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Community and Q&A

Panasonic WhisperSupply vs exhaust-only ventilation

KevinEJ | Posted in Green Products and Materials on

I’ve read here that supply-only ventilation might be a better choice than exhaust-only.

I have a 12×16 art studio/guest room with vaulted ceiling in climate zone 5b (1680 ft³). I’m unsure how tight it will be, we are doing as much as we can with airtight drywall, yet it has weak points like a low-end french door and a few cheap sliding windows.

HRVs like Lunos and TwinFresh are out of budget. I had planned to use a Panasonic bath fan (FV-0511VK2) at it’s lowest setting on a timer. No bathroom, the fan is just for ventilation.

What cfm/air exchange should I be shooting for with this small building?
Would a Panasonic WhisperSupply fan (FV-01WS2 or FV-04WS2) be a better alternative to the bath fan? Or is it something I should consider adding to my existing plan?
Seems unreasonable in winter to blow untempered cold air in, but I wonder will the exhaust-only system be any more comfortable or efficient in terms of heat gain/loss?

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Replies

  1. Expert Member
    Dana Dorsett | | #1

    In a heating dominated climate as cool as zone 5B supply-only ventilation carries some risk to the building, since it's driving humid indoor out to condense on colder materials where moisture can potentially collect on moisture susceptible materials during the winter.

    The bath fan would be safer for the building if it's occupied most of the time, but with uncertainty to the infiltration paths it could be drawing in radon or other soil gases, making that somewhat riskier for the occupants if the foundation isn't air sealed well. With good ground vapor barrier & foundation wall air sealing details the bath fan approach is low risk for both the house and the occupants.

    ASHRAE 62.2 would call out 0.03 cfm x 1680' = 50 cfm, plus 2 x 7.5 (presumed occupancy of 2, at 7.5 cfm each for a 1-bedroom)= 15 cfm making a grand total of 65 cfm.

    Building Science Corp recommends dropping back to 0.01 cfm x 1680= 17 cfm, plus the same occupancy based 15 cfm adding up to 35 cfm.

    1. KevinEJ | | #2

      Thank you, Dana. I'll stick with the bath fan.

  2. Maximilian T | | #3

    Hey Kevin - How's it working for your studio?

    I'm also looking at the 10 or 20/40 cfm WhisperSupply. In my case it's because I have 3 kids sleeping in one bedroom and the CO2 in there gets really high really fast at night per my Awair monitor. I have a WhisperCeiling 80 cfm in a nearby bathroom but as Martin mentions in https://www.greenbuildingadvisor.com/article/ensuring-fresh-air-in-bedrooms, I have no way ensuring that the makeup air comes from the boys' room. I'm in 4C so I don't think my moisture concerns would be as great, but maybe that's just my ignorance talking.

    Has anyone on heres found a way to wire a WhisperSupply or similar fan off of a CO2 monitor so as not to bring in more cold air than needed? If so I'd love to see the gear list!

    (also @Dana methinks you may have done the 62.2 math on Kevin's 1680 ft^3 as if it were ft^2 :) )

    -Max

    1. KevinEJ | | #4

      Hi Max, studio is still a work in progress. Hopefully someone else can assist with your questions.

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