Proper Ventilation Improves the Climate and Prevents Mould

November 4, 2021
  1. Where does the humidity come from?
  2. This will lower the humidity
  3. Proper ventilation in old buildings
  4. Proper ventilation in new or renovated buildings
  5. Proper ventilation in the living room
  6. Proper ventilation in the bedroom
  7. Proper ventilation in the kitchen and bathroom
  8. Proper ventilation in the mansard
  9. Proper ventilation in the cellar
  10. Proper ventilation in the basement
  11. This will save electricity and money
  12. This will improve the indoor climate

Proper ventilation is even more important in winter than in summer. When it is cold outside and hot inside, the humidity in the house or flat quickly rises to levels that can be detrimental to health and well-being without regular air exchange. The Federal Office of Public Health (FOPH) recommends a relative humidity of up to 50% and a room temperature of 20 degrees in the living room or 18 degrees in the bedroom during the heating season. Other experts recommend 40 to 60 per cent humidity, in the bathroom up to 70 per cent.

Good to know

If you overheat rooms in the cold season, the air becomes dry. Too dry air irritates the mucous membranes in the nose and can trigger headaches or nosebleeds.

Where does the humidity come from?

Humidity is completely natural. It arises, for example, when we shower, cook, water our plants, sweat or dry our laundry. In spring, summer and autumn, this humidity escapes easily because we regularly open the windows during the day and sleep with the windows tilted at night. In winter, on the other hand, when we want to keep warm in our house or flat and therefore open the windows less often, the moisture collects on the window frames, on the walls and in the joints of the bathroom or kitchen. Humidity is the ideal breeding ground for mould.

Good to know

You can measure the relative humidity with a simple hygrometer. If condensation forms on the window, the air in the room is too humid. You should definitely ventilate more and properly.

This will lower the humidity

The easiest way to reduce and regulate humidity is to ventilate regularly and, above all, correctly:

  • Ventilate for less time than in summer, otherwise the house or flat gets too cold.
  • Ventilate in the morning and in the evening, and if you are at home during the day or work in a home office, also at midday. Two or three times for 5-10 minutes is enough to ensure that not too much heat is lost.
  • Oblique ventilation is more efficient than impact ventilation and reduces heat loss. Open the windows and doors of opposite rooms at the same time. The draught accelerates the air exchange in the rooms.
  • Shock ventilation is much more efficient than tilt ventilation. Especially in winter. Open the windows completely for a few minutes so that the humidity can escape and fresh air can replace the used air.       
  • Tilt ventilation does not help at all in winter. On the contrary: on the one hand, mould forms anyway, and on the other hand, the rooms and even the floors get cold because all the surfaces around the slanted window get very cold. This increases your heat consumption and therefore your heating costs.
  • However, if condensation forms on windows, panels or other surfaces, simply wipe off the residual humidity with a cloth.

Good to know

In winter, the air outside is drier than the air inside. That is why proper ventilation is also useful when it is foggy, raining or snowing.

Proper ventilation in old buildings

In older buildings, a natural exchange of air takes place before the renovation, because the building envelope is not yet 100% tight. This has a big disadvantage: you lose a lot of heat to the outside. And a small advantage: you only have to ventilate twice a day for 5 minutes because air is exchanged 24 hours a day through leaking cracks or windows.

Proper winter ventilation: New exterior construction
New buildings are much better insulated, so there is no natural air exchange as in old buildings.

Proper ventilation in new or renovated buildings

If you live in a new house, a new flat or an old renovated building, you need to ventilate regularly because the building envelope is narrow and the windows have multiple panes of glass. This is why humidity is often higher than in old buildings. In addition, some building materials can release chemicals in the first few weeks. Proper ventilation also helps here.

Proper ventilation in the living room

The living room, children's room and study should be comfortably warm and cosy in winter. However, they must be ventilated regularly and the relative humidity must be kept between 40 and 60 per cent. Without a regular exchange of air, the humidity otherwise rises rapidly. For example, because of the plants in the living room or the laundry that dries in the study because it is cold outside.


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Proper ventilation in the bedroom

We spend a third of the day in the bedroom and exude a lot of humidity through our breath or sweat. So much so that the cooler air in the bedroom cannot absorb it all, humidity settles on the window frames or walls and mould can grow there. That is why you should ventilate a lot in the morning and evening and only turn down the heating instead of turning it off.

Proper ventilation in the kitchen and bathroom

A lot of water runs off and evaporates in the kitchen and bathroom. That's why the humidity is higher here. It prefers to accumulate in cold places, the perfect breeding ground for mould. That's why you should always open the window wide for a few minutes after cooking or taking a shower. Just tilting it is not enough. If your bathroom has no window, dry the floor and walls with a cloth.

Proper ventilation in winter: Modern bathroom
In bathrooms and kitchens, humidity is higher than elsewhere because a lot of water evaporates there.

Proper ventilation in the mansard

Nel sottotetto l'umidità ed il clima interno dipendono fortemente dall'isolamento. Se il sottotetto è poco isolato, è necessario ventilare meno che in estate. Soprattutto se c'è una corrente d'aria attraverso finestre o crepe porose. Se il sottotetto è ben isolato, però, il calore tende ad accumularsi. L'aria interna si raffredda intorno alle finestre, specialmente i lucernari, e si condensa. Ecco perché bisogna abbassare il riscaldamento, ventilare regolarmente e più a lungo e pulire la condensa.

Proper ventilation in the cellar

The cold unheated cellar is probably the coldest and most humid. That is why you should practise shock ventilation in the cellar for 10 minutes every day in winter, or even tilt ventilation during the day, until temperatures are no longer below zero degrees. The cool and dry air extracts a lot of humidity from the brickwork and slowly dries out the cellar.

Proper ventilation in the basement

In the basement as well as in the cellar it is cold. This is why you should heat the rooms in the basement, even if you only use them irregularly, for example as an office, guest room or home cinema. To avoid losing too much heat and therefore money, you should ventilate the basement no more than twice a day.

This will save electricity and money

If you ventilate regularly and correctly, you lose less energy. Never let the room temperature drop below 18 degrees to save on heating costs. Why? Cold air absorbs humidity worse than warm air, can no longer absorb it and condenses water. If you want to reduce your energy consumption and thus save money, there are other ways:

  • Do not let the rooms get cold.
  • Close all doors between heated and unheated rooms.
  • Practice shock ventilation or better oblique ventilation in the room at least twice a day for a few minutes instead of tilt ventilation.
  • Lower the temperature at night to 18 degrees if you live in an old, poorly insulated building and heat the rooms with conventional radiators with a high flow temperature.

Proper ventilation in winter: Child playing in the room
The indoor climate has a great influence on how comfortable we feel at home.

This will improve the indoor climate

Proper ventilation ensures a better indoor climate in your home. On the one hand, you keep the relative humidity constantly in the comfort range of 40 to 60 per cent, and on the other hand you avoid mould. In addition, pollutants that we emit when we breathe or sweat and chemicals contained in the fabric of the building, furniture or textiles can escape. However, you lose energy when you ventilate, even if you follow all the advice. You can prevent this with home ventilation. It has become standard in many new buildings and can be adapted in old buildings. Controlled home ventilation directs used air outside, replaces it with fresh air and filters out pollen, dirt particles and spores. Not only allergy sufferers appreciate this.

Good to know

A ventilation system with heat recovery is energy efficient. Warm exhaust air from inside is used to pre-heat cold supply air from outside via a heat pump. In this way, you protect the environment and your wallet.

With home ventilation you ensure a healthy indoor climate without having to ventilate. You also consume less energy for heating and therefore save money. This is why a modern ventilation system can be beneficial in the long term. The best thing to do is to talk to a qualified expert for ventilation and air conditioning technology in our network and get a non-binding consultation.

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