Basement ERV and Bath Exhaust Ducting
I am renovating a ~900sf basement in CZ5A which will have two bedrooms, a bathroom, and a living room. I’ve insulated basement walls and have a heat pump wall unit to condition the air year round (and provide some dehumidification). I would like to install a Panasonic WhisperComfort ERV in the main living space to help provide fresh air and exhaust stale basement air. Ideally, I would be installing something like the Intelli-Balance ERV to supply fresh air directly to bedrooms but I have very limited height in the basement (basically limited to just running ductwork between floor joists as there is no room to run perpendicular under joists).
I’ve seen a lot of back and forth about bath exhaust fans with ERVs but I feel I need one to exhaust smells and shower moisture. My fear is that without the dedicated bath exhaust fan, the WhisperComfort ERV would be pulling bathroom smells and shower moisture into the living space prior to being exhausted outside.
My challenge is finding a way to limit envelope penetrations and ductwork runs due to my limited basement floor-to-ceiling height. I believe I’ve found a strategy but my suspicion is that it is not permitted by code. The photo I’ve included shows how I’d like to install a wye duct to tie the bath exhaust into the outgoing air from the ERV. This would help me to keep my envelope penetrations to just the one I have planned for the ERV. Is this not allowed or a bad strategy?
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Here is a link to the Panasonic WhisperComfort ERV I intend to install. https://ftp.panasonic.com/ventilationfan/fv04ve1/whispercomfort_updated_sellsheet.pdf
If you are careful, you can drill a 3" hole into the casing of the ERV where the fresh air supply is and duct it elsewhere.
I've have done this in bathrooms, the ERV is mounted in the bathroom and picks up the stale air from there. The stock fresh air outlet port is blocked and the fresh air feed is ducted over to the intake of the heat pump for distribution. Works great and has no issues with clearing a bathroom when running on boost.
The blower on these units is underpowered, so you have to take care with ducting otherwise it will restrict airflow too much. The efficiency is also pretty poor so the fresh air feed will feel cold in the wintertime, in your case, best to dump it near the intake of the wall mount.
P.S. These units are surprisingly large in real life, make sure to leave plenty of space.
Akos, thank you for your reply. I think I understand what you're suggesting, but I don't believe it is exactly what I'm after. However, it is giving me more to think about and may be a good alternative solution to what I'm currently trying to do.
I'm simply trying to tie in my bath exhaust in line with the already outgoing exhaust air from the ERV to save from having to add another wall penetration for the bathroom exhaust. Does that make any sense?
I'm pretty sure that would be against code.
My suggestion was an option that is to code and not too hard to implement.
Thanks again, Akos.