During the past few months, the majority of commercial buildings have significantly ramped down their occupancy to being vacant. As buildings now prepare for reopening, the American Society for Heating, Refrigeration, and Air Conditioning (ASHRAE) created an Epidemic task for to provide recommendations and guidance for getting buildings ready for the workforce. The guidance is a great resource for building operators for ensure the downtime in operation will not impact the systems performance and provides recommendations for controls moving forward. The guidance also dispels some common myths on the virus transition through HVAC systems and provides step by step recommendations for tenants and building operators.
Here are a few key action items that can be implemented for centralized and floor-by-floor variable air volume (VAV) systems:
- Utilize a flushing sequence or mode to operate the HVAC system with maximum outside airflows for two hours before and after occupied times.
- If outside air is supplied centrally from outside air handling units (typically at mechanical levels) to all floors, and there are unoccupied tenant floors, divert the outside air to the occupied floors.
- Consider changing the floor level VAV air handling units’ discharge air temperature setpoint the maximum (typically no higher than 60º F). This will cause VAV terminal units (boxes) to open to try and satisfy space cooling loads which will increase the number of air changes in the space being served.