Do Furnace Humidifiers Really Work?

Grandparents Reading Kids a Story in Winter

We need our furnaces to survive Toronto’s deadly cold, but that heat comes at a price: dry winter air.

Most people notice their skin, hands and scalp getting dry in the winter. For some, sore throats and “perpetual colds” are an issue. Dry winter air can aggravate asthma, dust allergies, and even cause nosebleeds for some people.

It can be tempting to buy a small tabletop or freestanding humidifier. But the only way to really solve the problem is to get a furnace humidifier installed. It’s the only way to truly change the humidity level of your entire home at once.

More Advantages for Furnace Humidifiers

Plus, with a furnace humidifier, there are no boxes to clutter up the living areas of your home. They can even help you save money on heating, as moist air feels warmer, and you don’t need to keep the temperature set as high.

Best of all, there’s no tank to fill. Furnace humidifiers connect right to your water supply. So there’s no struggling with the weight of a larger tank, or the constant refilling needed with a smaller one.

How Do Furnace Humidifiers Work?

As you might guess, furnace humidifiers install right onto your main heating and cooling system, usually in the ductwork right leading out from your furnace. The warm air leaves the furnace, passes through the fan that pushes it through the ducts, and then flows past the humidifier and out into the rest of your home.

There are 3 main types of furnace humidifier:

  1. Steam humidifers produce either a warm or cool mist, and therefore produce the most moisture. They’re also easier to maintain, but they do require a small amount of electricity. There is almost no risk of mold.
  2. Flow through humidifiers expose the warm air from your furnace to a constant trickle of water. The water naturally evaporates into the air leaving your furnace. While there is a filter pad that needs to be changed periodically, they are low maintenance overall. Again, these have almost no risk of mold.
  3. Drum humidifiers have a pan of water, and a rotating belt that passes through the pan. The water from the moistened belt evaporates into the air leaving your furnace. Because this type of humidifier has a standing pan of water, you need to be diligent about cleaning it or mold can form. This is the least expensive type of furnace humidifier.

You can install a humidifier on almost any kind of furnace system, even older ones.

What’s the Right Humidity Level for a Home?

Not only do our bodies hate overly dry air, our homes do too. Wood floors and furniture need a minimum humidity level of 35% to prevent splitting along the grain (known as “checking”).

Our bodies love more humidity – but if it gets over 45% you run the risk of mold growth. High humidity levels (over 55%) can help germs thrive and can cause wood to warp.

How Dry is Your Winter Air?

There are some easy ways to tell if your home is too dry. Obviously, if you’re getting shocks from static electricity, it’s too dry. If you’re seeing moisture condensation on the windows (“sweat” or even frost) it’s too humid.

But to be sure, buy a hygrometer (also known as a humidistat) from your local hardware store. They’re not expensive and will let you know the humidity level accurately.

Does a Furnace Humidifier Cause Mold?

The short answer is no – if you take the basic steps to prevent it.

Mold spores are naturally everywhere – they’re just a natural part of our environment. Mold needs two things to grow: water and oxygen. But they don’t need light.

Mold can thrive in any damp area inside a home, often in bathrooms or near plumbing leaks. Furnace humidifiers do not cause mold unless they are set much too high, creating the conditions needed to help mold take over. Again, keeping your humidifier set to 45% should work, but don’t forget to keep checking your hygrometer to ensure you’re getting the right results.

Here are some other important steps to keeping mold in check in your home:

  • Ensure your bathroom has a ventilation fan that works. The humidity from an entire family taking long hot showers can help contribute to mold growth in the bathroom.
  • If you cook a lot using boiling water, you may want to turn your humidifier off for a while, and ensure you have a range hood that vents to the outdoors.
  • If your technician suspects you might develop mold in your ductwork, a UV purification system will help eliminate the problem. Getting your ductwork cleaned and sprayed can help.
  • Front loading washing machines can develop mold if they’re not cleaned out periodically.

Watch for Temperature Drops

The amount of moisture that your home’s air can hold varies with the temperature. Warmer air can hold more moisture than cold air, so if the temperature drops the water can form condensation if it’s too humid. For this reason, try to keep a nice consistent temperature throughout the home, and get your family to agree on a sensible temperature range.

If there’s a sudden cold snap, it can mean your windows get colder than ever, and frost can form. When it melts, it can drip down and pool in the walls if there are leaks around the window. Check the seal around your windows, and if caulking is worn replace it.

Getting the Most from Your Furnace Humidifier

Whole home humidifiers work best with modern variable-speed furnaces. That’s because these operate at lower, efficient speeds most of the time and can provide a more continuous flow of moistened air to your home. It’s also good to know that variable-speed furnaces are much more energy efficient.

Having a qualified technician assess your home is the smartest things you can do to ensure you stay warm and healthy all winter long.

Want to Know More?

There are actually several different kinds of furnace humidifier, and the right one will depend on your needs, the size of your home and your budget. You can learn about the different types on our main humidifiers page.

Learn more about furnace humidifiers >