Dew point
The amount of steam that can be contained by a mass of air decreases with decreasing of the temperature. The same way, a temperature decrease has a relative humidity increase as consequence.
For example, if we cool a mass of air at 20°C with relative humidity at 60% bringing it to + 19°C, the relative humidity will change to 63.85%.
If we cool it to 13°C, the relative humidity will changeto 93.7%.
Cooling it to 12.01°C, the relative humidity will reach 100% (saturated air). This temperature is called the dew point. Below this temperature, the water vapor begins to condense.
When we take a bottle of cold beer from the refrigerator, this is covered with droplets: it’s the air’s humidity that condenses on the surface of the bottle because the bottle has a temperature below the air’s dew point.
In kitchens and bathrooms of bad insulated houses, during cold days, humidity is formed on the walls. This is because the air in those environments is quite humid and, encountering the cold wall, reaches its dew point.
In order to prevent the phenomenon it’s possible to raise the temperature of the wall above the air dew point or decrease the dew point of the air below the temperature of the wall (by dehumidifying the air) .
For example, if we cool a mass of air at 20°C with relative humidity at 60% bringing it to + 19°C, the relative humidity will change to 63.85%.
If we cool it to 13°C, the relative humidity will changeto 93.7%.
Cooling it to 12.01°C, the relative humidity will reach 100% (saturated air). This temperature is called the dew point. Below this temperature, the water vapor begins to condense.
When we take a bottle of cold beer from the refrigerator, this is covered with droplets: it’s the air’s humidity that condenses on the surface of the bottle because the bottle has a temperature below the air’s dew point.
In kitchens and bathrooms of bad insulated houses, during cold days, humidity is formed on the walls. This is because the air in those environments is quite humid and, encountering the cold wall, reaches its dew point.
In order to prevent the phenomenon it’s possible to raise the temperature of the wall above the air dew point or decrease the dew point of the air below the temperature of the wall (by dehumidifying the air) .
