Glossary Term
Dew Point
Dew point is the temperature at which air becomes saturated enough for moisture to condense on a surface. ASHRAE describes dew-point condition as a measure of absolute humidity determined by cooling air until condensation starts or dew forms on a cold surface. In yacht work, the term appears in two main places: humidity control inside the vessel and environmental control before coating work.
In accommodation and technical spaces, dew point helps explain why condensation forms on glazing, metal liners, chilled pipes, air diffusers, or poorly insulated bulkheads. If a surface temperature falls below the local dew point, water can form even when the room air temperature feels acceptable. That relationship is part of why humidity control, airflow, and insulation work are tightly linked on yachts travelling between cold seawater, hot ambient air, and heavily cooled interiors.
Coating teams also use dew point as a go/no-go condition. ISO 8502-4 states that, unless otherwise agreed, the steel surface temperature should generally be at least 3 °C above the dew point when paints are used. On a yacht paint job, that check protects against hidden condensation on the substrate, which can damage adhesion and shorten the life of the coating system even when the steel looks visually dry.