Also in this article:

Types of Humidifiers
• Evaporative
• Cool-Mist Impellers
• Steam
• Ultrasonic

Balanced humidity is important not only for your family’s optimal health and comfort but also for your house. Lower levels of water vapor in the air can increase bothersome static electricity, and higher humidity levels can encourage molds and mildew.

During winter, the first sign of overly humid air is condensation forming on the inner surfaces of windows. Though this normally isn’t a serious problem, the same condensation may collect on the inner surfaces of exterior walls. This can rot the structure and ruin insulation. Peeling, blistering, or cracking paint—especially if bare siding is visible in spots—usually indicates this condition.

Keeping humidity at the proper level often demands mechanical assistance. On sultry summer days, when indoor humidity rises above the comfort range, many people turn on air conditioners or dehumidifiers to help dry the air. And when the dry winter heating season sets in and drops relative humidity to skin-chafing lows, boosting the humidity usually calls for a humidifier.

A humidifier is simply a device that puts water vapor into a home’s air. Depending upon its water-output capacity, it may serve a single room or the entire house. Room-size humidifiers are referred to as “tabletop” units. To humidify a whole house, you need either a freestanding cabinet “console” unit or a “central” humidifier that ties into the home’s forced-air heating system.

Tabletop and console models are relatively inexpensive, easy to move from one room to another, and easy to hook up. Both types must be filled manually—usually on a daily basis.

Regardless of the method they use to humidify air, tabletop models run from about $20 to $70, and consoles run from $75 to $150. Tabletop units output from 2 to 4 gallons per 24 hours. Small consoles output 8 gallons per 24-hour period. The latter can handle up to a 2,000-square-foot area. A large console may output 14 gallons, enough to humidify a 3,250-square-foot house.

Central evaporative humidifiers are hooked up to the heating equipment, and water is piped directly to them, so they’re out of sight and out of mind most of the time. Because they deliver humidified air directly to rooms throughout the house, they’re particularly efficient. The only drawbacks are that you need a forced-air system to operate a central humidifier and humidification takes place only when the forced-air system is running (this isn’t a problem in most homes because it is generally the heating process that dries out the air). Equipment prices range from $140 to $200; the cost of installation depends upon the complexity of the work, but it is likely to run about $100.

How to Select a Humidifier

The Association of Home Appliance Manufacturers (AHAM) tests room humidifiers using uniform methods to verify water-output ratings and to allow consumers to compare models accurately. (For AHAM’s Directory of Certified Humidifiers, visit www.aham.org.)

When buying a tabletop humidifier, check to see whether or not it has a humidistat, and evaluate the number of speeds or settings it has—some have two or three speeds or a quieter night setting, for example.

It’s also important to examine the types of controls on a console humidifier, which should have a low-water light, automatic humidistat, and air-flow controls. Multi-speed and variable air-flow settings and an automatic shut-off are also helpful. Some models even have a light that goes on when the filter is dirty.

For any type of humidifier that must be filled manually, find out how often it must be refilled when running at full speed.

If you’re looking into a central humidifier, be sure it can be installed relatively easily. In most cases, maintenance is limited to changing an evaporator pad about once a year; this component should be easy to inspect and access.

Central units are sold at home improvement centers or by heating equipment dealers. If you’re an accomplished do-it-yourselfer, a dealer can help you select the proper size, make sure you have all the necessary components, and give you installation advice. If you haven’t done this type of work before, have the unit professionally installed.

To ensure the lasting and safe performance of a humidifier, be sure to follow the manufacturer’s directions for use and care.

Following is a closer look at the four main types of humidifiers:

Evaporative

Evaporative humidifiers, the most popular technology on the market today, capture virtually all minerals and pollutants from even the hardest water, eliminating the white dust that ultrasonic humidifiers can create. They work by passing an air stream through a wet medium such as a sponge or dampened grille.

Some evaporative humidifiers have fiber honeycomb-type panels that wick water upward from a reservoir; others employ a foam or cloth drum that spins through a water-filled trough as air passes by. Still others blow air through a woven aluminum pad that is saturated by a constant stream of water. In some cases, filters are treated with a special compound that retards bacterial growth.

With tabletop and console models, a quiet fan blows air through the damp surfaces. Some whole-house models use the heating system’s blower to do this job. A filter collects the dissolved solids; with most models, this filter is disposable.

Central evaporative humidifiers are made to be attached to the home heating system. They can output up to 25 gallons per day. High-capacity models are fan powered; other types don’t require a motor. All are hooked up to your house’s plumbing so manual filling isn’t needed.

One newer product, which Emerson offers, utilizes no moving parts, electrical cords, hot water, or even a motor. Ideal for a child’s room, this unit sits directly over a forced-air floor register and can be easily moved from one place to another. It retails for about $20.

Cool-Mist Impellers
A cool-mist impeller humidifier spins tiny droplets of moisture into the air. Available primarily as tabletop units, these hold from 2 to 3 gallons of water, are filled manually, and are easy to move around.

Cool-mist impeller humidifiers don’t have the problem with white dust that ultrasonic units have because the droplets produced are larger. And unlike steam humidifiers, cool-mist units use electricity only to propel the air, not to provide heat. This means they consume far less power.

Steam

Some humidifiers disperse water vapor into the air the same way a tea kettle does: by boiling water. Steam units are manufactured as tabletop or wall-attached models that spray steam into a living space or forced-air heating ductwork through a dispersion tube.

With all models except for tabletop varieties, tap water is piped directly into a steam unit so that it doesn’t require manual filling. Because steam is evaporated water, it doesn’t contain bacteria or mineral deposits that might contaminate the air you breathe.

Ductwork systems, which are manufactured for both commercial and residential applications, can be custom designed to output any amount of steam a house might need—though custom units may be prohibitively expensive for most home applications. And they can be costly to operate.

Steam units employ an electrical element to heat the water; when this is on for extended periods, it can rack up the energy dollars.

Ultrasonic

Though ultrasonic humidifiers used to be popular, they have fallen into disfavor because of the suspicious “white dust” they create.

With ultrasonic humidifiers, a thin sheet of water is passed over a transducer that vibrates and excites the water, breaking it into millions of tiny droplets. The problem is that calcium and other minerals in the water become airborne with the moisture, particularly in areas that have hard water. This ends up as a dust that falls on objects and pollutes the air you breathe. The Environmental Protection Agency has warned that the tiny particles of minerals and microorganisms that may be propelled into the air can cause illness or allergies.