Humidity in living spaces
The correct humidity of the air is an important comfort factor in living space – both too high and too low humidity can have a negative impact. Each room has its own optimum humidity, depending on its use and condition.
This article provides basic information on this topic and highlights the optimal humidity for different living spaces. In addition, the consequences of too high and too low values on people and the building fabric are shown. Furthermore, tips are given on how this optimal value can be achieved with different means and how you can measure the humidity.
Absolute, relative and optimal humidity
Simply put, the term humidity, or humidity for short, means the proportion of water vapor in the ambient air. For a more precise definition, this term is divided into absolute and relative humidity.
The absolute humidity is the simple indication of how many grams of water are in one cubic meter of air. The determination of the relative humidity is more complicated because it indicates what percentage of the maximum water vapor content is currently in the air.
It is important to know that the air can only hold a certain amount of water. How large this amount is depends very much on the temperature. Cold air absorbs less water vapor than warm air. The rule here is: the higher the temperature, the more water vapor the air can absorb.
At a temperature of zero degrees Celsius, air can hold five grams of water vapor per cubic meter. At a much higher temperature—such as 30 degrees—this figure rises to 30 grams. These values represent the maximum amount of water vapor the air can hold at the respective temperature. However, determining the relative humidity requires knowing both the absolute humidity and the maximum humidity.
Optimal humidity is not a fixed value but rather a percentage range representing moisture levels that are safe for both health and the structural integrity of living spaces. Combined with the right temperature, these two factors create an optimal indoor climate.
The optimal humidity in different living spaces
Generally, a relative humidity of 50% and a room temperature of 20°C are considered the optimal indoor climate. However, conditions vary from room to room, as the indoor climate is influenced by several factors. One key factor is the number of people present in the room, as well as the duration and frequency of their stay. The activities performed in the rooms also play a significant role. Higher humidity levels are common in rooms such as bathrooms and kitchens due to the activities carried out there. In contrast, the ideal temperature for a basement is only 10–15°C, which corresponds to lower humidity levels. Nevertheless, excessive humidity is not advisable even in these areas and should be reduced through various measures.
The following table outlines the ideal conditions for specific living areas:
Room | Optimal humidity | Optimal temperature |
|---|---|---|
Living room and study (office) | 40 – 60 % | 20 °C |
Bedroom | 40 – 60 % | 16 – 18 °C |
Nursery | 40 – 60 % | 20 – 22 °C |
Kitchen | 50 – 60 % | 18 °C |
Bathroom | 50 – 70 % | 23 °C |
Cellar | 50 – 65 % | 10 – 15°C |
Consequences of too high or too low humidity
The temperature and humidity of the room not only contribute to well-being, but can also cause discomfort and other health consequences. In addition, the effects on the building fabric of the house should not be forgotten.
Falling below the optimal humidity
Eye, skin and mucous membrane irritations can already occur at a humidity level of less than 40 percent. This is clearly too little humidity, which manifests itself in the drying out of the skin with redness and itching. Furthermore, the immune defense is weakened, which can lead to more common colds. At a value below 23 percent, the loss of moisture can only be partially compensated for by breathing, which leads to a feeling of discomfort. Another consequence of too low a humidity level is increased light electric shocks when touching metallic objects, since dry air is electronically charged more quickly.
In addition to the health consequences, overdrying can lead to structural damage (too little humidity). Wood in particular suffers when it falls below the minimum value because it warps.
Exceeding the optimal humidity level
At what level of moisture does mold start to form?
As already mentioned, a permanently too high humidity of over 60 percent can lead to the formation of mold. This is also known as what is known as a damp apartment. An infestation is almost inevitable from a humidity of 70 percent or more. The formation of mold due to high humidity not only endangers the building structure of the house, it is also dangerous for human health. Increased inhalation of mold spores can cause diseases such as asthma or allergies.
A humidity of over 80 percent also creates a perfect environment for fungi, mites and other parasites to multiply.
Improvement of the humidity in the interiorMeasure the humidity
The basis of room climate regulation is first of all to measure the correct and current humidity in the living space.
A very complex way would be to measure the absolute and maximum humidity yourself and thus calculate the value of the relative humidity. Thanks to a hygrometer, however, this method is not necessary (hygrometer humidity).
Depending on the model, hygrometers can be set up or hung up. The ideal location is neither too close to an outside wall nor to a door, window or heater. Regular measurements of the air humidity are important when determining the room climate, as various influences mean that the room humidity is occasionally too high or too low. It is only necessary to act when the room climate permanently exceeds the upper or lower limit of the respective room.
Lower the humidity in rooms
Improvement measures if the humidity is too high
Removing moisture with salt in order to be able to lower the air humidity in rooms In order to achieve a lower air humidity by exchanging air, it is important to ventilate properly. In a damp apartment, the window should be opened completely for five to 25 minutes, depending on the time of year. This procedure should be repeated several times a day in order to be able to reduce the excessively high humidity in rooms. To make sure that the air quality has improved, you should measure the humidity before and after airing. In order to know in advance whether an improvement in the air humidity can be expected through ventilation, another air humidity hygrometer can be installed outside the house. If the humidity outside is higher than inside, opening the windows would be unsuccessful or even worsen the situation.
Another possibility is to remove moisture from the air with the help of salt. For this purpose, several bowls filled with salt are set up in the room. The bowl should be filled to a maximum of four centimeters. For this method, simple table salt is sufficient, which must be replaced as soon as there is more water than salt in the bowl.
In addition, in the case of increased humidity in a damp apartment, the use of indoor fountains should be avoided. Aquariums or terrariums, which give off water vapor into the room air, should also be covered in summer. It is also helpful to dry the laundry outdoors. Even moving some indoor plants to the balcony or terrace during the summer can help. The extractor hood should always be used during cooking and for a while afterwards.
Excessive humidity can have a negative impact on both human health and the structural integrity of a building. High levels of moisture in the air significantly promote mold growth in living spaces. Therefore, it is essential to regularly measure and monitor humidity levels to ensure they remain within an appropriate range and to reduce them if necessary. Bathrooms are particularly prone to mold growth, as they typically feature high temperatures and high levels of moisture in the air.
The warm air in the bathroom in particular can absorb a lot of water vapor. But the air you breathe and sweat that escapes also causes the humidity to rise in any room. It is necessary to keep the humidity in living rooms in the appropriate range, because there is a risk of mold from 60% humidity. In the following we have briefly summarized how you can reduce the humidity in rooms with simple measures.
Checklist of the top 10 tips for reducing indoor humidity
- Ventilate thoroughly and regularly by opening windows wide.
- Maintain an optimal room temperature and do not let rooms get cold.
- Keep doors closed
- Place a bowl filled with salt, cat litter, or silica sand.
- Remove indoor fountains, aquariums, terrariums, and houseplants.
- Use the cooker hood
- Let the laundry dry outdoors.
- Take a short, cold shower.
- Using a dehumidifier
- Install exhaust units / ventilation systems
Improvement measures if the humidity is too low
In a dry environment, ventilation at the right moment can not only remove the air that is too dry, but also increase the humidity. Even if the humidity is too low, it should also be determined in advance on the external hygrometer whether the outside air humidity is higher than that in the interior. The process of ventilation is analogous to ventilation when the humidity is too high.
In addition, all aids can be accessed that should be avoided when the air humidity is too high. Indoor fountains, aquariums and plants give off moisture to the room air and thus improve the room climate.
Ventilation systems for the optimal indoor climate
Regardless of the season, decentralized ventilation systems automatically ensure the ideal indoor climate without requiring any manual effort. A humidistat is usually already integrated into the associated control system.
Decentralized ventilation units are installed in exterior walls and handle air exchange without the need for manual airing. At least two units are required for optimal results. One unit exhausts stale air to the outside; thanks to a heat exchanger—specifically a ceramic core—the unit prevents the loss of moisture and heat. As stale air is extracted, the ceramic core retains a healthy level of base moisture (generated by condensation) and transfers it to the incoming fresh air. In addition to this moisture, the ceramic core also stores heat from the air, recovering up to 94 percent of it and returning it to the living space.
After the stale air has been exhausted, approximately 70 seconds elapse before the reversing fan changes direction and delivers fresh air into the living space. The second unit operates in counter-cycle; this means that while one fan supplies fresh air to the room, the other simultaneously extracts the stale indoor air. Through this reciprocal operation, the room is continuously supplied with fresh air and humidity is maintained at an appropriate level.
Conclusion – Humidity in Living Spaces
The indoor climate is a factor that not only affects the fabric of the apartment or house, but also the well-being and health of people. When regulating the climate, the relative humidity and the temperature of the rooms should be kept in mind. Occasionally exceeding or falling below the relative humidity is initially a risk factor neither for human health nor for the building fabric. However, if this condition persists, urgent measures must be taken to reduce or increase the humidity in rooms
Q&A – More questions about humidity
Fundamentally, it is not just the duration of ventilation that matters, but also the room temperature. Ensure your rooms are adequately heated, as warm air can absorb more moisture. Incidentally, energy-efficient ventilation with heat recovery can prevent the heated air from escaping when ventilating via the windows.
Another potential issue is that the outside air may have the same moisture content as the indoor air, making it impossible to lower the indoor humidity level.
This depends on the building material used. A moisture content of up to 10% in the wall is generally considered normal. However, consistently higher moisture levels can lead to extensive damage to the building structure. Even with regular ventilation, you should ensure that your furniture is kept a short distance away from the surrounding walls; this promotes air circulation and prevents unwanted condensation.
Relative humidity in the outside air is highest during the cooler autumn and winter months. However, absolute humidity tends to be lower, as cold air cannot hold as much moisture; this is why people often speak of a “dry winter.”
Note: Even if the outdoor humidity is around 100% due to rain or fog, you can still ventilate your living space without issue, as the warmed indoor air is capable of holding more moisture than the cold air from outside.
In summer, you should fully open windows and doors for 5–10 minutes to allow for a burst of fresh air and reduce humidity levels. Outdoor temperatures and atmospheric moisture are significantly lower, especially in the mornings and at night. Generally, higher humidity in summer is not a major issue, as building walls radiate heat during the warmer months. Consequently, the risk of condensation is low, given that warm air typically condenses on cold surfaces. Particular attention should therefore be paid to this risk in cold basements. Find out here how to
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