I. With COVID-19, indoor air quality makes all the difference

Certainly, such an upgrade is necessary – particularly when it comes to poor indoor air quality, one of the major burdens that building owners need to face during this pandemic. The virus, of course, is believed to be transferred from one person to another through micro-droplets expelled into the air while breathing, talking, sneezing, or coughing. Particles that are less than 10 µm may remain in the air and remain infectious for up to three hours, according to a study conducted on SARS-CoV-2. Meanwhile, these droplets that range from 10 to 100 µm (and sometimes more) usually fall directly to the ground. However, if these droplets splash anywhere near a return air outlet, they may be sucked into the air-conditioning system and may move through it.

In either case, it is clear that the risk of infection is higher in stagnant and poor quality indoor air. A good filtration system matters. Throughout the COVID-19 pandemic, high ventilation rates will be needed to dilute possible concentrations of the virus in the air. Tenants will need less air recirculation and more fresh air, but at the same time, space temperature and relative humidity must be maintained within the comfort zones. This poses a challenge for building operators, especially those dealing with constructed and operational systems with limited cooling capabilities. 

Balancing fresh air and energy concerns

Increasing the fresh-air-to-circulated-air ratio also poses a new concern, that of the building energy impact, which may see electricity consumption reach higher than last year’s benchmark. Operators with spare cooling capacity or those who possibly benefit from cooling diversity are more flexible and can increase the fresh-air-to-circulated-air ratio while maintaining space comfort in acceptable parameters. However, even here, questions remain. What is the extra expense posed by increasing the ratio? To what extent should fresh air be increased? And what is the optimal way to go about such a change?

The short answer is building owners and operators have to look at implementing emerging practices both during and after COVID-19. Seeking expert consultation to adapt these practices to each building condition can be the first step towards a comprehensive and efficient operational plan.

 The several of which tackle building-related operational issues and recommendations (ASHRAE Epidemic Task Force, Building Readiness. May 2020). A few of the main recommendations were extracted and can be found below. 

1. Increased ventilation and flushing bioburden

Ventilation can be increased as far as systems allow, while keeping in mind its inversely proportional relationship with space conditions such as temperature and humidity. It is worth mentioning that maintaining relative humidity in the range of 40%-60% has the added advantage of decreasing the bioburden and the infectivity of many viruses in the air.

For optimal results, the installed cooling and ventilation system should be evaluated by a qualified testing, adjusting, and balancing (TAB) agency before it is modified. Such an agency can determine to what extent the ventilation rate can be increased without heavily impacting the cooling system and space conditions. Different methodologies can be adopted here. One option could be increasing the fresh air rate based on cooling coil, where the amount of fresh air can be increased/altered depending on the control valve opening percentage, while maintaining acceptable space condition. Another option is increasing the fresh air rate based on space condition, where the fresh air rate is directly increased/altered based on the space set point condition.

The TAB agency will also be able to tackle the consequent impacts of increasing the ventilation rate, including any alterations to the exhaust rate needed to maintain acceptable building pressurisation.

2. Upgrading and improving filtration and disinfection

Filtration is a vital component of any ventilation system, and filters are rated by their Minimum Efficiency Reporting Values (MERVs). In order to mitigate the transmission of aerosols, ASHRAE recommends MERV 13 as a minimum and preferably MERV 14 or higher.

Implementing higher filtration, however, brings about a higher pressure drop. Here, a TAB agency can help enhance a system to ensure it is capable of handling the required increase in system pressure.

Several other disinfection methods may also be investigated and applied. These include ultraviolet (UV) technology, surface treatment, or other proven methods that tailor to the existing conditions and capabilities.

3. Energy saving

During the pandemic, the health and safety of building occupants should always come first. However, MEP system operators should still take every opportunity to implement appropriate energy conservation measures (ECMs).

For example, since many commercial facilities are currently experiencing reduced occupancy, building operators have the opportunity to save on cooling energy by operating in a semi-unoccupied mode while still maintaining high standards of hygiene as appropriate. Altering the set points of these unoccupied zones to a relaxed temperature and humidity can also save energy.

Moreover, limiting the bioburden flushing schedule by maximising fresh air only at certain intervals and durations – without compromising safe limit operation of reducing infectious particles – can also benefit energy saving.

Most of the energy conservation measures will rely heavily on the condition and accuracy of control system and field instruments. Therefore, building operators should pay heed to the mantra of “you can’t manage what you don’t measure” and periodically check the health of their control systems, to maintain safe operation and to facilitate correct decision making on any energy saving opportunity.

4. Exhaust air re-entrainment

Another aspect of the building ventilation system that needs to be looked at is exhaust air re-entrainment chances.

In order not to hinder the benefits of any increased ventilation practice during the pandemic, building operators should check that exhaust air is not pointed towards fresh air and is located away from any of the building’s fresh air intake means.

Additionally, system operators should check the condition of energy recovery air handling units, specifically the types in which exhaust and fresh air streams are in same cabinet. Operators should verify that there is no significant leakage from exhaust stream mixing with fresh air stream.

Spotlight: LEED Safety First

Like ASHRAE, many international green building rating systems have moved towards incorporating measures that keep building occupants heathy during the pandemic. International sustainability organisations have set COVID-19 taskforces to work on guidelines designed to enhance people’s health and safety.

To cite one example, the USGBC has introduced four new LEED pilot credits – the LEED Safety First Pilot Credits – which help building teams provide healthy spaces and assist with re-entry. The new pilot credits outline sustainable best practices that align with public health and industry guidelines related to cleaning and disinfecting activities, workplace re-occupancy, and HVAC and plumbing operations. The credits can be used by LEED projects that are certified or are undergoing certification.

II. Water quality

Water quality has also been impacted by the pandemic and specifically by the imposed lockdowns. Business closures left several buildings idle for weeks or months, which naturally led to a significantly drop in water demand. This, in turn, resulted in water stagnating both in tanks and in building networks.

Water aging in plumbing systems leads to a decrease in chlorine residuals, which may promote rapid growth of Legionella and other opportunistic pathogens and thus pose a significant risk to public health.  

Buildings using non potable water systems (treated grey water / captured rain or storm water) might pose a more serious concern on pathogen build-up.  While wastewater treatment plants are capable of treating viruses and other pathogens, the non-potable treated product in storage could impose higher health risks if kept in stagnation for days. Flushing or retreating this volume is the safe way to keep the water quality under control.

The responsibility of tracking water quality aspects lies with facility operators and should be further regulated by governments to put a shared responsibility plan of action among different entities.

1. Facility operator responsibilities

When reopening a building, the operator should follow the international and local industry guidance provided by organisations such as the Environmental Protection Agency (EPA), Centre for Disease Control and Prevention (CDC), American Water Works Association (AWWA) and others. Operators should also coordinate with water utility providers.

To maintain water quality during the pandemic, Maintaining or restoring water quality in buildings with low or no use, July 2020) recommends that the operator:

1. Review and understand the plumbing configuration and water usage in the building.
2. Inspect the plumbing to ensure that it is functioning properly and that it is in good condition.
3. Contact the water utility to learn more about the status of water usage and quality in the distribution system in the relevant area.
4. Maintain any water treatment systems used in the building, such as any point-of-entry or point-of-use, filters, or water softeners.
5. Maintain the hot water system, including keeping the temperature in the hot water heater at or above 140°F as per CDC guidance.
6. Flush the building’s plumbing system regularly. Flush cold and hot water at all water points of use (faucets, showers, toilets, drinking fountains, and water-using devices such as dishwashers and refrigerators/ice makers) to replace the water that has been standing in the pipes. Flushing involves opening taps and letting the water run to remove water that has been standing in the interior pipes and/or outlets. The flushing time can vary by the plumbing configuration and type of outlet being cleared.
7. Maintain all non-drinking-water building water systems and devices according to the manufacturer’s specifications
8. Consider the development of a water management program for building water systems and all devices that use water.

2. Municipality/utility provider responsibilities

With regards to domestic/potable water, re-opening requires draining the stagnant water and flushing the water distribution main system to ensure that water meets delivered to facilities adequate water quality parameters. 

In terms of sewage and waste water, the World Health Organization (WHO) has declared that “there is no evidence to date that the COVID-19 virus has been transmitted via sewerage systems, with or without wastewater treatment.” Still, municipalities should remain up-to-date with the latest local and international studies.

III. Towards the new normal

While COVID-19 pandemic took the world by surprise, its impact is here to stay, influencing and changing many practices. The building services industry can take a number of steps to adapt to the new normal.

1. Develop a pandemic readiness plan

Using lessons learned from the pandemic, experts should develop a pandemic readiness plan that tackles equipment, operation, logistic aspects, and any other aspect having impact on routine life. Governments can also work closely with experts to develop unified plans that in return will help in mitigating the effect of the pandemic on economies and businesses.

The readiness plan can include:

1. Ensuring a supply chain of consumable items, such as spare parts for equipment, etc.
2. Establishing a communication protocol with tenants
3. Implementing measures to make occupants feel safer.
4. Setting guidelines to establish training programs.
5. Providing updates on operation and maintenance practices and new modes of operation.

Meanwhile, building owners should promote a health check on all building components and hire experts to audit the operation and maintenance practices used by operators.

Additionally, a TAB Agency and BAS specialist can be hired to check or possibly upgrade the control system and field instruments and to integrate new operational modes experienced during the pandemic, such as bio-burden flushing mode.

2. Raise the IAQ target while considering energy aspects

Based on each unique building condition, a plan must be set to enhance indoor air quality. The plan take energy aspects and occupant comfort into consideration. Enhanced ventilation duration and intervals should also be linked directly to weather conditions and occupied/unoccupied sequencing.

3. Establish flexibility in system design

New or renovated facilities should be designed to have the flexibility to adapt to any future pandemic incident. Flexibility in system design should target optimal operation during pandemic and normal modes and can cover everything from equipment sizing and selection to system schemes, operating modes, and maintenance needs.

Conclusion

The pandemic has imposed heavy burdens on stakeholders in almost each and every major industry around the world, and the building services industry is no different. However, by benefiting from and implementing lessons learned, experts and stakeholders have an opportunity to move towards a more resilient model that safeguards communities against similar challenges in the future.