Retrofitting MVHR in Renovations: Meeting Modern Standards in Older Homes

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.

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.

Why MVHR Is Now Critical in Home Renovations

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:

• Internal or external wall insulation
• New sealed windows and doors
• Roof or loft insulation
• Airtight membranes or tapes

...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.

Understanding the Regulatory Context for Renovations

Part F – Ventilation

When you make major changes to the building fabric—such as window replacements, insulation, or room additions—Part F applies. You are required to:

• Ensure adequate background ventilation
• Deliver a minimum whole-house ventilation rate
• Install extraction in wet rooms
• Commission and document ventilation systems

MVHR meets these requirements as a continuous mechanical supply and extract system, providing consistent and measurable airflow.

Read Part F for existing buildings

Part L – Energy Conservation

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.

Case Study: Victorian Terrace MVHR Retrofit in West London

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:

• Installed a compact, quiet MVHR unit in the loft
• Routed semi-rigid ducting through wardrobe voids and stairwells
• Used low-profile ceiling valves
• Delivered supply to bedrooms and living room; extracted from kitchen and bathroom
• Provided full commissioning for Part F sign-off

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.

What to Consider When Retrofitting MVHR

Retrofitting MVHR is more complex than in new builds, but fully achievable in most homes with proper planning. Key factors include:

• Ducting Space: Look for ceiling voids, soffits, built-in wardrobes, or internal wall cavities
• Location of Unit: Lofts, utility cupboards, or plant rooms are best
• Noise Control: Use silencers and acoustic insulation to manage fan and airflow sound
• Access for Maintenance: Filters should be easy to change by the homeowner
• Airtightness Improvements: MVHR is most beneficial when paired with some degree of airtightness improvement (below 5 m³/h·m² ideally)

Bullet Summary: Steps to Retrofit MVHR in a Renovated Home

• Conduct a feasibility assessment (space, access, layout)
• Select the right MVHR unit for your floor area and number of wet rooms
• Plan duct routes carefully to avoid visual disruption
• Schedule installation before plastering or final finishes
• Balance and commission the system per Building Regs
• Provide maintenance instructions for long-term use

Where We Retrofit MVHR Systems

At ClimateWorks, we retrofit MVHR systems in homes undergoing:

• Full refurbishments
• Loft conversions
• Kitchen/diner reconfigurations
• Heritage property upgrades
• Energy performance improvements

We work in and around:

• Reading
• Woking
• Basingstoke
• Wokingham
• Newbury
• West London

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.

👉 Book a retrofit assessment

References

[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/

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.

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