How MVHR Helps Prevent Mould and Damp in Modern Homes

Author:
Dr. Julian Carter

Despite significant advances in home insulation and energy-saving design, one persistent issue continues to affect many UK households: mould and damp.

Why Mould and Moisture Are Still Common in ‘Energy-Efficient’ Homes

Despite significant advances in home insulation and energy-saving design, one persistent issue continues to affect many UK households: mould and damp.

You might assume that upgrading your home with double glazing, added insulation, or new doors would eliminate condensation problems. In reality, many of these improvements actually trap moisture indoors, worsening the conditions for mould growth. Without proper ventilation, moisture has nowhere to go—and in modern airtight homes, this quickly becomes a serious health and structural concern.

This is where Mechanical Ventilation with Heat Recovery (MVHR) comes in. MVHR doesn’t just manage airflow—it actively removes moisture from your home’s most humid areas while retaining valuable heat. If you’ve been battling black spots on the ceiling, musty smells, or condensation on windows, an MVHR system could be the long-term solution you need.

Why Modern Homes Still Suffer from Mould

Today’s homes are better sealed and insulated than ever before. While this helps reduce energy use, it also limits natural ventilation. The problem? Every day, we release litres of water vapour into the air through:

  • Cooking
  • Showering
  • Drying clothes indoors
  • Breathing during sleep

Without a system to continuously extract this humid air and replace it with fresh, filtered air, moisture begins to build. The result?

  • Condensation on windows and walls
  • Black mould in bathrooms and corners
  • Musty odours in bedrooms and wardrobes
  • Peeling paint or damp patches behind furniture
  • Structural damage over time

According to the NHS, exposure to indoor damp and mould can worsen asthma, allergies, and respiratory infections[1].

How MVHR Works to Prevent Damp and Mould

MVHR systems solve this problem by constantly extracting moist air from your home’s wet rooms (bathroom, kitchen, utility) and supplying clean, filtered air into living areas and bedrooms. All while recovering up to 90% of the heat from the outgoing air.

Here’s how it works:

  1. Moist, stale air is extracted from problem areas.
  2. The air passes through a heat exchanger, transferring warmth to the incoming air.
  3. Fresh, filtered air is supplied to habitable rooms at a comfortable temperature.
  4. This process runs 24/7, maintaining ideal humidity levels and stopping moisture build-up.

With MVHR, you no longer need to rely on extractor fans, open windows, or dehumidifiers.

Real-Life Example: MVHR Installed to Solve Chronic Damp in a London Flat

In 2023, a homeowner in South West London contacted ClimateWorks after ongoing mould problems in their two-bedroom flat. Despite repainting, treating surfaces, and running a dehumidifier, the issue persisted—particularly in the bathroom and main bedroom.

The property had recently been upgraded with new windows and insulation, which had reduced energy bills but worsened condensation.

What We Did:

  • Installed a low-profile MVHR system with ducting routed through loft voids
  • Extract grilles placed in the bathroom and kitchen
  • Supply grilles installed in both bedrooms and the living room
  • System balanced to meet Part F ventilation requirements
  • F7 filters added to improve indoor air quality

Results (After 4 Weeks):

  • No visible condensation on windows
  • Mould stopped forming behind wardrobes and on bathroom walls
  • Indoor humidity dropped from 72% to a consistent 50–55%
  • The home felt fresher, even with windows closed all day

Why Dehumidifiers and Extractor Fans Aren’t Enough

Many households rely on extractor fans in bathrooms or portable dehumidifiers to combat moisture. These can help temporarily—but they’re often:

  • Noisy and energy-intensive
  • Limited to one room at a time
  • Unable to prevent air stagnation elsewhere in the home
  • Lacking filtration, so allergens and pollutants remain in circulation

MVHR is the only system that provides whole-house, continuous, and balanced ventilation—ensuring every room is kept dry, healthy, and well-ventilated at all times.

Benefits of MVHR for Mould and Damp Prevention

  • Continuous moisture extraction from kitchens, bathrooms, and utility areas
  • Balanced airflow to avoid pressure imbalances or air leakage
  • Filter technology to remove airborne particles and spores
  • Stable humidity levels that discourage mould formation
  • No need to open windows, reducing the risk of cold surfaces and condensation
  • Energy-efficient heat recovery, keeping your home warm without moisture build-up

Installation Considerations in Damp-Prone Homes

When damp is already present, it’s essential to install MVHR correctly:

  • Position extract grilles as close to moisture sources as possible
  • Ensure ducting is insulated in colder spaces like lofts
  • Design system to achieve a consistent air change rate across the home
  • Use rigid ducting to prevent resistance and noise
  • Include access panels for easy filter maintenance

ClimateWorks designs each MVHR installation around your home’s specific layout and problem areas, ensuring the system solves rather than shifts the issue.

Maintenance Tips to Keep Mould at Bay

Even the best MVHR system needs regular upkeep to perform effectively:

  • Replace filters every 3–6 months, depending on use and environment
  • Check air grilles for blockages or dust
  • Monitor indoor humidity with a digital hygrometer (ideal range: 40–60%)
  • Book annual service inspections to maintain system performance

Neglecting maintenance can reduce airflow, allowing humidity to rise again and putting your home at risk.

Is MVHR Worth It for Damp Control?

If you’re dealing with recurring mould or condensation issues—especially after upgrading insulation or windows—MVHR could be the permanent fix.

It’s not just about air movement. It’s about smart ventilation, designed to improve your indoor environment, reduce health risks, and protect your property from hidden moisture damage.

To speak to a specialist or arrange a no-obligation home survey, contact the team at https://www.climateworks.co.uk

Author Bio

Dr. Julian Carter is a highly experienced thermal systems expert with over 15 years in the field, holding a PhD in thermal systems. His career spans academic research, consulting, and teaching, focusing on air conditioning and refrigeration systems. Dr. Carter bridges the gap between theoretical advancements and practical applications, providing expert insights to organisations like ClimateWorks, where his guidance informs decision-making and industry best practices. Notably, he has worked on international projects with organisations such as Daikin Industries, the International Institute of Refrigeration (IIR), and the United Nations Environment Programme (UNEP). Currently a lecturer at Edinburgh University, Dr. Carter combines his expertise with a passion for educating the next generation of engineers and advancing climate control technologies.

References

[1] NHS. (2023). Health risks of damp and mould in homes. Retrieved from https://www.nhs.uk/conditions/damp-and-mould
[2] UK Government. (2022). Approved Document F – Ventilation. Retrieved from https://www.gov.uk/government/publications/ventilation-approved-document-f
[3] Energy Saving Trust. (2024). How to Reduce Humidity in Your Home. Retrieved from https://energysavingtrust.org.uk

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