You’ve upgraded your insulation. Sealed your windows. Installed underfloor heating. Your home now holds heat better than ever—but something still feels off. The air feels heavy. Mould appears on bathroom ceilings. Condensation builds on windows every morning.
You’ve upgraded your insulation. Sealed your windows. Installed underfloor heating. Your home now holds heat better than ever—but something still feels off. The air feels heavy. Mould appears on bathroom ceilings. Condensation builds on windows every morning.
It’s not just you. As homes across the UK become more airtight, a silent issue is growing: lack of proper ventilation.
Searches like “do I need ventilation in a new build?” and “UK building regulations ventilation” are on the rise. Modern properties often trap stale air, moisture, and indoor pollutants unless a planned ventilation strategy is in place. In fact, updated Building Regulations now assume airtightness, meaning mechanical ventilation is required in most new builds and energy retrofits.
In this blog, we’ll explain why proper ventilation is crucial, what UK regulations demand, how systems like MVHR (Mechanical Ventilation with Heat Recovery) work, and what your next steps should be—whether you're building from scratch or upgrading an existing home.
Older homes breathe. Draughts through floorboards and old window frames allow air to move freely. Modern homes, on the other hand, are designed to be sealed.
This is great for energy efficiency—but terrible for fresh air circulation.
Without any gaps, the following issues start to appear:
The UK’s Part F Building Regulations, updated in 2022, now assume most homes will be sealed to a level of 5m³/h·m² or less. This triggers the need for purpose-built mechanical ventilation. You must provide a system that:
The days of relying on trickle vents and bathroom fans alone are over.
Mechanical Ventilation with Heat Recovery (MVHR) is a balanced system that draws fresh air into your home and extracts stale air simultaneously. A central unit recovers heat from the outgoing air and transfers it to the incoming supply—keeping your home warm and ventilated without wasting energy.
Air is distributed via ductwork to and from rooms like:
Unlike extract-only systems or natural ventilation, MVHR provides:
It’s no surprise that MVHR is now the preferred solution in most new homes and renovations aiming to meet energy performance targets.
A family moving into a new four-bedroom home near Basingstoke in 2023 quickly noticed condensation on windows and musty air despite double glazing and underfloor heating.
After a home survey, ClimateWorks installed a central MVHR system routed through the loft, with grilles in all bedrooms, bathrooms, and common areas.
The result?
The home passed Building Control with no delays, and the family now enjoys a healthier, more comfortable environment year-round.
While every home should have some form of ventilation, MVHR is typically required or strongly recommended in the following situations:
These change airflow patterns and often require mechanical solutions to remain compliant.
These upgrades can unintentionally block airflow and must be balanced with mechanical ventilation.
Without adequate ventilation, homeowners may face:
In short, ventilation isn’t optional anymore—it’s a vital part of building a healthy, durable home.
Your builder may commission a test to confirm how airtight your property is. If the result is under 5m³/h·m², you’ll need mechanical ventilation.
A professional ventilation designer will:
Most installations involve:
This can usually be done during first fix, or retrofitted with careful planning.
To comply with Part F, the system must be tested, balanced, and signed off with documentation provided to Building Control.
At ClimateWorks, we:
Start your project at https://www.climateworks.co.uk.
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.
[1] UK Government. (2022). Part F: Ventilation Approved Document. Retrieved from https://www.gov.uk/government/publications/ventilation-approved-document-f
[2] BRE Group. (2023). Indoor Air Quality and Home Health. Retrieved from https://www.bregroup.com
[3] Met Office. (2023). Rising Summer Temperatures in the UK. Retrieved from https://www.metoffice.gov.uk
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