Insulate tight and ventilate right

Recent research by Zehnder Group UK reveals a sobering picture: 99.2% of landlords report mould problems, with 10% saying it affects over half of their properties. Despite well-meaning attempts to address it, 51% of cases see the mould return. So, what’s going wrong, and how can we fix it?

In a recent discussion with Jenny Danson, Zehnder experts Stuart Smith and Mark Trowers offered insight into the scale of the crisis and practical solutions to tackle it.

The Invisible Danger: What’s in the Air We Breathe?

When we think of pollution, we often picture outdoor smog. But indoor air quality can be up to five times worse, filled with hidden dangers such as Volatile Organic Compounds (VOCs)—toxic gases emitted by furniture and building materials—and Particulate Matter (PM), microscopic particles that can penetrate deep into the lungs and bloodstream.

Compounding the problem is the condensation generated by everyday activities like cooking, showering, and drying clothes indoors. A typical family produces 24 pints of moisture daily, often with inadequate ventilation to manage it.

Why Social Housing is Uniquely Vulnerable

The UK’s 3.1 million socially rented homes range from century-old properties to modern builds, all facing unique challenges. Over time, efforts to make homes more energy efficient—through better insulation and airtight construction—have inadvertently worsened indoor air quality.

“We’ve almost created a ‘Tupperware box’ scenario,” says Trowers, describing airtight homes that trap moisture and pollutants. Insufficient education on ventilation worsens the issue, with many tenants believing extract fans waste energy or cause heat loss—leading to them being turned off.

A Call to Action: Insulate Tight and Ventilate Right

The solution lies in a balanced approach: improving energy efficiency while ensuring proper ventilation. Zehnder’s catchphrase, “Insulate tight and ventilate right,” encapsulates this. The company advocates for a system-based approach, including Mechanical Ventilation with Heat Recovery (MVHR) units. These systems maintain airflow while recovering heat, reducing both moisture and energy costs.

Education is also critical. Tenants, landlords, and housing teams need to understand the importance of ventilation—not just in wet rooms but throughout the home. “It’s not enough to install a fan in the bathroom and call it a day,” Smith explains. “Proper air movement requires a holistic system.”

Practical Steps for Landlords and Tenants

Zehnder and the Healthy Homes Hub recommend:

1. Educating Residents: Simple changes, like keeping trickle vents open, can make a difference.

2. Upgrading Systems: IoT-enabled ventilation solutions allow landlords to monitor and adjust air quality remotely, ensuring consistent performance.

3. Proactive Maintenance: Ventilation systems need regular cleaning and servicing to remain effective.

Looking Ahead

The impact of poor indoor air quality isn’t limited to property damage; it’s a health crisis. Mould spores, VOCs, and PM contribute to respiratory illnesses, allergies, and long-term health issues. With tenants spending 90% of their time indoors, addressing these invisible threats is urgent.

To support the sector, Healthy Homes Hub is hosting masterclasses on crafting and implementing ventilation strategies, alongside a webinar detailing Zehnder’s recent research findings. Resources are available at zehnder.co.uk and the Healthy Homes Hub.

It’s time for landlords, housing teams, and policymakers to make air quality a priority. Let’s embrace the mantra: “Insulate tight and ventilate right”—a small shift with the potential for huge impact.