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Best duct choices for ERVs and ventilation fans: PVC?

Kail_Z | Posted in Energy Efficiency and Durability on

I am installing two Panasonic ERV’s and two bath fans in a new house in climate zone 4C. Most mechanical contractors in this area use insulated plastic flew duct but I am worried about its longevity and off gassing. I am curious what duct material others would use.

Metal pipe seems best but more of a pain to seal and labor intensive.

I have heard of people using 4″ PVC pipe to vent there ERV’s. Does anyone have experience with this? Would off gassing of the plastic be a issue for the intake on the ERV’s?

Would PVC electrical conduit be any different then PVC drain pipe?

If I run flexible aluminum or rigid duct would the reflectix insulation be enough to stop condensation? Or is these are ran in a insulated cavity is insulation even necessary?

How long can can I run the intake and exhaust for a panasonic ERV before it becomes a performance problem? My gable ends are a ways away and I would have to run uphill to get into some scissor trusses. Or should I try to 90 from my attic space into a exterior wall and then 90 out? This seems like it would be tight and difficult.

Any advice would be great. I have appreciated the past consultations.

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Replies

  1. GBA Editor
    Martin Holladay | | #1

    Kail,
    The best duct for fresh air vents is galvanized steel duct. Here is a link to an article that explains everything you need to know about ducting an HRV or ERV: Installing a Heat-Recovery Ventilator.

    Exhaust ducts can be PVC, because even if the PVC has a little off-gassing, it doesn't matter for exhaust ducts. You really don't want to use PVC for a supply air (fresh air) duct, however.

    If money is no object, you can buy flexible polyethylene ducts from Zehnder. Zehnder has a comprehensive ducting systems that includes flexible polyethylene ducts and special distribution boxes. Expect to pay one arm + one leg for this approach.

    Ordinary flex duct is not recommended, for all the usual reasons: it's flimsy, and the corrugations interfere with air flow. (Zehnder ducts are smooth on the inside.)

  2. Kail_Z | | #2

    Thanks Martin. What are most people using for ducting bath fans? Is aluminum flex sufficient? Does this need to be insulated? Is having this in a insulated cavity enough? Thanks.

  3. GBA Editor
    Martin Holladay | | #3

    Kail,
    Here is a link to an article that should answer your questions: Bathroom Exhaust Fans.

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