We have learned several important lessons from the pandemic – not least that improving ventilation will play a crucial role in making people feel confident about buildings once more.
Everyone, it seems, wants to ‘build back better’. From Joe Biden to Boris Johnson to President Xi of China, the post-pandemic vision is all about resetting economies and driving growth through more progressive economic and technological methods.
In the UK, the vision is for a ‘green industrial revolution’ backed by £12bn in government investment, which could create up to 250,000 new jobs. Decarbonising the heating and cooling sectors sits at the heart of its 10-point plan, which includes a pledge to tackle energy efficiency in hospitals, schools, and other public buildings through the £1bn Public Sector Decarbonisation Scheme.
The Green Homes Grant for homeowners has also been extended by a year until March 2022, but the Construction Leadership Council wants to go further and is calling for a national education programme to persuade Britons to spend £525bn on home improvements. This would need an additional 500,000 people to join the industry’s workforce – doubling the present numbers over the next 20 years.
The biggest hospital building programme in a generation is also underway to use more standardised design elements and make use of modular construction methods to speed up delivery. Eventually, the plan is to deliver another 30 new much needed hospitals over the next decade,.
The COP26 climate summit hosted by the UK in November will also have a heavy focus on buildings after its president Alok Sharma announced plans to include a ‘built environment day’. In a letter to the World Green Building Council he said that “action to decarbonise the buildings and construction sector is critical to meeting our Paris Agreement goals”.
A new net zero building package worth over £3 billion will focus on making our “homes, schools and hospitals greener, warmer and more energy efficient, whilst supporting up to 50,000 jobs by 2030”, said Sharma.
All of this promises exciting economic opportunities for our industry; from the creation of ‘green’ jobs to being instrumental in tackling the climate crisis. However, the Covid-19 pandemic has also taught us some important technical lessons that we can use to improve the health and well-being of all building users.
The way building services supports critical infrastructure is now more widely understood and the part played particularly by ventilation in tacking virus transmission means our engineers are now regarded as having a vital healthcare role because they are instrumental in helping supress the spread of infection.
Scientists now believe that airborne aerosols are the most likely way to contract the disease. The World Health Organisation (WHO) took some time to recognise this threat, but by last autumn inhalation of aerosols was accepted as the main driving force behind the surging new wave of infections and this led to the increased emphasis on wearing face coverings.
The role of mechanical ventilation is also now better understood. Historically, the focus for indoor climate was on temperature control, which is of course important in terms of comfort, but the health and wellbeing role of ventilation is now more widely understood as a result of the pandemic. The higher the rate of ventilation, to give maximum dilution of contaminants, the better.
The government’s SAGE advisory group has, therefore, called for a national strategy on building ventilation backed up by research from Cambridge University recommending that air change rates should be adequate to keep carbon dioxide levels below 800 parts per million as an indicator that all potentially harmful contaminants are under control.
This may suggest that ‘all-air’ systems are the answer, but these will often be impractical or uneconomical because of the size of the plant and services necessary to deliver sufficient levels of cooling to the building. In such cases where secondary cooling systems will be required, there are choices; those that rely on a primary air supply to function would by default always ensure the designed ventilation rate is delivered, more so than recirculatory secondary cooling systems that can be run independently from the main ventilation system and so may not deliver adequate air change rates.
We need to be careful when increasing ventilation rates because this could come at a high cost if we simply increase our historic design figures by a given percentage. Larger ductwork and other services may lead to higher capital costs, less usable or lettable space, and of course higher energy usage. For these reasons Demand Controlled Ventilation (DCV) could offer a sensible solution by providing ventilation when and where it is necessary, based on the prevailing demand of occupancy or air quality, and avoid delivering air unnecessarily where there is little or no demand.
We also need to be sure that the outdoor air we are bringing into the building is not simply replacing one contaminant with another, so suitable levels of filtration to guard against pollutants such as pollen and NO2 should be a prerequisite. Secondary filtration inside the building on recirculatory cooling or heating devices is a more complicated issue. These can have coarse filters that do not filter smaller particles, but may still collect potentially contaminated particles which may then be released when fans start to operate.
At last year’s BESA National Conference, the importance of controlling relative humidity (RH) was also stressed by Dr Stephanie Taylor from Harvard Medical School, who said it was key to tackling Covid-19 and in preparing buildings for future health challenges.
She said managing the indoor environment was “the best medicine for treatment and prevention” and dubbed building professionals as the “physicians of the future”.
The ASHRAE Distinguished Lecturer said numerous studies had identified an RH ‘sweet spot’ between 40% and 60%. Air that is too dry will allow viruses to thrive and be more active, she added.
“We need to start regarding human health as a key measure of success for our buildings,” said Taylor; adding that RH should not be sacrificed to reduce energy use. “We need to get that balance right.”
We have also recently had another stark reminder of why we should be highly motivated to deliver the very best indoor environment: Late last year, Ella Kissi-Debrah became the first person in the world to have air pollution officially listed as a cause of death following a landmark ruling by the coroner presiding over a second inquest into her case.
He ruled that air pollution "made a material contribution" to the nine-year-old’s death in 2013 following a series of severe asthma attacks.
Poor air quality is thought to contribute to the deaths of up to 36,000 people in the UK every year and over seven million worldwide, but Ella is the first person to have it stated on her death certificate.
By improving the quality of the air we breathe, both inside and outside buildings, we will be able to ensure the overall health and wellbeing of our population, lessening the strain on the healthcare sector in the long term. This does, of course, require multiple professions to communicate the importance of air quality and collaborate effectively, which will allow us to balance project demands at an early stage, ensuring all targets are met both environmentally and economically, and improving the health and wellbeing our population.
As we look to emerge from the current crisis, the role of ventilation in reassuring people that buildings are safe and can, in fact, protect them from some of the worst threats in the outside air could play a crucial role in getting our country moving again and returning society to normal.
Yes, the economic opportunities are clear and promise a better future for our sector, but the social benefits we can offer society because of what we have learned in the past 12 months are, potentially, far greater.