A new report, released by the Zero Carbon Hub, presents the findings from 33 dwellings construction site visits in an effort to see how effectively their mechanical ventilation systems were designed, installed, commissioned and handed over to occupants. The document is intended for organisations with an interest in quality assuring the delivery of ventilation systems, including government policymakers, developers and their advisers.

The findings reveal a significant underperformance of the systems; At 5 of the 6 sites, fans were operating at only half the required duty or lower, i.e. flow rates were far too low. Furthermore, nearly all occupants interviewed had turned off their ventilation systems, due to noise, especially at night. According to the report, poor installation of flexible ducting leads to fans having to work harder to deliver the minimum ventilation rates required by Approved Document Part F of Building Regulations (ADF), and to systems being noisy.

Despite the availability of good practice guidance and training, minimum ventilation rates in the units reviewed were not achieved in practice. Interviews with installers, site managers and Standard Assessment Procedure (SAP) assessors suggest three key reasons for issues continuing to occur, and provide three strategic responses.