Tackling Damp and Mould:

The homeowner had become increasingly concerned about mould affecting both internal and external walls - spotted in the living room, kitchen, entrance hallway, and bedrooms. Understandably, they feared a potential structural problem.

Our initial visual inspection found no evidence of rainwater penetration, rising damp, or structural defects. Moisture meter readings were within a dry range. The house, like many of its age, had solid 19-inch-thick walls - brick-faced at the front, rendered at the rear, and located in a coastal area with high exposure to sea air.

Some maintenance issues were present: small holes in the brickwork, poor pointing (likely cement-based rather than lime), slightly raised ground levels at the front, and a lack of air bricks at the rear reducing subfloor ventilation. However, none of these were actively contributing to the mould, and we advised sensible maintenance: fill the holes, reduce ground levels, monitor, and repoint in lime when the time comes.

With no obvious external cause, we turned our attention indoors.

The original timber windows had been replaced with modern UPVC units - which, while energy efficient, had no trickle vents to allow background ventilation. Original fireplaces had also been blocked up, reducing passive airflow further.

There was a recirculating cooker hood (not vented externally) and no extractor fans in the bathroom or shower room. These limitations were trapping moisture inside the home.

Our recommendations at this stage included:

Despite having a room thermostat, the family didn’t know what temperatures were being reached throughout the home. We provided a mini hygro-thermometer to help. It revealed a common issue: the thermostat was located upstairs in a warm, central hallway. While this space was reaching temperature, cooler ground floor rooms - especially those affected by mould - were not. The heating often shut off before the rest of the home was adequately warm.

The homeowners agreed to participate in a longer-term environmental monitoring trial using the Aico HomeLINK system. This allowed us to track:

Over several weeks, the data painted a clear picture. Despite the thermostat being set to 20°C, internal temperatures regularly fell well below the healthy 16°C minimum - sometimes down to 12°C. The heating wasn’t on long enough to bring wall temperatures up, and the walls were acting as cold surfaces where air reached dew point - leading to condensation and mould growth.

Carbon dioxide levels also peaked at unhealthy levels, particularly around the busy morning and evening routines. This indicated poor ventilation and stagnant air, which can affect concentration, sleep quality, and overall wellbeing. High CO₂ is also a useful proxy for other indoor pollutants.

Humidity levels were consistently over 70% - the threshold at which mould becomes more likely to grow.

It’s important to understand that masonry walls have high thermal mass. When heated regularly, they help regulate indoor humidity by absorbing and later releasing moisture and warmth - like a passive storage heater. But when homes are underheated, walls stay cold, absorb heat instead of radiating it, and contribute to rapid heat loss when the heating switches off.

Inconsistent heating leads to cold walls and elevated relative humidity - ideal conditions for mould to thrive.

Following our review of the monitoring data, we worked with the family to trial a new approach:

The homeowners weren’t in a position to install extractor fans yet, so we focused on simple, repeatable routines - and they stuck with them.

The Result: Immediate Improvements

We saw rapid improvements in indoor temperature, carbon dioxide levels, and relative humidity - which consistently fell just below the critical 70% threshold for mould growth. That alone was a major win.

Although the new temperature settings felt a bit too warm overnight for the family, we helped them adjust to a setback temperature of 16°C, with 18–20°C during the day, which maintained the improvements while keeping them comfortable.

Mould Sampling and Final Steps

We also carried out mould sampling. Interestingly, some areas that appeared stained returned normal background mould levels, while others showed slightly elevated counts. This confirmed what the family had told us: the mould had developed gradually, wasn’t spreading fast, and had been left untreated due to busy family life.

All affected areas were treated with Maxam Pura+ non-toxic mould spray and redecorated using emulsion with a mould inhibitor additive.

A return visit showed no recurrence of mould, though we’ll continue to monitor through the next winter.

While long-term environmental monitoring provided valuable insights in this case, it is not typically required for straightforward situations like this one. Most damp and mould issues in similar homes can be resolved with practical advice, consistent heating and ventilation habits, and minor building maintenance. In this instance, the homeowners kindly agreed to participate in the monitoring trial so that we could better understand and illustrate what happens behind the scenes - inside the building fabric and air environment - before and after these changes are made. This data now serves as a helpful reference point for similar households, demonstrating how simple behavioural adjustments can make a measurable difference. In most cases, we can take simple readings during surveys, or use low-cost humidity sensors, and assess based on this.

A Low-Cost, High-Impact Outcome

We often hear stories of homeowners being advised to invest in major internal plastering or damp-proofing works to resolve issues such as this, only to find the problems return, because the root cause was never an external one.

This case study demonstrates what we believe is a gold standard approach to damp and mould, although we don't often have to go to this level of investigation. Key features include:

No expensive remedial works. No blame. Just practical advice rooted in experience, science, and care. 

If you're a homeowner, landlord, or housing provider facing persistent mould problems - or want to prevent them before they start - get in touch. We offer independent advice, detailed surveys, and training tailored to your needs.