Managing Humidity Levels in Your Home

Published on: June 24, 2013

Humidity is a sticky issue. When it’s warm, it’s usually too humid, and during the winter, the air can be too dry. In temperate climates that have distinct heating and cooling seasons, it’s common for homeowners to experience problems with moisture levels that are too high and too low depending on the weather. Relative humidity (RH) measures the percent of water vapor that is suspended in the air. Moisture levels also affect how actual temperatures are perceived. For example, with an RH level of 100 percent, a room that is 75 degrees actually feels like a steamy 79 degrees. In the winter, higher RH levels work to your advantage by making a room feel slightly warmer without additional heat. Ambient moisture levels make a small but noticeable difference in overall comfort, and maintaining proper moisture levels improves indoor air quality significantly.

Ideal Moisture Levels

Although the effects are different, low RH can be just as bad as high RH. Viruses, bacteria and allergens can adapt to both extremes on the moisture scale, and these airborne irritants are detrimental to your health. Problems with RH can also be harmful to wood floors, furniture and fine instruments that are susceptible to dampness and dryness. Textiles, paper collectibles and art collections also require precise levels of moisture to stay in the best possible condition.

  • For optimal health and comfort, experts recommend maintaining RH levels between 40 and 60 percent.
  • Spaces where RH levels are below 25 percent are too dry. This is most likely to occur in dry climates or when humidified air escapes in the winter.
  • Homes where RH exceeds 60 percent are too moist and would benefit from air conditioning, dehumidification or additional ventilation. Ideal RH levels for comfort depend on your tolerance to humid conditions.
  • Special considerations should be taken for individuals who have allergies or asthma. To reduce triggers, the Cleveland Clinic recommends using a dehumidifier to keep indoor moisture levels between 25 and 50 percent.

Measuring Indoor Humidity

Indoor moisture levels aren’t a top concern for most families. Sometimes, problems come with obvious signs like condensation on windows or mold growth. It’s also possible for moisture problems to go undetected. In humid homes, residents are more likely to experience dust mite allergies, termite infestations and serious structural problems. While condensation on windows is one sign that a home is too humid, it could also mean that condensation is building up inside the walls and could contribute to secondary structural issues or health problems. That’s why tools that measure RH are important.

  • Digital or analog weather stations often include a hygrometer that measures ambient moisture levels. These systems are affordable, readily available and can be placed anywhere.
  • RH levels can also be measured with a simple indicator card. This basic tool for determining RH uses a soft felt-like material containing a moisture-sensitive ingredient that changes color.
  • Weather.com offers an indoor RH estimator tool that considers your thermostat settings, current moisture levels and outdoor temperatures based on your location.
  • For a more accurate reading and for more control over RH levels, consider a programmable thermostat with moisture controls. Bryant and Carrier both offer thermostats that control humidifying products and provide several dehumidification options.

Excessive Moisture

Overly humid environments are prone to a number of moisture-related problems, including several that pose serious health concerns. The average family releases nearly six gallons of vaporized water into the air each day. During the cooling season, the air conditioner also pulls in hot, humid air that has to be dehumidified by cooling the air below the dew point and collecting that moisture in a condensate pan. Sometimes, basic climate controls aren’t enough to prevent unwanted moisture accumulations. Buildings where moisture levels remain above 60 percent are prone to these problems.

  • Condensation on windows
  • Stains on walls and ceilings
  • Peeling and flaking paint
  • Mold and mildew growth
  • Dust mite growth and allergens

Managing moisture-generating activities and addressing areas where water or humid air can enter your home are simple ways to help prevent excessive RH levels. The majority of moisture issues can be attributed to structural deficiencies, household features and problems related to HVAC equipment.

Causes of High RH and Solutions

Managing unregulated moisture sources is the key to controlling RH. Structural problems are among the most serious and difficult to correct. Here are a few of the potential problems and how they can be corrected.

  • Improve grading to reduce water infiltration in basements and foundations.
  • Crawlspaces and basements with dirt floors should be covered with a vapor barrier.
  • Weatherize cracks around windows and doors to prevent drafts.
  • Insulation should be applied to attic spaces and walls but should not cover roof vents.
  • Attic and roof vents should be clear and configured to provide “attic wind.”

Regular household activities generate moisture that stays in the air unless dehumidification equipment and exhaust fans are used. Homeowners should evaluate solutions for these problem areas that contribute to high RH.

  • Exhaust fans with external vents should be installed in kitchens and bathrooms to remove water vapors.
  • All laundry machines should be connected to exterior vents.
  • Portable dehumidifiers should be placed in basements and areas that aren’t air conditioned.
  • Carpets absorb moisture from the air. These cushiony floor coverings are also breeding grounds for dust mites that require moisture to survive. Allergy experts say that those populations die when RH is below 45 percent, which helps improve air quality.

Air conditioners are vital for keeping homes comfortable and removing excess moisture. However, some problems can prevent an HVAC system from doing its job. To successfully remove moisture, HVAC drip pans and drains must be clear and functioning properly.

Improperly sized HVAC units also have problems removing moisture from the air. AC Southeast® contractors calculate system requirements based on a home’s square footage and various heat loss and heat gain factors. Improper load calculations and upsizing units to compensate for low insulation, leaky ducts and old windows can cause a unit to “short cycle.” This means that the unit releases an intense blast of cold air but shuts off before the air circulates enough for a significant amount of moisture to be removed. Pollutants are also removed along with moisture, so this deficiency also compromises the natural air cleaning effect.

Low Moisture Levels

Although low moisture levels are generally preferable to hot, humid conditions, low RH can have unexpected effects on your home and your health. Everything dries out when RH levels fall below 30 percent. This can be damaging for wood products, hardwood floors and fine instruments that are also susceptible to excessive moisture. Static electricity is particularly apparent in homes with low moisture, and these random shocks can disable sensitive electronics. Conditions that are overly dry are rough on the skin and mucus membranes. In dry conditions, skin irritations, nosebleeds and airborne diseases are more prevalent. Some people even experience throat irritation and difficulty breathing due to dryness.

Low RH is a common problem in the winter when humidified air escapes through cracks. Carrier and Bryant both offer a range of whole-house humidifiers that are compatible with heat pumps, furnaces and other heating systems. These state-of-the-art humidifying products release pure water vapor directly into heating ducts and are controlled by your primary thermostat.

Humidity Managing Products

Today, there are a number of innovative products designed to improve indoor air quality and overall comfort. In addition to integrated humidifiers and whole-house air cleaners, advanced thermostats and system controls can help homeowners improve their comfort. Carrier and Bryant both have programmable thermostats with accurate moisture controls. These products allow homeowners to program daily temperature and moisture settings. With the appropriate equipment and controls, homeowners can humidify their home with or without heat and enjoy additional dehumidification in cooling mode.

In conclusion, lowering RH in the summer improves comfort, controls dust mites and reduces moisture that damages buildings. On the other hand, increasing moisture levels in the winter improves comfort, reduces dust and slows the transmission of airborne viruses. Maintaining the perfect balance of temperature and moisture is the secret for creating a healthy, comfortable home. Find a local AC Southeast® contractor for help taking control of indoor moisture levels.