Zehnder Group UK – From Condensation to Clean Indoor Air Quality: How a Two-Part Ventilation System Can Transform Home Health By Holly Bramwell, Divisional Manager, Vents at Zehnder Group UK
odern homes are now more airtight than ever, which is great for energy efficiency but creates a serious challenge for indoor air quality. Without air movement, moisture, pollutants and stale air become trapped, leading to problems like condensation build-up, damp and toxic black mould outbreaks. These pose significant health risks to residents, such as severe respiratory issues from prolonged exposure. No building is immune. Condensation, for example, is an often-overlooked issue that silently develops inside buildings, leaving behind a trail of potentially severe consequences. Whilst it might seem harmless at first glance - after all, it is just a bit of water - the impact if left to its own devices can significantly affect the structural integrity of a building and the health of occupants inside. Last year, during mould and condensation season, we conducted a research study that unveiled almost three quarters of British residents (73%) experience condensation on their windows and nearly a half (45.1%) say they experience mould in their homes.
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Condensation occurs when warm, moisture- laden air comes into contact with cooler surfaces. In winter, closed windows, cold surfaces, and running heating systems create ideal conditions for moisture to settle. A typical household produces up to 24 pints of water vapour daily through
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everyday activities such as cooking, bathing, drying laundry indoors, and even breathing. Without sufficient ventilation, this moisture becomes trapped, providing an ideal environment for mould, which can be toxic and harmful to health. But condensation isn’t just an aesthetic or
maintenance issue. Persistent damp can compromise building materials, reducing structural integrity and the thermal efficiency of insulation.
Exposure to mould, particularly black mould, has also been linked to respiratory problems and can exacerbate conditions such as asthma. Vulnerable groups, including children and the elderly, are especially at risk.
There is a simple ventilation strategy that can help create effective airflow through the property to counter these issues, but many don’t realise its impact.
The first important part is the trickle vents. Fitted into windows, trickle vents are designed to work harmoniously with the second part - extractor fans in the bathroom or kitchen. Together they form an effective whole-home ventilation system. By allowing a continuous flow of fresh air into a property, the vents work in tandem with the extractor fans to pull fresh air through the home and efficiently remove the stale, moisture-laden air. But once vents and fans are installed, it is important to check that the ventilation system is working effectively. Are extract fans and trickle vent systems turned off or closed? If so, this would compromise their ability to operate effectively. Furthermore, if fans are over 5-10 years old, you might find a newer model will give better performance, less noise and increased efficiency. Bathroom extractor fan and vent technology has come a long way in recent years, meaning no resident should feel the need to close vents or switch off their fan due to nuisance noise or draughts. This is vital because effective ventilation
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