Whole House Humidifiers Types, Performance and Tips


A whole house humidifier or furnace mounted whole house humidifier is just another example of an extremely neglected component of our house – on top of a brick chimney, an attic, and a crawlspace, which fall into the same basket.

If you’re not going to maintain it, it’s probably a bad idea to get a whole house humidifier. Since it is attached to a forced air heating system that constantly circulates air throughout the house, poor maintenance can create environment attracting mold growth and help reproduce of dust mites.

Properly operating and maintaining a whole house humidifier helps us relieve many physical discomforts associated with cold / dry weather, including respiratory problems and dry skin and lips. It also lowers or completely eliminates static electricity, cosmetic wall trim separations, cracks in finishes, separating hardwood floor boards, etc.

The trick is to balance the amount of moisture in your home at such a level, which will benefit your health, living environment, and save energy instead of creating conditions which sometimes cause mold or other biological organism growth (excessive moisture could do that).

For a proper humidity balancing, you either have to observe and monitor your environment, or purchase an electronic device which will do it for you. In general, the humidity in your house should not exceed 50% (35% – 50% is the most comfortable).

Higher levels will usually create condensation on windows, sometimes on walls and ceiling surfaces, or possible mold and mildew growth.

No matter how advanced the whole house humidifier system installed on your property is – it will require regular maintenance because it won’t work properly or at all without it. The truth is – I rarely see one properly maintained or even operating at all.

Fan Assisted Flow-Through (bypass) Whole House HumidifierMold Contaminated Flow-Through Whole House Humidifier Water PanelFlow-Through (bypass) Whole House Humidifiers (passive and fan assisted) – they use a so-called water pad made out of foam, expanded aluminum, and some other materials. The water drips on top of the square pad and the air from the heating system flowing through the pad picks up the water particles and carries them through the air ducts and around the house. The remaining water (whatever wasn’t picked up by the air) drains through the base of the whole house humidifier.

Passive Flow-Through (bypass) Whole House HumidifierMold Contaminated Water Panel of a Flow-Through (bypass) Whole House HumidifierA whole house humidifier’s water pad has to be replaced once a year before every cold season to perform efficiently and to prevent mold growth. For the homes utilizing private well or other sources with high levels of minerals, cleaning might be required more often.

For every gallon of water evaporated into humidity, Whole House Flow-Through Humidifiers waste between 5-8 gallons down the drain.

Drum Whole House Humidifiers – they have a drum shaped rotating frame (powered by a small, low voltage motor) and a foam or fabric sleeve pulled over it. The bottom section of the drum is always submerged in water which keeps the rotating foam / fabric moist and allows air flowing through the drum to pick up that moisture.

The foam / fabric and the water in a small reservoir under the drum require regular maintenance! If you leave that water standing in an unused humidifier (for example during the summer), and then just start the whole house humidifier unit without cleaning it first, I guarantee that you’ll be spreading mold spores through the entire house.


Wick Type Whole House HumidifierWick type whole house humidifier has no humidistatWick type whole house humidifier openWick Type Whole House Humidifiers – assembled out of a small reservoir and a filter (wick) that absorbs water from it. The entire humidifier is mounted inside the air duct, and in order to inspect it, you have to unscrew the cover plate and remove the entire unit – I don’t recommended it, very cheap and easy to install, but there’s no device (humidistat) to control humidity level.

Spray Mist Whole House Humidifiers – as the name suggests, they spray water mist into the air duct and the mist is picked up by the flow through the air duct. Don’t even consider this type if your house’s water supply is a private or community well – it will contaminate the spray head immediately. Those are one of the cheapest and easiest to install types out of all the whole house humidifiers.

Honeywell steam whole house humidifier closedHoneywell steam whole house humidifier openSteam Whole House Humidifiers – being the most expensive to purchase / install and not that cheap to operate, it consists of advanced technology and complicated designs. Steam whole house humidifier might operate with or independently from your system heat cycle.

Whenever the humidity drops below the setting, they will activate your furnace blower and get the humidity to the right level independently from the thermostat settings. One of the known problems associated with this type of the whole house humidifier is that the water distributed with cold air (with operating furnace blower only / no heat) does not completely evaporate.

Condensing on the air duct cold walls might sometimes cause bacteria and mold growth. If you like new gadgets and don’t mind spending some serious money for it – go ahead – but it sill does require maintenance. One more type of a Flow – Through type humidifier but this time almost 100% efficient (as claimed by the manufacturer).

Rotary Disc Furnace Mount Whole House Humidifier by Desert Spring: To be honest with you, I can’t say much about it except for relaying information from the manufacturer’s website, forums, and discussion boards. It sounds great because it is (as claimed by the manufacturer)

  • the most effective furnace-mount humidifier on the market
  • 100% efficient – 1:1 conversion of water to humidity
  • uses only 4 Watts/hr of energy
  • drain-less system – there’s no need for a drain in your utility room / furnace location area
  • very little maintenance with Auto-Flush accessory (you can do it manually every few days, depending on usage, minerals would only need to be removed every month or two in most regions of North America)
  • never needs filters or pads replacement – uses self cleaning polycarbonate discs (non-absorbent plastic)

As with every product, there are those who love it and hate it. I’ll show you how to install one of those units… at least I’ll try, and by clicking on the picture or link below, you can find out about its performance.

Desert Spring Humidifier ReviewRotary Disc Humidifier by Desert Spring Review

Just like with every type of equipment, whole house humidifiers require regular maintenance – follow this link for details furnace humidifier maintenance.

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  1. John D says

    You don’t seem to like any of these systems. We have well water and I am considering a spray system. Can’t I just install a prefilter to reduce mineral clogging?

    1. CTH Experts says

      Hi John,

      I know how much water most of them waste and how much damage they cause to HVAC equipment that even considering that a lot of it was simply lack of maintenance, there are only a couple I would recommend. NO – I’m not being paid by the manufacturers for that / I’m not their affiliate.

      All I can say is Try It. Make sure you can return it within 30 days if you don’t like it. Install one and monitor interior of the air duct to make sure that it doesn’t overspray / that there’s no residue from drying mist on the air duct interior walls. If you notice stains (assuming that you have a galvanized or aluminum air ducts) it will eventually cause corrosion of the air duct. Also, depending on the installation / placement of the nozzle, that un-vaporized completely mist often drips onto the heat exchanger causing more corrosion.

      Yes, the filter is a MUST with well water, plus, remember:

      FURNACE REQUIREMENTS: For use in homes with conventional gas or oil forced-air central heating systems only. Not for use with electric furnaces, 90+ condensing furnaces, or electric heat pumps. DO NOT INSTALL with an attic furnace of any type.
      WATER REQUIREMENTS: Operates on normal city water supply pressure. If any other type of water supply is to be used, it must be capable of providing a minimum pressure of 50 psi.
      If your water has a high calcium and mineral content, dust may be created as the water evaporates. The problem can be minimized by installing an in-line water filter that uses replaceable cartridges in the water supply line.

  2. Ron says

    We have two attic mounted electric Heat exchanger furnaces, and are in need of some type of humidifier, as my wife has asthsma and is on Oxygen 24/7, and needs moist air in winter. We live in Round Rock TX (Central TX). We have tried both types of stand alone, fill every day types, and would like to get away from the fill ruteen.

    1. admin says

      Hi Ron,
      Since you have an electric furnace I would only consider a whole house humidifier that mounts on an air supplying duct / not on the return. This would minimize amount of moisture that may compromise electric coils and prevent possibility of a spillage onto the electrical components of the furnace.

      Since your furnace(s) is mounted in the attic, you may consider a steam type humidifier by Honeywell. I don’t know if this would be possible in your configuration, but those whole house steam humidifiers can be mounted in some remote, more accessible than attic locations, and steam delivered to the air distributing ducts through the hose. This way you have more control over it.

      You have to remember that all humidifiers require maintenance, and will eventually stop functioning properly or at all without it.

      You can get more details about this particular type here – steam humidifier
      Also, they are more expensive than the conventional types (price will depend on the sq footage of your home / size of the unit), but at the same time claim to be more efficient. If you can’t do it yourself, call a few local HVAC companies for a quote.

      Let me know if you have any further questions.

      Thank you

  3. admin says

    Still testing Desert Spring… furnace blower and humidifier running constantly “on” for 10 hours, 2% humidity increase

  4. Spencer Mullens says

    Did you ever evaluate the Desert Spring Rotary humidifier? And if you did how did it do?

    1. admin says

      Almost perfect timing :-)… A month later than anticipated, I just finished installation today. I’ll try to do a installation manual over the weekend and post it by Monday. Humidifier installation itself very easy, it looks nice, and I should know about performance in a few days. So far, the humidity went up only 3% in about 5 hours, but it was warmer today and the furnace didn’t run that much.

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