutes. This is about a three time per year event IF that. On my new build I am installing a 36" hood made by XO that has a custom wood surround to match cabinets. It has three settings, 100,200 and 300 CFM. I expect to need the 100 occasionally and it is ducted via a 6" round hood with a damper. We are also installing an induction cook top. Our new house has a very convenient covered back porch where I will place my amazing infrared grill made by TEC. The grill itself is worthy of a blog post but suffice to say if I want an occasional steak, or chop, I am happy to think I can more easily grill outdoors year round in the future. In the past I have brought my grill indoors to the garage in winter because I did not have such a set up to step out into the porch to grill. If you need a small hood, there are some out there that will only draw 100cfm so good luck looking.