The UK is currently on a retrofitting drive - the process of adding technology or machinery to a home to make it more energy efficient and better for the planet.
This comes amid the government’s Energy Company Obligation scheme - a plan designed to decrease carbon emissions through the increased airtightness and energy efficiency performance of homes.
Yet, while retrofitting comes with enormous benefits, it also has one important invisible problem - Radon.
In this article, we will explain what Radon is and ways to mitigate radon to keep your home safe from it, both now and when you decide to retrofit.
What Is Radon Gas and Why Is It a Problem?
Radon is a radioactive gas which is produced by the breakdown of uranium in soil and rock beneath buildings. It rises from the ground and can seep into properties through small openings, such as through cracks or gaps in slabs on ground floors and walls.
Crucially, Radon is both colourless and odourless, which means it can enter a property unnoticed and over time can steadily accumulate indoors.
But most importantly, it can have severe health implications: It is believed that 1,100 annual UK lung cancer deaths are caused by Radon exposure, the second highest cause of lung cancer fatalities after smoking.
Why Radon Testing Should Come Before Any Retrofit Work
Before carrying out insulation upgrades or other energy efficiency improvements, it’s important to understand your home’s existing radon levels. While these upgrades are highly beneficial for reducing heat loss and improving comfort, they can also unintentionally reduce ventilation, which may affect how radon accumulates indoors.
A radon test carried out in advance provides a clear baseline of exposure within the property. This allows any risk to be properly assessed before work begins, rather than reacting after changes have already been made.
By identifying radon levels early, appropriate mitigation measures can be incorporated into the retrofit plan from the outset, ensuring energy efficiency improvements do not compromise indoor air quality or occupant health.
Older Homes vs Newer Homes: Why Modern Techniques Can Trap Radon
Older Homes
Many older UK properties were built long before airtightness and energy efficiency became priorities in construction. Features such as suspended timber floors, open chimneys, draughty windows, and gaps around floorboards or pipe penetrations naturally allow air to move in and out of the building.
While this uncontrolled ventilation makes older homes less energy efficient and often harder to heat, it can also reduce the build-up of indoor pollutants, including radon gas. In effect, radon entering the property is more likely to be diluted and dispersed through continuous natural airflow.
However, this does not mean older homes are automatically safe from radon. Properties built in high-radon areas can still experience elevated levels, particularly in basements, ground-floor rooms, or areas with poor ventilation.
Newer Homes & Retrofitted Properties
Modern homes (and older homes that have undergone significant retrofit work) are typically designed to be far more airtight. Measures such as upgraded insulation, double or triple glazing, draught-proofing, and sealed building envelopes help reduce heat loss and improve energy efficiency.
The challenge is that these same improvements can also reduce the natural ventilation that previously allowed radon to escape. If radon enters the property through cracks in floors or the ground beneath the building, it can become trapped indoors for longer periods.
In some cases, retrofitting can unintentionally change air pressure dynamics within the home, drawing more radon from the ground into living spaces. Without appropriate ventilation or mitigation measures, a property that previously showed no obvious signs of a radon issue may begin to experience higher indoor radon levels after energy efficiency upgrades are completed.
Ventilation Solutions to Support Retrofitting & Radon Mitigation
Without proper ventilation, a radon problem that previously went unnoticed can become significantly worse after retrofitting. Here’s a look at some ventilation systems that can work to mitigate and reduce radon levels:
Positive Pressure Ventilation (PIV/Whole-Building Ventilation):
Positive Input Ventilation systems introduce a continuous supply of fresh, filtered air into the home, typically from a unit located in the loft space. This air is gently distributed throughout the property via a central diffuser, helping to dilute indoor pollutants, including radon.
By increasing overall air change rates, PIV systems can reduce radon concentrations in some homes, particularly where levels are moderate. However, effectiveness can vary depending on building type, floor construction, and existing radon entry pathways, so system suitability should always be assessed as part of a wider mitigation approach.
Find out more about PIV systems
Mechanical Ventilation With Heat Recovery (MVHR)
MVHR systems provide controlled ventilation by extracting stale air from wet rooms such as kitchens and bathrooms, while simultaneously supplying fresh air to living spaces. A heat exchanger transfers warmth from the outgoing air to the incoming air, helping to retain energy efficiency within a well-sealed home.
While MVHR systems are not designed specifically as radon mitigation solutions, they can play an important supporting role in energy-efficient buildings where natural ventilation has been significantly reduced. When correctly designed, installed, and commissioned, MVHR can help maintain balanced airflow exchange rates and reduce the conditions that allow radon to accumulate indoors.
It is important to note that MVHR performance depends heavily on correct installation and ongoing maintenance, and it should not be relied upon as a standalone radon protection measure in higher-risk properties.
Find out more about MHVR systems
Active Radon Sump Extraction Systems
Active sump systems are one of the most effective and widely used methods of radon mitigation, particularly in properties with solid floors. The system works by creating a low-pressure zone beneath the building, typically via a sump installed under the floor slab.
A continuously running fan extracts radon-laden air from beneath the property, which prevents radon from entering the indoor environment. This air is then safely discharged outside through a vent pipe, usually positioned on an external wall above roof height.
Unlike ventilation-based approaches, sump extraction targets radon at its entry point, making it highly effective in many building types. However, suitability depends on ground conditions and property construction, and in some cases, additional measures may be required to achieve optimal results.
Find out more about our Sump Extraction Systems
How Better Indoors Can Help
At Better Indoors, we provide comprehensive and bespoke ventilation retrofit services designed to mitigate the impact of radon and create healthier indoor environments.
Working UK-wide, we are a trusted and accredited national leader in improving the health of UK homes. We can conduct surveys to diagnose the radon problem, and then implement high-quality measures to support your retrofit.
