Click here to Find a Contractor in your area.
Welcome! Here are the website rules, as well as some tips for using this forum.
Need to contact us? Visit

Adding Humidity

Being a wethead for so many years, a topic that has popped into my head recently has been humidification to a home.

More specifically, a home with Radiant Floor Heating throughout, chilled water AC system with hot water coils also included in the ductwork.

The radiant is installed to be the primary heat source and can handle the load without any supplemental.

My question, how does one go about designing and installing a whole house humidifier without ;

1) turning on the fan coil and blowing cold air in the space,

2) making sure the air is warm to accept the humidifier, and

3) not overheat the spaces

Thanks in advance

Dave H
Dave H


  • BillW
    BillW Member Posts: 198

    Hi, Dave.  You can consider a Honeywell True-Steam humidfifer for that application.  They don't require a call for heat to work, just wire them into the fan, and when the humidistat call for heat the fan and humidifier will operate together.  You also can use one of the VisionPro thermostats, which has an on-board humidity sensor.  Make sure the ductwork is insulated, and you might also consider a "re-heat", an hydronic coil on a zone valve wired into the humidifier/fan that opens and allows tempering of the air to prevent cold drafts and minimize possible condensation.  There are several different capacity units, if you're a contratctor, see your supply house for details, if you are a homeowner, ask your contractor, and both can go to [url=] for literature. TrueSteams are not sold at retail.
  • Dave H_2
    Dave H_2 Member Posts: 492
    Humidity and RFH

    Thanks for the response Bill.

    I am working on a system with  a customer that has that exact setup. Honeywell trusteam unit (not sure of the size and model) and placed into the ductwork.

     I originally had it controlled by when a call for humidity, it just turned on the fan. Yes it was blowing cool air but it was also puddling in the ductwork and dripping all over the floor (air handler is in basement).

    So based upon your response, there is not an absolute need for heated air to work with the humidifier.

    So how is the puddling happening? Humidifier oversized or ductwork undersized? Do we need to adjust the flow from the humidifier?

    Thanks again

    Dave H.
    Dave H
  • BillW
    BillW Member Posts: 198
    edited January 2010
    Possible cause for liquid water

    The ductwork may not be insulated well enough.  The steam could be condensing. I doubt that water is carrying over, those have a steam dome built in that should eliminate that. Did the installer use the insulated hose that comes in the remote mount kit, and if that was used, how far from the duct is the humidifier? Also, during off cycles, moisture from daily living like taking showers, cooking and laundry can put considerable moisture into the air that may condense in the ductwork, if it isn't properly insulated.  Is it sheet metal or flex?
This discussion has been closed.