Adding a Humidifier to Your Furnace or HVAC System? What You Need to Know

Adding a humidifier to your HVAC system may seem complicated, but with the proper training and know-how, anyone can do it.

But before you jump the shark, find out which type of whole humidifier is right for you.

Below you’ll find out how much it costs to install a humidifier to your HVAC system or furnace, how to install a whole-home humidifier and if a whole-home humidifier is right for you.

Let’s get started.

How Much Does it Cost to Install a Humidifier in Your Furnace?

A furnace humidifier by itself costs around $100 to $500 for drum and flow units while steam humidifiers can cost from $300-1300.

To install a humidifier, it can cost anywhere from $100 to $900 depending on where you live.

Types of Humidifiers


Drum humidifiers use a rotating evaporator pad that spins along with the unit’s water pan.

The evaporator pad brings moisture into the warm air that’s passing into your home’s ductwork.

Drum humidifiers are recommended as they have higher moisture outputs than any other type of whole-home humidifier.

One disadvantage of a drum humidifier is that the stagnant water in the water pan can become susceptible to mildew, bacteria, and mold buildup.

They also require more cleaning.

Flow Through

As the name suggests, flow-through humidifiers work by passing the air through an evaporator pad which is absorbed by the warm air that passes through it.

Moist air is then flowed through the ductwork and into your home.

Flow through humidifiers can stay cleaner for longer periods compared to drum or steam humidifiers.

The evaporator pad will need to be replaced once per year.

Flow through humidifiers cost more than drum humidifiers but may be worth it considering they’re more efficient to run.


A steam humidifier utilizes a humidistat that turns the unit on or off once it senses the humidity has reached a certain threshold.

Once it turns on, it will start heating water in a reservoir that is turned into steam and enters the ductwork of your furnace.

Steam humidifiers cost more and can cost more to install as they’re a bit more complex than drum and flow through humidifiers.

When to Add a Humidifier to Your HVAC System Over a Portable Unit

The problem with residential humidifiers (the portable ones you’re likely familiar with) is that they are only capable of humidifying one room at a time.

They also require to be filled every so often and cleaned as well.

If you find that you are moving from room to room, are tired of maintaining your portable humidifier, or your entire family suffers from dry skin, or allergies, then a whole-home humidifier may be right for you.

The biggest benefit of a whole-home humidifier is that you won’t have to worry about filling any tanks and you’ll only need to do maintenance around once a year.

You do however need to factor in that the cost of installing a humidifier as well as purchasing the unit can cost almost 10-15x more than a cheap humidifier.

How to Install a Humidifier to Your HVAC System

Before you install your humidifier, understand that you will need to drill and do electric work.

If you aren’t comfortable doing this type of work, it’s advisable to hire a professional HVAC technician who can do the heavy lifting for you.

It’s vital that it’s installed properly or your furnace may leak and cause damage to your home.

Every humidifier is going to be installed differently, the below instructions are for a furnace humidifier.

1. Mark where you’ll cut your hole

Some humidifiers come with a template that will allow you to mark where exactly you need to cut a hole into your plenum or return drop.

Start by drilling in the corner of the outline and then cut the hole out with a pair of tin snips.

Before you drill any holes, ensure that the mounting plate is positioned and attached, and drilled in with sheet metal screws.

You can also put foam backing around the hole to keep it air-tight.

2. Cut out a hole for your humidistat

The humidistat is what turns your humidifier off and on by sensing the surrounding humidity level.

You’ll need to connect the humidistat to the cold air return at least 1 foot above your whole-home humidifier.

Once you’ve cut out a hole, you’ll need to secure the thermostat with the screws it came with and connect it to the low voltage.

3. Run the ductwork

Now you need to run the ductwork from your humidifier to the supply line. This is so that the moist air makes it back into your home.

4. Hook up to the water line

If your humidifier came with a saddle valve, ensure that you’re using it with copper pipe.

If you don’t have a copper pipe to use it with, then do not use it as it will not be suitable.

If you can’t use the saddle valve, then you’ll need to connect it to the hot water line. Turn off the water and then remove any water that’s built up.

Then hook up your hot water line to your humidifier, you may need to cut the water line to hook it up to your humidifier.

5. Set up the drain

Hook up the drain to the furnace condensate pump so that the excess water can be removed.

6. Hook up the electrical

Turn off the power before proceeding. Hook up the humidifier, humidistat as well as a transformer as per your humidifier’s instructions.

7. Put your humidifier together and attach the water line

Once everything is hooked up and you’ve attached the water line to the humidifier, you can turn it on to see if everything is working as planned.

Should You Leave Your Humidifier on All Day?

You should never leave your humidifier on all day if you don’t have a humidistat.

You want to keep the humidity level in the optimal 30-50% range, or you run the risk of over-humidifying your home.

Final Thoughts

Not everyone is going to require a whole-home humidifier.

They can cost quite a bit, and installation can also drive up the price.

If however you suffer from dry skin and your home is being damaged from low humidity, then the investment may be worth it.

Never do any electric work yourself if you aren’t comfortable doing so. To install a humidifier, hiring an HVAC technician will be the easiest method.

You can rely on our technicians to give you a hand, simply click on the button below for a free quote.

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About Roy Cohen

Roy Cohen has a burning passion for heating, cooling, and ventilation. He aims to help you save money on expensive repairs and bring you the best HVAC products. He has years of experience behind him in HVAC repair and garage maintenance.

You can find Roy at his LinkedIn or his email: [email protected]

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