While often used interchangeably, moisture and humidity are not the same—and understanding the difference helps you take better control of your indoor environment.

• Moisture refers to water that is present on surfaces or within materials—like wet walls, damp carpet, or steam rising from a pot.
• Humidity refers to the amount of water vapor in the air, and it’s measured as relative humidity (RH).

Relative humidity tells us how much moisture is in the air compared to how much it can hold at a given temperature. For example, a RH of 50% means the air is holding half of the moisture it’s capable of holding at that temperature.

Here’s where two important processes come into play:

• Condensation is when water vapor turns into liquid. This happens when warm, moist air touches a cool surface—like when you see fog on your bathroom mirror or water droplets on the inside of your windows.
• Evaporation is the opposite—it’s when liquid water becomes vapor, adding moisture to the air. This happens when water evaporates from showers, cooking, or even houseplants.

Keeping indoor RH between 30% and 50% helps maintain a healthy balance. Higher than 50% can encourage mold and dust mites, while lower than 30% can lead to dry skin, irritated sinuses, and even damage to furniture or wood structures.

By recognizing how moisture and humidity interact—and how they move between vapor and liquid—you can better manage conditions that support a healthy home.