Disclaimer
Our web-based Mould Risk Calculator is open-source, developed by Smart Air UK in collaboration with Emmanuel Costa as part of a student research project at the University of Westminster.
The tool is based on models from the peer-reviewed study Modelling mould growth in domestic environments using relative humidity and temperature (Menneer et al., 2022).
⚠️ Key considerations and assumptions
- Surface vs air humidity: The original model estimates mould risk on wood surfaces, but we use air humidity due to the limits of most indoor sensors. This may lead to underestimates, especially during fluctuating conditions.
- Material sensitivity: The research found that mould growth can begin below 80% relative humidity in real homes, so the model has been calibrated to reflect those real-world conditions, not just lab thresholds.
- Surface vs air humidity: Results assume a typical indoor surface like softwood. Surfaces such as concrete, painted walls or insulation may behave differently. This tool does not adjust for material type.
- Mould decline in dry conditions: The model includes a simplified rate of mould reduction when humidity falls. In practice, this may vary depending on surface type, airflow, and prior mould activity.
- Starting condition: Each analysis assumes a starting mould level of zero unless otherwise indicated. If mould is already present, this model may underestimate risk.
- Data requirements: Tested with Smart Air CO₂ Monitors or QP Lite/Pro devices but built to work with any air quality monitor that exports data for both Temperature and Humidity. The tool accepts datasets from 24 hours to 1 year but will give the best results with 3+ months of data.
- Expected accuracy: Based on the source study, the model provides around 70% accuracy in identifying mould risk, though this varies by building and sensor quality.
🚨 Important
This tool is for informational and educational use only. It does not replace professional assessments or laboratory testing. Each home is different - materials, ventilation, history of mould, and occupant behaviour all affect actual risk.
If your results look unusual:
- Check your data format and time intervals
- Consider the assumptions (e.g. surface type, existing mould)
- Review the guidance and notes included in the calculator
