Humidity is the amount of water vapor suspended in the air. While high humidity causes discomfort, air that is excessively dry can cause a range of problems for both human health and the integrity of a home’s structure. This dryness is especially common during winter when heating systems warm the air, significantly lowering its capacity to hold moisture. Recognizing the subtle signs of dry air is the first step toward creating a more comfortable and healthy living environment.
Physical Signs of Low Humidity
The human body is highly susceptible to a moisture-depleted atmosphere because dry air accelerates the rate at which water evaporates from skin and mucous membranes. This rapid moisture loss often leads to noticeable physical symptoms that can be the first indication of low indoor humidity. People frequently wake up with a scratchy throat, dry nasal passages, or chapped lips because moisture has been pulled from the delicate lining of the respiratory tract overnight.
Irritation to the mucous membranes can increase susceptibility to colds and the flu, as these tissues serve as a barrier against airborne pathogens. When the lining of the sinuses becomes too dry, it can crack, sometimes leading to nosebleeds. Dry air also strips the skin of its natural moisture barrier, resulting in increased itchiness, flaking, and tightness. This can worsen existing conditions like eczema.
Environmental Indicators in the Home
Beyond personal discomfort, dry air manifests through visible changes in the home environment. A common indicator is a noticeable increase in static electricity, which occurs because the air lacks the moisture needed to conduct and dissipate electrical charges. This results in frequent shocks when touching doorknobs, pets, or electronics.
Wood materials naturally contain moisture, but they begin to release that water into the dry air, leading to shrinkage and structural damage. This process causes gaps to appear between hardwood floorboards and can lead to cracking or warping in wooden furniture, cabinetry, and trim. Even houseplants show signs of distress, with leaves developing brown tips or wilting rapidly as the parched air pulls moisture from them.
Measuring and Defining Optimal Humidity
To confirm the presence of dry air, it is necessary to measure the relative humidity (RH). RH is the ratio of water vapor in the air compared to the maximum amount the air can hold at that temperature. The device used for this measurement is called a hygrometer or a thermo-hygrometer, which is often included in modern thermostats. For the most accurate reading, the device should be placed away from direct heat sources or windows that could skew the local temperature.
The generally accepted optimal range for indoor relative humidity is between 30% and 50%. Levels consistently below 30% are considered excessively dry and can lead to the health and environmental issues described. Maintaining a level below 60% is important because humidity above this threshold encourages the growth of mold, mildew, and dust mites.
Practical Steps for Increasing Moisture
The most direct and effective solution for consistently low indoor humidity is the use of a humidifier. Portable units, which come in evaporative and ultrasonic varieties, can treat single rooms and are suitable for localized dry air issues, such as in a bedroom. Whole-house humidifiers integrate directly with the home’s heating and cooling system to manage moisture levels throughout the entire structure.
Regular maintenance, especially cleaning, is necessary for any humidifier to prevent the growth of bacteria and mold that could be released into the air along with the moisture. Less intensive methods can also provide a temporary or supplementary boost to humidity. Simple activities can release water vapor into the surrounding air:
- Boiling water on the stove.
- Leaving the bathroom door open after a hot shower.
- Drying laundry indoors.
- Strategically placing bowls of water near heat sources for passive evaporation.