Indoor Humidity and Dew Point

A percentage without temperature is incomplete.

Relative humidity describes how close the air is to saturation at its current temperature. Warm air can contain more water vapor than cold air, so the percentage changes when air warms or cools even if moisture is not added.

Surfaces below the dew point can collect moisture.

Use the calculator to estimate dew point, then compare it with windows, ducts, pipes, or basement surfaces. Condensation is a surface-temperature and moisture-source problem, not merely a thermostat preference.

EPA guidance emphasizes moisture control and readings below 60%.

Season, climate, envelope, and surface temperatures matter. In cold weather, a lower indoor humidity may be needed to prevent window condensation. Verify the sensor and watch the trend rather than reacting to one instant reading.

Leaks, drying materials, cooking, showers, and outdoor air can dominate.

Log when and where humidity rises. Address active water leaks and wet materials promptly. Vent source activities where appropriate and size dehumidification or cooling only after understanding the load.