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What Should the Humidity Be In My House?

Indoor humidity plays an important role in the comfort and health of household occupants and has a substantial effect on the costs of cooling and heating a home. If it’s difficult to sustain comfortable temperatures in your home, whether if it feels too dry in the winter months or too hot and sticky during the summer, learn the many benefits of maintaining optimal indoor humidity from season to season. You may also lower your energy bills and enjoy healthful indoor-air quality (IAQ) as a bonus.

Humidity Inside the Home

The level of humidity, or moisture, inside a home is referred to as relative humidity. Relative humidity is a measurement of how humid air feels, as opposed to the actual amount of moisture in the air. The reason for this apparent disparity is because as outside air enters a home and becomes heated or cooled, the air expands (heating) or condenses (cooling), but the volume of moisture (humidity) stays the same.

For instance, during the cooling months, warm and humid outside air enters a home through entryways, air leaks around windows and doors, or other places in the home’s shell. As the warm and humid air is cooled by the cooling system, the air condenses, which makes the apparent moisture level increase, feeling even more humid and sticky.

The opposite sensation occurs during the heating months. As cold outside air enters a home and becomes heated, the air expands. This makes the air feel dry even though the total volume of moisture has not changed.

What Should the Humidity Be in My House?

Optimal indoor humidity levels should be between 35 and 55 percent (i.e., 35 to 45 percent during the cooling months and 45 to 55 percent during the heating months). For homeowners throughout the Chicago area, Northwest Indiana and Southwest Michigan, indoor humidity management is a challenge from season to season, with the average annual humidity levels hovering around 50 percent or higher (70 to 80 percent humidity) than optimal conditions.

This has adverse effects for many aspects of daily living, depending on the season. During the cooling months, high indoor humidity creates or exacerbates the following:

  • Mold, mildew and bacteria take root and grow, which can exacerbate health ailments in household occupants.
  • Porous objects, structure and possessions, such as home structure, furnishings, wooden cabinetry and more, absorb excessive moisture and may become damaged.
  • Dust mites proliferate in humidity levels above 55 percent.
  • Overly humid air holds more heat, which increases cooling expenses.

The heating months tend to below normal humidity levels that has these adverse effects:

  • The flu virus spreads and infects hosts more easily in dry air.
  • Dry air feels cooler than optimally humidified air, which lends to increased heating costs and home comfort suffers.
  • Dry air pulls moisture out of porous objects, structure and possessions, which can lead to cracking, splitting and other damage.
  • Dry air causes other health ailments and discomforts, such as dry skin and eyes, sore and scratchy throat, fatigue and dry nasal passages, making occupants more susceptible to illness.

Managing Indoor Humidity

The most effective and energy-efficient method to manage indoor humidity from season to season is with a whole-house dehumidifier and/or humidifier. A whole-house dehumidifier and humidifier attach to the existing duct system, or dedicated ducts may be installed by your HVAC professional if no ducts exist. Operation is fully automatic with water dispersed (humidifier) through the plumbing. Here's how they work:

  • A humidistat monitors indoor humidity levels with a built-in hygrometer.
  • When indoor humidity is above optimal conditions (e.g., during the cooling months) as set by a household occupant using the humidistat, a whole-house dehumidifier activates and begins to remove moisture from ducted airflow using a chilled coil (much like an air conditioner). Moisture condenses onto the coil and drains away.
  • When indoor humidity is below optimal conditions (e.g., during the heating months), the humidistat for the whole-house humidifier signals a solenoid valve to open water flow through a plumbing line. Water flows down a media panel, which allows ducted airflow to transport water vapor throughout the home.
  • When optimal indoor humidity levels are reached, the dehumidifier or humidifier deactivates.

One of the nice benefits of whole-house dehumidification and humidification for homeowners throughout the greater Chicago, Northwest Indiana and Southwest Michigan areas is that by maintaining optimal humidity levels, cooling and heating are not necessary for much of the year, especially when combined with proper ceiling fan strategies.

For more information about indoor humidity management, contact 24 hours a day, seven days a week.

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