You’ve probably heard this before: “Running a gas furnace during the winter may keep you warm, but it also dries out the air.” Since winter conditions are already drier than the rest of the year because more moisture has solidified out of the air, this can create serious problems for a house. Low humidity makes it harder to keep warm, which means running the furnace even more often. Low humidity also creates potential health problems by drying up sinus membranes, and it can cause damage to wood and painted surfaces.

But is it true that a gas furnace lowers indoor humidity?

The answer isn’t a straightforward one.

The first part of addressing the question is to note that nothing about the way a gas furnace transfers heat to the air that is sent through the ducts removes moisture from it. The gas burners create hot combustion gas that gathers in a heat exchanger. The heat exchanger becomes hot, and the metal exterior transfers its heat to the air passing around it. This does not lower the humidity of the air.

However, the way many gas furnaces work can contribute to dry outdoor air entering the home. These furnaces use atmospheric combustion , and they have been the standard furnace type until recently. If you have an older furnace, it probably uses atmospheric combustion.

What this means is that the burners in the furnaces draw the air they require for combustion from the air around the furnace—i.e. from inside the house. You can tell an atmospheric furnace by looking into it: if you can see the flames of the burners, the furnace is drawing air from the house. This creates an air deficit in the building, allowing outdoor air a chance to move in through any thermal gap in the home’s envelope. Because this outside air is drier than the indoor air, it lowers the house’s humidity level. 

Many newer furnaces have sealed combustion: the burners are in a sealed chamber and not exposed to the air of the home. They draw the air they need through a PVC pipe that leads to the outside. This type of combustion not only prevents a drop in humidity, but it’s also more efficient and safer. If you have trouble with dry air and you have an old furnace, we recommend making the upgrade to sealed combustion.

You can also combat dry conditions in your house with the installation of a whole-house humidifier. We can do this job for you: the humidity is integrated into the HVAC system and you can control it from the thermostat so the humidity is properly balanced—you won’t end up making the house too humid. 

For the heating services in Indianapolis, IN you need for comfort, whether it’s installing a new furnace, fixing your current one, or putting in a whole-house humidifier. You can put your trust in us. 

At Vital Heating & Air, we know “Your Comfort Is Vital!” Schedule service today.