Temperature and Steam Relationship, Absolute and Relative Humidity, Vapor Pressure

One of the gases that bring out the atmosphere in which we live is water vapor. The level of each of the components in the atmosphere, which is a mixture of gases, is constant. In contrast, the water vapor level changes with the temperature of the atmosphere.

The maximum water level that 1 m³ of air can carry under constant pressure at certain temperatures is called the saturated water vapor level (Gs). As the temperature increases, this value increases. For example, under normal atmospheric pressure at 20°C, 1 m3 of air can carry up to 17.2 g of water vapor, while at 25°C this rate can increase to 22.9 g, and at 100°C to 599 g.

The level of water vapor that 1 m3 of the air contains at a certain temperature is called absolute humidity. The saturated water vapor level of absolute humidity is called relative humidity (cp) (relative, relative, relative humidity). As can be understood from here, the relative humidity numerical value of saturated water vapor is 100%. Relative humidity values ​​below this numerical value will reach 100% if the temperature decreases, that is, this situation will be seen as condensation .

The water vapor contained in the air that fills any space has its own pressure. This pressure is called the saturated vapor pressure (Ps) depending on the temperature. At any numerical value of relative humidity, this pressure can be obtained by multiplying the saturated vapor pressure at the same temperature with the numerical value of relative humidity. The pressure of the water vapor also varies depending on the interior and exterior conditions. The main reason for this difference is that the indoor and outdoor temperatures are different.

Here, the relative humidity being very different is not that effective on the pressure. In winter conditions, since the interior is generally warmer than the exterior, the interior air holds more water vapor, and as a result, higher water vapor pressure occurs in the interior than outside. Due to this pressure difference, a steam flow emerges from the inner region to the outer region. Roughly, it can be said that the steam flow is in the same direction as the heat flow. The best way to keep all this formation under control would be to have exterior cladding, that is, sheathing .

---

What is Condensation in Buildings?

Exterior Thermal Insulation Materials and Technical Specifications

What is Exterior Cladding?, External Wall Cladding (Sheathing) Methods

What are the Benefits of Thermal Insulation?

Exteriror Cladding (Insulation) Materials?

---