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ERV Ventilation

EliSc | Posted in Mechanicals on

We’re rehabbing an old 3 family brownstone in the Northeast. Planning on installing a Zhender ComfoAir 350 in each unit (floors Cellar+1, 2 ,3)

Because we are not replacing the floor joists and don’t want to sacrifice ceiling height. My Engineer advised that we run a separate Fresh Air and Exhaust shaft to the roof, and have the ERV’s connect with them at each floor. 

Anyone have any similar experiences and has it worked? 
Also open to feedback and ideas for potentially alternative ideas. 

I appreciate your time in advance.

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  1. CramerSilkworth | | #1

    I've done many a brownstone with Zehnder. I usually put it on the top floor and run supply and return trunks down, with manifolds branching off at each floor. Being multifamily you'll need fire dampers between each unit, properly installed this isn't a big deal but they do leak a bit. If you're in NYC there's a (dumb) code rule about not mixing baths & kitchens from multiple dwelling units on common ventilation systems - let me know if that applies to you.

    But I'm not sure I'd run a common FA & XA riser through the building and then tap each ERV into it. That's cold air running through your building, those ducts need to be well insulated. Ideally the ERV's connection to outside is short & sweet - 10' at most if possible, then the interior ductwork (with room temp air) can be longer and has no energy implications (other than fan power) on the building. And common risers could make balancing difficult. This is done on larger scales with pressure-balancing fans on top of the risers that adjust as each ERV changes its airflow, but that tech is rather expensive for a small building like this.

    Consider maintenance, too. Two filters in each, changed 3-4 times a year. Times 3 for three ERVs, plus needing access to 3 different apartments, unless you can be clever and put them in closets that open to the common hall/stair.

    Cost, duct work, space, etc all factor in too - it's not a clear cut decision.

    1. EliSc | | #2

      I really appreciate your detailed response. Yes I’m in Brooklyn. It’s a small condo project. Problem with running it out the rear facade is having to either create an ugly soffit (it’s also about 15’ to the back)

      1. CramerSilkworth | | #3

        Ah, condos change the ownership & maintenance picture. What about the CA200, can you fit those in the ceiling somewhere?

  2. CraigRo | | #4

    Do you have 21.5" between ceiling joists? Renewaire makes a small unit, SL, designed to fit between 24"O.C. joists. Not sure if that's a good fit, airflow and duct routing, but an option to consider.

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