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ERV install questions- dryer periscopes, return air grilles, and flex duct

brandons | Posted in General Questions on

I am installing the Renewaire EV200 to run continuous as a dedicated ducted system.  The home has 6 bedrooms and 4 bathrooms.  

-Any issues with using dryer periscopes for the fresh air supply to the bedrooms?  The periscope would stub into the joist cavity and up into the 2×4 wall about 24” high for the fresh air supply register.  The install requires two 90 degree transitions per room, then straight to the plenum.  The periscope appears to simplify things. 

-Is flex duct still recommended for at least 6’ from the registers to reduce noise?

-Are the round adjustable air grilles by Fantech etc sufficient for balancing the airflow and use in the bathroom return air locations?

Thank you, 

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  1. Expert Member
    Akos | | #1

    I haven't tried these, I would guess they will be fine on low flow, but could be loud when the unit is on boost.

    You generally don't want to hear the unit ramping up in a bedroom at all, this is partly why there is the recommendation of larger ducting plus the length of flex. A length of flex between the ERV supply and the main supply trunk also helps. You can try to mock up one of these and see how loud it is.

    A 5" oval hard pipe with an oval round 90° boot on the bottom and oval stackhead on the top can work inside a 2x4 wall. The simpler option is to bump up the framing depth slightly there and run 4" flex to a 3x10 boot.

    Flow control is always best set with a damper. These are not something you should need to adjust after commissioning.

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