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Community and Q&A

Exhausting multiple bathrooms

raul4817 | Posted in Mechanicals on

I know this is topic that has been discussed previously. I have 3 baths on my 2nd floor and 1 on my first floor. I have windows in all but my master. So I believe code does not require ventilation in 3 of the 4 baths.  I would feel better having the option.

The exhaust for 2nd floor baths would have to go through the roof no other way. I originally looked at an inline ventilator with 4 inlet ports. Mainly because I can poke a single 6” hole in the shingles and be done. The price on one of these units is around $325. So if I where to spend a few more on a budget erv or hrv I was looking at the 600-700 range.

Going this route I would need two roof penetrations but I would get the added benefit of the recovery ventilation. I have no qualms about how Long it will take to Defog the mirrors.

We currently share the 1st floor bath. And I am the only member of the family that actually uses the current exhaust fan. I suspect this trend will continue once we finally move upstairs. So I really like that an erv or hrv will basically put me in control of venting all baths automatically even when the wife and kids consistently forget to hit the switch.

I read Martin’s article on the need for bath fans in conjunction with an hrv and towards the end of the article he cautions the use of an erv for this function. So am I correct that an hrv is a safer? I know it’s cheaper .

Do any HRVs have an exhaust only function for the extremely humid times of the year that I don’t necessarily want to pump the humid outdoor air in? In a previous thread Martin mentioned that most HRVs have a booster feature.

And what are the downsides/upsides to running an hrv in the summer? I found a soler  & Palau tr90 erv for around $650. But as mentioned this is an erv and maybe not the best option for my purpose.

I really just want the baths the be ventilated whether code requires me to or not and not pop 3 vent holes out of the roof. So I figured if I’m spending a few extra dollars, why not get an option that replaces some air and semi conditions it on the way in?

I plan to duct the hrv independently by installing return air registers to each of the 3 upstairs baths and possibly the 1st floor bath. I have a centrally located staircase that I can pump the incoming air to and maybe one more location(master bed,living room).

Would one fresh air output be enough? What are some recommendations on equipment that stay within reason? I live in zone 5 and with basement I will have 3000sf  of conditioned space. My 2nd story is pretty tight but the 1st and basement still need a lot of love but I will address these two floors within the next 5 years.

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  1. Trevor Lambert | | #1

    I don't know where you are and what code applies to you. I know where I am, the window no longer counts for bathroom ventilation. But you're planning on doing it anyway, so it's academic.

    "Do any HRVs have an exhaust only function..."


    ..."for the extremely humid times of the year that I don’t necessarily want to pump the humid outdoor air in?"

    The humid air is still going to come in, it's just going to come in from leaks in the house. Or if your house is extremely air tight, it will just depressurize your house and you won't actually be evacuating the air in the bathroom. It's more likely the first scenario, but in any case I can't see a circumstance where it would make sense to run the HRV in exhaust only mode.

    One fresh air register is enough, if it's sized correctly. The exact size depends on the total airflow.

    If the entire purpose of this device is to remove moisture from the bathrooms, an HRV is better than an ERV. I can't comment on whether it makes sense over an exhaust fan. You also want to consider long term plans for ventilation and air quality, if you plan to tighten up the rest of the house down the road.

    1. raul4817 | | #2

      Thanks Trevor,
      Yes I would mostly use the hrv for moisture control in bathrooms. I plan on sealing up the house over the next few years and then the hrv will serve dual purpose. As far as erv vs hrv what should I be cautious about in regard to using an erv in this application with no dedicated exhaust fans? From I gathered it would also transfer moisture content to the fresh air side?

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