Preparing office for return to work after COVID
In preparation for office staff returning to work, those unable to work from home needed assurance from the company that their working environment posed no risk to their health and safety with respect to infection control.
EMS Ltd surveyed the existing installation, assessed the risk, then re-designed the system to mitigate those risks.
Existing ventilation design
The company’s premises comprise 230m2 office space over two floors and occupied by 12 people. Heating and cooling is provided by a multi-split heat pump system comprising a number of indoor ceiling cassette units and fresh air ventilation is provided by a heat recovery air handling unit. The ventilation design is based on providing 10 litres/second of outside air per person at full occupancy.
Assessment
Filtration Efficiency
The filtration efficiency within both heating /cooling systems and ventilation unit falls well below what would be required to filter out potential viruses at source, and it was found to be impractical to upgrade this.
Increase in Fresh Air
The volume of outside fresh air was then considered and, in line with the latest CIBSE recommendations, it was decided to re-design the ventilation system based on a threefold increase in fresh air rate per person – i.e. 30 litres/sec per person.
Targeting high risk areas
The existing ventilation unit was re-assigned to the first floor only and a new system purchased to serve the ground floor. The ductwork was re-sized based on the increased volumes and reconfigured to concentrate the extract in high risk areas: reception lobby and first floor kitchen.
Achieving the right fresh air volumes
Tests have shown that the company is achieving the revised design fresh air volumes.
The air conditioning units have been left on 24 hours/day to maintain room air circulation and compressor run times have subsequently increased to cater for increased daytime cooling demand and night time heating demand with anticipated energy costs to come.
Noise levels from grilles have increased due to duct air velocities – there was insufficient void space to increase duct sizes.
In summary the company is satisfied with the results which, in line with other safety precautions, have given the staff confidence in its COVID-19 strategy.