The way into the cold season forces us to arrange our life in rooms in times of viral infections. First of all, due to corona, distance rules must be observed, supported by mouth-nose protection and as much outside air as possible, in order to reduce the concentration of harmful aerosols as much as possible. How does ventilation work during the corona pandemic, and especially now in the cold season, without the risk of rooms and buildings cooling down?
Interview with Andreas Stehling, Managing director at CANZLER and head of the technical equipment department for the trades sanitary, media and fire extinguishing technology, heating, ventilation and cooling technology.
The subject of outside air is equated with "sufficient" ventilation. This is especially true for schools, where it is essential to maintain operations, as demanded by politicians and the Minister of Education. How this can work and how it is to be implemented, they have determined for the start of school after the autumn holidays. The final stipulation is: pulse airing every 20 minutes, cross airing wherever possible and airing during the entire break period.
What follows from this?
If we use our common sense, we have to realise that no heating system in Germany has been planned and built for such conditions in buildings where people live, work and stay. Our buildings and, as here, our schools will no longer provide comfort. The rooms cool down. Open windows cause draughts and let in all weathers like rain and wind. Colds and colds are likely to become more common among students and teachers.
How could this be prevented?
Proper ventilation must be considered individually, depending on the weather and outside temperature. The colder it is outside, the faster the exchange of air. This can mean, for example, opening windows completely when airing outdoors and always opening windows or doors on opposite sides. Depending on the outside temperature, we quickly notice that the air exchange has already taken place after one minute, so windows and doors should be closed again. This short time means air exchange, but not cooling the rooms by cooling the walls.
Why is continuous airing during breaks not sensible?
Ventilation should not be provided during the entire duration of the break, as afterwards and depending on the outside temperatures, the classrooms can no longer be used for approximately orderly lessons. People feel comfortable in a comfortable environment. Such comfort can neither be created nor maintained with such ventilation. The installed heating system will certainly need 20 minutes or considerably longer to restore a reasonably comfortable temperature. But then, according to the current specifications, ventilation should already be carried out again. The heating costs produced by this are completely disregarded.
How can this be transferred to office and administration buildings?
In office and administration buildings there are often so-called facade devices. These are these large-volume metal boxes under the windows with ventilation grilles; heating and, if necessary, cooling is provided above them. They are operated by circulating air so that they can heat effectively. So are these the virus spinners? What is the reason for ventilation? Nobody really knows whether there are viruses in our environment, whether one of our colleagues is blowing them around. As a precautionary measure, we use ventilation to dilute the air, and we do this as regularly as possible. As a purely precautionary measure, the fans of the façade units have also been switched off - we don't want to hurl viruses! Without a fan, however, the heating effect is negligible.
What is a concrete recommendation for offices?
Ventilation makes the room cold, the heating does not reach power because there is no fan running. Plausible and recommended would be short ventilation, as described above, and ventilation across the room, i.e. with windows open on opposite sides. So short and clear; we notice when the air is changed. Then close the windows again and let the facade units with fan run as usual. Finally, these move fresh air. The walls do not cool down and the air quickly reaches room temperatures again.