What is the ideal humidity in an apartment?

What does the term “relative humidity” mean?

Relative humidity or RH (from English Relative Humidity) = the amount of moisture in the air in relation to temperature.

Relative humidity is expressed in percentages (%) – how much moisture is in the room depending on the temperature. 50% humidity at 30°C will be a different volume of moisture than at 15°C. When reaching 100% (maximum moisture in the air at a specific temperature), moisture begins to condense – to precipitate.

For example, if we take a bottle out of the refrigerator, it is cold and cools the air around it, causing the moisture in the surrounding warmer air to condense, and we see a misted bottle.

Besides CO₂ (read about its impact on the indoor environment here), humidity is another very significant factor that affects the comfort and well-being of people living in indoor environments. And we also spend a lot of time here – according to recent research, up to 90% of our daily time!

What is the ideal humidity?

This range changes based on the season. While in winter we should maintain humidity in the apartment between 40 – 60 %, in summer the upper limit is slightly lower, and humidity should be between 40 – 55%.

Higher or lower values often lead to overall discomfort in the indoor environment and also to various health problems.

On the right, you can see a graph of the comfort zone depending on humidity and temperature of the environment around us:

Signs of too high humidity

High humidity can be easily recognized by misted windows, damp walls, and possibly furniture or floors. This contributes to the formation of mold on windows, joints, and walls of rooms. Mold can then negatively affect not only the building elements and furnishings of the apartment but also the health of individuals. Unpleasant manifestations include allergies, atopic eczema, or other respiratory issues.

How to reduce humidity in an apartment

Usually, this is not a complicated task. In newly renovated buildings and apartments, humidity is often higher at first – but gradually, the building elements that may have been damp due to construction/renovation dry out.

The recommended method is, of course, sufficient ventilation – whether of the entire house/apartment or, for example, in the most used bathroom, drying laundry outside, and using a hood. The best way is ventilation based on humidity sensors. This monitors air quality – humidity in the apartment/house and, based on the measured data, controls, for example, the fan in the bathroom or the entire air conditioning system.

Signs of too low humidity

Low humidity (below 40%) is probably even more uncomfortable than high humidity. Symptoms can include:

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• sore throat in the morning, cough,

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• dry skin, cracked lips,

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• fatigue,

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• stuffy nose

Additionally, at low humidity (i.e., high evaporation of water), volatile organic compounds (VOCs) are released into the air from furniture, carpets, etc., which are the main cause of negative manifestations associated with polluted indoor air – you can read more about them here.

How to increase humidity in an apartment

We can increase humidity in the apartment through opposite processes. It is recommended to dry laundry in indoor rooms, grow houseplants, or place a container of water on the heating. Another solution can also be a humidifier that divides water into micro-particles and releases them into the space.