Moisture tool
Dew point and condensation risk tool
Calculate indoor dew point and compare it with a measured duct, grille, pipe, wall, or window surface.
What dew point means
Dew point is the temperature at which air becomes saturated with water vapor. When a duct, pipe, grille, window, or wall surface is at or below the surrounding air’s dew point, moisture can condense on it.
Dew point is not relative humidity. Relative humidity changes when the air temperature changes, even if the amount of water vapor stays the same; dew point describes the moisture that is actually present, which is why the National Weather Service treats it as the better indicator of how humid air feels.
If condensation keeps returning, find and correct the moisture, air-leakage, insulation, or equipment cause rather than wiping surfaces — EPA’s mold guidance centers on controlling moisture and drying wet materials promptly. For how New Orleans’ outdoor moisture load shapes all of this, see New Orleans dew point and your house.