This is a legacy version of the WELL Building Standard. Please check the latest version here.

Humidity control

Humidity control


To limit the growth of pathogens, reduce off-gassing, and maintain thermal comfort by providing the appropriate level of humidity.


Extremely low humidity can lead to dryness and irritation of the skin, eyes, throat and mucous membranes. Conversely, high humidity may promote the accumulation and growth of microbial pathogens, including bacteria, dust mites and mold, which can lead to odors and cause respiratory irritation and allergies in sensitive individuals. Additionally, higher humidity levels can lead to increased off-gassing: an increase in relative humidity of 35% can increase the emissions of formaldehyde by a factor of 1.8–2.6.

Part 1
Relative Humidity

At least one of the following is required:
A ventilation system with the capability to maintain relative humidity between 30% to 50% at all times by adding or removing moisture from the air.
Modeled humidity levels in the space are within 30% to 50% for at least 95% of all business hours of the year. Buildings in climates with narrow humidity ranges are encouraged to pursue this option.

Part 2
Shower Moisture Barrier

The following is required between showers and changing rooms, if present:
An airlock or ventilation barrier.