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Building Science

Five Ways to Do Balanced Ventilation

Including some you can use to convert an exhaust-only system

An energy-recovery ventilator (ERV) is one way to do balanced ventilation. But it's not the only way.
Image Credit: Energy Vanguard

Ventilation is a great thing. Bringing outdoor air into the home and exhausting stale indoor air . Well, most of the time, anyway. Sometimes the outdoor air quality is worse than indoor air. Sometimes you bring in too much humidity and start growing mold. And sometimes you bring in the wrong outdoor air. But the issue of outdoor air vs. indoor air is a topic for another article.

Probably the most common type of whole-house mechanical ventilation system in homes is an exhaust-only system. You put some controls on the exhaust fans that are already in the home and those fans are set to exhaust stale air from the home, either continuously or intermittently. The problem is this type of system sucks. Literally. And if your house is sucking from an attached garage, a moldy crawl space, or dirty attic, you could be making things worse.

One way to avoid having a house that sucks is to do balanced ventilation. You exhaust stale air from the house and you supply an equal amount of outdoor air directly rather than relying on the negative pressure of the house to bring in the outdoor air.

Here are five ways to do balanced ventilation. I’ve put them in increasing order of cost, complexity, and efficiency.

1. Open the windows

OK, technically I shouldn’t include this one because it’s not a real solution for most homes. This one works only if the home is in a mild climate that needs to little to no conditioning. But if that’s your situation, you don’t need a fancy ventilation system. Just open the windows.

2. Pair a central-fan integrated supply system with the exhaust fans

A lot of homes get exhaust-only whole-house ventilation (fans plus controls). One easy way to upgrade…

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14 Comments

  1. Anders Lewendal | | #1

    small house ventilation
    Allison: Thank you for the article on balanced ventilation. Since we are building tighter homes, I am sure this issue will come up again many times.

    I do have an issue that you might help me with. I volunteer with the city of Bozeman and its Community Affordable Housing Advisory Board. We are collaborating with MSU's architecture department and some local non profits to build some very small, affordable, transitional housing.

    Here's where you come in: These homes are about 170 square feet with a 1 ACH or less. I just finished a house that tested .35 ACH at completion. You can imagine with one person living, showering, cooking in a very small unit that is so tight there are virtually no air exchanges, there are going to be moisture issues. I asked the architecture students where they think all of the moisture is going with only one bath fan. We should consider that the tenant may turn off that fan. A couple of them speculated, correctly, that the moisture would end up in the walls.

    Do you have a low cost solution? How much moisture do we need to remove? Will a Panasonic fan/ERV solve the problem or do they need a more elaborate solution? Opening the windows when it is zero outside probably will not cut it.

    Let me know if you have any ideas?

  2. User avater GBA Editor
    Martin Holladay | | #2

    Response to Anders Lewendal
    Anders,
    An exhaust-only system using a high-quality bathroom exhaust fan like the Panasonic will work. Of course, the homeowners have to use the fan properly. If the fan is disabled or turned off, it clearly won't work.

    The other option is a pair of Lunos fans.

    -- Martin Holladay

  3. Steve Knapp CZ 3A Georgia | | #3

    Question for Martin
    What about the TwinFresh? (I'm not familiar with this products.) It makes a single room ERV and HRV. Both units are low-cost and good to -4 degrees.

  4. User avater
    Armando Cobo | | #4

    Panasonic Whisper ERV family
    IMO, for high-performing houses there is no other choice than ERV/HRVs. Panasonic ERVs are very affordable with wide range outputs, from 40/20 cfm for small houses, to 80-150 cfm ranges for mid and large homes, and the best part is that all are between $250-$500 plus install. Broan has some fairly affordable units too in the mid-rage size.

  5. User avater GBA Editor
    Martin Holladay | | #5

    Response to Steve Knapp (Comment #3)
    Steve,
    I have no direct experience with the TwinFresh products. I agree with you that the prices are low.

    -- Martin Holladay

  6. User avater
    Ethan ; Climate Zone 5A ; ~6000HDD | | #6

    Lunos
    In addition to the Twinfresh and Panasonic Whispercomfort, the Lunos () also has an in-wall solution for HRV functionality. The Lunos units are paired to create a ventilation system. It seems like a great idea, though perhaps not a cost savings (depending on what the ductwork costs.). To echo Anders' question above, I don't see how an HRV can take care of humidity. Minotair has an interesting ERV+dehumidificatino system () but again we are getting into higher cost and higher complexity. I also worry about the fabled toaster+coffeemaker problem (or DVD+TV) problem, which ties two separate systems together making it impossible to upgrade just one, and rendering the system useless if 1/2 breaks.

  7. Jon R | | #7

    IMO, there there should be
    IMO, there there should be more emphasis on "pressure managed" ventilation (vs balanced ventilation). There is potential to improve things, not just leave them unchanged.

    Also note that a HRV can easily cause unbalanced or non-pressure-neutral ventilation. For example, when sharing ducts with an intermittent furnace. Or a supply duct in a room with no return duct.

  8. User avater
    Ethan ; Climate Zone 5A ; ~6000HDD | | #8

    More info on VENTS-US HRV
    I was able to track down the VENTS-US single room HRV at an orange big box store for about $450. Interestingly, it is listed under Hydroponic Gardening - Grow Room Ventilation. Perhaps this has to do with UL listing (just speculating here). It is intersting to compare the VENTS-US website documentation of the TwinFresh Comfo RA1-50-2 with its USA marketing as a grow room ventilator.

  9. User avater
    Ethan ; Climate Zone 5A ; ~6000HDD | | #9

    CERV/Minotair pricing
    Again, back to my toaster+coffeemaker analogy, is there any cost savings to combining conditioning with an ERV system? Or is the impetus to do so enhanced functionality? Could combining these systems be detrimental by creating enhanced complexity and be prone to system failure? The thought of it kind of makes me long for Option 1 (opening some windows).

  10. Jon R | | #10

    If all you need to deliver is
    If all you need to deliver is ventilation air and dehumidification, then combining ducts can be a significant cost savings.

  11. User avater
    Ethan ; Climate Zone 5A ; ~6000HDD | | #11

    what's wrong with...
    What's wrong with a simple (through wall?) ERV or HRV and a stand alone dehumidifier like we used to run in the old days. Seems to me the less ductwork the better.

  12. User avater
    Ethan ; Climate Zone 5A ; ~6000HDD | | #12

    I think I'm talking to myself here...
    But what I find now is that when I factor in all the duct-work, the cost of installing multiple systems, etc, the Minotair is looking more and more interesting for a ~1800SF home, since it should be able to accomplish all the heating, cooling, and dehumidification with little need for the $500 supplemental heater (which I will probably install just for safety). I also have begun to loathe the idea of a split system whirring next to my house, but this has to do with the design and the lack of any "dead" facades which would not be impacted by the outdoor unit.

  13. Malcolm Taylor | | #13

    Ethan
    " the lack any 'dead' facades which would not be impacted..."

    Well done. I hate going to see a new house and finding a throw-away facade you just walk by to get to something nice.

  14. User avater
    Ethan ; Climate Zone 5A ; ~6000HDD | | #14

    worse is...
    A nice home with 2 or 3 mini split condensers stuck to the side that the designer forgot to plan for. I think it is important to consider the visual impact of mechanical systems since we think of the visual impact of most other parts of the house. Imagine if cars were really cool looking except they had the engine bolted onto the hood.

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