I'd like to add two bath fans to our house. This sub has let me know that Panasonic are probably the best. But I figured I'd ask here about the venting and lighting options. I have good access to the attic space.

Bathroom #1: -Has an older nutone fan that seems a little weak, and I was thinking of doing the Panasonic Whisper choice DC Pick-a-Flow. https://www.homedepot.com/p/Panasonic-Whisper-Choice-DC-Pick-A-Flow-80-110-CFM-Ceiling-Bathroom-Exhaust-Fan-with-Flex-Z-Fast-Bracket-RG-C811A/320520625. Would this work? There's so many panasonic options to pick from... -I have questions about the existing ducting. Currently, it's going into a flex silver duct and then a black ABS T-piece. (the ABS from the floor below is a powder room only; no humidity). It terminates through the roof. Is this going to be a problem or something I should rectify? I'm not sure I have the skills to put in a new roof vent. Also, I don't want humidity being pumped into the downstairs powder room....

Bathroom 2: Has an existing light, and I'd like to replace with a lighted fan. Panasonic Whisperfit DC/LED Pick-a-flow seems like one home depot option: https://www.homedepot.com/p/Panasonic-WhisperFit-DC-LED-Pick-A-Flow-50-80-110-CFM-ENERGY-STAR-Quiet-Ceiling-Bathroom-Exhaust-Fan-Flex-Z-Fast-Install-Bracket-FV-0511VFL1/317716369. Does this seem like a good option? Not sure how the wiring would go with this one though; would love if someone had some tips.

Anyway, thanks for any help you can provide. Would love to just know if the ducting is OK or if there is a better option.

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  • Since you've taken the tour, you should know that we operate on a one-question-per-post basis here. You've asked multiple questions, so please edit it down to just one. Also, be aware that asking if a product is a good option will lead to your question being closed as "opinion based" or possibly "shopping recommendation" since both of those are off-topic. Feel free to post multiple questions at once, just not multiple in one.
    – FreeMan
    Commented Sep 6, 2023 at 18:51
  • The "recommendation" could be as simple and ugly as: "Panasonic gives the best kickbacks" or "I make the most profit on Panasonics" or...
    – Ecnerwal
    Commented Sep 6, 2023 at 19:10
  • This answer appears to apply: diy.stackexchange.com/a/278130/18078
    – Ecnerwal
    Commented Sep 6, 2023 at 19:13

2 Answers 2


First- is that black ABS the vent stack? That is, is it hooked to your toilet and sink drains? If so, DO NOT use that for the fan's exhaust. It's against code, and possibly lethal with sewer gas coming back into the house. Even with the fan's "flapper" that is supposed to prevent backdrafts, they're not perfect and negative pressure in the house will cause sewer gas and smell to come into the living space.

The fan needs to be vented on its own duct/pipe, out the roof or out the soffit if possible. Going out the soffit avoids a roof penetration, which is almost always more desirable.

And yes, it needs to go out. I've seen people just duct their bath fan to the attic. If you live in a place with climate (cold and hot), it's a recipe for mold and rotting out your roof sheeting. Even if the bathroom is "low humidity", you're still pulling air from the rest of your house. In the winter, that warm air hits the cold attic and moisture condenses everywhere.

As for your bathroom 2 question, I've had very good luck with those Whisperfit fans. Because I was retrofitting it, I wired the nightlight and fan to the same switch, so when you turn the fan on, the nightlight comes on with it. They could also be run on separate switches if you'd like to run some wire to a new switch.

  • Yes, that would be an extra-specially bad way of combining two very different vent functions for bathrooms...since using ABS pipe for fan ducts is highly non-standard, it's a very good question...
    – Ecnerwal
    Commented Sep 6, 2023 at 19:16
  • Sorry, i should have mentioned it. The plumbing vent stacks are a different system. Still the same black ABS, but they are definitely not connected. In the picture it's the downstairs bathroom fan that its connected to (but there is no shower/bath tub in that bathroom, so no humidity).
    – Klonepeak
    Commented Sep 7, 2023 at 23:01
  • I guess my question is if I can keep using the black ABS to vent a fan replacement, since it already goes to the roof? Or is that ABS too small/undesirable for a bath vent? It would be a hassle to make a new roof access, but I suppose I could attache a larger diameter flexible vent directly to the roof hole... And now that i think about it, venting just the bathroom smells from the floor below directly into the attic wouldn't bother me because there is no humidity... Thanks all for your help
    – Klonepeak
    Commented Sep 7, 2023 at 23:04

for bathroom fans such as that, if what you listed does not have a replaceable or serviceable light bulb, they are ok if it is easy to access on the attic side and easy to remove and install and you're ok with the price... knowing that when the LED light fails and that it's not replaceable you're out the (currently priced at $188) of the entire fan, and would be replacing the entire thing if you value the light part of it.

There's a fair amount of negative reviews on those types of combo fans + LED (non replaceable) light units. I can't tell if the 2nd one you listed with the light is such a unit (with a non-serviceable light).

  • One would want to verify that a particular model of fan does or does not have a replaceable ‘bulb’. Frankly, I’d be astonished if Panasonic didn’t do parts, but I’ve never been in a position to wonder about it. Commented Sep 6, 2023 at 20:07
  • Yeah, there is good attic access, but verifying that the bulb is replaceable would be smart.
    – Klonepeak
    Commented Sep 7, 2023 at 22:59

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