Has anyone had tried to vent their bathrooms by connecting the house ventilation to the bathroom so that it continuously pulls air from the bathrooms (in addition to pulling air from the main HVAC return air duct)? It would be easy to put in a 3" or 4" flexible line to the bathrooms, but is it the right thing to do? My HVAC guy thought the humidity might not get out of the house and might get into the HVAC unit (geothermal Climate Master).

you want to use an ERV to do that, I have mine taking from the master bath and laundry room thru the erv exhaust and the fresh air intake into the greatroom, the two never mix , but you do not want bath exhaust going back into the fresh air return, it must be exhausted

What you describe is - exactly - what I did.  I wrote a blog post about this very topic here: http://www.gouingreen.com/node/39

We've been in the house for a year now.  No signs of mold in any of the bathrooms (not even on the plastic shower curtains).  We used the Ultimate Air 200DX in our house.  During the summer months, it will work to reject the humidity.  During the winter months it works to retain the humidity.  Best of all, it works!  Take a little extra effort for sound isolation of this unit if the noise is going to bother you.

I am sitting in my kitchen right now.  The humidistat on the counter is reading 51% in the middle of winter, with no supplemental humidification.  Do you know what is great about that...?  We don't have the usual winter static electricity in the house!  I also have found that my skin and sinuses are not as dry as they usually are in the winter.  The higher humidity also makes a lower temperatures much more comfortable.  We are almost always very comfortable at 68-69F.

I have also not seen any signs of mold growth inside the ductwork or on the (MERV 12 or 13) filters, however, I did install a UV sterilization unit.  Even if mold wanted to grow, it doesn't have a chance.

I hope this helps.

Regards,
Ed   

thanks Chris, after I posted, I found where our ERV model ER150C (Honeywell) is able to pull stale bathroom air out. Here is shows a picture on page 10 of this PDF file... http://customer.honeywell.com/techlit/pdf/69-0000s/69-1563.pdf it shows where the "stale air from baths" goes through the side of the ERV that pulls air out of the house. I think that is what you are describing in your home except the fresh air intake will go straight into the HVAC system instead of the living room. My HVAC guy is about to pull air from the main return for air going out of the house, and I asked him about pulling air from the bathrooms more directly as Honeywell describes. *** He (the HVAC guy) is concerned that the ER150 will transfer humidity to the incoming air, as humidity exchange is a feature of how the ER150C works. *** Honeywell personnel will not answer questions about installation in any way, at least I can't find anyone.

By "house ventilation" I may have mistakenly assumed you meant an Energy Recovery Ventilator (ERV) tied to your central ductwork.  I would NOT bring the bathroom air directly into the house!!!  Humidity is one issue, odors are the other!  Think... Grandma visits for the holidays and uses the powder room after a big meal.  Any odors will be directly circulated throughout your entire house!  Not good for you or Grandma!

The ERV exhausts this stale air while retaining the heat and humidity you want (during the winter).  I would strongly advise against this unless you are using an ERV.

Ed

got it, just got off the phone with Honeywell. The ER150C is the energy and humidity recovery combined, and it can exhaust air from bathrooms or any room in any amount. Thanks for everyone's help. Hope I provide some with some insights too. By the way, I'm not sure how bathroom air would go into the HVAC unit if installed correctly because all air taken from the house will go into the ERV to exhaust out. Anyway, over and out.

Ed;

I initially thought the same thing but didn't want to throw poor Grandma under the bus, sure would put a damper on Thanksgiving Dinner.

Its great to smell the turkey cooking while in the bathroom, but not vice versa?

My story was based on a true story in our old house (with an unused manual vent fan). That taught me a lesson for the new house which is much tighter than most... automatic venting! ;-)

One thing that is interesting in this house is that NO smells linger... Cook fish... a short time later the smell is gone. My wife likes smelly candles. I don't. Luckily, even the smelliest of candles are neither overwhelming, nor does the scent linger for long in this house. We also have five dogs. Yes, five. On rainy days one might expect a lot of "wet dog" smell, but there isn't. Sure the dogs will smell, but the house doesn't.

Controlled ventilation really is a wonderful thing!

Ed

Just curious, are you running the thing continuously, running timed duty-cycles, have it on de-humidistat control or...???

(Are you monitoring the indoor RH?)

Thanks!

Sounds like you have the flow about right, as well as a VERY tight house! (SIPS are good for that.)

I assume you have to run the geo in AC mode (or a smaller dehumidifier) to keep the RH under 60% in summer?

We have no issues turning on the A/C when needed.  If it gets too warm, too humid, or both, we close the windows and turn on the A/C.  50F groundwater makes for a wonderful and efficient heat sink.  Until that point, we designed the house for good cross-ventilation.

Ed