Posted By MSG79 on 07 Nov 2012 04:02 AM
I’ve got a couple of questions concerning some research I’ve done and a couple things mentioned in this thread. When reading a book on designing a healthy home it says that good places for intake vents are in a closets and bathrooms. (I saw that mentioned here also.) I also know that many people install ERV/HRVs using existing HVAC duct work. However, I was recently doing some research in the IRC and while I couldn’t find anything on ERV/HRV they did say the return vents were not allowed inside closets and bathrooms! This had me scratching my head and I could only speculate that they were concerned about the moisture (in the bathroom) and maybe high level of bad air in the closets would be circulated around the house. It also made me think that if I wanted to pull nasty and moist air out of those places (besides a direct vent to the outside) that the duct work for the ERV/HRV would have to be a separate system. I would love to hear your thoughts or experience on this?

What are your thoughts on using a separate duct system for the ERV/HRV?

Thanks for the tips on the Seiho vent caps!

MSG79;
The exit ducts MUST be to the exterior of the house, why would you want to take moist air from the bathroom and put it in another area of the house?
the ERV/HRV is designed to transfer the exiting temerature energy (heat/cold) to the incoming fresh air thru a core similar to a small radiator, but instead of aor to water transferance it is air to air transferance,
energy transfered thru the core and air to air never coming in contact with each other, inth this process the incoming air is conditioned and tempered, the exiting air removing moisture/ condensation
the HVAC system can be used to distribute the incoming fresh air, but the exhaust air must be separately ducted out since a HVAC system does not have that capabilitys ducting

Thanks Chris. I understand the operation of the ERV/HRV. So let me make sure I've got the rest of what you are saying straight:

1. Use the HVAC duct to distribute the fresh air pulled in by the ERV/HRV.
2. Use a separate ERV/HRV return duct system to pull the exhaust/dirty air out.
3. No return ducts in bath from HVAC or ERV/HRV (Use another separate “system” direct vent to pull moisture out of the bathroom.)

Did I get that right?

So, is the best way to eliminate moisture in a bathroom to have a direct vent ceiling fan controlled by a humidistat to ensure the fan stays on long enough to remove all the moisture? But doesn’t this kind of take the ERV/HRV out of the loop? Why wouldn’t I want to pull that moisture out via a humidistat controlled ERV return duct and recover some of the energy before blowing it to the outdoors?

Sorry to jump in here, but there is an important distinction between ERV and HRV. Separate ducting for an ERV simplifies the job of balancing the two air streams, which is essential for transfer of humidity. It matters a great deal in a cooling dominated climate; if the ERV isn't moving moisture from intake to exhaust effectively, it places a greater load on the air conditioner. Don't assume your installer understands this phenomenon.

To answer your other questions, you don't want HVAC returns in closets or bathrooms because of air quality/efficiiency concerns. It doesn't matter where you put ERV/HRV exhaust ducts because the air is going outside and at much less velocity than HVAC.

Posted By toddm on 07 Nov 2012 11:13 AM
Sorry to jump in here, but there is an important distinction between ERV and HRV. Separate ducting for an ERV simplifies the job of balancing the two air streams, which is essential for transfer of humidity. It matters a great deal in a cooling dominated climate; if the ERV isn't moving moisture from intake to exhaust effectively, it places a greater load on the air conditioner. Don't assume your installer understands this phenomenon.

To answer your other questions, you don't want HVAC returns in closets or bathrooms because of air quality/efficiiency concerns. It doesn't matter where you put ERV/HRV exhaust ducts because the air is going outside and at much less velocity than HVAC.

I would not advise HVAC returns in the bathroom ....unless you want everyone in the house to share what is going on in the crapper?

Chris, I believe that's what I wrote, citing "air quality" somewhat more delicately. Again, an HRV/ERV vent in the bathroom exhausts air to the outside, 20 feet up in my case, posing some risk I suppose to low-flying waterfowl.