Mould risk evaluations in residential buildings via site audits and longitudinal monitoring

The health implications of mould contamination in housing are widely accepted, however preventing and treating mould growth is a complicated issue of interrelated factors. Building design, location, ambient conditions and occupant behaviour all affect mould, creating difficulty in both identifying and addressing the root cause. In this study, a cohort of 233 residential properties with recently remediated mould issues were investigated to understand remediation methods employed and identify factors contributing to mould growth. The root cause and success of remediation was explored for a subset of 30 of the properties. The study showed that remediation without sufficiently addressing the root cause of mould issues is not effective in preventing mould growth from reoccurring in the short term, with 40% of the subset of properties experiencing regrowth within 12 months. Subsequently, indoor environment conditions were monitored for five (5) of these properties over the course of a year including temperature and humidity, to identify contributing or correlated factors to mould growth. Properties with extensive mould growth were found to have particularly high wall surface temperatures compared to the room air dewpoint temperature. Humidity levels in all properties were elevated, with mould affected properties experiencing bedroom humidity levels above 80% for between 7 and 45% of the time. These conditions were evaluated against mould risk indicators such as those from BS5250, ISO13788, CIBSE Guide A and ASHRAE 160, however none of these indicators were able to reliably predict the risk of mould occurrence in the specific cohort of five monitored properties in our study.

Automated summary

The study investigated 233 residential properties with previously remediated mould issues, revealing that 40% experienced regrowth within 12 months. Among the 30 properties where root cause and success of remediation were explored, it was found that remediation without addressing the root cause effectively could not prevent mould growth in the short term. Furthermore, monitoring indoor environment conditions of five properties over a year showed that high wall surface temperatures and elevated humidity levels were contributing factors to mould growth.