Controlling the humidity level inside your house during winter is important for your overall comfort and the health of you and your family. Winter air already tends to be drier, and having your heating system running to keep warm just makes things worse.
Why Dry Indoor Air Is a Common Issue During Winter
To understand why dry air is so common during winter, it’s first necessary to explain the difference between the concepts of absolute humidity and relative humidity. Absolute humidity just refers to how much total moisture there is in the air. Unless moisture is added to the air through evaporation or is removed from the air through condensation, absolute humidity stays the same regardless of the air temperature.
Relative humidity is how saturated the air is, i.e., the amount of moisture the air contains as a percentage of how much moisture it could potentially hold. Unlike absolute humidity, relative humidity consistently changes as the air temperature goes up and down. Warmer air can hold more moisture than colder air. That’s because the molecules in warmer air are more spread out, meaning there is more room for water vapor molecules. As long as the absolute humidity stays the same, the relative humidity continually decreases as the air temperature increases.
Another way to think about relative humidity is how humid the air feels. The fact that the water vapor molecules in warmer air are more spread out means that fewer of them come into contact with your skin, resulting in the air feeling drier.
Winter air is already drier due to it not being able to hold as much moisture. When your furnace runs and heats the air, the relative humidity then decreases. Furnaces don’t actually dry the air out, but they do cause the air to feel drier.
Another issue with conventional furnaces is that they pull in air from the surrounding area to supply the burner flames with oxygen. This causes the air pressure in the house to drop, which can result in cold, dry outdoor air getting drawn in through gaps in the house’s exterior. The fact that the incoming air is drier leads to the humidity level inside the house being further reduced. This generally isn’t a problem with high-efficiency condensing furnaces, as they draw the air they need to supply the burners directly in from outside instead of from the surrounding areas. As such, they don’t cause the air pressure in the house to decrease.
Why Dry Air Can Be a Concern
Dry air can create a variety of issues, such as an increase in static electricity that can result in you frequently getting shocked. Overly dry air also saps moisture out of your body. That’s why you usually have more issues with dry, itchy skin, dry hair, irritated eyes, and chapped lips during the winter.
Low humidity levels cause your mucous membranes to dry out as well, leading to your throat, nose, and sinuses feeling dry and irritated. Mucous membranes are one of your body’s main lines of defense against infection, as they work to trap bacteria and viruses from getting inside your body. When your mucous membranes are dry, they can’t do their job properly. That’s the main reason why people are more prone to illness and infections during the winter when they’re constantly exposed to drier air.
Low humidity levels can damage furnishings and your home’s structure as well. Dry air saps moisture out of wood and leather in the same way it does your body. This can lead to leather cracking and wood cracking, warping, and twisting.
What Is the Ideal Humidity Level During Winter?
Ideally, you should always try to keep the relative humidity level in your house between 40% and 50%. Anything below 40% and you won’t feel as comfortable and will be more likely to experience the issues we discussed in the previous section. If the humidity level is frequently much above 50%, you can experience issues with condensation inside your house that creates the potential for mold growth. Dust mites also thrive in warm, moist conditions, which can create problems for people with allergies and asthma.
How Your HVAC System Can Help You Avoid Dry Winter Air
While running your heating makes your house feel drier in winter, your HVAC system can also help you tackle issues with dry winter air. The only way that you can raise the humidity level is by adding moisture or steam to the air, and the most effective option for doing this is by running a humidifier.
Many people turn to humidifiers during the winter, especially when they have a cold, and their throat, nose, and sinuses are already irritated. Portable humidifiers can provide relief from dry air, but they aren’t an effective solution for increasing the humidity level throughout the entire house unless you have one running in nearly every room. They also require quite a bit of maintenance in terms of regularly washing and refilling the water reservoir and changing the air filters.
Adding a whole-house humidifier to your HVAC system is the most effective option for controlling the humidity level throughout every room of your house. These units add moisture to the air flowing through the ductwork so that the hot air blowing out of the vents in each room isn’t nearly as dry. Many whole-house units can be controlled with a humidistat, which allows you to set your desired humidity level. In this case, the humidifier will only run when the air is below the desired level to ensure that your house never gets too humid. Another advantage of whole-house units is that you can connect them to your house’s water supply, eliminating the need to refill the water reservoir.
There are three types of whole-house units: bypass humidifiers, fan-powered humidifiers, and steam humidifiers. Both bypass and fan-powered units rely on the heat from the furnace to cause water on a mat or wick to evaporate. Bypass humidifiers work passively, meaning that some of the hot air from the furnace just naturally gets forced through them by the furnace blower. Fan-powered units actively draw in hot air, allowing them to work more effectively.
Steam humidifiers use electricity to boil water and produce steam, which enables them to add much more moisture to the air. The downside is that they are fairly costly to run due to the amount of energy they use. The plus side is that you can run a steam humidifier when your furnace is off, since it doesn’t rely on the hot air from the furnace.
Joyce Cooling & Heating Inc. is a local, veteran-owned family company providing top-notch HVAC services throughout the Greater Nashua area. We specialize in indoor air quality and have a range of options to meet your needs. Whether it’s installing a humidifier or an air purification system, you can trust us to keep your air clean and your home comfortable. For more information on our humidity control solutions or to schedule an appointment, contact us today.
