Best duct choices for ERVs and ventilation fans: PVC?
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
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.)
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.
Kail,
Here is a link to an article that should answer your questions: Bathroom Exhaust Fans.