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Decentralized ventilation shortcomings?

Markiz_von_Schnitzel | Posted in Mechanicals on

I have read all of the articles here, and of the article comments and all of the Q&A posts and replies. So it’s safe to say I have all of the info. But, it might have been to much info to make a confident decision when choosing a ventilation system.

Decentralized systems seem really great to me.

much cheaper. For my planned 1900sqft house, a Zehnder/Paul central ventilation system is ~10000$ installed price. Lunos sytsem with 3 pairs of e2 and 2 egos installed price is ~4500$.
granular control. I guess not as important and prone to human error, but nevertheless, I personaly see it as an advantage
less space taken. Central ventilation with flexible plastic ducting would take an additional 3 inches vertically, and a couple of m2 in the utility room.
much easier installation. At least in my case. Some of the work we could do ourselves, for the stuff we can’t, it’s easier to find.

not as quiet (?). Looking at datasheets, Lunos e.g. produced only 16.5db in the lowest setting, and only 26db in the highest setting. My laptop when in load produces 35db, and I don’t find it annoying loud, not even at night.
– granular control. I can see how it’s a con. It’s not as KISS. For example, if there was smoke outside, and I wanted to turn of ventilation, I’d have to do it on 2-4 places, instead of one. I don’t see that I’d do it that often though.

– efficiency is of no concern to me. It’s similar enough not to make the difference.
– cost-effectiveness is likewise not important to me. It’s simlar enough in both cases (neither is probably cost effective in a reasonable timeframe)

Are there any more important reasons to go with the much more expensive central ventilation solution, even when dealing with a new build (clay brick)?

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  1. Markiz_von_Schnitzel | | #1

    I did read the following complaints in 1 review by the company that has a steak in CENTRAL HRV ventilation, so not sure how much of it might be true.

    -energy efficiency and CFM rate is fake and is at least half of claimed

    Because it's measured by EN308 and not PHI, it's not corroborated enough. Also, and this does make some sense: if a pair of Lunos e2 fans keeps switching directions, and we have set them to cross ventilate a bigger room, they will 50% of the time just be moving interior polluted air from one side to the other, instead of bringing claimed CFMs of fresh air inside the house. So the ACTUAL CFM is on average half of claimed by Lunos.

    - most of the time, it's hard to achieve good ventilation, because of similar issues in previous point. Basically, they say it's hard to actually extract used polluted interior air, and that through-wall ventilators like the Lunos at least half of the time just move stale air around.

    - price is similar to central.
    This one I know is not true, because I have offers on both. Lunos system, as I said in my OP, is at least 50% cheaper. It's a big difference. And the article is made by an owner of the company from which i got the central ventilation offer. So he is in similar geographical location as I, prices are similar. I could understand if he was in USA

    A pair of Lunos is ~650$ here + commisioning is ~70$ per pair. Drilling holes and bringing electricity, I am not sure, but this I could do myself.

    With central, I need a lot of extra EPS, and I also need a lot of holes, in both interior walls and also concrete.

  2. mackstann | | #2

    Filter maintenance: Cleaning/replacing one central filter is easier than several spread out through the home.

  3. Markiz_von_Schnitzel | | #3


    Yeah, forgot to mention this.

    Though, how often does one does that? Once or twice a year? It's definitely something to think about for someone who really wants minimize all distractions, but this is not something I personally would mind much. Because currently, ventilating using windows is a much, much greater undertaking, so even having to mind 8 filters is a vast improvement in comparison :)

    I keep hearing that decentralized systems, like Lunos or ComfoAir 70 or other similar systems, are only ever used in remodeling. So there has got to be a bigger reason I am missing. After all, mechanical ventilation is only a recent development, it's not like there is a tradition of centralized ventilation systems. I am currently looking for new builds that have it and people who are willing to share subjective experiences. Those would be valuable.

    Not to mention that there are now "copycats" of Lunos, like Marley HRV ( ), at half the price still.
    I would not go for this specific one, as it's much louder (3db at the lowest setting, which is double?), but I've been to houses where ventilation is sorely needed and where at the same time background noise from all the appliances is probably louder even than those 19db.

    1. this_page_left_blank | | #5

      3dB is double the sound pressure level, but human hearing is logarithmic. 10dB is a perceived doubling. 3dB is noticeable, but pretty modest. Given the different ways they can be testing it and reporting it, I wouldn't even count it representing any real difference. If it was the same manufacturer, sure.

  4. this_page_left_blank | | #4

    As for price, you're comparing just about the most expensive option in Zehnder. I'm sure you can find options on distributed systems that are much closer to the Lunos price.

    1. Markiz_von_Schnitzel | | #6

      You would think that, but not really. At least not here in central Europe that I can find.
      AFAIK, all of them (including Zehnder) are using exchanger cores made by Paul, so prices are very similar.

      Ducting and labor is the same.

      Where I live, I only have Zehnder, Paul and Helios available, and they have very similar pricepoints.

      I did hear that maybe I could find Mitsubishi Lossnay devices, but AFAICT, not officially.

      1. this_page_left_blank | | #13

        I'm sorry, I assumed you were in the US (because most on here are, you quoted prices in $ and cited two commonly mentioned brands).

        I'm even more shocked you don't have more options there. The Passivhaus Institute lists literally dozens of HRV/ERV manufacturers in Europe. Jablotron is in the Czech Republic, although I'd be surprised if their unit is cheaper.

  5. STEPHEN SHEEHY | | #7

    We're pleased with our Zehnder HRV. It's quiet, efficient, and was easy for our electrician to install. Mounted on the ceiling in the mechanical room, it doesn't take up much space. The boost switch is something we use a lot. The two MERV 13 filters are replaced in seconds. It was expensive, i.e. about $6,000 or so, installed about three years ago. We're glad we decided to spend the money.

  6. shorowit | | #8

    We have 2 pairs of Lunos e2s, installed as part of a retrofit. We've been pretty satisfied with them, but one thing to realize about the sound level is that it is not constant. Rather, you will hear the fan slow down, stop, and then speed up every minute or so. We've become accustomed to it so don't notice it anymore, but we noticed it when first installed it, and any guests will notice it (this is especially true at night when trying to sleep in the bedrooms).

    I recall reading that many people keep their Lunos operating at lowest speed to reduce noise level. We do this as well, so we're only pushing 20 cfm, though this is fine for our upgraded 1960s ranch home. But even this 20 cfm is not equivalent to a 20 cfm centralized system. Decentralized systems rely on air mixing so as to not keep moving the same slug of air back and forth and thus should be considered less effective than centralized systems.

    We went with Lunos because it was relatively cheap for our retrofit situation and wanted to avoid running ducts through the attic (we were considering cathedralizing). Now that we've decided not to cathedralize our attic, if we had to do over again, I might opt for a centralized system. We're satisfied with the Lunos, but would probably be happier with a centralized system.

    Long story short, my recommendation to others is to only pursue a decentralized system if you're planning to move the target amount of air on lowest setting. Probably not ideal for a larger Passive House, but could be fine for a smaller Pretty Good House.

    1. Jon_R | | #14

      > Decentralized systems ... should be considered less effective than centralized systems.

      Let's see the data on this claim. I expect that any connection of door size or larger will have an insignificant effect on air quality.

  7. Jon_R | | #9

    > they will 50% of the time just be moving interior polluted air from one side to the other,

    I don't understand where this claim comes from. Whenever the fan is running, it is exchanging air with the exterior.

    1. Markiz_von_Schnitzel | | #10

      Yes, but if there are two fans, a pair, and they are in sync, as others have also pinted out, only one of them will be supplying fresh air. So if each is set to 20cfm, you don't get 40 cfm, just 20. Or?

      1. Jon_R | | #11

        My guess is that like traditional ERV/HRVs, the CFM rating is for the system as a whole (ie, a pair of fans).

        The eGo model spec is clear "3/12 CFM with heat recovery / 27 CFM in exhuast mode".

        1. Markiz_von_Schnitzel | | #12

          Hm, yeah, but.. Systems like TwinFresh, they can also work each by itself. Meaning, they don't have to be balanced. And they are rated with similar CFM as Lunos. Syncing is optional with them, so I would reckon they would give the single fan CFM rating.

          In any case, it's something that i should investigate further.

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