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Fresh Air Ventilation – NASA CO2 “Scrubber” Instead of HRV/ERV

T_Barker | Posted in Green Products and Materials on

Instead of using an HRV/ERV for “fresh air” ventilation, is anyone aware of any CO2 “scrubber” units being used in residential construction?

Same technology NASA uses in spacecraft to remove CO2 from the environment for the astronauts.

Assuming CO2 is the primary reason for fresh air (ignore VOC’s for a minute), this would eliminate the need to bring in outside air. Change the scrubber filters once in a while, and eliminate the need for HRV heat exchanger, ducting, energy wasted running the HRV, etc.

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  1. Trevor_Lambert | | #1

    I don't know the answers, but a couple of guesses:

    If such a device is available, it's going to be a lot more expensive than an ERV. This is a guess, but I'm pretty confident about this.

    Why are you ignoring the VOCs and other contaminants for even a minute? Unless you have a way of scrubbing every one of those, you're still going to end up needing to bring in fresh air.

    Even if you manage to scrub the CO2 and all the other contaminants, where are you getting oxygen from? NASA uses oxygen tanks, so I imagine you'd need the same thing.

    Add all of the stuff up, and there's no way you're going to come out ahead economically. Ask yourself this, what does NASA, who have this technology at their disposal, use in their buildings here on earth?

    If you want an economical scrubber that removes both CO2 and VOCs, as well as delivering some oxygen, check this out:
    I don't think it's going to replace ventilation, however.

  2. T_Barker | | #2

    I'm not sure about price being an issue. This technology has been used for over 50 years so it's had time to become commercialized. Just like Kevlar, now used widely in canoes, flack jackets, etc., and the $3 emergency "space blanket" I carry on hunting trips.

    I wanted to temporarily ignore VOC's to simplify the discussion and hopefully avoid the automatic naysayers...

    Good point about the oxygen levels. I don't know, but maybe if the CO2 is scrubbed, then the amount of "new" oxygen required would be minimal and would already be supplied by the HVAC system.

    Fill my house with plants, lol. Good one! But now I'd have a major humidity problem.

  3. Trevor_Lambert | | #3

    You were concerned about having too little humidity. Seems like the house plants could solve that problem, while reducing the amount of mechanical ventilation required, saving heating energy. Just limit the number of plants such that the humidity is not too high.

    If your idea was to substitute ERV with the scrubber, then what in the HVAC system would be supplying any oxygen at all?

    1. T_Barker | | #5

      When the HVAC heating or cooling is called for then new oxygen would enter the house. I have no idea what the numbers are, or if this would be enough.

      1. Expert Member
        Peter Engle | | #6

        The HVAC system doesn't create new oxygen or bring it into the house. That is unless it is hooked into an outside air system. Most HVAC systems just circulate what you've already got, good or bad.

        1. T_Barker | | #9

          I was assuming if you didn't have an HRV, then your HVAC system would be connected to outside air.

  4. mackstann | | #4

    I did a google search for a CO2 scrubber and couldn't find any consumer units for purchase.

    The closest thing I found was this monster which only serves a single room:

    Looks like a dead end to me.

  5. AlanB4 | | #7

    "Good point about the oxygen levels. I don't know, but maybe if the CO2 is scrubbed, then the amount of "new" oxygen required would be minimal and would already be supplied by the HVAC system."
    Are you nuts?
    If you remove CO2 and your house is airtight then you will eventually run out of oxygen. Just to clear up any misunderstanding without oxygen your body cannot produce enough energy to keep you alive. Then you die.

    Oxygen comes from photosynthesis which is done by plants, green algae and cyanobacteria. HVAC systems contain no oxygen creation ability which would require either nuclear fusion, nuclear fission or Star Trek style matter/energy replicators

    1. Expert Member
      MALCOLM TAYLOR | | #8

      " or Star Trek style matter/energy replicators"

      Now we are getting somewhere!

      1. AlanB4 | | #13

        Yup :D
        We should think out of the box but we do need to understand the reality of what we are dealing with.

    2. T_Barker | | #10

      I'm assuming if you don't have an HRV, then your HVAC system would be connected to outside air.

  6. T_Barker | | #11

    I knew this would degenerate into a naysayers conference.

    Mark my words, 50 years from now they'll look back at our building systems and laugh hysterically at us. "Those idiots built two or three completely separate ducting systems through their entire house. One system brought in cold air and tried to heat it with some Mickey Mouse contraption before replacing the mostly good warm air they just threw out the other vent. In the meantime a completely separate system generated its own heat and blasted it through pieces of tin cobbled together on site where they cut holes in all of the structural elements of the house."

    1. Expert Member
      MALCOLM TAYLOR | | #12

      T. Barker,

      You may well be right, and no doubt our current systems will seem as primitive and antiquated as the ones installed 50 years ago, but that in no way makes what you are currently suggesting any more realistic.

      1. AlanB4 | | #14


    2. AlanB4 | | #15

      "I'm not sure about price being an issue. This technology has been used for over 50 years so it's had time to become commercialized"

      "I'm assuming if you don't have an HRV, then your HVAC system would be connected to outside air."

      "When the HVAC heating or cooling is called for then new oxygen would enter the house. I have no idea what the numbers are, or if this would be enough."

      You don't even understand the problem yet proclaim solutions that "should" exist but don't.

      The future will be different then what we envision but wishing things into existence does not make them so. You can't violate the laws of physics but you can work with them and we can further understand them. If someone invents technology that can use energy to convert CO2 to O and remove VOCs and particulates then thats great. But scientists take current understanding and work with it to invent new technologies not concepts that make no sense.

      And the old rule says we can live 3 minutes without air, 3 days without water and 3 weeks without food. This is not exact but a referent to work with, we can't hold our breaths for your proclaimed 50 years before we use modern technology (and who decides at what level technology is ready for use?). We can only use what we have now and keep open minds. If something better is invented then we can either integrate it or use it where applicable.

      An example, i live in a century old very inefficiently designed home, Since it was built knob and tube wiring has long fallen out of favour, natural gas heating became a thing, hot water tanks became a thing, air conditioning became a thing, LED bulbs became a thing, blower door tests and insulation became a thing, fridges, stoves, microwaves, hair dryers, TVs, radios, computers, cell phones and a whole host of electronics devices became invented and put into use.
      All of these can be retrofitted to varying degrees, some require structural changes, some just need some creative placement. Some are very pricey to retrofit and are not done or only partially retrofitted.

  7. GBA Editor
    Martin Holladay | | #16

    T. Barker,
    You wrote, "I'm assuming if you don't have an HRV, then your HVAC system would be connected to outside air."

    There are two types of systems can can be described that way:

    1. A sealed-combustion furnace brings outdoor air directly to the gas burner. This type of outside air duct does not provide any oxygen to the inhabitants of the house.

    2. A central-fan-integrated supply ventilation system has an outdoor air duct that brings outdoor air to the return plenum of the furnace. This type of outdoor air duct will certainly provide oxygen to the inhabitants of the house, but the efficiency of this type of ventilation system is worse than that of an HRV with dedicated ductwork.

    Clearly, if having dedicated ductwork for ventilation gets you all worked up, then you should install a central-fan-integrated supply ventilation system. Unlike a CO2 scrubber assisted by bottled oxygen, a central-fan-integrated supply ventilation system is technology that is available right now.

    1. AlanB4 | | #17

      I am starting to wonder if the OP does not know how non-HRV homes get ventilated.

      No house is airtight, a blower door test can measure the air leakiness of a house and expresses its value in air changes per hour under 50 Pascals of pressure (an artificial but constant value used to compare one house to another). Air movement between outdoors and indoors is driven by the stack effect, pressure differences and outdoor wind. Its uneven, variable and energy wasting.

    2. T_Barker | | #21

      Regarding #1.) I didn't think about the fact that these systems might burn all of the oxygen.

  8. Expert Member
    Peter Engle | | #18

    I think I get a part of what bugs him, and it bugs me too. Here we've gone and made houses that are tight enough and insulated well enough that we can dispense with all of that expensive, space-consuming and leaky ductwork, and just heat and cool our houses with minisplits. But then we realize that we made our houses so tight that they need ventilation, and to do that, we have to introduce a whole new set of (usually poorly designed) ductwork. The whole HRV/ERV thing really is a kluge, and someday, some smart person is going to figure out a better solution. I don't think T. has the right solution, but at least he's thinking outside the box.

    1. Robert Opaluch | | #19

      HRVs/ERVs reduce heating, cooling, and humidification/dehumidification costs (save energy), not just provide fresh air and exhaust stale from chosen locations. Otherwise you could use windows or kitchen, bath and other fans or a balanced fan system to get fresh air, or to exhaust stale, polluted or humid air. What's so objectionable about HRVs/ERVs? Lunos has nice HRV units requiring no extra ducting, if you object to two separate ducting systems.

      If you don't like separate HRV and central heating systems, or two separate systems each requiring ducting...HRV/ERVs can be equipped with a heating element if the building is so very airtight and well-insulated. Or you can use other electrical heating units if you don't want mini splits or a central heating system.

      If looking at out of the box ways to get oxygen into the home, there are supplementary oxygen systems and tanks for those with lung disease or mountaineers who climb the tallest peaks. Maybe the systems that supply those tanks could be re-engineered for supplying homes or larger buildings with oxygen. Or electrolysis allows water to be split into oxygen and hydrogen using electrical current. You could supply oxygen and use the hydrogen to power the house! I'm sure not cost-effectively.

      1. T_Barker | | #25

        Part of the problem is I've worked in the technology industry for a long time, and there are ground breaking, practical devices invented or substantially improved every single week. Then I look at HRV's for example, and they're essentially the same rudimentary contraptions as the 20 year old one in my basement.

      2. T_Barker | | #34

        Interesting that you mention Lunos. Last week I was revisiting the whole Lunos solution. If the details add up (controls, etc.), that's probably what I'm leaning towards. As much as I like the Zender, it just drives me crazy to install that monster in the house.

    2. T_Barker | | #20

      @Peter Engle,
      BINGO! At least one person gets it.

      And I may not have the right solution, but in this thread I have yet to hear any of the naysayers prove that it won't work or that it's too expensive. The technology was invented and used successfully over 50 years ago.

      1. AlanB4 | | #23

        You don't even fully understand the problem, removing CO2 is the only piece of your proposed solution and your pretending the rest of the problem doesn't exist.
        And you seem to believe because the technology was invented long ago it must be cheap now, a fallacy.

        1. T_Barker | | #26

          And you seem to believe that since you probably never heard of the technology until I mentioned it, then it must be expensive. Another fallacy.

          1. AlanB4 | | #27

            I remember in the movie Apollo 13 where they wanted to connect a round shaped orifice to a square shaped one and the CO2 scrubbers were a critical concern. Since i have never heard of it till now i *obviously* just watched the whole movie since your reply.
            I would enjoy seeing a CO2 scrubber that costs less then HRV in purchase price and lifetime operational cost.
            And once again without a source of oxygen if your house is airtight you will not survive.

            Go ahead, prove me wrong.

          2. Trevor_Lambert | | #32

            No one said it must be expensive. I said it likely is.

            Have you heard of the null hypothesis? You're suggesting a device, which may or may not even exist, and expecting someone to prove that it's too expensive. Does that sound reasonable?

            If a technology is one that NASA used in spacecraft, I think it's reasonable to begin with the assumption that if you can find version fit for residential use, that it's going to be expensive. That's the default position that needs to be disproved.

    3. AlanB4 | | #22

      That makes no sense, if you put a ductless unit in a leaky house it will not need an HRV either. Yes it will use more energy but thats the point of building tight. The ductless means nothing in this scenario.
      If the answer is to build leaky so you don't need an HRV then your shooting yourself in both feet, the ventilation is haphazard and your wasting energy the HRV would save most of.

  9. Yupster | | #24

    It may not cover all the bases or be something that's available but it's a fun thought! It is something that could be useful as part of an overall system. While it lacks some of the fundamental reasons for having ventilation such as exhausting moisture and providing oxygen, it's not as absurd as has been implied by some comments. This system can be used to reduce the overall ventilation requirements in commercial applications and is similar to what T. Barker was referencing. While I doubt it would ever be cost effective to have such a system in a typical residential home, it might make some sense in heavily polluted cities where fresh air isn't fresh at all.

    1. AlanB4 | | #28

      Is this an HRV with an air filter?

      1. Yupster | | #31

        Not at all. It's essentially a re-circulating fan with a sorbent that, according to the website, removes CO² and VOC's. I can't testify to it's effectiveness but it is basically a "scrubber".

        1. T_Barker | | #35

          Interesting find. Although they probably haven't tackled residential yet. Tried to call, but can't reach anyone.

    2. Trevor_Lambert | | #33

      From the link:
      " Removing these hard-to-capture contaminants decreases the required volume of outside air ventilation"
      So, not surprisingly, you still need the thing that the OP is trying to replace. You just need a smaller one. There's no pricing information there, but I am willing to take any bets that it's more expensive than the ERV it will not actually replace, but help out.

      Yes, it would make sense to have something like this if the outside air is not very fresh. That's a different application.

  10. AlanB4 | | #29

    I am reminded of a biodome many years ago where they attempted to create a self sustaining system of humans and animals living in an isolated dome with plants and full recycling of resources. I believe it was intended to figure out how to make a contained dome on Mars but they had problems with the concrete affecting the CO2/O2 numbers and were never able to get it working right. If anyone remembers the name of it it would be interesting to see what the final results where.

  11. GBA Editor
    Martin Holladay | | #30

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