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District cooling is one of the most impacting strategies within the energy equation and a key enabler in putting up an effective fight against COVID-19 and future pandemics, argue Dominic Mc Polin and Patrick Andrew Shiel

| | Aug 9, 2021 | 8:54 am
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On June 6, 2021, a new monument was erected to commemorate British troops landing on the beaches of Normandy on D-Day, 77 years ago. June 2021 also saw a victory in a scientific dispute that has been quietly raging since the beginning of the COVID-19 pandemic.

That dispute was brought to the attention of professionals in the field in this region, last year, through the efforts of CPI Industry, publishers of Climate Control Middle East magazine, in conducting a webinar series, titled ‘The Air We Breathe’. Dr Stephanie Taylor, Infection Control Consultant, Harvard Medical School, was a participant in one of the webinars – on June 24, 2020 – of the series, in which she commenced a serious debate on the role of aerosol viral infection.

It was, indeed, an honour to share a platform with Dr Taylor, who in addition to her role as an infectious disease medical expert, is an architect. A subsequent webinar in the series – the fourth edition, on September 30, 2020 – further explored the theme of the importance of air quality and humidity controls in defence against COVID-19.


Broadly speaking, we have lived with chatter regarding sick building syndrome for a generation in the lecture halls of architectural colleges and in the literature, punctuated only with occasional brief hot-topic headline episodes, such as the discovery of Legionnaire’s Disease emanating from a hotel cooling system. But still, in 2021, we live, work and are entertained in buildings that are poorly ventilated; and yes, that brings us back to that V-word again, “ventilation”.

V day, I suggest, commemorates the day that ventilation was quietly inserted into the official advice of a) The World Health Organization (WHO), b) Centers for Disease Control and Prevention (CDC), in the United States, and c) Other national government advisory outputs in the United Kingdom, Ireland and Europe. It’s official!

Ventilation is now part of the package. It may be the case that the recognition of ventilation as a major disease control mechanism was a difficult and slow-coming decision for the following reasons: 1) Resistance emanating from a scientific paradigm, which was based on a now-accepted unsafe premise regarding the airborne transmission of virus (the five microns fulcrum particle/aerosol dichotomy).

2) Society and the built-environment were not – and still are not – prepared for the full ramifications of such a recognition of aerosol transmission of COVID-19.

3) The general public has been subjected to lockdown and one of the most comprehensive and continuous worldwide media campaigns regarding the threats to life, safety and the economy from the virus that instigates COVID-19. It is difficult to raise such an additional issue just as lockdowns thaw and pent-up social interaction restarts.

4) The fear or doubt regarding the health of the air quality in communal buildings may be a further layer of psychological stress that could have a detrimental impact on mental health and certainly an impact on the level of comfort in offices and enclosed assembly areas, such as cinemas, restaurants, malls and auditoria.

These factors may be the reason for the quiet and undramatic introduction of ventilation as a major factor in COVID-19 control in June 2021. However, now that it is across the line, I predict that it will become an increasingly important focus, as economies try to return to a new post-COVID normality.

To understand the history of this internal debate, which came to the surface in this region through the CPI Industry webinars in 2020, I advise a revisit to the webinars and the advice on monitoring of air quality, filtration and building management. Lastly, for a very clear description of the resolution to the aerosol science, I suggest reference to an article from Wired (May 2021 issue), authored by Megan Molteni.


Many in the building ventilation business, along with many others in the building management field, might have been surprised at the confused and oft-corrected messaging from the WHO over the past year. This is what we referred to as the emerging science in the CPI webinar series, ‘The Air We Breathe’. Among physicists and engineers, whose professional interests are dedicated to the better understanding of aerosol transmission in air, the medical world must have seemed an unwelcoming and hostile place. In her article, Molteni explains with great flourish the issues at the heart of why the WHO has repeatedly backed away from engineering advice that COVID-19 can, indeed, be carried as an aerosol for much greater distances than previously thought.

It seems a 60-year-old issue of interpretation of aerosols versus droplets/particles may have been finally resolved. The issue seems to have arisen between the Harvard engineer, William Wells, who studied transmission of infectious aerosols, and Alexander Langmuir, the influential chief epidemiologist of the newly established CDC in the early 1950s. Molteni explains the history behind the widely accepted 5-micron measurement of aerosol particles versus what the research demonstrated – it was closer to 100 microns.

This implies that decades of medical advice may have wrongly suggested that particles larger than 5 microns will not remain in air as aerosols. Given the renewed focus on COVID-19 and its transmissibility in free air, particularly within occupied building spaces, this has profound implications for how we ventilate our buildings.

The process of more fully understanding how air flows work in enclosed spaces has been predominantly within the confines of Computational Fluid Dynamics (CFD). However, we were clearly alerted to these factors in the Keynote Address Dr Taylor gave during the webinar series. This was the voice of a frontline experience; however, another year was to pass before the universal acceptance of this experience was to appear as official advice from public health organisations. Particle movement simulation adds another dimension of complexity, usually involving Lagrangian Analysis techniques.

The only reason I mention these computational techniques is to highlight the fact that these are seldom carried out for new buildings. In most cases, the volume of the building space is considered alongside the likely occupant numbers and other environmental factors to determine the required flow rates of fresh air. We know from many hundreds of building inspections that fresh air supply grilles are often badly placed and poorly maintained. This can often result in dead zones in building spaces, where the fresh air almost never reaches. The commissioning process simply verifies the design figures; it does not validate that the design is solving the problem at hand – how to properly ventilate buildings.

The problem is further compounded by the fact that construction budgets are always under pressure, and somewhere along the complex timeline of building construction, the first candidates for consideration to be dropped from the budget are energy[1]saving devices, such as variable speed drives (VSDs), but more importantly, any “superfluous” sensors, such as CO2 or volatile organic compound (VOC) sensors. Both sensor types, depending on their placed location, can provide invaluable data as to the ongoing air quality being experienced by the occupants. Again, we have explored these issues previously through other CPI Industry webinars – ‘Disinfection 360’ conducted in July 2020, and ‘IAQ strategies and Solutions’, conducted in September 2020. The cost of such sensors is a miniscule fraction of any construction budget but can provide years of safe working environment. This is a particularly thorny issue, given how little we understand about the buildings we currently construct in this age of renewed awareness of transmissible pathogens. What we do know is there are new air quality standards emerging, which will inevitably impact building running costs.

Here are some such standards…

  • ANSI/ASHRAE Standard 62.1 – 2019, Ventilation for Acceptable Indoor Air Quality
  • ANSI/ASHRAE Standard 52.2 – 2019, Method of Testing General Ventilation Air-Cleaning Devices for Removal Efficiency by Particle Size
  • ANSI/ASHRAE Standard 55 – 2020, Thermal Environmental Conditions for Human Occupancy
  • ANSI/ASHRAE Standard 90.1 – 2019, Energy Standard for Buildings Except Low-Rise Residential Buildings
  • ASHRAE core-recommendations-for-reducing-airborne-infectious-aerosol-exposure
  • ASHRAE guidance for the Re-opening of Schools

COVID-19 has probably been the biggest wake-up call we have received in many decades when it comes to how we provide suitable levels of physical – and now – psychological comfort in our buildings. Today, the video signboard advertisement for Andrew Lloyd Webber’s new show, Cinderella, in London’s West End, reverts to a message stating that the theatre is ventilated and that the air circulation is switched off.


In hot and humid climates – such as the Middle East, in particular – summer cooling in commercial and domestic buildings has been a long-standing issue for electricity consumers and business overheads, plus the pressure on electricity authorities to plan production levels and secure continuity of supply through increasingly complex system controls. There is still a hesitancy in the construction industry and among design consultants to accept communal cooling solutions. District cooling is recognised as probably one of the most impacting strategies within the energy equation, as continuously reinforced at CPI Industry’s DC Dialogue conference, and endorsed by the UN Habitat Report on district energy. Despite individual national initiatives on promoting district cooling, major obstacles still persist with regard to its wider roll outside of developer-led masterplans.

Governments around the region recognise the key to winning the environmental benefits of district cooling is in the change in the business model from a purely market-driven, entrepreneurial industry and investment strategy into an instrument of government policy on climate change. Meaningful change is only possible through regulation. The emerging regulations vary across the region, but themes in common are securing energy efficiency and, of increasing importance, consumer protection.

Whilst all governments concerned were focused on the financial and environmental opportunities associated with district cooling, along came a worldwide pandemic, COVID-19. We are slowly coming to the understanding that the restarting of our economies must be on a controlled and safe basis. All action required must be taken to avoid the recurrence of infection, as the virus mutates, and ultimately, to learn all the lessons from this catastrophic pandemic and to ensure that next time – and we are reliability assured there will be a next time – we are much better prepared to save lives and reduce economic impact.

The link between district cooling and COVID-19 is obvious and, in a nutshell, the required ventilation to keep levels of cool fresh air available in all areas during the working day is going to cost significantly more than it costs now. This is because following the ASHRAE, AICM and EICM indoor air quality (IAQ) guidance would suggest not running the ventilation/cooling system in recirculation mode. In fact, many systems, which have been designed to ventilate buildings, are built on the fact that recirculation is included. In recent pilot cases carried out by co-author, Professor Patrick Shiel, in conjunction with Siemens, in Vienna, Austria, during this Spring 2021, we have shown that overall, building running costs may increase by up to 28% if the guidance on higher levels of ventilation and fresh air flushing is adhered to. We need a way to mitigate that cost whilst still maintaining sufficient IAQ.

The Vienna case study involved two buildings – a school, 24,000 square metres in area, and an office block, 12,400 square metres in area – where cooling plants and ventilation were adjusted to comply with recommended guidance. The results showed a 28% weekly increase in energy use/cost, mainly down to longer running times and turning off recirculation, and CO2 monitoring in all occupied areas.

By way of mitigation, applied advance machine learning (ML) techniques, coupled with energy modelling, resulted in reduction of 24% energy usage. The study examined the impact of district cooling on energy usage, which showed a further decrease of nine per cent.

The business case for district cooling must now be reassessed as part of the preparation for allowing the congregation of people in close proximity in public and private buildings. Discussions to manage aerosol transmission of viruses must also include the discussion to mitigate those increased running costs. Evidence is worldwide that district cooling is simply more efficient, cheaper and significantly better for our environment than the individual building chiller solution.


1) A more aggressive district cooling strategy for urban areas is required as part of COVID-19 response and a key element in preparation for future pandemics

2) Removal of barriers to the implementation of an increased role of district cooling in national energy strategies.

3) District cooling must become a fully integrated member of the infrastructure family in this region and a first-choice cooling option, where available, which is enforced through the planning system and building permit system.

4) A formula must be developed for regulated cost sharing, and importantly, the sharing of savings from the deployment of district cooling must be addressed to bring this industry into a partnership relationship with government. This is essential to bring the CAPEX of district cooling down to meet the expectation of consumers.

5) Governments can look to the district cooling industry as a target for direct investment either through direct participation within an investment portfolio or by direct involvement through the provision of public land for district cooling plants, access to the public road system for the development of more extensive networks outside of real estate masterplans and possibly the development of pipe networks for plug-and-play district cooling concession agreements.


The answer is now even more clear than before. If the current recommendations on mitigation of aerosol transmission of viruses within our buildings are taken seriously, the efforts made in the energy efficiency field will be negated by the required recalibration of the energy demand figures for our schools, universities, offices, apartments, shopping malls, hospitals and places of entertainment.

This can be a major setback for all those efforts made so far in individual building facilities management and for national governments dealing with the power demand factors and system control challenges. We have demonstrated in the case study in Vienna that district cooling is no longer an energy question but is now part of the frontline health strategy.

Dominic Mc Polin is Chief, Central Planning – Central Planning Office, Ministry of Works, Municipalities Affairs and Urban Planning, Bahrain. He may be contacted at xo@works.gov.bh.

Patrick Andrew Shiel is Adjunct Professor, Stanford University, California, in the United States. He may be contacted at Pat.shiel@verteco.ie.

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