Types of Whole House Humidifiers

There are three main types of whole-home humidifiers: evaporative, steam, and self-contained. The first two connect directly to your central forced-air heating system. The last one works independently. Humidifiers are controlled by a humidistat, which monitors relative humidity levels.

Evaporative Humidifiers

Evaporative humidifiers are further divided into two main types:

• Bypass humidifiers redirect furnace air through a bypass duct. The bypassed air blows over the humidifier pad to pick up moisture before being distributed around the home. A bypass humidifier can be installed on either the supply or return duct and requires two connections to the ductwork. If you don't need the humidifier running, you can simply close the bypass damper.

• Powered humidifiers use a fan to pull water across the humidifier pad, which allows for a better distribution of moisture in the air than in a bypass type. They connect directly to the supply side ductwork.

At the beginning of the heating season, the damper on the return duct is switched from summer mode to winter mode so that the return air will be directed over the humidifier pad.

Both types of evaporative humidifiers use little to no electricity. It’s the heat from the furnace that evaporates the water. They are also both relatively simple and have few moving parts that can fail.

Although less expensive to operate, evaporative humidifiers aren’t very efficient, converting only 20-30% of the water they use into humidity. The excess water needs to be drained. Also, your furnace system needs to be running for evaporative units to work properly. Otherwise, there is no heat source to evaporate the water.

You may decide to go with an evaporative humidifier if you are on a budget but want to add humidity to your entire home. They will get the job done simply and out of sight.

Steam Humidifier

Steam humidifiers store water in a canister instead of using a pad. When it detects low humidity, the steam humidifier electrically boils the stored water into steam, which is then distributed into your furnace duct system.

The main difference between a whole house steam humidifier and an evaporative humidifier is power. A steam humidifier uses electricity to produce its own power. That means it can run as long as your blower fan is on, whether or not your furnace is running.

As a result of their power draw, steam humidifiers are much more expensive to operate than evaporative models, although they can be up to 90% efficient when it comes to water use. They can be installed without ductwork, which cuts down on labor and material costs.

Overall, steam humidifiers outperform evaporative types because they can provide more consistent levels of moisture, but they will cost you more money.