@Niko, as you point out, ERV’s add moisture to the house, although not nearly as much as other ventilation methods. However, ERV’s do a poor job of removing shower moisture and should never be used for that purpose. Since steam from a hot shower has a higher dew point than outside air, the ERV will dutifully recycle a high percentage of shower moisture to the rest of the house, bedrooms in your case.

It’s OK to exhaust the ERV from the bathrooms as long as you use a conventional bath fan while showering. If you want to recover heat from shower exhaust, you’d need an HRV, but I can’t imagine how that would ever be cost effective.

1) Zehnder ERV for balanced ventilation (bath exhaust, bedroom supply)
2) Whole house dehumidifier with dedicated return and supply ducting
3) Variable speed Trane AC

The reason for this combination: I am looking for balanced ventilation for bathrooms exhaust to take moisture out of the house. Additionally I want to supply fresh air to the bedrooms to keep the CO2 levels and VOC low. I realize the ERV will in general add moisture to the house. Therefore I am installing a whole house dehumidifier. I looked into the CERV ventilating heat pump option but for some reason I am not sold on that particular product. So I am hoping my setup will allow me to achieve balanced ventilation and humidity control in a hot humid climate. A ventilating dehumidifier won’t allow me to be balanced so ill either end up with too much pressure (dehumidifier on) or too low pressure (bathroom fans on) in the house.

I’d love comments or advice on this planed setup.

Thank you

Genry, I wish I had a before my encapsulation blower door measurement when I encapsulated 5 years ago. But as part of the sizing process for my dehu installation 2 months ago, my contractor did a blower door test. Results: Depressurize 5.43 ACH 50 Pressurize 5.66 ACH 50. My house was built in 1993, so from what my contractor told me, I’d fail current building code standards. But based on houses built during that era, I’m not in terrible shape.

It’s interesting that this article was published just one day after I finally got my ventilation system installed! It’s the supply-only type. And its working great at it’s intended purpose: reducing CO2. VOCs are down too, which is nice.

Last fall, after installing IAQ sensors (AirThings brand), I came the conclusion that my 2012 built house was too tight and spent the fall, winter and spring pondering the best solution for my situation.

ERVs look enticing, but since I don’t have a basement, that would mean an attic installation and unfortunately the attic is mostly occupied by the resident HVAC ductzilla.

Ventilating dehumidifiers looked good until I noticed that unit I was quoted would not meet the ASHRAE recommended ventilation rate for the square footage it would be dehumidifing. Furthermore, the unit in question was nearly the size of a Fiat and the models with enough ventilation CFMs were even bigger.

So I opted for the simple supply only ventilation. I realize its low on the totem pole of solutions, but it was the only practical option. But regarding your (and Terry’s) concerns:

Humidity: supposedly the fan will shut itself off if it detects too much humidity. However, should it do that, then I’ll just do what I did prior to installing it: open the windows.

Energy: the max draw is 0.7A, not much really. And I don’t care anyways: I’ll gladly pay more money in order to keep my daughter from being subjected to >1100ppm CO2 throughout the night.

Pollution: I had the unit installed with a wall control that will allow me to turn it off should the neighbors be grilling, letting off fireworks, or should our subdivision be attacked with chemical weapons. Otherwise, the typical pollutants in the outside air can’t be much worse than the VOCs indoors. Additionally, the fan accepts filters up to MERV 11 which I’ll installing shortly. Plus the HVAC has its own MERV 8 Media filter, so I think we’ll be ok.

For me, my journey continues. My humidity is under control, but I’m genuinely puzzled why my VOCs spike on certain days (measured by a FooBot). I can’t yet find any correlation between weather/temp/humidity. And ventilation — not sure yet. My crawls space is encapsulated, but I’m sure I still have plenty of stack effect going on.

My point in all of this is like Terry, I’d like to attack the problem once and for all, but the industry needs to get out of the mid 90s. I could trying and keep shooting in the dark to find the right expert to tell me what is going on, but it seems like the standard for the “experts” is still pretty low.

Also, these higher performing units like you see here don’t perform well unless they are operating in the right flow range and in balance. That means not connecting to HVAC air handlers. You’re right its impossible to balance. The unit in the picture is in my home and its balanced. It self balances and I can see the flow and fan speed on my iPhone. Pretty easy. Without balanced flow you can’t get heat or enthalpy recovery. Not even the modest 50% – let alone 68% – 80%.

And yes, do not use paper cores. Good units don’t offer paper cores because they are good units.

Lastly, the picture in this article has an extra steel box on the supply. It has a MERV 15 filter in it. Thats in addition to the MERV 13 pre-filter that’s already in the unit. I have the supply air monitored. The current status in the home for US EPA PM2.5 = 2. Getting down to the really small stuff – its showing Particles <0.3um = 167. Those are pretty low numbers.

So, yes you can have airflow with less moisture, you can balance or let the unit self balance, not get mold on your core, and put some pretty strong filtration in. You just can't do by using inexpensive low performance equipment connected to an HVAC system. Its that old "you get what you design for" thing.