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Community and Q&A

Humidifiers do they equal mold?

NEplumber | Posted in General Questions on


Avid reader of the posts here. Always interesting to see the replies! Tbh, I’m sometimes shocked at the questions. I assume these are from home owners and not industry pros.

I own a plumbing heating and cooling outfit. We specialize in all things hydronic heat. However we work on everything from a toilet flapper in a residential home to healthcare HVAC and boiler rooms (with great success I may add).

I have been on the fence about Humidifiers. Never installed one. Easy for me to say since we dont have a whole lot of forced air here. 
I am considering the Honeywell HM750A humidifier.
My own home is hydronic baseboard and radiant heat (walls and floors!). The humidity can easily go down to 30%. I have noticed this and thought the temperature was hot due to the thermostat being raised up, yet the home was 68f.
I run the central air system in fan mode using the “circ” setting on the honeywell T4 thermostat. Keeps the air clean and prevents any rooms from developing a smell over night when the doors are closed and people are sleeping in the rooms.

I am not a fan of adding humidity to cold dark places.
Can I use my central air distribution system for a humidifier?
Or should I inject the steam into the main room of the home and let it dissipate? 

Lastly, the home is rather leaky and not sealed well. Do we risk cold air and a 50% humidity in the home to cause issues where the air crashes or cold spots in the walls are?

I must add, that a properly sized and installed 13 seer central air is all one needs to keep the humidity at bay in the summer months. We maintain 55% most of the summer with exception of the very rainy cool days.
Moe from Turnupthecomfort

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  1. user-3258290 | | #1

    Since you recognize that the air leaks are the issue, why not work towards improving that issue instead of applying a (risky) band-aid?

    1. NEplumber | | #4

      It's an almost 100 yo rental home. I redid all mechanicals, every pipe and wire in this house. It's time to pay bandages while I build my home.

  2. walta100 | | #2

    If you could stop some of the cold dry air from leaking in and keep more of the warm moist air in you could find the house more comfortable.

    I see humidifiers as dangerous band aid used to cover up a problem not fixes it.


    1. NEplumber | | #5

      I agree

  3. Expert Member
    BILL WICHERS | | #3

    You should try to correct the leaks first. Air sealing goes a long way and can really help with reducing energy consumption in the home.

    I’d use a humidifier on your central system over a steam injection system in only one room. The reason is that the central system will more evenly distributed the humid air and you’ll be less likely to have one room that is much higher humidity than you really want. I’m thinking the room with the steam humidifier would have much higher humidity than you really want and that could lead to problems. With the central air distribution system handling the humidifier, you have more even distribution and less chance of any one area having excessively high humidity compared to the others.

    Excessive levels of humidity CAN lead to mold and rot, and often times these problems will be hidden inside walls where you don’t notice them until they’ve become BIG problems.


    1. NEplumber | | #6

      Bill, thanks for the reply. As mentioned above this is not my home so insulation and air sealing aren't on the priority list. My worry is that the steam injection to the duct work would cause mold since it's not a furnace.

      1. Expert Member
        BILL WICHERS | | #7

        As long as the blower is running whenever the steam humidifier is running you should be ok. I’d thought you were going to use a dedicated steam humidifier in only one room.

        Steam humidifiers are very efficient in regards to water use, but aren’t very efficient with energy use. Evaporative pad humidifiers are much more efficient in regards to energy use, but they’re more wasteful with water. You’ll want to pick whichever type is most efficient with whichever resource is more scarce or expensive in your area.


  4. Jon_R | | #8

    There are climates and houses where even if you eliminated all air leaks, it would still be too dry. So humidification isn't always a band-aid. On the other hand, drier does reduce moisture risk to the house. And at some point, you even get condensation on the windows.

  5. tommay | | #9

    Beside adding plants to your environment, just using one or more of the small hot air vaporizers, that they sell at your local drug store, may be more than enough to add the moisture you need.

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