This Nordtest method specifies a test method for the ability and capacity of coatings to absorb water condensed from the surrounding air on the coating surface.
The type of material tested is porous and classified as "anticondensation” paints and coatings. Coatings of the type are used on non-insulated roofs or outdoor roofs where water will condense from the air during periods of cooling, that is during evenings and nights.
The material is applied on the underside of the roof (the ceiling) in amounts in the range 500-1000 g/m2. The absorption capacity is often 200-400 g/m2 which is considered sufficient capacity for suitable delay of water drip from the ceiling.
During the day and during periods of heating the material is designed to release the absorbed water almost completely by evaporation. Therefore repeated determination of capacity is relevant in cycles of absorption by cooling and evaporative release by heat.