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AC and duct cleaning has no effect on COVID-19 Spread


HVAC associations from across the world have advised that humidification, air conditioning and duct cleaning has no practical effect on the transmission of the coronavirus.


Filed under
Energy & Waste Management

April 24, 2020
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AC and duct cleaning has no effect on COVID-19 Spread

The information is contained in a new advisory document issued by REHVA and said to be based on current best knowledge as contained in the World Health Organisation document Getting workplaces ready for COVID-19.

Primarily intended for HVAC professionals and facility managers, the scope of the six-page document is limited to commercial and public buildings, eg offices, schools, shopping areas, sport premises, etc, where only occasional occupancy of infected persons is expected. Hospital and healthcare facilities are excluded.

Crucially, the document insists that humidification and air conditioning have no practical effect on transmission of the virus. Unlike some other viruses, SARS-CoV-2, the virus which causes the Covid-19 disease, is quite resistant to environmental changes and is susceptible only to high relative humidities above 80% and a temperature above 30˚C.

Heating and cooling systems, the document says, can be operated normally as there are no direct implications on Covid-19 spread. In addition, the document maintains that duct cleaning is not effective against room-to-room infection.

Heat recovery

It is thought that heat recovery devices may carry over virus attached to particles from the exhaust air side to the supply air side via leaks. In rotary heat exchangers (including enthalpy wheels) particles deposit on the return air side of the heat exchanger surface after which they might be re-suspended when heat exchanger turns to the supply air side.

As a result, REHVA recommends turning off rotary heat exchangers during SARS-CoV-2 episodes. If leaks are suspected in the heat recovery sections, pressure adjustment or bypassing can be an option in order to avoid a situation where higher pressure on extract side will cause air leakages to the supply side.  Virus particle transmission via heat recovery devices is thought not to be an issue when a HVAC system is equipped with a twin coil unit or another heat recovery device that guarantees 100% air separation between return and supply side.


Virus particles in return ducts can also re-enter a building when centralised air handling units are equipped with recirculation sectors. So, it is recommended to avoid central recirculation during SARSCoV-2 episodes by closing the recirculation dampers.

When possible, it advises that decentralised systems such as fan coil units that use local recirculation, also should be turned off to avoid resuspension of virus particles at room level. Fan coil units have coarse filters which practically do not filter out particles with viruses. If not possible to turn off, these units are to be included into cleaning campaigns, because they might collect particles as any other surface in the room.

The document also contradicts recent assertions that duct cleaning is effective against room-to-room infection. It maintains that the ventilation system is not a contamination source if guidance about heat recovery and recirculation is followed. Viruses attached to small particles will not deposit easily in ventilation ducts and normally will be carried out by the air flow anyhow. Therefore, no changes are needed to normal duct cleaning and maintenance procedures.

REHVA represents over 120,000 HVAC designers, building services engineers, technicians and experts across 27 European countries. Knowledge of the virus is constantly being updated, so REHVA accepts that this can be considered as interim guidance. The document may be complemented with new evidence and information when it becomes available.

HVAC: On a sustainable path

Megha S Anthony talks to experts in the HVAC industry to explore the current move towards sustainability

HVAC systems function in a critical role in any building. Everyone becomes acutely aware of HVAC performance when malfunctions occur. The level of interest has only increased today. Whether concerns about energy efficiency, building sustainability, operations, and maintenance, or indoor air quality (IAQ), more visibility is required.

Especially when your living in a region where 80 percent of energy is consumed by buildings, and almost a third of this is down to HVAC systems, the industry has begun to innovate and take up a role in assisting the region’s drive towards sustainability. Especially with energy savings and improved efficiency the industry is certainly helping the region to deliver better buildings to live and work in.

Experts assert that it is vital that the market takes a more sustainable approach in the HVAC industry. And this is in large driven by the Government strategies and vision to better utilize the available resources of energy and water in countries throughout the Middle East.

Ronak Monga, Segment Manager – Commercial Building Services, Grundfos, says that the district cooling is one such key application focus within these strategies driving sustainability in the HVAC sector throughout the Middle East. “Another is an increased focus on retrofit and energy optimisation in the building and utility segments have lead to clients and endusers becoming more aware of innovating technologies and new strategies that help reduce energy consumption throughout their install base,” he adds. This is also leading to an increased awareness amongst the clients and stakeholders of utilising these new innovative technologies in new constructions. “ESCOs and Facility Management companies are playing a critical role in driving sustainability the agenda within the HVAC segment as well by looking at all minor and major elements within the HVAC application and asset maintenance/management to ensure efficient and reliable operation of our HVAC systems.

The only way to continue and accelerate this journey is to keep on increasing awareness amongst stakeholders, and drive both innovation and adoption amongst all involved in the HVAC industry,” adds Monga. The introduction of minimum energy performance requirements in local regulations is an important step to raise the bar for products sold on the market. Finding the balance between energy efficiency and affordable cooling for people isn’t an easy task though. In price-sensitive markets, the push to higher efficiencies leaves the best products with a competitive disadvantage due to their higher price level.

Giving his insight into this move towards a more sustainable path is Markus Lattner, Managing Director, Eurovent Middle East. “Aside from big investments in research and development to find new, low emission solutions, the industry has to look beyond its immediate responsibilities. Studies have shown that with simple correct maintenance of existing HVACR installations, significant savings in energy consumption can be achieved. Thus, governments should not forget to pay attention to the existing build stock and introduce programs, incentives or rules to address the proper operation, maintenance, and installation of HVACR systems,” he adds.

So when it comes to complying with less environmental impact, newer design and operation philosophies have been introduced to HVAC systems. One can see how more automation has helped utilize the equipment and assets more efficiently. The focus has moved away from individual equipment, to a more macro view, how the overall complete system works. “So even within research and development, our company Grundfos is not focusing on just pumps, but rather looking at a complete Air-Conditioning system, or a District Energy Network and developing solutions to overcome issues/challenges that plague these systems leading to reduced efficiencies, adds Monga.

Another key strategy, says Monga, is to look at individual controls from specialised manufacturers to improve the efficiency of each equipment in the building, as example: Chillers shall be operated by controls manufactured and designed by the chiller manufacturer, pumps shall be operated by controls manufactured by the pump manufacturer, similarly for valves, cooling towers, etc. but they shall be incompatible and all being monitored/connected via SCADA/BMS systems to ensure compliant operation between the individual systems. He goes on to add that rather than a common brain that will be good at operating the system, but not the best, it is important to apply the best controls to each of the equipment individually and then monitor them using a common BMS/SCADA central system.

The next step is digitalization. Digitalization is one of the key pillars driving technology innovation in the HVAC segment. When it comes to digitalization, it is clear that it’s opening new opportunities to optimise systems and integrate different components, allowing them to operate in better synergy. Both parties agree that the adoption of new digitally-driven technologies is key to ensuring sustainability and a minimal environmental impact.

“Digitalisation is bringing improvements on the operation and maintenance side by permanent monitoring and enabling preventive maintenance. Big data will enable further improvements by combining weather data with occupancy rates and estimating cooling demand. Many manufacturers already provide such solutions. But to harvest those saving potentials, regulators need to ensure that the proper legislative environment along with market surveillance is provided,” adds Lattner.

In the past few decades technology innovation and efficiency improvements in HVAC equipment have come from improving manufacturing techniques, material sciences and technologies, and better equipment design. “However in many of the equipment utilised, we are already at a ceiling of efficiency gains through these methods. So now we are focused on how we can better utilise/better operate the already efficient equipment being installed in our systems, and this is being driven by control technologies and digitalization,” says Monga.

He goes on to add that digitalization is key to improving efficiency in the HVAC applications as it helps utilize data from systems, buildings, and even cities to better respond to the varying demands in HVAC systems. “We have accelerated our journeys by utilising smart devices such as smartphones, smart home devices, smarter more autonomous cars, etc. and our buildings are moving in the same direction. Critical to the success of digitalization in the HVAC segment will be standardization (so different technologies can be benchmarked) and adoption, as adoption will drive the need for further innovation. ‘If we weren’t all buying smartphones, the smartphone manufacturers won’t be interested in innovating year over year on their products,” sums up Monga.