Thermostat Settings and Indoor Air Quality

One of the most important things in your home is the thermostat. You can save yourself hundreds or even thousands of dollars by simply understanding how your thermostat and HVAC system interact with and affect your home’s indoor environment. Something that might surprise some homeowners is that there is such a thing as running your fans TOO much.

An air conditioning unit does not run all the time, so when faced with a hot home it can be tempting to try and beat the heat by setting your fans to “ON” as opposed to “AUTO” or “CIRC.” Be careful about this, as forgetting to reverse the settings can lead to moisture problems in the coming months. One reason why is condensation. Just like a soda can or a water bottle on a hot day, your HVAC coils will start to condensate or “sweat.”

Condensation becomes a real problem when it happens constantly. Normally, condensation is removed from HVAC coils through a drain pan when the unit shuts off and the fans stop blowing air. However, by operating the fans constantly, you are doing a number of things:

•      You are potentially putting moisture back into the air. With no break for the fan, as the drain pan fills from condensation, the fan can actually suck some of the excess moisture from the coils and increase the humidity in your home. Water - be it from moisture in the air or condensation from the unit itself - is the biggest cause of mold issues in a home.
•      You are putting more stress on the system. With more demand on your HVAC, you’re encouraging not only mechanical failure, but undeniably driving up your electricity bill.
•      You are still cycling the air! Your HVAC unit shuts off after it conditions (removes the heat and moisture) in your home to keep the indoor environment at the temperature you set. By keeping the fans “ON” you’re actually removing some of the air your unit just conditioned for you!

In conclusion, it’s usually best to set your fans on your thermostat to “AUTO” or “CIRC,” as setting them to “ON” can lead to potential problems if left on that option for long periods of time. Condensation from too much cooling can lead to moisture problems, more stress on the system means more problems in the future, and moving more air through your home means you may need to condition more air. Turns out Dad might have been right to tell you not to touch the thermostat - one change has a big impact on both your home and your wallet.