Here in the UK, we’re a bit like bears or, for people of a certain age, the Blue Peter Tortoise: as soon as it gets cold, we lock up our homes, whack the heating up and hibernate until we have to go out or it gets warm enough to do so.
That would seem to make sense. With energy prices still incredibly high, wasting any heat feels like throwing money out of the window. Yet, ther’s a real danger of closing up our homes, and opening windows for a short time each day, even in the middle of winter is not only a brilliant idea, it can reduce condensation and mould.
That may fly in the face of convention, as we’re often told to seal all gaps in winter, especially in old, draughty homes. But opening a window to let cold air in has a big impact on our overall health. Here’s why.
## Why do we get condensation?
Air holds water. The amount of water in the air is usually noted down as the relative humidity (RH, but normally just referred to as humidity), and is quoted as a percentage. The issue with this is that the percentage is used to describe the amount of moisture in the air versus how much moisture the air is capable of holding. As the air temperature rises, the amount of moisture it holds also increases.
Condensation in the home occurs when warm air in your home meets a cold surface, such as an external wall or window (particularly single-glazed). As the air cools, the amount of water it can hold decreases, and the dew point is reached. The dew point is the temperature that air has to be cooled to for its contained moisture to turn into condensation (or fog, mist or dew on the grass). The exact dew point changes based on the relative humidity and current temperature.
The simple thing you need to know is that if your home is humid, as it cools overnight, the air cools and, as it makes contact with a cold surface, condensation is formed. As mentioned,you’re most likely to meet condensation on a window pane or external wall,but you can find it forms on clothes,or even on furniture touching a wall.
With a moist environment, you’re more likely to get black mould appearing in your home, on walls, clothes, books, furniture and more. And, condensation is the biggest cause of black mould, according to the Centre for Sustainable Energy.
The issue in the colder months is that we shut our homes up, so moisture is trapped in the air. That excess water comes from drying clothes indoors, showering, cooking and, horribly, breathing.With no escape, the moisture builds up and our homes become more humid. Condensation should be removed when spotted, either by using a cloth or, more easily, with a window vacuum.However, proper ventilation and opening windows can have a bigger impact in the long term.
Ventilation and Humidity Control for a Healthier Home
Maintaining good indoor air quality is crucial for both comfort and health.While a consistent 60% humidity level is ideal, simply aiming for that number isn’t enough. Incorporating ventilation strategies can help achieve this target and offer additional benefits.
Opening windows for 15-20 minutes, even if it doesn’t completely replace the warm air, is a valuable practice. The incoming cool air reduces indoor humidity and introduces fresh air, which in turn minimizes condensation and the risk of black mould growth. https://www.epa.gov/indoor-air-quality-iaq/mold-and-health
Lowering humidity also makes your heating system more efficient. With less moisture in the air, your heating system doesn’t have to work as hard to warm your home, leading to potential energy savings.
More Ventilation Strategies
Ventilation is particularly critically important in older homes with solid walls, where natural airflow is limited. Daily window opening is a simple solution,but several methods can minimize heat loss while maximizing ventilation.
Smart heating systems with open window detection, like the Tado X system, are a smart investment. These systems automatically pause heating when a sudden temperature drop is detected, preventing energy waste. https://www.tado.com/gb-en/
for those who prefer not to open windows frequently, a Positive Input Ventilation (PIV) system offers a good option. Typically installed in the loft, PIV systems use a fan to draw air from the loft space and gently introduce it into the home, reducing humidity levels. PIV systems can also be wall-mounted for use in flats.
https://www.ventilation-superstore.com/positive-input-ventilation
Using a dehumidifier is another effective option, especially when drying clothes indoors. A dehumidifier, such as the MeacoDry Arete Two, removes excess moisture from the air, helping to maintain optimal humidity levels. https://www.meaco.com/