Everything You Need to Know About Furnace Humidifiers

A furnace humidifier attached to the ductwork

A furnace humidifier is, as the name suggests, a humidifier that is attached to the furnace so that all of the air pumping out of your furnace is humidified. The operation is not unlike a standard small humidifier that you might keep in your bedroom. The difference is that, while a regular portable humidifier will keep a small portion of your home humid (sometimes not even a full room), a furnace humidifier will affect entire home.

Stand-alone humidifiers are by far the most common humidifiers, the ones that most people are familiar with. This is because furnace humidifiers are relative newcomers to the market and many people don’t know about them and the many benefits that a furnace humidifier can provide.

In this article, we’re going to talk about the benefits of a furnace whole house humidifier and why you might want to install one in your home.

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What Are the Benefits of a Humidifier for the Furnace?

Humidifiers make a house more humid, and that’s especially important in the winter when the air is cold and dry. Skin can get easily chapped in cold air–this is the reason why you use more moisturizer in the winter, and why you are much more likely to apply ChapStick in the winter than in the summer. Your skin dries out, and that is not healthy.

Clearly, you want your skin to be as healthy as possible, and that can’t happen if it’s constantly dry, cracking, rough, and chapped.

Aside from the outside of your skin, the inside of your body needs moist air as well. The lack of moisture in the air is one of the reasons why we’re constantly sick with ear, nose and throat issues in the winter. A stuffy nose, a sinus infection, a cold–these can all be exacerbated by dry air. Bacteria and viruses prefer drier air to thrive.

But there’s a flip side to a furnace humidifier. When you look at how furnace humidifiers work, they do more than just make the air more humid. They actually control the humidity in the house. A good furnace humidifier will add humidity to the house when necessary, and also decrease humidity within the house in case it’s getting too moist.

Remember: too much moisture can lead to mold and rot, two things that you definitely want to keep out of your house. Rot will make your home less structurally sound, and mold can lead to all sorts of health problems–some dangerous, even fatal.

How Do Furnace Humidifiers Work?

A furnace humidifier connects to your heating and cooling system so that when air is pushed through your house, it is moistened.

(It’s important to note that, although we often think of the benefits of a humidifier coming in the colder months, a furnace humidifier increases the humidity levels in the air in your home through either the furnace or the air conditioner. The humidifier works all year round, so you get the benefit of controlled humidity in the air regardless of year.

This is especially important if you live in a very hot, dry place like Arizona or New Mexico, where summers can give you dry skin just as easily as cold air can give you dry skin.)

There are three different types of furnace humidifiers, and we’ll look at them in turn:

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Flow-Through Humidifiers

With a flow-through humidifier, the humidifier is connected to a water supply (so, yes, there is an added cost to your water bill, but it’s minimal). These humidifiers monitor the humidity in the air and will only turn on when they recognize that the air needs moisture.

There is a water panel in a flow-through humidifier, where water is flowing over a surface and evaporating, and air from the HVAC equipment blows through that water panel and absorbs the wet air there, then disperses it through the ducts into the house. One of the benefits of this type of system is that the water used by the flow-through humidifier is always replenishing, so there is never a stagnant reservoir of water for it to pull from.

Steam Humidifiers

A steam humidifier works as it sounds: a hot air supply heats so that the water is boiling, letting off steam, and the air that passes through it, being blown by the HVAC system, will disperse into the house. Steam humidifiers are generally considered the best option for large homes and homes that have the most trouble with dry air.

That doesn’t mean they’re the best in every situation, but if you had a large home in a cold place, like Alberta, then a steam humidifier would probably be your best bet.

Reservoir Humidifiers

These types of humidifiers are connected directly to the HVAC system and have a drum in them. As air blows, the drum rotates, rolling through a reservoir of water and then presenting itself for air to pass through. The main difference between a reservoir humidifier and a flow-through humidifier is that the reservoir has a regular container of water that it rotates through, rather than being moistened by a stream of water.

How To Install a Humidifier on a Furnace

It’s not hard to install a furnace humidifier in your home, although installation instructions may vary depending on the type of furnace humidifier you’re installing. We always recommend having a professional perform any repairs or installation needed. You can use our free quoter to quickly find the right professional for the job in your area. For this example, we are going to describe the mounting of a flow-through humidifier.

The first thing you will need to do in humidifier installation is to cut a hole in the ductwork directly above the furnace. The diagrams that come with the humidifier unit will show exactly where this needs to be cut.

Cutting into a duct isn’t hard, you simply need to drill a hole in one corner, and then cut out the hole with tin snips. Mark out the hole with a marker and a straight edge before you cut so you can be sure you’re getting it in the right position.

Next, you’ll cut a hole for the humidistat. As the name suggests, this is like a thermostat except, instead of measuring temperature, it measures humidity. It is a small box with sensors that will also need to be mounted on the duct so that the sensors can measure the air moisture.

Installing the humidistat will require you to connect it to the furnace controls. This means–as always–make sure that the breakers are turned off before you do any electrical work. As different furnace humidifier manufacturers use different electronics, follow the electrical diagrams to make the attachments. This doesn’t require a degree in electrical engineering, but you will need to attach wires properly.

Then you connect the humidifier. There will be leads from the humidistat that lead to the solenoid valve on the furnace humidifier. Follow the directions of the manufacturer to get the right wires attached in the right places.

Next, you will want to connect a water line to the humidifier. This will ideally be a line coming from the water heater so that the humid air blowing from the humidifier feels warmer.

In the event that your humidifier needs a bypass duct (the manufacturer will specify) then you will need to cut a hole in the ductwork that is approximately 6 inches in diameter. Cut the ductwork as you did before, and attach the vent with a round collar and sheet metal screws. The other end of the air vent will attach to the basement’s vent pipe.

In the event that you need a humidifier filter, the furnace and the humidifier you just installed should make it easy to place this filter.

If you think that sounds complicated and difficult, call one of our certified installers. They can specify the proper equipment for your house, and do the installation properly for you.