Dew Point Calculation
How to Calculate the Dew Point
To determine the dew point temperature using a Xiaomi Mijia 2 thermometer or any other device, enter the temperature and humidity readings into the calculator. This helps assess the risk of condensation and excess moisture.
If you need to find the optimal humidity for a given temperature, enter only the temperature and adjust the humidity value until the dew point reaches 10°C. This helps prevent mold growth and ensures a comfortable indoor climate. Use ventilation, air circulation, or dehumidifiers to maintain humidity at a level where the dew point stays at or below 10°C.
What Is Dew Point?
The dew point is the temperature at which water vapor in the air begins to condense on a surface. A fogged-up bathroom mirror or a “crying” kitchen window are common examples of this phenomenon. The temperature at which a mirror or window starts accumulating condensation is called the dew point temperature.
The dew point can be calculated using a specific formula, which depends on indoor air temperature and relative humidity. The higher the humidity, the higher the dew point temperature.
For example, if the indoor temperature is 25°C and the relative humidity is 60%, the dew point temperature will be 16.7°C. Any surface, such as a window or a wall, with a temperature below this value will accumulate condensation.
At the same 25°C but with 90% humidity, the dew point rises to 23.2°C, meaning that any surface just 1.8°C cooler than the air will constantly be wet due to condensation. At 100% humidity, the dew point matches the air temperature, leading to air saturation with water vapor indoors.
Why Is Dew Point Important?
The relative humidity displayed by a hygrometer can be difficult to interpret without knowing the optimal range for each temperature. For example, 60% humidity at 18°C is ideal, but 60% humidity at 28°C can lead to mold growth. This is why using the dew point as a reference is more convenient.
At 18°C and 60% humidity, the dew point is 10°C, which is optimal. However, at 28°C and the same 60% humidity, the dew point rises to 19.5°C, indicating excessive moisture. If your indoor temperature is 24°C, you can enter this value into the calculator to find the optimal humidity level. For 24°C, the ideal humidity is 42%, corresponding to a 10.3°C dew point.
Condensation of water vapor on various surfaces is one of the most common causes of mold growth indoors, usually due to high humidity and, less often, poor insulation. It’s important to note that walls dampened by condensation lose their thermal insulation properties, making it harder to retain heat.
If you’re dealing with mold issues, we offer mold treatment services, protective coatings, and consultations to identify the exact causes of mold growth and prevent future problems.
We recommend using this calculator along with a thermo-hygrometer to maintain indoor relative humidity at a level where the dew point does not exceed 10°C, especially in areas prone to mold issues. A dew point below 10°C may feel too dry, while a higher dew point increases the risk of mold growth.