How MVHR Simplifies Overheating Compliance in Residential Developments

Overheating is now a major planning risk for residential schemes. Local authorities across Hampshire, Berkshire and Surrey are enforcing stricter thermal comfort targets. Traditional mitigation methods like larger windows or ceiling fans often clash with design or energy goals.

Mechanical Ventilation with Heat Recovery (MVHR) offers a solution. It improves airflow, controls indoor temperature and supports compliance with Part O and SAP overheating checks. This blog explains how MVHR helps you meet thermal regulations without changing your architectural design.

What overheating compliance requires

The 2021 update to Building Regulations Part O introduced targets to:

• Limit solar gain
• Reduce internal temperature spikes during summer
• Avoid reliance on openable windows where not viable
• Maintain night-time comfort in urban or high-noise areas

Part O now applies to all new residential buildings and conversions. If your SAP model shows frequent overheating risk, planners may reject your proposal.

How MVHR helps prevent overheating

MVHR provides:

• Consistent airflow during summer, even when windows are closed
• Night purge capability by increasing extract rates
• Balanced internal temperatures through zoned ventilation
• Reduced reliance on passive cooling strategies
• Improved indoor air quality in sealed units

In Winchester and Oxford, projects using MVHR passed thermal comfort checks while retaining narrow window openings.

Real project examples

Reading infill flats (Completed January 2024)

On a constrained site with noise constraints, MVHR allowed windows to stay small. Night ventilation mode helped internal temps stay under the critical threshold in SAP. Planning was approved without objection.

Newbury townhouses (Autumn 2023)

Each unit used centralised MVHR with night boost. The developer avoided ceiling fans or openable roof lights and achieved SAP compliance under TM59 overheating checks.

Guildford student housing (Spring 2024)

MVHR systems with intelligent controls maintained airflow during overnight peak temperature events. Energy use remained within modelled expectations and acoustic targets were achieved.

Planner and architect endorsements

“The MVHR strategy let us keep the façade consistent without extra shading or redesign.”
Architect, Newbury (2023)

“The planners wanted proof that overheating would not be an issue. The system helped us make that case with clear SAP data.”
Developer, Reading (2024)

When to specify MVHR for overheating risk

Include MVHR when:

• Your site is in a high-density or urban noise zone
• The window-to-floor ratio is limited by design
• Passive cooling is not enough to meet TM59 targets
• You want to avoid visible external shading features
• SAP outputs flag temperature risks in top-floor or south-facing rooms

On a project in Woking during Winter 2023, MVHR helped reduce peak internal temps by over 3 degrees Celsius compared to a natural ventilation-only model.

Key regulations and supporting guidance

To support your design and planning application, use:

• Building Regulations Part O
• CIBSE TM59 for residential overheating analysis
• Future Homes Standard for expected updates to building performance targets

These documents shape how planning officers assess your thermal strategy.

Why ClimateWorks is the right MVHR partner

We support compliance and performance on projects in Alton, Petersfield and Farnham by:

• Running pre-application overheating checks with your SAP assessor
• Recommending MVHR systems that support night cooling
• Providing layout drawings that support RIBA Stage 3 and 4
• Offering full commissioning and documentation for handover
• Advising on planning notes and acoustic documentation

With us, your overheating mitigation plan becomes part of a fully coordinated ventilation solution.

About the author

Dr. Julian Carter
Thermal Systems Expert and Technical Advisor at ClimateWorks

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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