Relative humidity and absolute humidity: differences

Summer is approaching and with it the high temperatures. There are also changes in how we feel the change of season on our skin, the differences in the sensation of heat, and even the appearance of colds. All these phenomena involve relative humidity and absolute humidity, which are not only noticeable outdoors. Indoors, excess water vapor in the air also greatly affects our day-to-day life.

We must take into account that in Spain, the situation that usually occurs is that of an excess of humidity. While we enjoy dry and humid climates, the high temperatures in Spain and its geographical location mean that it is a country that does not usually suffer from low humidity. The areas where there may be greater impact are coastal areas or where there is a large concentration of water. Indoors, we must control the values of relative humidity and absolute humidity. Because in our home, an excess of humidity can lead to different problems:

• Respiratory complications for the people living in the house.
• Appearance of diseases such as asthma or allergies.
• Greater sensation of heat indoors and high sweating.
• Defects in walls and ceilings and also in furniture.

We can say that humidity affects our comfort and also our environment. It is very common to hear the concepts of absolute humidity and relative humidity, as well as that of specific humidity. However, which of them will matter more to understand the importance of this phenomenon, which is the condensation of water vapor in the air? We detail it for you.

1. Absolute humidity. It is the total amount of water vapor contained in a given volume of air. Water vapor is measured in grams and air in m3. Therefore, we will express absolute humidity in grams of water vapor per cubic meter of air.
2. Specific humidity. It is actually the same analytical phenomenon as absolute humidity, only the type of measurement is changed. In the case of specific, the calculation is made in kilograms of water per kilograms of dry air. Just like in absolute humidity, specific humidity counts the water in vapor form.
3. Relative humidity. It is the relationship between the amount of water vapor contained in the air - which is absolute humidity - and the maximum amount of air that can hold at that temperature, considering the absolute saturation humidity. Relative humidity is a calculation that is presented in a definitive value in percentage.

In general, only relative humidity is usually taken into account due to its simplicity of reading. Although absolute and specific calculations are the most precise technical values, they are more difficult to understand as they are not as easy to comprehend.

Relative humidity considers that the maximum value is 100%, so it is easy to remember when we have high humidity, which will be when the indicative percentage is very high. But in addition to that, the human body is only sensitive to relative humidity and not to specific or absolute humidity.

Why should we worry about relative humidity and not absolute humidity?

The air will influence all of us differently depending on relative humidity. If the percentage humidity value is very low, the air will dry us out as well as the objects and the rest of the environment. If, on the other hand, relative humidity is very high and approaches one hundred percent, it will be the opposite: it will transfer humidity to everything it touches.

That is why the relative humidity value is what we must take into consideration at all times to know whether it will affect us one way or another. Absolute humidity and specific humidity, on the other hand, will serve to calculate the percentage in the environment.

What value of relative humidity will be the most beneficial for all of us? We can calculate that the ideal humidity value would be between 40% and 60%. If a value below 40% is given - which is more difficult in Spain due to its particular orography and climatology - it would be necessary to use humidifiers or other solutions to increase humidity.

If relative humidity is very high, efforts should be made to reduce the value using dehumidifiers. Since in that case, health problems and deterioration of interiors could arise. To calculate the level of relative humidity, we can use moisture detectors, which for an economical price indicate the specific value at all times.