Informational Guide

How Does a Whole House Humidifier Work?

Whole-house humidifiers aren’t as complicated as they may seem. Our guide showcases how they work and explains which type of home they are most suitable for.

by Josh M

The air quality in your home matters. It can impact your overall health and wellbeing, and having the right air quality can help you focus more and get more from your day. However, getting good quality air isn’t just about temperature; it’s about the humidity.

Air humidifiers help you to regulate the moisture levels in the air. This is particularly important if you live in a very hot or cold climate because your air can become too dry. Humidifiers are becoming a lot more common in the home, but you might find yourself asking, how does a whole house humidifier work?

This guide will give you a complete breakdown and help you understand how whole-house humidifiers work and the benefits they can bring.

Humidifying your whole home isn’t difficult and gives you a range of benefits that you’ll start to feel almost immediately. Here are the top reasons to install one:

Help Your Health

Humidifying your home helps to improve the overall air quality. This helps reduce the risk of airborne diseases or infections like coughs and colds and keeps you healthy.

It can also help regulate any other particles in the air that can cause irritation to your respiratory system and even relieve some asthma symptoms.

Increase Personal Comfort

A lot of allergies in the home are caused by the quality of the air. Dry air can irritate your skin and your respiratory system, making you itchy, giving you a sore throat, and drying out your skin. A whole home humidifier helps to regular the air and prevent this from happening.

Preserve Your Home

Moisture in the air, or overly dry air, can cause damage to your home. Your floors can start to show cracks, your walls can peel, and paint can begin to become noticeably damaged. Your furniture can also be impacted, and wood may even start to warp.

Electricals can become damaged too and unusable too if the moisture levels in the air are wrong. A good humidifier will help protect your home from unnecessary damage.

Save Energy & Money

You can actually save a great deal of money with a whole house humidifier because it helps regulate the temperature in your home. This means that you won’t need to use your heaters as much, and you can lower your overall energy bill.

Major Components Of Whole House Humidifier

Before you can install a whole house humidifier, you need to understand the different components. Here’s a quick breakdown:

  • Water Tap/Supply Line
    This is where your humidifier is connected to your water supply. This allows it access to water which will be released into your air supply if it’s too dry.
  • Water Inlet Orifice
    This helps control water flow into the humidifier to prevent too much water from being released into your home.
  • Water Inlet Valve
    This is the primary control of water in the humidifier. These are usually electric and connected to your solenoid valve in the humidistat, giving you full control of how much water is allowed to flow into your humidifier. This, in turn, gives you control of how much humidity is in the air in your home.
  • Water Feed Tube
    These are used to feed water down through the cover and onto the evaporator pad where it will be released, as steam, into your home.
  • Evaporator Pad
    This is what holds the water before it’s evaporated and released into the air.
Evaporator Pad
  • Drain Pan
    The drain pan sits underneath the evaporator pad and is where unneeded water flows. The drain pan empties into your drainage system so it can be safely taken from your home.
  • Air Damper/Air Duct
    These are used in models which combine air conditioning with air humidifying. This air duct allows cool air to flow into the humidifier and hot air to pass out of your home to give a cooling effect.

How Does A Whole House Humidifier Work?

Whole home humidifiers are designed to add moisture into the air when it becomes too dry. They connect into your water supply so that moisture can be introduced, as needed, into the air supply.

Typically, water is evaporated and released or blown around your home to quickly relieve any dry air issues.

An effective humidifier can help heat your home by regulating the air temperature, but they are different from heating systems. Steam humidifiers are connected into your heating supply, but other whole-house humidifiers aren’t.

Humidifiers can sometimes be combined with an air conditioning system which allows you to control the temperature and the humidity of the air with one device.

There are three main types of whole house humidifiers:

Steam Humidifier

These are the most common type of humidifiers and work in a pretty simple way. They connect to your electrical and water supplies and evaporate water, so it turns into steam. The steam is then released through your heating ducts and spread throughout your home.

Steam Humidifier

Drum Humidifier

Drum humidifiers are comprised of a rotating drum and an absorbent pad. The drum rotates through a pan of standing water, and the absorbent pad absorbs it.

Air flows through the center of the drum, and water is evaporated from the pad into the air supply. It then flows into your home. Drum humidifiers also need to be connected to your water and electrical supplies.

Drum Humidifier

Flow-Through Or Moisture Pad Humidifiers

Flow through humidifiers don’t need any electricity but will require a water supply. Water is absorbed onto the moisture pad, and hot air from a furnace flows over the pad.

It picks up the moisture from the water as it passes and travels into your home. You will need an extra floor drain for this type of humidifier.

Flow-Through Or Moisture Pad Humidifiers

How To Install A Whole House Humidifier

It’s pretty simple to install a whole house humidifier, but you need to make sure you have the right equipment. You’ll need:

Once you’ve got everything ready, follow these steps:

1. Mark Your Hole

The manufacturer will typically provide a template and some instructions on how to do this. Mark it out on your wall using your felt tip marker, and then use your drill and aviation snips to cut the section out. Attach the sheet metal mounting plate and secure it in place with screws.

2. Cut The Humidistat Hole

The humidistat will be used to control the humidity in the air. Measure out the hole for it by following the manufacturer’s guidelines, use your marker to draw it out, and then cut the hole to the right size.

3. Install The Humidistat

Connect the thermostat to the mounting plate and attach it in place. Follow the instructions and connect the furnace controls to the thermostat.

4. Wire The Humidifier

Connect the wires from the humidistat to the humidifier. The leads from the humidistat should connect onto the solenoid valves on the humidifier. Insert the wires into the nuts and tighten them.

Humidifier Thermostatic Wiring Diagram
5. Connect The Water Supply

Install a saddle valve into the hot water line (or cold-water line if you can’t connect it to the hot) and run a line into the humidifier. Fasten it with a compression fitting.

6. Test The Humidifier

It should all be connected up now, so switch it on and test the unit to make sure it’s working.

Remember that you should switch off all electricals before doing your wiring and switch off your water supply before doing anything with your plumbing. Some parts of the process can be tricky, and it’s always worthwhile getting a friend to help you lift different parts into place.

A full guide to installing a whole house humidifier can be found here: How to Install a Whole-House Humidifier | Ask This Old House – YouTube

People Also Ask (FAQ)

How do I know if my whole house humidifier is working?

When you turn the humidifier on, you should hear a click. You should also be able to see water flowing through the drain tube out of the humidifier. If you don’t hear or see this, then your humidifier may not be working properly.

How long does a whole house humidifier take to work?

It will typically take about 24 hours for a whole house humidifier to have the desired effect.

Do whole house humidifiers cause mold?

Mold is caused by an excess of moisture, so if the right amount of moisture is added, then it shouldn’t be an issue. Whole house humidifiers will only cause mold if they’re used or installed incorrectly.

Are whole house humidifiers dangerous?

No, whole house humidifiers aren’t dangerous, but at first, the change in air humidity can cause some irritation to your respiratory system. It should have any long-term effects on your health, though.

How long do whole house humidifiers last?

On average, a whole house humidifier should last about 10 years. This will depend on the make and model of the unit, though.

Where should I put my whole house humidifier?

Whole-house humidifiers should be put in the busiest room in the house because this is where you’ll see the most benefit. Make sure to keep it out of the way, though, because they can be a bit of an eyesore.

Are whole house humidifiers loud?

No, whole house humidifiers should run silently. If you can hear it, then there is likely something wrong with the humidifier.


Whole house humidifiers are really useful, particularly for those who suffer from dry air. If they are installed correctly, they offer a lot, and you can see some real benefits to your health and wellbeing.

Whole-house humidifiers aren’t as complicated as they may seem, and there are a few different options out there. Hopefully, this article has given you a useful overview of how they work, how to install them, and the benefits they offer.

Last Updated on July 16, 2021

Josh M

My name is Josh and I am obsessed with the HVAC industry. I created this website to help HVAC techs of all levels get the best out of their heating & cooling systems. I have spent thousands of hours studying air conditioners, heaters and home air products so you can learn & buy with confidence. Learn more about the team here.