Ventilation Finally Accepted as Key To COVID-19 Transmission

This is a design issue as much as it is a health issue.

Open the window!
CDC says: Open the window!.


Since shortly after the Coronavirus hit North America, building scientists and engineers have been complaining that the health science and medical people didn't understand how air and tiny particles like viruses actually move. Health scientists claimed that the virus traveled on heavy droplets that would fall to the ground within six feet, while the building scientists said it was more like smoke, and that it was airborne.

It got so bad that in November, citizens and scientists were signing petitions demanding that the World Health Organization "recognize the compelling scientific evidence that SARS-CoV-2 spreads by aerosol transmission ('airborne') and urge the WHO to immediately develop and initiate clear recommendations to enable people to protect themselves." It all sounded like a turf war to me, but it was really people in different silos talking over each other; as engineer Robert Bean told Treehugger:

"There is definitely a disconnect between professionals that should be collaborating. So your basis for turf wars holds some validity; as many in the medical community are working from a medical model, the epidemiology from an epi model, the virologist from the virus model, the aerosols scientists from the aerosol model."

This Is Not Just a Health Problem, It Is a Design Problem

We have been following this closely because it has become a design issue, critical to healthy homes and offices, that isn't solved by plastic screens. It becomes an issue of adequate ventilation in a world where windows often don't open or if they do, they don't open very far or have any cross-ventilation to actually bring in air.

Fortunately, things have finally started to change. In December, the Centers for Disease Control (CDC) issued some pretty clear guidelines for ventilation in buildings and on January 7 issued updated guidelines for improving ventilation in your home. The key concept, as the CDC notes:

"Bring as much fresh air into your home as possible."
CDC strip

Centers for Disease Control

"If it’s safe to do so, open doors and windows as much as you can to bring in fresh, outdoor air," the CDC continues. "While it’s better to open them wide, even having a window cracked open slightly can help. If you can, open multiple doors and windows to allow more fresh air to move inside."

Bremer plan of house
Every room has cross-ventilation.

Aymar Embury II

Of course, this isn't as easy as it used to be. A hundred years ago, every room had cross-ventilation and everybody slept with the windows open. It wasn't just because of the flu and tuberculosis; doctors had been pushing this since the 1890s. Dr. Joseph Edwards famously set the pattern by suggesting that the best place to live would be a tent, because of the amount of fresh air. Edwards wrote:

"Large windows and large doors will help much to make a healthy house. You cannot have them too wide and too high. You remember what I said about tent life. The larger you make your openings, the nearer will your house approach a tent."

Now, few rooms are designed for cross-ventilation, windows on upper floors often have stops to keep them from opening more than 4 inches to keep kids from falling out, and people have safety and security issues about who comes through the bathroom windows. The alternative to open windows, if you have a forced-air heating and cooling system, is to run the fan all the time, get a MERV 16 filter that fits properly, and change it often. The backup to that is to build your own Comparetto Cube COVID-19 air filter.

Recently the Canadian government issued clear and sensible guidelines that cover much the same ground as the CDC does, but with a northern twist. They are very clear about recognizing the importance of aerosols as the main mode of transmission, something still not explicit everywhere.

"Aerosols laden with infectious virus increase the risk of spreading COVID-19, particularly if a person stays within an enclosed indoor space with little air circulation for a long time. Thus, indoor air quality may play a role in COVID-19 transmission and other health conditions by affecting the concentration of pollutants, as well as viral and bacterial particles suspended in the air."

They recommend opening the windows but recognize that it can be cold out there.

"Opening windows in winter may not always be comfortable or possible. Doing so for a few minutes at a time during the day can still improve air quality, with minimal impact on the indoor temperature. If occupants will be indoors for longer periods, for example at schools, occupants should have regular outdoor breaks, to allow for ventilation of the room."

Schools are a huge problem. A hundred years ago, they were all built with giant walls of windows that were left open in winter, while heating was provided with big steam radiators that were sized to heat the space even though the windows were opened. Most of those steam systems are gone, and there is not enough heat. According to Curbed, New York kids will be shivering in class all winter.

At least they have windows. Schools built 50 years ago have a bigger problem: tiny windows and not enough ventilation, designed to recirculate air. They need portable filters.

The "Experts" Are Still Arguing

The guidance from the CDC and Canadian Authorities is so new that other agencies have not yet figured it out; in Ontario, Canada, Public Health Ontario is still issuing documents that say "Transmission of SARS-CoV-2 occurs predominantly through close (<2 m), unprotected contact with an infected individual(s)" and "Transmission over longer distances (>2 m) is less common but possible under certain conditions such as prolonged exposure in a poorly ventilated space." (PDF here)

So now the Ontario Society of Professional Engineers (OSPE) is weighing in, and calling on the government to refocus efforts on airborne transmission, once again showing the split between the health experts and the air quality experts.

"OSPE believes that airborne transmission is one of the main reasons why we are seeing so many outbreaks in schools and long-term care facilities across the province. With outdoor temperatures dropping, many of these buildings have shut themselves off from fresh air that would have helped get rid of these COVID aerosol particles. Instead, many of these buildings have closed HVAC systems that recirculate the same, potentially infected, air...OSPE is calling on the Ontario government to immediately address the airborne transmission of COVID-19 to help slow the spread of the virus."

Fighting Disease With Design


Duiker and Bijvoet

A few years ago we did a series titled Fighting Disease with Design, most of which has been archived. Then, it was architects and engineers leading the fight against tuberculosis, designing for sunlight and ventilation.

The reason I keep writing about this in Treehugger is that architects, engineers, and building scientists have a major role to play in this pandemic. They understand how air moves, how moisture moves, how to ventilate a building properly, how to do it without it costing the earth in energy. If the public health experts had listened to them nine months ago, we would be a lot further along. This is a home, office, urban, and transportation design issue as much as a health issue.