Radon Mitigation Calculator
Size a sub-slab depressurisation system and estimate the post-mitigation level.
About Radon Mitigation Calculator
A single suction point can serve a large area over clean gravel but very little over clay, which is why the sub-slab material drives the design. Well-designed systems typically achieve 80 to 95 per cent reduction. Radon is a leading cause of lung cancer after smoking, and because concentration varies by season and by house, post-mitigation testing is not optional.
Formula
Radon Mitigation
Suction points = slab area ÷ area served per point, which depends on sub-slab permeability
- sub-slab permeability
- How freely air moves beneath the slab, which sets the reach of each point
- action level
- Concentration above which mitigation is recommended
Worked example
With the default values below, Radon Mitigation Calculator returns Suction Points Required of 1. Change any input above and every figure here is recalculated in your browser.
Inputs used
- Slab areaminimum 1 m2
- 110 m2
- Measured radon levelminimum 0 Bq/m3
- 400 Bq/m3
- Sub-slab materialone of Clean gravel, Mixed fill, Sand, Clay or soil
- Clean gravel
- Expected system efficiencyaccepts 10–99 %
- 85 %
- Action levelminimum 1 Bq/m3
- 200 Bq/m3
Results
- Suction Points Required
- 1
- Fan Airflow Required
- 70.0 m3/h
- Projected Post-Mitigation Level
- 60.0 Bq/m3
- Meets the Action Level
- Yes
- Reduction Achieved
- 85.00%
Step by step
- 1Values used
- 2Radon Mitigation
- 3Suction Points Required= 1
- 4Fan Airflow Required= 70.0 m3/h
- 5Projected Post-Mitigation Level= 60.0 Bq/m3
- 6Meets the Action Level= Yes
- 7Reduction Achieved= 85.00
Assumptions and limits
- The result is derived only from the 5 inputs listed above. Anything not among them is not part of the calculation.
- In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
- Figures are rounded for display to 2 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.
- This is a system sizing estimate, not a health assessment or a substitute for measurement. Radon levels must be confirmed by testing before and after any mitigation work, and design should be carried out by a qualified radon professional.
How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.
This is a system sizing estimate, not a health assessment or a substitute for measurement. Radon levels must be confirmed by testing before and after any mitigation work, and design should be carried out by a qualified radon professional.
Frequently Asked Questions
How is Radon Mitigation calculated?
Suction points = slab area ÷ area served per point, which depends on sub-slab permeability A single suction point can serve a large area over clean gravel but very little over clay, which is why the sub-slab material drives the design. Well-designed systems typically achieve 80 to 95 per cent reduction.
Why does Radon Mitigation matter?
Radon is a leading cause of lung cancer after smoking, and because concentration varies by season and by house, post-mitigation testing is not optional.
What values do I need to enter?
This calculator takes 5 inputs: Slab area, Measured radon level, Sub-slab material, Expected system efficiency, Action level. The pre-filled defaults are a realistic starting point — replace them with figures from your own environment for a result you can act on.