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The Safe Office - Pivoting Building Ventilation Strategies

Tony Comber • 20/05/2020

The start of 2020 saw our team of engineers focused on the imminent introduction of new minimum energy efficiency standards and the UK Government’s drive to net zero carbon by 2050.  

The last few months have been anything other than business as usual. We have pivoted to looking at how safe our office buildings are for occupiers upon a return to work. There are a number of key factors that have to be addressed as part of this process:   

Considering the effects of the COVID-19 pandemic on ventilation and air conditioning systems 

It is recognised through Public Health England guidance that the transmission of the virus occurs mainly through two main routes; respiratory droplets generated by coughing and sneezing and through contact with contaminated surfaces. The predominant mode of transmission is assumed to be by droplets that generally fall out of the airstream within a short distance hence the guidance to remain 2 metres apart and observe social distancing. There is evidence to suggest that it can be spread through the air, particularly in poorly ventilated indoor spaces. 

A third transmission route is via faecal-oral contamination within WC’s. It is recommended that toilet lids are closed when flushing and to check that drains in sanitary devices do not dry-out. 

The primary prevention mechanisms against COVID-19 remain regular personal and office environment hygiene, strictly adhering to social distancing requirements and staying at home. 

Are building ventilation systems safe during a pandemic? 

Return to work will be gradual and social distancing guidance will remain in force where practicable. Initially this is likely to reduce the typical office occupancy density from a standard of between 1 person per 8 or 10m2 to at least 1 person per 12.5m2 or more dependent on the site. 

Current guidance from CIBSE (the Chartered Institute of Building Services Engineers) recommends running mechanical ventilation systems for longer periods to ensure that the air is purged to reduce any risk of potential airborne viral transmission by reducing exposure time to any airborne viral aerosols. For non-ventilated buildings the increased use of operable windows is highly recommended. Combined with reduced occupancy densities, ventilation systems should provide a safe environment. 

There are a few important things to look out for:  

  • Reducing any potential for cross contamination from exhaust to incoming fresh air is vital. Any recirculation paths should be identified and removed. This is particularly important between office and WC extract systems where maintaining positive and negative pressures in both respectively is key.

  • Some forms of ventilation heat recovery systems can cause cross contamination and should be decommissioned. 

  • In the UK most buildings either have not been fitted with or have disconnected the humidification plant. In winter low humidity levels make the human body more susceptible to infection and could aid the transmission of the virus. It is recommended that a humidification plant is fitted. 

  • Fan coils, VAV terminal units, passive and active chilled beams recirculate air and these systems should be frequently cleaned.  

Can existing building ventilation systems be more effective? 

It seems obvious that fitting improved filtration to building ventilation systems will reduce the risk of respiratory droplets being transmitted throughout the building. HEPA (High Efficiency Particulate Air) and MERV (Minimum Efficiency Reporting Value) filters can be used where the installed systems manufacturer recommends them. However most building ventilation systems have not been designed for this level of filtration and would not work effectively, inadvertently reducing the required ventilation rates required for effective air purging.  

Where there are concerns over air quality it is recommended that portable air purifiers are installed. These can be installed at desk and office locations requiring no connection to the main building ventilation systems.  

Indoor air quality sensors are also good indicators of the effectiveness of ventilation systems. These can be quite easily fitted but ideally would be linked to a responsive building management system so that the building ventilation systems respond to occupancy and conditions. 

Will future building ventilation systems be pandemic proof? 

The basics of building ventilation systems are unlikely to significantly change although much more consideration will be given to occupant wellbeing and future building and energy use than previously. Future office design will require greater flexibility in terms of use, the ventilation systems will need to be responsive and adaptable. Use of smart technology should aid the responsiveness and drive the energy efficiencies necessary for buildings to achieve net zero carbon aspirations. 

Adopting ventilation strategies that incorporate the principles of the WELL Building Standard in terms of enhancing indoor air quality and raising the awareness of the internal conditions to the occupants should all be considered. While there will be no guarantee of being pandemic “proof” adopting these standards will drive improved occupant wellbeing and, through the monitoring process, provide instant reporting on internal conditions. 

You can download our Safe Six: Workplace Readiness Essentials to find out how real estate owners can most effectively prepare for the return of building occupants. And how employers can make sure they are prepared to receive their workforce—and ensure employees are also prepared.

Tony heads up the UK Building Engineering Services team within Cushman & Wakefield. The team will be able to assist clients in assessing the current condition of their building ventilation systems and advising on next steps to improve them. 

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