This is a pretty frequent question we get as we get closer to winter, since homeowners often do notice dry air around this time of the year.
During winter, the moisture level in the air drops as more and more water vapor gets pulled out of the air outside. Dry conditions are often considered helpful in the summer, as it makes it easier for us to cool off from our air conditioners. However, dry air during the rest of the year threatens not only our comfort but also our health.
Furnaces and forced-air heat pumps are often blamed for causing the air to be dried out even more, but is this really the case?
Yes, But Also No
We get it—this isn’t an answer. Bear with us though!
The issue is a bit more complicated than a simple “yeah your heater dries out your air.” Technically speaking, heating up the air doesn’t directly cause the air to become drier. What does happen is that older furnaces—known as atmospheric combustion furnaces—draw air from the home into their combustion chambers, which allows combustion to occurs.
This causes a bit of a deficit of the air in the home, and outdoor air moves in to replace that deficit. Since the outdoor air is drier during the winter than the indoor air, this can lead to a drop in relative humidity levels.
“But wait, it sounds like you basically just said yes, my furnace is drying out my air!”
Well, newer furnaces can be and are constructed as sealed combustion furnaces. Their combustion chambers are shielded from the inside of the house and draw the air they need for combustion through a pipe that leads to the outdoors. This prevents the furnace from pulling in indoor air and creating that deficit—so in this case, the dry air you feel indoors is not coming from your heater!
In conclusion, yes, dry air is a problem in the winter—the relative humidity level in homes often drops below 30% which is considered too dry. But this isn’t caused by your furnace, it’s caused by our climate.
So, What Can You Do About It?
Alright, so your furnace isn’t causing your dry air, but that doesn’t mean you like it—and we don’t blame you! After all, dry air dries out our sinuses, making us more susceptible to colds and other illnesses since we can’t fight off germs as well. It also dries out furniture, wooden floorboards, and even precision instruments like pianos if you have one in your home.
The solution here isn’t to stop using your heating system, but rather to add a whole-house humidifier to your home. These systems are installed directly into your HVAC system and help keep humidity at a reasonable level as your heater runs. Or, it can even be run independently of your heater!