How to Size a Humidifier: 2 Factors to Consider
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How to Size a Humidifier: 2 Factors to Consider


In the winter, the air in your home tends to be drier than at other times of the year, typically because you’re running your HVAC (heating, ventilation and air conditioning) system’s heating components. An effective way of dealing with the many problems that dry air can cause is with a properly sized whole-house humidifier.

Here are some suggestions on how to size a humidifier and choose a system that will increase your home’s relative humidity and comfort.

The output of a humidifier is measured in the number of gallons of water that the humidifier can produce for absorption into the air during a 24-hour period, in gallons per day. Two main factors affect the necessary gallons per day, including the:

  1. Size of area to be humidified, which will affect how much moisture the humidifier should be able to produce.
  2. Tightness of the structure’s seal, which is how well the home is insulated and sealed against energy and moisture loss. A tight home has good levels of insulation, storm doors and windows installed, weatherstripping applied to reduce drafts, air and energy leaks sealed, fireplace dampers closed, and an effective vapor barrier in place.

On average, a tightly sealed home of 1,500 square feet should require a humidifier output of 3.2 gallons per day. An average home of the same size would need a humidifier output of 5.5 gallons per day, while a loose home would need 7.0 gallons per day.

As you are comparing home humidification systems, keep in mind the many problems that dry air can cause in your home, including:

  • Uncomfortable physical effects, such as dry, itchy skin; irritated eyes and throats; nosebleeds; and respiratory issues.
  • Increased amounts of static electricity, which is annoying to people, but downright dangerous for your delicate electrical equipment. One zap of static electricity can destroy it.
  • Damage to wood furnishings, paneling, flooring and other wooden objects or construction features.
  • Decreased comfort, since dry air makes you feel colder than the actual room’s temperature. This happens because dry air absorbs moisture from your skin, producing a cooling effect.

Roth Heating & Cooling provides reliable, expert HVAC services to heating, cooling, plumbing and electrical customers in Portland, Bend, Salem and the surrounding areas in Oregon. Contact us today for more information whole-house humidification, how to size a humidifier, and for assistance in the correct method of how to size a humidifier for your home.

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