Making Buildings Healthier

Every winter we suffer a rise in colds, flu and respiratory illnesses. It seems as inevitable as an increase in pollen allergies in the spring or sunburn in the summer.

The main reasons put forward for this seasonality of illness are that people spend more time together indoors, cold dry air weakens our immune system and it offers a more hospitable environment for viruses to thrive in. These factors combine to create a situation where respiratory viruses spread more easily from person to person, resulting in increased infection.

But, does it need to be this way? Could we better manage our indoor environments to counter these factors, curb the rise of seasonal illness and provide a return on the investment through increased productivity and reduced healthcare costs? I think the answer is yes, yes and yes!

The SARS-CoV-2 pandemic has focused public attention on how viruses are transmitted. Public awareness has already come a long way from washing hands whilst singing happy birthday, to understanding more about how a room’s CO2 concentrations provide an indication of adequate ventilation in a building.

In the recent online BESA Conference, Dr Taylor, of ASHRAE’s Epidemic Task Force, gave a thorough presentation on the science behind why 40-60%RH is the optimum indoor humidity for respiratory infection control. The ASHRAE Distinguished Lecturer said numerous studies had identified an RH “sweet spot” of between 40% and 60%, because “there are fewer virus particles in the air, they are less infectious and our health and immunity is much better, when we have our humidity in this zone.”

Dr Taylor also presented a study she recently undertook in association with the MIT research university in the US. COVID-19 infection and death rates were examined in 125 different countries alongside a huge variety of other variables and examined for correlations. The study found that when the indoor relative humidity was low, the COVID-19 infection rates were higher. Conversely, when the indoor humidity was midrange, death rates were at their lowest.

In the UK, we can expect to experience an indoor humidity below this “sweet spot” of 40-60%, when the outside temperature is around 8°C and the indoor environment is heated to 20°C or more. This will typically happen from around November through to March. This indoor dry season corresponds perfectly to the rise and fall of seasonal winter respiratory illnesses in the UK.

We routinely humidify factories, data centres, museums, storage facilities and a whole host of other buildings, big and small, when a manufacturing or process application requires it. Humidification of offices for health is reasonably commonplace among informed building operators. Humidification of hospital environments is also routine, but is limited to areas where humidity control is deemed necessary for the particular application, such as in MRI suites. The return on investment in performing more accurate scans is evident but the return on investment in humidifying wards and waiting rooms, to protect staff and patients from aerosol cross infection is, unfortunately, not so immediately perceivable.

Given that the health benefits of humidification are scientifically clear, but not immediately obvious to the occupants’ senses, I feel it will take government regulatory change to ensure optimum indoor humidity levels are maintained in public buildings. Otherwise, in the drive to minimise operating costs, humidification will frequently be omitted, along with other beneficial but concealed services.

In the battle to make our buildings healthier, there are many weapons in the building services’ arsenal. Humidity control is an important but individual factor, alongside other activities such as correct ventilation, air filtration, lighting and occupant density. Many of these protective strategies complement each other and when combined will significantly improve occupant health.

By upgrading our built environment in this way we will be protecting society, not just from the threat of potential future pandemics, but also by significantly reducing the many deaths, sick days, lost productivity and healthcare costs associated with winter seasonal illness.