Understanding Moisture, Mould, and the Built Environment: A Conversation with Hector Altamirano
Mould is an ever-present challenge in buildings, especially in social housing, yet the way we talk about it is often overly simplistic. It’s either there or it isn’t, and the goal is always to eradicate it. But the reality is much more nuanced. Mould is a natural part of our environment, and its presence tells us something important about the conditions of our buildings. In a recent conversation, I sat down with Dr Hector Altamirano-Medina , professor at UCL and Academic Director of the UK Centre for Moisture in Buildings UCL ), to explore the complexities of mould, moisture balance, and what needs to be done to create healthier buildings.
Mould: A Sign of an Imbalance
Mould is not just a nuisance—it’s an indicator. As Hector puts it, mould is like a messenger, signaling that a building’s moisture balance is off. Whether due to high indoor humidity, cold surfaces, or structural issues, mould growth is a symptom of an underlying problem.
In social housing, the challenge is even greater because buildings are occupied by a wide range of individuals, each with different habits, health conditions, and vulnerabilities. A home with persistent damp and mould issues is not just unpleasant—it can be a serious health risk, especially for those with respiratory conditions or weakened immune systems. But, as Hector points out, complete eradication isn’t realistic. Instead, the goal should be to manage moisture levels effectively.
Moisture Balance: The Key to Mould Control
At its core, mould needs three things to grow: moisture, food (which can be as simple as dust or organic materials on surfaces), and a suitable temperature. Of these, the only factor we can truly control is moisture. This is where the concept of moisture balance comes into play.
Moisture balance refers to the equilibrium within a building—how moisture is generated, how it moves, and how it is removed. Several factors influence this balance, including:
Ventilation: Ensuring adequate airflow to remove excess moisture.
Heating: Maintaining stable temperatures to prevent cold surfaces where condensation can occur.
Building materials: The ability of materials to absorb and release moisture without causing problems.
Occupant behavior: Activities such as drying clothes indoors or failing to use extractor fans can tip the balance.
A house in balance is one where mould doesn’t take hold. However, when the balance shifts—due to poor insulation, inadequate ventilation, or external leaks—moisture builds up, and mould follows.
Diagnostics: Understanding the Root Cause
One of the biggest challenges in dealing with mould is diagnosing the root cause. Too often, the response is to clean visible mould without addressing why it appeared in the first place. Hector emphasises the importance of proper diagnostics—understanding whether mould is caused by structural issues, lack of ventilation, occupant behaviour, or a combination of factors.
This requires looking beyond a single moment in time. Many mould issues are seasonal, appearing in winter due to increased condensation. Others are the result of persistent leaks that go unnoticed for months. Monitoring long-term trends—such as temperature, humidity levels, and ventilation rates—can provide critical insights into what’s really happening in a building.
Health Impacts of Mold: What We Know and What We Don’t
While it’s well established that mould spores can trigger allergies and respiratory issues, there is growing interested in the broader health effects of mould exposure. Hector and his team at UKCMB are currently reviewing the literature on the psychological effects of mould, with early indications that conditions such as anxiety, depression, and cognitive impairment may be linked to long-term exposure.
However, measuring these effects is complex. Many studies struggle to isolate mould exposure from other environmental factors like poor air quality, inadequate heating, or general household stress. More research is needed to understand precisely how mould affects mental health, but one thing is clear: improving indoor environments can only be beneficial.
The Path Forward: What Needs to Change?
The tragic death of Awaab Ishak in 2020 brought national attention to the dangers of damp and mould in housing. As a result, policies are changing, and housing providers are being pushed to take mould more seriously. But this is not a short-term fix. As Hector points out, addressing damp and mould is a long-term challenge that requires:
Better regulation and enforcement: Ensuring housing providers follow best practices.
Education for residents: Helping people understand how their habits affect indoor moisture levels.
Improved building standards: Designing and retrofitting homes to manage moisture more effectively.
Interdisciplinary collaboration: Bringing together experts from architecture, microbiology, and environmental science to tackle the problem holistically.
Mould is not just a problem to be removed; it signals that something is wrong. The key to long-term mould management is understanding and maintaining moisture balance in buildings. With better diagnostics, improved building standards, and a more nuanced approach, we can create healthier indoor environments.
Hector’s work at UKCMB is helping to drive this conversation forward, providing the research, tools, and training needed to make meaningful change. The challenge is big, but the momentum is building. The question now is whether we can sustain this effort over the next decade and beyond.
If you’re interested in learning more, check out the UK Centre for Moisture in Buildings for resources, training, and updates on the latest research.
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