Radon Sumps vs Positive Input Ventilation (PIV): Which Is Right for Your Home?

Radon Protection UK
Nov 6, 2025
6 min read

Updated: Nov 14, 2025

When radon levels in your home exceed the UK Action Level of 200 Becquerels per cubic metre (Bq m⁻³), immediate action is required to protect your family's health. Radon is a naturally occurring radioactive gas that enters buildings from the ground and is responsible for over 1,100 lung cancer deaths annually in the UK. Fortunately, UK homeowners have effective mitigation options: radon sumps and Positive Input Ventilation (PIV) systems. Understanding which system suits your property can mean the difference between successful radon reduction and ongoing health risks.

What Is a Radon Sump and How Does It Work?

A radon sump is a small cavity or void created beneath a building's foundation, designed to collect radon gas before it enters your home. The system works by creating a low-pressure zone under your property, drawing radon-laden air from the surrounding soil and safely venting it outside.

Active radon sumps, fitted with an electric fan, are the most effective method for reducing indoor radon levels. These systems can achieve reduction factors of up to 6-fold on average, making them particularly effective for high radon concentrations exceeding 1,000 Bq m⁻³. The sump typically requires a bucket-sized cavity beneath the floor, connected to pipework that extends through an external wall and up to roof level.

Passive radon sumps operate without fans, relying on natural pressure differences and the stack effect to draw radon away. Whilst less effective than active systems, passive sumps can reduce radon levels by factors of around 1.8, making them suitable for concentrations up to 300 Bq m⁻³.

What Is Positive Input Ventilation (PIV) and How Does It Work?

PIV is a whole-house ventilation system that introduces fresh, filtered air into your property, typically through a unit installed in the loft space. The system creates positive pressure inside your home, which prevents radon gas from being drawn up through the ground and into living spaces.

PIV systems work by gently supplying fresh air that displaces contaminated indoor air, effectively diluting radon concentrations. The system reverses the normal pressure differential between your home's interior and the ground below, making it difficult for radon to enter through cracks and gaps in foundations.

PIV units are most effective in properties with radon levels up to 500 Bq m⁻³, providing typical reduction factors of around 2.1. Beyond radon mitigation, PIV systems improve overall indoor air quality, reduce condensation, and help control humidity levels.

Radon Sump or PIV: Which System Is More Effective for UK Homes?

The effectiveness of radon sumps versus PIV depends primarily on your property's radon levels and construction type. Active radon sumps consistently outperform PIV systems, with sumps achieving 74% success rates in reducing radon below the Action Level compared to 56% success rates for PIV systems.

For high radon levels (above 500 Bq m⁻³), active radon sumps are the recommended solution. These systems can handle even the most severe radon problems, often reducing levels exceeding 1,000 Bq m⁻³ to safe levels. PIV systems, whilst effective for moderate radon levels, become less reliable as concentrations increase.

Building construction significantly influences system choice. Radon sumps work best under solid concrete floors and suspended floors with covered ground. PIV systems are suitable for most property types but prove particularly effective in homes with good structural integrity and minimal air leakage paths.

Radon Sump or PIV: How Do Installation Costs Compare Between Systems?

Radon sump installation typically costs around £800 - £3000 for standard residential properties, with complex installations potentially reaching higher costs. The cost reflects the excavation work required, electrical connections for fan systems, and pipework installation through external walls. Installation usually takes 1-2 days and requires core drilling through walls and floors.

PIV system installation costs approximately £1500 - £2500, making it a more budget-friendly option for many homeowners. PIV installation is typically completed within a day and requires minimal structural modification. The system connects to existing electrical supplies and can be installed in loft spaces or mounted on internal walls.

Running costs favour PIV systems, with lower annual electricity costs compared to active radon sumps. Active radon sumps require continuous operation, resulting in higher annual running costs. Both systems require periodic maintenance, though PIV units generally have lower maintenance requirements. For expert advice on the best solution for your property, contact Radon Protection UK today to discuss professional installation of PIV systems and active radon sumps tailored to your home.

Contact Radon Protection UK fro information and advice about Radon Sumps vs Positive Input Ventilation (PIV)

Radon Sump or PIV: Which Properties Are Best Suited for Each System?

Radon sumps are ideal for:

Properties with solid concrete floors or suspended floors over covered ground
Homes with radon levels exceeding 500 Bq m⁻³
Properties where maximum effectiveness is required regardless of cost
Buildings with accessible underfloor areas for installation

PIV systems are recommended for:

Properties with radon levels below 500 Bq m⁻³
Homes requiring whole-house air quality improvement
Properties without suitable underfloor access
Budget-conscious homeowners seeking cost-effective mitigation
Buildings with existing condensation or humidity issues

When Is Professional Installation Necessary?

UK regulations under the Ionising Radiations Regulations 2017 (IRR17) require professional assessment when workplace radon exceeds 300 Bq m⁻³. For domestic properties, professional installation ensures compliance with Building Regulations and manufacturer warranties.

The UK Health Security Agency recommends consulting certified contractors for radon levels at or above the Action Level. Professional installers ensure proper system sizing, adequate ventilation rates, and compliance with safety standards. Members of the UK Radon Association or The Radon Council provide quality-assured installation services.

Professional installation becomes essential for complex properties, high radon concentrations, or when combining multiple mitigation methods. Certified installers can assess your property's specific requirements and recommend the most appropriate system configuration.

Can You Combine Radon Sumps and PIV Systems?

Combining radon sumps with PIV systems can provide enhanced protection for challenging properties. This hybrid approach proves particularly effective in buildings with mixed floor construction, extremely high radon levels, or where single systems have proven inadequate.

Professional assessment determines whether combined systems offer cost-effective benefits over single-system solutions. The Health and Safety Executive guidance supports multi-method approaches when justified by risk assessment.

Combined installations require careful design to prevent system interference and ensure optimal performance. Professional contractors can design integrated solutions that maximise effectiveness whilst minimising installation complexity and costs.

Choosing between radon sumps and PIV systems depends on your property's radon levels, construction type, and budget considerations. Active radon sumps provide maximum effectiveness for high radon concentrations but require higher investment. PIV systems offer cost-effective whole-house air quality improvement for moderate radon levels.

For properties with radon levels at or above the UK Action Level of 200 Bq m⁻³, professional assessment ensures the most appropriate mitigation strategy. Radon Protection UK offers comprehensive testing and tailored mitigation solutions to protect your family's health. Contact us today for expert advice on the right radon mitigation system for your home or work environment.

Frequently Asked Questions

How long do radon mitigation systems last?

Professional radon mitigation systems typically operate effectively for 10-20 years with proper maintenance. Active radon sumps require periodic fan replacement, whilst PIV systems need filter changes and annual servicing to maintain optimal performance.

Can I install a radon mitigation system myself?

Whilst DIY installation is technically possible for some systems, professional installation ensures compliance with safety standards and manufacturer warranties. The UK Health Security Agency recommends professional installation for properties with radon levels at or above the Action Level.

How quickly do radon mitigation systems work?

Active radon sumps typically reduce radon levels within 24-48 hours of activation. PIV systems may take several weeks to achieve optimal radon reduction as they gradually change the home's air pressure dynamics and ventilation patterns.

Do radon mitigation systems affect home insurance?

Most UK home insurance policies do not require disclosure of radon mitigation systems. However, some insurers may offer premium reductions for properties with professional radon mitigation, particularly in high-risk areas.

What happens if my mitigation system fails?

Professional systems include monitoring capabilities to detect failures. Active radon sumps feature fan failure indicators, whilst PIV systems include service alerts. Regular maintenance prevents most failures, and professional contractors provide warranty support for installed systems.