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Community and Q&A

Point source ERV (or HRV) and mixing

VapourOpen | Posted in Mechanicals on

In my home, the whole basement has been renovated from a leaky post ww2 bungalow(Southern Ontario), making it much tighter than it used to be. The ventilation on the main floor is and has always been old, leaky and sufficient, but it is the basement where IAQ needs improvement.

With a forced air HVAC, Dr. Lstibrek says that mixing occurs anyway in supply/exhaust and balanced systems in this great article (if i read this correctly):

Could a centrally placed point source ERV in the basement be just as effective at improving IAQ as a Multi-point HRV with partial connection to the air handler since mixing occurs anyways, especially if you don’t have an ECM motor?

Could 1 point source ERVs on each floor in a small home such as the Panasonic model be a viable alternative to a traditional HRV balanced system

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  1. mackstann | | #1

    Several of the reviews on Amazon mention successfully using the Panasonic WhisperComfort to get fresh air in a basement.

  2. GBA Editor
    Martin Holladay | | #2

    If perfect distribution of ventilation air is important to you, then you should install an HRV or ERV system with dedicated ventilation ductwork. Such systems can be very expensive, but they provide the best distribution of ventilation air.

    Many homeowners are happy with less expensive systems, including exhaust-only systems, central-fan-integrated supply ventilation systems, or systems using the Panasonic spot ERV. It's your choice. You get what you pay for.

    Remember, your furnace fan won't be on during the swing seasons (in spring and fall). If you want to use your furnace fan to mix your interior air, you will have to leave the furnace fan running all year long -- and that uses a tremendous amount of electricity, unless you have a furnace with an ECM blower.

    For more information on ventilation options, see Designing a Good Ventilation System.

  3. VapourOpen | | #3

    Unfortunately, in this existing house, dedicated ducting for exhaust and supply are not possible, I can't get either to supply to the bedrooms, there is no space to do so, however common hallways are assessable. so i have to go with a different option rather than totally dedicated.

    I am choosing between the dedicated exhaust HRV versus the point source, and am not convinced which would be a better choice. My furnace is exhaust type.

  4. jinmtvt | | #4

    Out of curiosity, what is the mixing speed of "used" air in a steady sate room ? ( co2 etc.. )
    I know i read somewhere here in the past , that the ovygen moves very quickly through diffusion??

    was wondering how much effort should be put toward mixing fresh air in all rooms etc..

  5. VapourOpen | | #5

    If you ever slept in a room with no exhaust, and wake up the next morning, the air is sometimes stuffy as airlfow is minimal. Diffusion is associated with vapour flow through the air, and contaminants other than oxygen is what you want to get rid of.

    There is no purpose exhausting fresh air intentionally, so it must be mixed with the ambient air to disperse the "freshness" to other areas of the house someway. This is the concern i have with point source if airflow at the source is not mixed. I think mixing is very important.

  6. VapourOpen | | #6

    If furnace without ECM mixing causes a huge electricity penalty, is there way to run it on a timer so that the furnace air runs x minutes per hour?

  7. GBA Editor
    Martin Holladay | | #7

    I'm pretty sure that you can use a FanCycler or an AirCycler to program the operation of your furnace blower.

  8. ntisdell | | #8

    Also a lot of thermostats by honeywell allow for setting the fan to cycle on for a bit each hour. if you have interest in getting a Wifi thermostat the newer ones have both features. (along with remote temp alarm emails and remote checking of temp/schedule)

    although it wouldn't allow for adjusting the duty cycle - its just fixed (i think 15min per hr)

    so depending on the design that might not be enough for your needs.

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