Why Renovation Projects Need to Think Beyond Insulation Renovation work in the UK has moved far beyond aesthetic upgrades. With building performance targets now embedded in regulations, more homeowners are taking on insulation improvements, airtightness upgrades, and energy-saving enhancements during refurbishments. But there's one major issue that’s often overlooked: ventilation.
Renovation work in the UK has moved far beyond aesthetic upgrades. With building performance targets now embedded in regulations, more homeowners are taking on insulation improvements, airtightness upgrades, and energy-saving enhancements during refurbishments. But there's one major issue that’s often overlooked: ventilation.
Once you've sealed a home to prevent heat loss, airflow is reduced to a level that may no longer be healthy or compliant. That’s where Mechanical Ventilation with Heat Recovery (MVHR) comes in. Originally associated with new builds, MVHR is now being widely adopted in retrofits across the country.
Retrofitting MVHR systems not only helps properties meet ventilation requirements under Approved Document F, but also improves comfort, indoor air quality, and long-term energy savings—key goals for modernised homes in places like Reading, Woking, and West London.
Older homes were built to breathe. Draughts under floorboards and gaps in windows allowed fresh air in (whether you wanted it or not). But once a renovation project adds:
...that "natural ventilation" disappears. The result? Stale air, condensation, mould growth, and poor indoor health.
An MVHR system extracts stale air from wet rooms (kitchens, bathrooms, utility spaces) and supplies fresh filtered air to living rooms and bedrooms—all while recovering the heat from outgoing air. It’s the only solution that balances airtight upgrades with legal airflow requirements.
When you make major changes to the building fabric—such as window replacements, insulation, or room additions—Part F applies. You are required to:
MVHR meets these requirements as a continuous mechanical supply and extract system, providing consistent and measurable airflow.
Read Part F for existing buildings
If your renovation improves the building’s energy performance, it’s likely subject to Part L. MVHR helps by retaining heat that would otherwise be lost through traditional extract ventilation or trickle vents.
A couple renovating a three-storey Victorian terrace in Ealing added insulation to external walls, replaced all windows with double glazing, and sealed the roof. Post-renovation, the home felt stuffy, with condensation forming on window panes each morning.
ClimateWorks was called in to retrofit a central MVHR system. Due to the layout and space constraints, we:
The result was fresh air throughout the home, no more condensation, and a noticeable improvement in comfort. The property’s EPC rating improved, and the homeowners now run the heating system less often thanks to heat recovery.
Retrofitting MVHR is more complex than in new builds, but fully achievable in most homes with proper planning. Key factors include:
At ClimateWorks, we retrofit MVHR systems in homes undergoing:
We work in and around:
Our team ensures installations are not only discreet and quiet, but also fully compliant with Building Regulations. Every system is tailored to the unique constraints of older and character properties.
[1] GOV.UK – Approved Document F: Ventilation
https://www.gov.uk/government/publications/ventilation-approved-document-f
[2] Energy Saving Trust – Whole House Ventilation in Retrofit Homes
https://energysavingtrust.org.uk/advice/ventilation/
[3] NHBC Foundation – Retrofit MVHR in Existing Homes
https://www.nhbcfoundation.org/publication/retrofit-mvhr-in-existing-homes/
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.