Experience with Miele recirculating range hood?
My clients have chosen a Miele DA 2920 recirculating range hood. My advice is always to vent to the exterior but they really don’t want a hole in their wall; the house very nearly meets Passive House criteria and they don’t want to deal with makeup air.
They will have a professionally designed Zehnder ERV with an extract point 10′ from the range; the range is induction, and they don’t cook greasy foods etc.. I still recommend venting to the exterior, for all the reasons it’s a good idea, but they asked me to research whether this specific hood, which includes both a stainless steel filter and a washable rechargeable charcoal filter, will be good enough.
They said their research shows that it’s a popular model or technology in Europe, which often (but not always) means superior quality. Does anyone have experience with this type of or specific range hood?
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You're still spreading around around whatever got airborne from the food. The filter will catch things like grease droplets, but it won't do much, if anything, for smells, smoke, etc. The carbon filters tend to clog up pretty quickly and lose their ability to do chemical filtration, so they may still pass air through just fine, but the smell-filtering ability will be gone. Typical charcoal filters in these are just relatively thin sheets so they don't do much for long.
Using induction at least means you don't have to deal with combustion byproducts from a gas cooktop, which you CANNOT filter out with a recirculating hood.
I would advise them that they should really vent to the outdoors. If they're really concerned about passive haus levels of air sealing, I would recommend a GOOD power damper interlocked with the vent hood, so that the damper is only open while the hood is running. Power dampers tend to seal much, much better than the more typically used spring-type dampers that open from airflow alone.
The carbon filter is a lot better than nothing (the stainless "filters" mostly just catch relatively large grease droplets), but it's far inferior to venting the unit outdoors.
Bill
Oh believe me I have done my best to convince them (well, him) and he has been responsive to almost all of my suggestions, but he's very hands-on and very smart and is doing his own research on pretty much everything. He knows that venting to the outdoors is best, it's simply not an option in this case.
So now I'm trying to see if this specific hood would work as well as he said his research says it will. He said the charcoal filters in this model (or product line) are not the same as typical charcoal filters; I know that conventional ones don't work. I've spent enough time trying to find solid answers online so I thought I'd look here for people with experience with this specific type of hood and filter.
I didn't realize it was you when I posted that response -- you probably already knew most of what I said :-)
There are two kinds of activated carbon water filters (granular and block), but, AFAIK, only granular carbon filters for air. The primary thing that's going to determine how well those work and last is the thickness of the air filter cartridge. If it's the typical 1/2" or thinner, it's not going to last very long. It should seal around the filter reasonably well too. The problem is that when the activated carbon "fills up", it stops filtering, and it can fill up with chemical compounds it's filtered out before it looks "filled up" from things like lint and debris.
I suppose my primary concern would be the longevity of that carbon filter, and it's probably not very much. How easy it is to replace is another concern. No one is going to bother replacing it if it's really hard to access, in which case it might as well not even be there.
Most of my fancy filter experience is with water filters, but I'll have a look at that Miele unit and see if anything looks interesting and let you know.
Bill
Thanks Bill. I'm always happy to revisit the basics, and I have no experience with carbon filters--I'm usually successful in my quest to vent outdoors--so this is new territory for me. That's very interesting about the two types of carbon filters but it makes sense. We have what I assume is a carbon block water filter in a pitcher to deal with the PFAS in our drinking water, until we get a whole-house filter, which is probably carbon as well?
The datasheet is pretty sparse, only a few bullet points and the lines of text don't even stretch across the entirety of the page. Not much for me to go on.
From what I did see, it's activated charcoal, which would be a granular-type filter, a little like a bunch of gravel in a bag. That's typical of these types of filters. It appears to be fairly thick, which is good -- usually I see a sort of "stretched flat bag" arrangement, with a layer of filter material only about 1/4" thick or a bit more. The Miele unit appears to have quite a bit more filter media in it than I'm used to seeing, which is a Good Thing here. They also appear to have designed their filter cartridge to be relatively easy to replace, another Good Thing. I always like when manufacturers appear to have put some thought into the practicality of their products, and that appears to be the case here.
I don't believe their "three year" life rating, but that would depend on how much the system is used. Do a lot of deep fat frying making smoke, get a lot less life on that filter than if you just steam some veggies every other week. More stuff going through the filter means a shorter life. Activated charcoal/carbon works by having huuuuge surface area, since the baking process opens up a bazillion tiny pores in the material. That huuuge surface area and all the tiny pores are what trap the contaminants. You can regenerate the material by baking it and releasing the trapped material, but I've never thought that gets you 100% back to where you started (i.e. the material still gradually degrades, you can just buy yourself more time).
If your client is adament to go with this and no outdoor vent connection, I think this Miele unit is at least well designed to do the best you can with what is basically a bad situation. I'd warn the customer that everything depends on that filter cartridge, and how long it will last depends on lot on what kind of cooking they do and how often. You might also want to keep a spare cartridge on hand, since this isn't likely to be something you can pick up at a box store when you need a replacement.
BTW, the water pitchers like the Brita et al tend use granular carbon filters, not carbon block filters. Carbon block filters are solid blocks of activated carbon, not little granuals like gravel. It takes more pressure to force water through a carbon block filter compared to a granular filter. The block type filters tend to be better and filtering more stuff out though. You tend to find carbon block filters on reverse osmosis systems (although I've seen granular filters used with those systems too). A typical basic RO system will have a carbon block filter on both sides of the RO membrane, so you have three cartridges. Some systems add a fine particulate filter, typically a spun yarn type of filter, ahead of the first carbon block to protect the carbon block. Some systems add additional filter cartridges downstream of the RO membrane too.
I highly recommend a small RO system if you want really clean water to drink. Small systems can fit under your kitchen sink. Do yourself a favor and hook your fridge's ice maker up to the RO water if you have such a fridge, since that avoids the need to use (and replace) the fridge's own filter -- just leave the bypass plug in place. You get awesome super clear ice cubes that way and less maintenance to deal with. Get a decent size pressure tank downstream of the RO system, which will make the system much nicer to use. I use a 14 gallon tank in addition to two small 1.5 gallon tanks (I added the larger tank). If you like coffee, for example, you want to make sure the system has enough water to be able to fill your coffee pot at full speed, so you need a big enough tank to hold enough water in reserve to maintain pressure while you fill stuff. RO systems are slow to make more water, usually 10-20 gallons PER DAY, so that pressure tank full of RO water is what supplies you when you turn on the little faucet. The RO membrane then gradually refills that tank over time.
I find that using RO water for things like coffee makers and tea pots makes those things last forever -- ZERO mineral buildup. Same for the fridge. You'll want a TDS meter (cheap to buy), since the RO membrane will eventually wear out, and the TDS reading will increase when that starts to happen. There is no need to replace the membrane on a fixed schedule, just monitor it with the meter. A fine particular filter (I use a 1 micron spun filter) ahead of the first carbon filter ahead of the RO membrane does most of the work, protecting the much more expensive carbon block filter cartridges. RO systems can filter out all kinds of things (even the sodium ions from water softeners, which always impresses me), but you can add a deionization filter after the RO membrane if you want lab-pure output water. That gives you an RO/DI system. Usually you don't need that much to get clean water, but if you know what you want to filter out of your water, you can look up what the RO membrane itself can filter, and determine if you need to add the DI cartridge or not.
I love my RO system. I find that I use RO water as a cleaner all the time since it evaporates cleanly away leaving no residue behind. This cuts down on my need for solvent-based cleaners, which I suppose is an extra green benefit to the RO system. You can use the RO's waste water to water plants if you don't want to just run it down the drain.
One last thing: if you have low(ish) water pressure, a booster pump can really help an RO system to operate more efficiently, and can also give you better delivery pressure at the little RO faucet.
Bill
Awesome advice, thanks Bill! I guess our current pitcher-type filter is granular-style; it operates like a Brita, just slower and is supposed to remove PFAS. If I weren't in the middle of several other home renovation projects I would prioritize the setup you recommend. Our water pressure is decent, even though we're on a well, but I like the idea of adding a second pressure tank. We don't use much ice and our PFAS levels aren't terribly high, but it would be easy enough to add the fridge to the system. Thanks again.
I checked the specs and the special part about this hood is that there is indeed an activated carbon filter available, and it's "rechargeable" by heating it in an oven: https://www.mieleusa.com/e/reactivatable-longlife-airclean-charcoal-filter-dkfs-31-r-11793540-p. I didn't know enough to search for that term before. Thanks for your help!
Check out comments 10 and 18 in this article.
https://www.greenbuildingadvisor.com/article/can-a-range-hood-and-an-erv-be-integrated
Kyle,
What do you make of my response in comment #19 - particularly the imbalance between the air being sent to the mechanical room by the hood, and the amount being exhausted by the ERV?
Malcom,
I agree with your comment. I don't know that the ERV is actually contributing much, I think it is the quality of the filtration.
Very interesting! I like the idea of building a large filter box in an adjacent space. In this case the range is on an exterior wall with no usable space below, but the ceiling has deep open-web joists where a filter box could go.
Just make sure you can access the filters!
I think my client will go with the Miele unit with built-in filtration, but I'll keep this idea in mind for the future, definitely with good access for the filters.
I have a client in a historic condo building that has a Vent-A-Hood that has filtration in it to recirculate. They were not allowed to penetrate the wall to vent out. I've been very impressed. The Vent-A-Hood fan and catch tray is loads better than any stainless mesh filter I've seen. They are heavy cooks and I needed to adjust some lighting on top of a cabinet near the exhaust a month or so ago and there was none of the expected greasiness that would normally be there.
I can't remember the exact model but from their site it is an ARS system hood.
https://www.ventahood.com/index.php/about/innovation/ars
The Miele looks like a very slim profile and it does not look like there is a similar profile Vent-a-hood but they do make an insert in the ARS line.
Good information, thank you!
That is too bad your client won’t listen to you and vent outside. All to be able to say he has a “passive house”… This bothers me, but anyway… if they insist on spreading around toxic cooking pollutants in the living space, I’d definitely suggest additional air purification!
I decided to get Blueair devices once we are able to move into our new home. I just got one to test out now and it’s quite nice. Your client could get some of these, it’s not a bad idea after construction anyway since the IAQ won’t be great at first.
They are a bit large, but at least they look decent. I got this one for the bedroom: https://www.blueair.com/ca/air-purifiers/blue-pure-411i-max/3538.html?
I’m fairly certain, not 100% though, that the Miele hood on its own will not be sufficient if your client is at all interested in a healthy breathing environment. I have AirThings view plus monitors and if your client insists on a recirculating hood you should urge them to get an IAQ monitor like this in case the air ever gets really unsafe. https://www.airthings.com/en-ca/view-plus
Also I would definitely choose the Vent-a-Hood recirculating over Miele. I found Miele hoods pretty poorly designed.
Thanks, but they actually don't care much about the Passive House label, they want exceptional performance, and part of that is controlling air flow. I just used the Passive House label to explain the performance level.
The ERV extract point is nearby and they plan to use it on boost mode when cooking, which will help. I've also suggested an air quality monitor and if they find that particulate levels are consistently high, they may decide to vent to the exterior, but they want to try it this way first. He mentioned getting a standalone air purifier similar to yours, or maybe I suggested it.
It might be a good idea to interlock the HRV's boost mode with the vent hood, so that the HRV goes into boost mode automatically whenever the vent hood is running. If you add a small 24v control transformer to the vent hood in parallel with the vent van, you can then use low-voltage thermostat wire to run to the HRV and use a relay to trigger boost mode. Easy, and automatic.
Bill
That's a good idea, Bill. Thanks again.
Years ago, while working on a project with a large integrated design firm, the architect's engineer told me he had a "two button push rule". The rule went basically as follows "anything requiring more than two button pushes to activate won't be used". I find that is often the case, so simple automation systems can really help useful systems to get used more often.
Bill
Haha, that's a good rule!
I have a similar one for kitchen design: I want to be able to access anything I use daily with a single motion--i.e., opening a door or drawer, NOT opening a door then pulling out a tray, though that would be ok for things accessed weekly or monthly.
I'll give you another idea then that you'll probably like:
I have a customer with a large pantry in their kitchen that has swing out doors with shelves on each, so the the doors are maybe 6-8" or so deep. On the inside edge of these doors, I ran vertical LED strip lights, so that when the door opens (there are two doors that open in opposite directions, a left and a right door), the light strips on the doors face into the deeper main shelving area within the pantry.
The neat part is I used some magnet switches (like you'd use with an alarm system on a windor or door) and a simple control setup I designed, so that when you open the door, the light on that door turns on automatically -- no seperate light switch needed. The customer loves that opening the door also turns on the light, and since it's a push-latch type of door, you can bump the door to open it while your hands are full, so you have a complete hands-free setup.
The only downside that was reported back to me was that the dog likes to sleep against the door, sometimes pushing it enough to unlatch it, which also opens it enough to turn on the light. I could work out a way to prevent this, but the customer hasn't been very concerned.
Bill
Those are good ideas!
For many years now I've been thinking about writing down my thoughts on why clever built-ins and details are part of "green" building. They save space and materials, and make life more enjoyable.
Some simple automation like the automatic light switch adds "greeness" by cutting down on lights being left on by accident. Energy code already requires occupancy sensors almost everywhere now in commercial buildings. I think occupancy sensors in residential structures would be very annoying, but there are simple tricks that can help. I really like my Lutron Caseta system as one example, since I can schedule all kinds of timers for things -- no forgetting to turn stuff off that way!
I'm a big believer in finding simple ways to accomplish things like this. Simple is easy, often cheap, and not difficult for people to learn to use (if they even have to, in the case of automation).
Bill
The one I really like but never seen around here is the switch by the door to turn all lights off. So simple and effective. It is also not that hard to do as now most places have lighting only circuits because of the number of pot lights in a new build.
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