What is the interplay between temperature and relative humidity?
Temperature and relative humidity (RH) go hand-in-hand. Both factors play a major role in indoor comfort and well-being of residents. There is a direct and continuous interplay between both basic parameters. Understanding this relationship is essential for maintaining stable indoor conditions, preventing condensation, and improving overall comfort and health.
How temperature influences relative humidity
Temperature directly determines how much water vapour air can hold. Warm air can contain much more moisture than cold air.
- When air is heated without adding moisture, its relative humidity decreases.
- When air is cooled down, its relative humidity increases, even if the actual amount of water vapour stays the same.
This means that for a fixed amount of water vapour, RH will always be higher in cool air and lower in warm air.
How relative humidity influences (perceived) temperature
Relative humidity affects how warm or cold air feels, even if the measured temperature does not change.
- High RH combined with high(er) temperatures makes warm air feel significantly hotter, because moisture slows down the evaporation of sweat.
- High RH combined with low(er) temperatures makes cold air feel cooler and chilly, because the body loses heat more quickly.
- Low RH combined with high(er) temperatures makes warm air feel cooler and drier, and can cause discomfort such as dry skin or irritation.
- Low RH combined with low(er) temperatures makes cold air feel crisp but may also feel uncomfortably dry.
This explains why the apparent temperature can differ significantly from the actual air temperature depending on the humidity level. It impacts heat transfer from the human body and thus alters thermal comfort.
Combined monitoring
Monitoring both temperature and humidity (or dew point) provides a complete picture of the indoor climate. Because adjusting one affects the other, maintaining balance between both ensures a comfortable and healthy environment.
Most Sentera sensors can measure both ambient temperature and relative humidity.
Ventilation in function of temperature and relative humidity level is interesting in rooms where large fluctuations in temperature or relative humidity regularly occur, such as kitchens, bathrooms and laundry rooms. The outside temperature and relative humidity are also important parameters to measure before fresh air enters the ventilation system and the building.
Dew point delta control
The dew point is the temperature at which air becomes fully saturated with moisture and condensation begins to form on surfaces at that temperature or lower. It depends on both air temperature and relative humidity (RH), making it a more precise measure of moisture content than temperature or humidity alone. Dew point delta is the difference between air temperature and its dew point, indicating how close the air is to saturation. Measuring this parameter offers an extra feature for efficient ventilation control.
Traditional ventilation control often relies on temperature or RH alone. However, these parameters can be misleading because air with the same temperature or RH can have very different moisture levels, which may lead to condensation, mould growth, or material damage. Adjusting ventilation based on dew point delta provides a direct and more accurate measure of the condensation risk. This allows systems to maintain stable indoor conditions, prevent moisture-related problems, and improve energy efficiency by avoiding unnecessary over-ventilation. This approach ensures optimal climate control for sensitive environments, equipment, and processes.