A dehumidifier that is adjusted incorrectly might be just as worthless as one that is not there.
What setting should your dehumidifier be in?
It pays useful to educate oneself about relative humidity levels even before you purchase a dehumidifier.
What humidity level is ideal for a basement?
The fundamental concept is to maintain indoor relative humidity between 30 and 50 percent.
This includes the dehumidifier setting for the basement.
But sometimes we’re confused about how to set the dehumidifier in the basement—should it be set to 30 percent, 40 percent, 50 percent, or even 60 percent relative humidity? This is crucial for determining the ideal dehumidifier setting to stop mold from growing.
The EPA explicitly stated the following in the third lesson on humidity under “Mold Course Chapter 2“:
Sometimes, air dampness or humidity (water vapor) may provide enough moisture for mold to thrive.
Relative humidity (RH) inside should be maintained below 60%, preferably between 30% and 50%, if practical.
Low humidity may help deter dust mites and pests like cockroaches.
The temperature is a crucial factor that we often overlook when setting a basement dehumidifier.
For instance, mold develops in:
- A moist atmosphere. Example: An 80 percent relative humidity basement.
- A warm climate. The likelihood of mold growth increases with the indoor temperature.
As a result, we must be conscious of the relative humidity and temperature in the basement.
The comments for settings of 30%, 40%, 50%, and 60% relative humidity may be found in the conclusion.
What Dehumidifier Relative Humidity Setting Is Best For Preventing Mold?
It might be difficult to pinpoint at what relative humidity level mold thrives. The following scientific resources may aid HVAC engineers:
- Less than 65%. According to an article from Portland State University that quotes a report from Canada Mortgage Housing Corporation.
- Between 30% and 60%. Aspen Environmental Services claims.
- Less than 75%. According to S. S. Block’s 1953 essay, “Humidity Requirements for Mold Growth,” written when he was a professor at the University of Florida’s Department of Chemical Engineering.
In other words, the answer is ambiguous.
However, the majority of HVAC professionals agree that a basement dehumidifier set to 40% is the best option.
It’s possible that 50% would be sufficient.
On the other hand, the chance of mold development is greatly raised at higher temperatures, such as 80°F or 90°F.
Dehumidifiers should always be adjusted to a level of 40% or below to avoid this and stop the formation of mold.
Additionally, some HVAC manuals include temperature-dependent dehumidifier setting charts, such as these:
Chart for Dehumidifier Settings
| Outdoor Temperature | Max. Indoor Humidity (At 68°F) |
| -20°F Or Below | 15-25% |
| -20°F To 0°F | 20-35% |
| 0°F to 25°F | 30-40% |
| 25°F To 50°F | 40% Or Below |
| 50°F And Higher (Most Common) | 50% Or Below |
As we can see, the dehumidifier setting is also influenced by the weather outside.
Of course, the safest but not the most energy-efficient setting for a basement dehumidifier would be 30%.
All the power required to reduce relative humidity from 40% to 30% would be wasted if the 40% relative air humidity in the basement could ensure the absence of mold development (or would be of no consequence as far as mold growth is concerned).
The complete list of basement dehumidifier setting choices is shown below with explanations:
- 60%. When too high, mold could develop. Is a basement too humid at 60 percent? Without a doubt.
- 50%. Not safe enough; there may be a small chance of mold formation at hot temperatures (usually localized to a corner).
- 40%. Just right; highly secure with no possibility of mold development.
- 30%. Low enough to be ineffective in lowering humidity from 40% to 30% while maintaining anti-mold safety.
