How to Air Your Home in Winter
How do you bring in fresh air without getting cold or wasting energy? Consider this expert advice
Alexandra Oertel
1 December 2020
Some people can only stand winter if they can walk around the house in a T-shirt; others prefer their homes to be a bit colder. Either way, when the heating is on, one thing is certain – it’s vital to air your home and ensure the circulation of fresh air.
Airing naturally through open windows is considered to be a big part of responsible home care in Germany, and it has recently been given a boost through its inclusion in government guidelines for combatting Covid-19. Here, German expert Oliver Frank advises on how to ventilate correctly when the heating is on.
Airing naturally through open windows is considered to be a big part of responsible home care in Germany, and it has recently been given a boost through its inclusion in government guidelines for combatting Covid-19. Here, German expert Oliver Frank advises on how to ventilate correctly when the heating is on.
Treat ventilation and heating as a single process
It takes some willpower to throw the windows open in winter, but it is nonetheless vital. “There is no such thing as airing correctly or heating correctly. There is only the intelligent and sensible combination of the two. Thinking of them in isolation is the first big mistake,” says Oliver Frank, owner of Innovation to Reality.
It takes some willpower to throw the windows open in winter, but it is nonetheless vital. “There is no such thing as airing correctly or heating correctly. There is only the intelligent and sensible combination of the two. Thinking of them in isolation is the first big mistake,” says Oliver Frank, owner of Innovation to Reality.
Stop the growth of mould
Frank points to two primary benefits of correctly airing your home in winter. “Firstly, exchanging old, spent air for fresh, oxygen-rich air is crucial for overall wellbeing,” he says. “Secondly, it’s important to be aware that incorrect airing can lead to the build-up of condensation and therefore mould, especially in winter.”
Spores can multiply unnoticed in hidden spots, such as on an exterior wall behind a wardrobe. “In extreme cases, homes can get rundown through ignorance or misguided frugality,” Frank says.
It’s therefore vital to air bedrooms in the morning and bathrooms after showering, since a lot of humidity can collect in these spaces. Open the window completely, even in winter; simply opening it a crack is often insufficient. In a bathroom with no windows, leave the door to the neighbouring room or hallway open for five, or better yet 10 minutes. The other rooms should stay closed.
Humidity enters the air not only through showering, but also cooking, drying clothes and even breathing. For a three-person household, this can amount to about 10 litres of water a day appearing as humidity in the air. A relative humidity of 40-60% is optimal, according to German consumer advice centre, Verbraucherzentrale. You can check this with a hygrometer (which can be bought fairly cheaply).
Frank points to two primary benefits of correctly airing your home in winter. “Firstly, exchanging old, spent air for fresh, oxygen-rich air is crucial for overall wellbeing,” he says. “Secondly, it’s important to be aware that incorrect airing can lead to the build-up of condensation and therefore mould, especially in winter.”
Spores can multiply unnoticed in hidden spots, such as on an exterior wall behind a wardrobe. “In extreme cases, homes can get rundown through ignorance or misguided frugality,” Frank says.
It’s therefore vital to air bedrooms in the morning and bathrooms after showering, since a lot of humidity can collect in these spaces. Open the window completely, even in winter; simply opening it a crack is often insufficient. In a bathroom with no windows, leave the door to the neighbouring room or hallway open for five, or better yet 10 minutes. The other rooms should stay closed.
Humidity enters the air not only through showering, but also cooking, drying clothes and even breathing. For a three-person household, this can amount to about 10 litres of water a day appearing as humidity in the air. A relative humidity of 40-60% is optimal, according to German consumer advice centre, Verbraucherzentrale. You can check this with a hygrometer (which can be bought fairly cheaply).
Air a home with radiators for a set time
Radiators actually transfer most of their heat through convection, warming the air above. So, especially in large rooms with high ceilings, it’s important to be deliberate about airing – choosing when and for how long windows are open – in order to save energy.
“With every airing cycle, the heated air is sucked to the outside,” Frank says. “This energy is completely lost to the building, and has to be replaced with vigorous heating afterwards. Moreover, from a physical point of view, air stores heat poorly and relatively inefficiently.”
The right choice here is short periods of high-impact airing. This involves opening the windows completely for a short time, rather than just leaving them open a crack for a longer period. Otherwise, the room might cool completely when it’s very cold outside.
This works best through cross-ventilation – that is, creating a draught. If possible, open two windows that are far away from one another. Room doors that are open for a long time can also allow warm air to escape.
Air every two hours, leaving the windows open for:
Radiators actually transfer most of their heat through convection, warming the air above. So, especially in large rooms with high ceilings, it’s important to be deliberate about airing – choosing when and for how long windows are open – in order to save energy.
“With every airing cycle, the heated air is sucked to the outside,” Frank says. “This energy is completely lost to the building, and has to be replaced with vigorous heating afterwards. Moreover, from a physical point of view, air stores heat poorly and relatively inefficiently.”
The right choice here is short periods of high-impact airing. This involves opening the windows completely for a short time, rather than just leaving them open a crack for a longer period. Otherwise, the room might cool completely when it’s very cold outside.
This works best through cross-ventilation – that is, creating a draught. If possible, open two windows that are far away from one another. Room doors that are open for a long time can also allow warm air to escape.
Air every two hours, leaving the windows open for:
- December, January, February: 4 to 6 minutes.
- March, November: 8 to 10 minutes.
- April, October: 12 to 15 minutes.
- May, September: 16 to 20 minutes.
- June, July, August: 25 to 30 minutes.
Don’t be too frugal with heating
Many renters and homeowners want to save on heating costs, but they rarely do themselves a favour with incorrect airing and heating.
“For example, it’s a fact that only 4% residual wall moisture can reduce the thermal performance of a property by over 50%,” Frank says. “However strange it may sound at first, through heating and keeping the building fabric dry, one can actively support the building’s thermal performance.”
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Many renters and homeowners want to save on heating costs, but they rarely do themselves a favour with incorrect airing and heating.
“For example, it’s a fact that only 4% residual wall moisture can reduce the thermal performance of a property by over 50%,” Frank says. “However strange it may sound at first, through heating and keeping the building fabric dry, one can actively support the building’s thermal performance.”
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Invest in thermostats for intelligent heat regulation
“Normally, thermostats regulate the heating, whether it operates on oil, gas or electricity,” Frank says. They determine when additional heat is necessary in order to reach the target temperature.
“Modern thermostats recognise when you’re airing the house,” he says. “For example, if the temperature falls by two degrees within five minutes, it will detect an airing cycle and pause for a while, and not necessarily frantically give out a heating command.”
“Normally, thermostats regulate the heating, whether it operates on oil, gas or electricity,” Frank says. They determine when additional heat is necessary in order to reach the target temperature.
“Modern thermostats recognise when you’re airing the house,” he says. “For example, if the temperature falls by two degrees within five minutes, it will detect an airing cycle and pause for a while, and not necessarily frantically give out a heating command.”
Modern thermostats that can be programmed to suit the room and the way it’s used help save energy. “Why would you heat through the entire day if the inhabitants aren’t there most of the time?” Frank says.
On the other hand, the temperature of the room should also not sink too much. “The absolute worst idea is allowing the temperature to fall too much, for example at night, during the day or during a longer absence. The outcome could be the build-up of condensation and mould,” he warns.
On the other hand, the temperature of the room should also not sink too much. “The absolute worst idea is allowing the temperature to fall too much, for example at night, during the day or during a longer absence. The outcome could be the build-up of condensation and mould,” he warns.
Mitigate Covid-19 transmission
As we head into the winter months and our lives increasingly move indoors, airing is becoming a public health issue. It’s now suggested that, while not the primary route of transmission, aerosols – tiny particles that can remain airborne for a longer time than larger droplets – might have a role in the transmission of Covid-19 “in enclosed spaces with poor ventilation”.
One of the ways the German government is addressing this problem is by including ventilation – specifically cross-ventilation with as much exchange of indoor air for fresh air as possible – alongside ongoing physical distancing, hand washing, and mask wearing.
However, it’s important to remember that, like the other protection measures, airing can only reduce, not eliminate, the risk of exposure. The four protective measures should be used together, and the UK government recommends maintaining distance, wearing masks and being vigilant about hand washing, even in well-ventilated rooms.
Tell us…
Will you be using this method of airing your home? Or do you frequently ventilate already? Share your thoughts and ideas in the Comments.
As we head into the winter months and our lives increasingly move indoors, airing is becoming a public health issue. It’s now suggested that, while not the primary route of transmission, aerosols – tiny particles that can remain airborne for a longer time than larger droplets – might have a role in the transmission of Covid-19 “in enclosed spaces with poor ventilation”.
One of the ways the German government is addressing this problem is by including ventilation – specifically cross-ventilation with as much exchange of indoor air for fresh air as possible – alongside ongoing physical distancing, hand washing, and mask wearing.
However, it’s important to remember that, like the other protection measures, airing can only reduce, not eliminate, the risk of exposure. The four protective measures should be used together, and the UK government recommends maintaining distance, wearing masks and being vigilant about hand washing, even in well-ventilated rooms.
Tell us…
Will you be using this method of airing your home? Or do you frequently ventilate already? Share your thoughts and ideas in the Comments.
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deborah/cassandra/littlejem
Worth adding that some types of heaters, including gas-bottle Super Sers (I remember those) and paraffin heaters, actually create humidity as well as desired-for heat. Our Super Ser would make our gloss white kitchen walls run with water..
I think having a little hygrometer you can check humidity with in different rooms every now and then is a really good idea. I bought a v cheap set of 3 off the internet as i have an expensive piano that needs minimum 50% humidity (which is good for human beans too). During a dry, cold winter patch when we've needed more heating indoors it sometimes falls below 40%, and that feels uncomfortably dry for me as well as the piano. But now i'm talking about too dry, not too damp! Maybe i should air the room at those times - to let humidity in with the fresh air..
@helena - When I started teaching (some 45 years ago !!), I rented an unheated top floor flat in a Victorian block. I bought a Super-Ser heater for the living room, which also heated the bedroom if you left the door open. I had an electric fan heater in the kitchen, and ate breakfast with my gloves on because the cutlery was too cold to handle ! Icicles hung down from the skylight ... However, I don't remember missing a day of school for illness !?! Ventilation wasn't really a problem, as none of the windows fitted properly, and there was a door up onto the roof. Nowadays, we live in a centrally heated house which can sometimes bvecome very humid, especially in Summer. A friend who was clearing out her deceased aunt's property found several de-humidifiers, one of which she offered to me. I have been most grateful for it ever since. It keeps the bedroom at a much more bearable level of humidity, amd when we did our renovations, we put our laundered clothes on an airer in a small bedroom, together with the de-humidifier, which helped to dry the clothes more quickly. Can thoroughly recommend ! Our piano seems reasonably happy, but maybe a hygrometer would be a good investment. Not sure about furniture, but I prefer a drier atmosphere - I don't do well in heat and humidity !!
Be careful with your doors. Mine slam shut if I have all the windows open!