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Community and Q&A

ERV ducting options for existing construction?

Jeremy K | Posted in GBA Pro Help on

I have taken Martins advice from a past discussion and added an ERV to our home. Currently the ERV is setup in the easiest install method by adding the fresh air and exhaust air ducting from the ERV to our return air for our furnace. Our furnace blower has an ecm blower so we are not taking a huge power hit as it pulls about 100 watts. The drawback to this is that we have two independent HVAC units serving the home, each on opposite ends of the two story house. Since we are only connected to one HVAC unit we are not servicing one of the upstairs bedrooms, laundry room, or basement with the ERV.

My question is in regards to alternative methods of ducting. There is no way to get dedicated ERV ducts to the 3 upstairs bedrooms without a lot of sheetrock removal. Would it be better to add fresh air ducting to both units instead of one and then pull exhaust air from the areas of the house I can reach? The rooms I can easily reach include the basement and the following rooms on the first floor……..3 bathrooms, kitchen, laundry, master bedroom, living room, laundry room. I would think exhaust ducts would be best in the one bathroom with a shower and tub, laundry, and kitchen.

If going this route my next question is in regards to the fresh air being supplied to the HVAC ducts. Do I need to interlock the HVAC blower with the ERV so they run at the same time or can I just let the fresh air disperse through the return ducts at the point of least resistance for the few periods of the year when the HVAC is not used?


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  1. GBA Editor
    Martin Holladay | | #1

    The short answer is that you can connect the fresh air supply of the ERV to the main return ducts of both furnaces, and you can connect the exhaust duct of the ERV directly to the rooms where you want to pull stale air from (using dedicated ventilation ductwork), without installing an interlock with the furnace fans.

    For more information on this approach, see Ducting HRVs and ERVs.

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