Humidity refers to the amount of water vapour present in the air. It is a very important parameter for assessing air quality in domestic or workplace environments. Indeed, an environment that is too dry or too humid poses risks to both health and the building structure itself. A low level of water vapour over the long term causes dryness of the mucous membranes, leading to a weakening of the immune system. Similarly, excessively high levels encourage the growth of mould and fungi.
What is humidity?
Humidity is an important parameter for understanding how much water vapour is contained in the air. This information can be provided by considering either absolute humidity or relative humidity.
Absolute humidity indicates the mass of water vapour contained in a unit of air volume. In this case, it provides direct information on the amount of water vapour present in the air; a value of 10 g/m³ indicates that there are 10 g of water vapour in 1 m³ of air.
To better understand what relative humidity represents, it is useful to consider the concept of saturation. When the water vapour in the air reaches its maximum quantity, the air is saturated. Saturated air cannot hold any more water vapour, and some of it begins to condense into liquid water. Relative humidity represents the percentage of water vapour contained in the air compared to the maximum amount that the air could hold at the same temperature. Formally, it is calculated by taking the ratio of the partial pressure of water vapour in the air to the saturation vapour pressure of water vapour at the same temperature. A value of 40 per cent indicates that, at the temperature in question, the air contains 40 per cent of the water vapour required to reach saturation.
When discussing relative humidity, it is important to specify the air temperature at which it was calculated. For example, 40 per cent relative humidity at 10°C and 40 per cent at 20°C represent different absolute values. This is because as the temperature rises, the maximum amount of water vapour that the air can hold also increases. Consequently, for the same relative humidity, there will be more absolute humidity as the temperature rises.
The importance of mechanical ventilation
When assessing air quality, one of the parameters to take into account is humidity. An ideal range for relative humidity is between 40 per cent and 60 per cent.
Ensuring a continuous exchange of air in rooms is essential for maintaining ideal air conditions. However, traditional air exchange, such as opening windows, may not be entirely efficient. Using a controlled mechanical ventilation unit is the best solution for maintaining indoor air quality and preventing humidity levels from becoming too high or too low. Thanks to controlled mechanical ventilation, the air introduced into the room is filtered and distributed correctly at all times of the day. Depending on the situation, various technologies are employed to ensure the most effective approach for guaranteeing energy savings and high efficiency. The inclusion of an enthalpy exchanger, thermal bypass devices, and the possible addition of air post-treatment coils or a refrigeration circuit are options that ensure the best possible solution is always achieved.
