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Dedicated Duct HRV/ERV Retrofit Balance Between Floors

Joe_Curious_but_not_handy | Posted in General Questions on

Climate zone 5A, 1600 sqft ranch with a basement. 

I’m planning a dedicated ERV unit (CERV2) with supply in bedrooms/living space and exhaust from bathrooms/kitchen.

4 Supply: 3 bedrooms and a living space on the main floor.
4 Exhaust: 2 bathrooms, a laundry/bathroom, and a kitchen on the main floor. 

My question is for the basement. I’m planning 2 bedrooms, a living space, and a bathroom. 

3 supply and 1 exhaust. 

Are there any best practices to ensure the space/house is balanced?
Is supplying more  points in the basement and exhausting more points from the main floor OK as long as the CFM itself is balanced? 
Does this cause issues as I seal the penetrations between the basement and the main floor? 

I was thinking about scheduled zoning of supply (upstairs supply on a zone and basement supply on a zone), but still not sure if I should plan for a second basement exhaust in the living area.

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  1. charlie_sullivan | | #1

    Number of supply/exhaust points does not need to be balanced. As far at the CFM, you have two choices. Either you balance them floor by floor, or you make sure you have unrestricted paths between the floors for that air to flow, whether that's an open stairwell or deliberate vents or "jump ducts".

    Note that the CERV2 is not an ERV. An ERV recovers the energy in the exhaust at no energy cost other than running the fan. The energy to run the fan can be very small if it's an ECM fan. The CERV2 is a heat pump. It can't transfer energy between the air streams passively like an ERV can. It can only do that if you spend energy on running a compressor, which takes a lot more energy than a fan.

    1. Joe_Curious_but_not_handy | | #2

      Awesome. I think I'll make sure the bedroom doors have enough space for the airflow to pass through and plan to keep the stairwell open as well.

      And a great clarification about the CERV vs ERV. I titled it that way since I think ERV is more recognizable than CERV and ducting can be the same. True that energy is only exchanged with the pump operating. I chose it to help handle humidity a bit better (and I think smart home stuff is cool).

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