Whole House Furnace Humidifier: Everything You need To Know

You might have heard about how humidity levels can affect our overall comfort and health. A furnace humidifier is a device that is going to help add moisture to the air in your house even when it’s freezing cold outside.

You should invest in a furnace humidifier, in case you live in an area with cold winters and low humidity or someone in the household suffers from dry skin and asthma. Such units offer automatic humidity control, improve the air quality, and add value to your house.

How much does it cost to install a humidifier? Is the thing hard to install and does this device have any cons?

We present to you ‘Furnace humidifier: everything you need to know’.

What Is a Furnace Humidifier?

Furnace humidifiers connect with your HVAC system and create a certain amount of moisture that is added to the air that is travelling through the system.

There are bypass humidifiers that fully rely on the blower of the furnace, flow-through units that have their own fan, and steam humidifiers that add moisture to the air by generating steam.

Humidistats help ensure that your house doesn’t get over humidified. These devices start sending signals to the humidifier only once the humidity levels in the house drop to a certain set point. 

Why Does Your House Need a Furnace Humidifier?

You certainly can live a happy life without a furnace humidifier.

However, such a unit is going to make a huge difference if you live in an area that tends to have cold, dry winters or if someone from the household suffers from various health conditions associated with dry air. 

  • Climate conditions

The natural humidity levels drop as soon as it starts getting colder outside.

You might not have even noticed the difference if you live in an area that doesn’t experience a significant change in the seasons.

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But if you live in a cold-weather region, then dry air can become a problem. By the way, running your furnace on freezing days makes the air even drier.

Such air can not only worsen certain health conditions but also cause damage to your house.

  • Health issues

If you or someone from the household is suffering from asthma and dry skin and has problems falling asleep at night, then dry air can worsen the situation even more.

In such a case, a humidifier becomes a necessity.

Furnace Humidifier Pros and Cons

The Pros

  • Health Benefits

People living in a house with a mid-range humidity level suffer less from allergies and asthma. Moreover, they are less prone to respiratory infections.

If you manage to keep the indoor humidity below 50% (and above around 40%), you are going to fully control the growth of fungi and mites’ population.

Finally, it is simply much more comfortable to live in a house with the right humidity levels.

  • Automatic Humidity Control

A furnace humidifier is able to automatically control the humidity levels in your house. 

The majority of units come with a humidistat that lets you set the desired humidity. The device is then going to make sure that the humidifier is working until your humidity of choice is reached.

Fact: the Environmental Protection Agency recommends keeping your relative indoor humidity between 30% and 60%.

  • Low Maintenance

In general, all you would have to do is change the evaporator panel filter once a year and quickly wipe the humidifier.

  • Added Value

A furnace humidifier adds value to your house. You won’t exactly be offered a lot more, in case your place has the right humidity levels, but a humidifier can certainly influence the decision of potential buyers.

The Cons

  • Can Cause the Growth of Mold and Mildew

If the system fails to control the humidity levels, it might end up adding too much moisture to your house which will cause the growth of mold and mildew.

Another thing to consider is that a humidifier adds moisture to the actual furnace, so mold can start growing inside the HVAC system.

  • High Price

Furnace humidifiers are definitely an investment.

The unit alone costs around $200, but be prepared to pay $150-$400 for the installation and around $25-$50 for the materials needed.

  • Can Mask HVAC Air Leaks

Unsealed air ducts can lower the humidity levels in your house. So, potentially, a humidifier might end up masking bigger problems that the HVAC system has.

For the houses that don’t have a humidifier, a sudden drop in the humidity levels might be a signal that there is a disconnected duct, a large hole, or a poorly insulated area somewhere in the ductwork.

That’s why it is crucial to double-check the system before installing a whole-house humidifier. 

How Much Does It Cost to Add a Humidifier to Your Furnace?

The cost of adding a furnace humidifier would depend on the model that you choose, the service time, labor rate, and plenty of other factors.

The national average for the job is $577.

Let’s take a closer look at what makes up the price.

Type of humidifierA drum model is the simplest one and will cost you anywhere between $150 and $250.A flow-through unit – over $200.A steam humidifier – between $300 and $1100.
Rate of HVAC techniciansUsually, technicians charge $50-$70 per hour, but some professionals have a flat rate.It will take the expert 2-3 hours to install a simple model and up to 6 hours to make a more complex unit work.
MaterialsTo install a whole-house humidifier, you or the technician are going to need copper tubing, wires, air pipes, and so on.The materials are going to cost you around $25 – $50.
Hygrometer (additional)This device will be monitoring the percentage of moisture in the air. It will cost $10 – $60 to install a humidity gauge.
Humidistat (additional)A humidistat not only shows the humidity level in your house, but it can also adjust the percentage.A lot of humidifiers already come with a humidistat. However, if your model doesn’t have one, be prepared to pay up to $100 for such a device.
Annual maintenanceOverall, annual maintenance is priced between $70 and $100. If you decide to go for duct cleaning, the operation is going to cost you $350.In case a technician finds mold, you might be required to undergo mold testing and have the thing removed for $700.
The total annual cost to run your humidifierIf you have a bypass or a fan-powered type, it is going to cost you only around $10 to run the unit per year.Steam-powered models are much more expensive – they are going to add around $170 to your annual bills.

Is It Hard to Install a Whole House Humidifier?

To install the system, you would have to cut a hole in the venting, install the humidistat, connect the actual humidifier, take care of the waterline, and, in some cases, install the bypass vent.

Sounds like something that shouldn’t be too challenging, but the job requires quite a few skills (including electricity skills).

So, handing the job over to a professional technician is definitely a better decision.

Moreover, an expert will be able to install the system in any location and will make sure that the humidifier is able to work at its full capacity once finally installed.

No matter whether you have decided to take care of the task yourself or to invite a professional, below you will find a list of the most common humidifier installation mistakes that you should avoid (or make sure that the technician avoids) at all costs.

Size ; Type

Unlike with an air conditioner, it is okay to go bigger, when it comes to a whole-house humidifier

When picking the right size take into consideration the square footage, quality of insulation, the design of the space, and the use of additional heating sources (like a fireplace).

When choosing the type of humidifier, the type of your heating system and the hardness of the water should be considered. 

For the areas that have hard running water, for example, going for a spray humidifier would be a mistake as the system will get clogged in no time.


Ideally, furnace humidifiers should not be installed in hard-to-reach places as it would be practically impossible to properly maintain the whole system in such a case.

Wiring ; Integration

If you can, don’t go for a humidifier that works only when the furnace is operating. Find a system that can be controlled independently and a technician who can wire the whole thing properly.

In case your house has a smart home automation system, you would want to make sure that the humidifier can integrate with the existing systems. 

Remember that no matter how experienced the technician is, the professional should be following the installation instructions provided by the manufacturers, as there are differences between the various models.

How to Clean a Furnace Humidifier

Warning! Before attempting to clean your furnace humidifier, make sure to carefully read through the manufacturer’s instructions.

  • Switch the power off

The most important step is to switch the device off. After that, disassemble the unit, so that you can get ‘inside’. 

  • Clean the water reservoir

Empty the reservoir, remove any build-up, and refill it with clean water (about 2/3 of the way up). 

  • Clean the water panel

If the instructions allow cleaning these parts, then you can take out the water panel (it consists of a filter, water pad, and an evaporator pad) and put it in cold water for around 20 minutes.

Rinse the filter and wipe it down.

After that, you would want to either replace the filter or place the cleaned one back in the unit.

Hint: the water panel in your furnace’s humidifier has to be fully replaced once a year.

  • Clean the outer body

You might notice mineral build-up on the outer body. In such a case, simply wipe the parts down with a water and vinegar solution.

  • Re-assemble everything correctly

If you have managed to re-assemble the unit correctly, there will be no leaks.

Tip: if you are not planning on using your humidifier for a few weeks or months or in case you are going away for a couple of weeks or more, make sure to drain the humidifier beforehand to avoid bacterial growth in stagnant water.

How to Test a Furnace Humidifier

A humidifier that is working properly is going to make a click sound whenever it gets turned on. Right after that, you should hear the sound of the unit’s fan.

You can also check the drain tube. When the system is working, you should see water running through it.

Finally, if the humidifier has been working well throughout the whole season, you should see a build-up of mineral deposits in the water panel. If this part of the unit is relatively clean, then the system hasn’t been receiving enough water.

Read: Why Do Humidifiers Need Distilled Water?

How to Replace Filter in a Furnace Humidifier

paper hepa air filter from humidifier texture which helps to clean air in the house

Follow these simple steps:

  1. Switch the power off.
  2. Open the cover and disconnect the water tube, if your humidifier has one.
  3. Dislodge the tray that houses the filter. Make sure to remember the positioning of all the parts.
  4. Usually, you will be able to pull the filter out of the tray.
  5. Clean the tray and then dry it.
  6. Unpack a new filter and simply slip it into the dried tray. All filters have a colorful indication of some sort, make sure that the mark is on top.
  7. Place the filter into the unit. Remember that the drain hole should be at the bottom.
  8. Attach the water tube, close the cover, and switch the power on.

Tip: you can buy a new filter immediately after replacing the old one, so you don’t have to worry about it when the time comes to change the filter once again.

Frequently Asked Questions

Do whole house humidifiers cause mold?

If not installed properly or misused, a humidifier may cause excessive moisture to appear in the ductwork.

The moisture causes mold growth that might then be ‘pushed’ into your house together with the airflow.

You should also make sure to keep the humidistat settings below 50%.

Can you run furnace without humidifier?

Yes, you can.

You can either turn your humidistat to the ‘off’ position or close the damper/valve on the waterline if you have one.

When should you stop using a humidifier?

You should stop using your furnace humidifier once the heating season is over as the humidity levels will start to naturally rise.

If your humidifier has a damper, simply close it or turn the knob to the ‘summer’ position.

You can also stop using your humidifier if the moisture levels are too high during the colder season. To monitor that, use a hygrometer.

What should you set your furnace humidifier at in the winter?

The settings of your humidistat are going to depend on the outdoor temperature (especially, during the colder season).

It is generally recommended to set your humidistat to 40% or less if the outside temperature is between 20 F and 40 F; 30% for 10-20 F; 30% or slightly lower for 0-10 F; 25% for temperatures between -10 and 0; 20 % for lower temperatures. 

Do furnace humidifiers run all the time?

Some humidifiers run only when the furnace is on, while others can work independently. 

It is safe to leave your unit running all the time, if you are at home and if it is necessary. 

However, make sure that you are not over-humidifying the house. 

Does humidifier help heating costs?

The truth is that a furnace humidifier can actually help you save on your energy bills during the winter season.

The higher the humidity levels, the warmer you feel. That means that you can easily set your thermostat a few degrees lower without feeling cold.

We have already mentioned above that usually it costs only around $10 per year to run a furnace humidifier. But the fact that you are lowering the temperature in the house will help you save a much bigger sum on your heating bills.

To Sum Up

This was everything that you need to know about furnace humidifiers – the good, the bad, and the unexpected.

Such units have a lot of benefits, are relatively low maintenance, and even though the systems can be quite expensive, a high-quality furnace humidifier will help you save on heating bills.