REHVA published its first COVID-19 guidance mid-March 2020. After two updates (April and August), the fourth version is focusing on how to reopen and safely use buildings after the lockdown, providing advice on specific components, buildings/space types, and suggesting mitigation measures.

The REHVA guidance summarises advice on the operation and use of building service systems during an epidemic of a coronavirus disease. The fourth version of the guidance document overwrites all previous ones. Updates are expected in the upcoming months as more academic data becomes available.

Principal updates compared to the previous version

• Extended ventilation operation time recommendation is complemented with possibility to switch ventilation off at nights and on weekends, applying also for the toilet ventilation
• Recommendation to operate fan coils and split units according to cooling and heating needs
• Advice to secure outdoor air ventilation and avoid directed air flows from one person to another
• Precaution to avoid high air velocities (>0.3m/s) in the occupied zone
• Introduction to an infection probability calculation method, supported by a ventilation calculation tool for implementing infection risk assessment in indoor spaces