Where does water vapor condense?
In walls, water vapor condenses on cold surfaces. If the temperature of a surface is colder that the dew point temperature (such as OSB sheathing or studs in the winter), water vapor will condense on that surface. If the temperature of the surface is warmer than the dew point temperature, such as a Fullback® Thermal Support System product, the water vapor will not condense. Good examples are the hot and cold water pipes in a home. On a warm, humid day, water vapor will condense (“sweat”) on the cold water pipe, because the temperature of the pipe is colder than the dew point temperature. However, water vapor will not condense on the warm water pipe, because the temperature is warmer than the dew point temperature.
