Ventilating Correctly: The Best Tips

Through regular ventilation, you bring fresh air into your indoor spaces and ensure that humidity, off-gassing pollutants from furniture, carpets, or chemical cleaning products, or other disruptive odors like tobacco smoke escape outside. Only when there's enough oxygen in a room do people and pets feel comfortable and stay productive. Besides health, factors like legal requirements also play a major role. Tenants, for example, are obligated to ventilate their apartment adequately. If they fail to meet this obligation, tenants can be held liable for any resulting damage and defects, such as mold. To help you get ventilation right, we answer the most important questions about ventilating.

Is constant ventilation good?

Proper ventilation depends heavily on duration. Here, "more" isn't better. This is about removing humidity. Constant ventilation with a tilted window, however, can't ensure the necessary air exchange. Especially when temperatures inside and outside differ greatly. For example, fresh winter air contains less moisture than room air. It doesn't matter whether it's raining or snowing. The temperature difference makes an exchange harder. Constant ventilation also wastes heating energy, cools down window reveals, and promotes mold growth.

How do I ventilate correctly at home?

Mistakes often happen when ventilating. For comfort reasons, for example, windows are only opened a crack and then left tilted for quite a while. But with tilt ventilation, air exchange is minimal. Usually only the room cools down and heating costs rise. This still won't give you a pleasant  indoor climate, though. Proper ventilation is quick cross-ventilation: open the windows wide, so there's air circulation in the room. Also remember to push aside any curtains. This increases the effect. The more effective the air exchange, the sooner you can close the windows again.

How long do you need to ventilate?

Better than constant ventilation is to quick-ventilate several times a day. Ideally, open several opposite windows at the same time. The resulting airflow removes stale air from the rooms faster. Also adjust your ventilation behavior to the season. Our season-dependent recommendation for ventilation duration:

• December to February: about 5 minutes
• March and November: about 10 minutes
• April and September: about 15 minutes
• May and October: about 20 minutes
• June to August: about 30 minutes

Both in April and in September, the combination of temperature and humidity favors faster air exchange than in the adjacent months.

Can too much ventilation cause mold?

Due to modern construction methods and energy-efficient modernization, buildings are becoming increasingly well insulated. Air exchange through gaps and moisture diffusion through walls no longer work. If humidity can't escape outside, mold and moisture damage to the building structure threaten. Mold spores and pollutants in room air can lead to breathing problems and allergies. If mold spores exceed limit values, rooms become uninhabitable for health reasons. You should therefore watch humidity as an indicator of mold growth.

Tip: learn how to detect possible mold growth based on air components, and even prevent it, in our dedicated blog post.

Especially through constant ventilation with a tilted window, so-called thermal bridges form. At these thermal bridges, heat escapes outside significantly faster than at neighboring building components. This is a weak point in thermal insulation. A tilted window, due to the lower temperature of its immediate surroundings, promotes energy and heat loss. Condensation also forms increasingly here, which can lead to moisture problems in the masonry and thus to mold growth. If walls and ceilings cool down, there's a risk of black spots and mold.

Does ventilating help against viruses like Covid-19?

During cold and flu season, especially as protection against Covid-19 infection, ventilating is considered one of the most important measures. After all, cold-like illnesses like Covid are transmitted through the air. Here, viruses attach to aerosols, small particles in the air, and thus spread throughout the room. By removing stale room air laden with pathogens and exchanging it for fresh air, you significantly reduce the risk of infection indoors.

A high carbon dioxide concentration (CO2) is a reliable indicator that especially many germs and aerosols are present in room air. A study by scientists shows the risk of infection with the flu. During the test period, 30 people spent four hours in a classroom. One of them had an acute case of the flu. The result: at 1,000 CO2 parts per million, five people got infected, at 2,000 ppm already twelve, and at 3,000 ppm, 15 people were infected. A clear connection between rising CO2 exposure and increased infection risk is thus evident.

Follow these ventilation tips:

• Ensure regular air exchange — especially when several people are in a smaller room. In this case, ventilate at least once an hour for 5 minutes.

• When ventilating, close the doors to adjacent rooms to prevent virus exchange through drafts.
• Ventilate situationally: if someone coughs or sneezes, briefly open the windows.
• Keep an eye on CO2 levels in the room, they're a good indicator of rising viral load in the air.

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Poor air quality from excessive CO2 levels

Too much carbon dioxide in the air you breathe is a risk to your health. As air pollution rises, so do complaints like discomfort, poor concentration, or lost productivity. From as little as 1,200–1,500 ppm (parts per million), drowsiness, inattentiveness, reduced concentration, and headaches increase. The tricky part about CO2 exposure: symptoms already appear before you notice the high CO2 concentration in room air.

Depending on the number of people in a room and how it's used, carbon dioxide levels rise and the quality of the air you breathe drops significantly. Our bodies, however, depend on oxygen to function properly. With too much CO2 in the air, your body is prevented from absorbing oxygen. Too much carbon dioxide in room air even demonstrably leads to increased absences at workplaces and in schools and daycare centers. 

Measuring air components & ventilating correctly

Air quality is hard to assess. We therefore often miss the right moment to ventilate. The most important thing on the way to a good, pleasant indoor climate is the best possible ventilation strategy. Air quality monitors that measure air components and warn when limit values are reached help with this. With up to 14 sensors and additional calculated readings as well as its own health and performance index, the air-Q is by far the most comprehensive air quality monitor — made in Germany. For example, it determines carbon dioxide via an optical sensor. This works through what's known as infrared absorption. The CO₂ molecule absorbs certain wavelengths of infrared radiation. This is also, for example, how the greenhouse effect occurs, since this thermal radiation can't leave the Earth. The sensor measures how strong this thermal radiation is. To be truly precise, the intensity of the infrared LED is additionally monitored with a second measurement beam.

Besides carbon dioxide, the air-Q assesses the impact of other pollutants on your physical health and performance. Using the air-Q health index™ and the air-Q performance index™, you can see, both on the device and in detail via the air-Q app and web app, how your room air is composed. Based on its results, the air analyzer doesn't just tell you when it's time to ventilate. Rather, it gives you comprehensive guidance on how to locate sources of pollutants and thus improve air quality.

(Cover image: Canva/ Gal Daniel from Getty Images)