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Community and Q&A

Make up air – passive solution?

drewintoledo | Posted in General Questions on

I will be implementing a Broan ERV140TE ERV system during my build however this system is not intended to introduce additional fresh air when turning on additional negative pressure producing devices such as a kitchen hood or bathroom fans. 
I’ve seen plenty of solutions utilizing motorized dampers which turn on in conjunction with the negative pressure device such as a kitchen hood exhaust but it would be nice to keep it simple and avoid those mechanicals.  Is it truly the best solution?  I’m wondering if a passive make up air solution exists as to avoid electric motors and circuitry to operate said dampers?   
Would it make sense to install something like a Dundas Jafine BPSH4WZW in reverse or could high wind simply blow it open?

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  1. Jon_R | | #1

    I encourage you to do the calculations - for many cases, even motorized dampers on an otherwise passive supply don't work well - you need an active supply fan to keep the house pressure near neutral. Eg, the negative house pressure needed to pull 300 CFM through a 4" vent (even when fully open) is likely to cause back-drafting.

    1. drewintoledo | | #4

      Jon, Do you have a Make or model number you appreciate for reference? I understand the CFM is dependent on calcs, I’m just looking to browse around.

  2. Trevor_Lambert | | #2

    I would ditch the bathroom fans and place stale air exhausts for the ERV in there.

    Do you have any combustion appliances? Some negative pressure won't be the end of the world for brief periods of running a range hood (I'd still have at least a passive supply if the house is built tight).

    1. drewintoledo | | #3

      I spoke with Broan and they don’t want moisture from the bathroom or potential grease laden air from the kitchen in the system. They encourage me to implant separate exhausts.

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