# Vent Bath Exhaust to Cold Air Return?



## brandon272 (Dec 19, 2008)

We live in a new house with an air exchanger (HRV) installed. Every bathroom in the house has a cold air return vent that vents out bathroom moisture regulraly and whenever the bathroom is in use (each bathroom as a button on the wall that activates the HRV at full speed for 15 mins).

We are currrently in the process of finishing our basement and I am wondering if it would be a remotely acceptable practice to install an actual bathroom exhaust fan in the bathroom ceiling, but instead of having it vent outside, have it vent directly into the cold air return.

Is this acceptable?


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## integlikewhoa (Dec 31, 2007)

I'm not really up on these, but have you thought about bathroom smells. I have a/c returns in all my rooms, except the bathroom and kitchen, do to the fact I don't want the smell's venting into my a/c system and threw the house. Hope this helps.


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## yuri (Nov 29, 2008)

Especially after chili night. The bad gases will circulate thru the house. See if a contractor can hookup the new bathroom (I assume it is a new one) to the HRV or have a basic exhaust fan installed and vent it to an outside wall.


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## mastertech (Mar 14, 2011)

I dont think that is permissable by code.Not only the odor issues but the extra moisture as it will put an extra load on a/c. Excuse me but Im not exactly sure what HRV stands for.Dont mean to sound stupid but havent ever heard that before.Thats whats nice about this industry,If a man says he knows it all thats scary because this trade always gets better and better!:thumbsup:


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## hvac benny (Dec 29, 2009)

1mastertech said:


> I dont think that is permissable by code.Not only the odor issues but the extra moisture as it will put an extra load on a/c. Excuse me but Im not exactly sure what HRV stands for.Dont mean to sound stupid but havent ever heard that before.Thats whats nice about this industry,If a man says he knows it all thats scary because this trade always gets better and better!:thumbsup:


Heat Recovery Ventilator. Basically, it's a way of bringing in fresh air without the great loss of heat that is encountered when opening a window, or piping fresh air directly into the return air of a forced air system. It's becoming quite common in new construction as most new homes are fairly air tight. The city of Vancouver now requires it for new construction.


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## hvac benny (Dec 29, 2009)

brandon272 said:


> We live in a new house with an air exchanger (HRV) installed. Every bathroom in the house has a cold air return vent that vents out bathroom moisture regulraly and whenever the bathroom is in use (each bathroom as a button on the wall that activates the HRV at full speed for 15 mins).
> 
> We are currrently in the process of finishing our basement and I am wondering if it would be a remotely acceptable practice to install an actual bathroom exhaust fan in the bathroom ceiling, but instead of having it vent outside, have it vent directly into the cold air return.
> 
> Is this acceptable?


All of the HRV systems that I have installed do not permit the exhausting of external fans into the return ducts. The main reason that pops into my head is because it is a positive pressure, not a negative pressure like the other returns. Without the use of back flow dampers, the air will take the path of least resistance, which most likely be into the nearest bathroom's exhaust. 

Your options are to vent the new bath fan outdoors, or to see if a new exhaust can be incorporated into the current system. If the existing ducting can support the additional airflow, then you need to assess if the controls are able to support a new switch and can be run to the bathroom. Typically, the wiring is in series, so a path from the nearest switch is all you will need. Check the installation instruction for maximum number of switches and and other wiring specs.


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## yuri (Nov 29, 2008)

2 1/2 yr old post. I doubt if he is coming back soon. :no:

New home construction in Winnipeg must have a HRV and they use it for bathroom exhausting also. Couple of yrs from now and I will have a HUGE market for replacing the el cheapo plastic units the builders are going to use.:thumbup:


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## unicursalhex (Jan 18, 2011)

hahah I love the smell of a deuce throughout the house


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## hvac benny (Dec 29, 2009)

yuri said:


> 2 1/2 yr old post. I doubt if he is coming back soon. :no:


Ahhh! Damn it, missed the dates! 

How's the biz in Winterpeg, Yuri? What kind of units are you installing out there? I was installing Venmar and Eneready. The latter was sold by a local guy who insisted on quality and would perform an inspection and duct blast to ensure that the installation was up to his standards. The guy I worked for was a sheet metal guru... all of his systems went above and beyond what was required.


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## yuri (Nov 29, 2008)

Winter is technically over but we have several feet of snow still. Going to be the flood of the century as North Dakota has huge amounts of snow/ flooding and going to send all the water to us down the Red River. They doubled the depth of the Red River Floodway (google it for more info) so we should be OK.

We sell Lennox Healthy Climate which is a high quality Lifebreath unit. All metal core etc and won't fall apart in a couple of years. I am sure the builders will slap in the cheapest plastic generic unit they can find to meet the code. Better than straight exhaust fans though.


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## mastertech (Mar 14, 2011)

Heat Recovery Ventilators.OK what the hell is that! What heat is it recovering? Now I understand when a home is made quite well and is a supergoodsense home,you need to actually bring in fresh air for health purposes.how they do this is bring in air everytime theres a demand it will actually open a damper thats on a 6 inch run to the outside.The damper will open up and bring in a certain amount of fresh air to the conditioned air at the same time.These units are actually pretty extravagant and have seperate filters and actually can be set up on seperate timers that will bring in a certain amount of fresh air weather the heat cool is on or not.Theres a interlock with the blower and you can set it up for how many airchanges you want in a 24 hr period.There pretty nice and they do accomodate a fairly tight house with good air changes to keep more oxygen in the house and better health reasons.These systems also have there own filter system before it even drawn into the duct system! Cool huh!~


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## Jackofall1 (Dec 5, 2010)

yuri said:


> Winter is technically over but we have several feet of snow still. Going to be the flood of the century as North Dakota has huge amounts of snow/ flooding and going to send all the water to us down the Red River. They doubled the depth of the Red River Floodway (google it for more info) so we should be OK.
> 
> We sell Lennox Healthy Climate which is a high quality Lifebreath unit. All metal core etc and won't fall apart in a couple of years. I am sure the builders will slap in the cheapest plastic generic unit they can find to meet the code. Better than straight exhaust fans though.


And I read yesterday the Army Corp of Engineers is predicting the Great Lakes water level will be down 6-9" from last year. 

Mark


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## 747 (Feb 11, 2005)

brandon272 said:


> We live in a new house with an air exchanger (HRV) installed. Every bathroom in the house has a cold air return vent that vents out bathroom moisture regulraly and whenever the bathroom is in use (each bathroom as a button on the wall that activates the HRV at full speed for 15 mins).
> 
> We are currrently in the process of finishing our basement and I am wondering if it would be a remotely acceptable practice to install an actual bathroom exhaust fan in the bathroom ceiling, but instead of having it vent outside, have it vent directly into the cold air return.
> 
> Is this acceptable?


First how far to get outside with the vent. Is there a wall rite there. If not make sure fan is enough cpms to make the distance. The longer the duct has to run the more cpms necessary. If a outside wall is rite there. Then no problem 70cpm with a nose level of 2.5 or below. They also rate them for noise.


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