Thread by @DavidElfstrom

What's the risk of COVID in apartment buildings? This review covers much of the basics but I believe the prevalence is much higher ... (THREAD) /1
ncceh.ca/documents/evid…

We've long known air flows throughout a building despite walls and floors because there's strong driving forces and little attention to air sealing, both on the building envelope, and between units. /2
Figure: Ueno, Lstiburek, Bergey 2012 buildingscience.com/documents/bare…

The three driving pressure forces are: Wind, Stack (chimney) effect, and Mechanical (both negative and positive). /3
Figure: Air Leakage Control for Multi-Unit Residential Buildings, CMHC 2017 agency.coop/media/747/down…

The stack effect is a dominant factor in winter, and is directly related to the height of the building AND the temperature difference between indoors and outdoors. Remove the temperature difference and the stack effect is minimal. /4
Figure: Cdn building digest number 104, 1968

Wind effect can exert very strong pressures that overwhelm other pressures, from minutes to hours, causing significant air movement within a building. /5
Figure: Handegord & Hutcheon, Building Science for a Cold Climate, 1983

Dynamic pressures on a building can be very high. Note a 5 Pa pressure difference from a kitchen exhaust fan in a home is enough to backdraft a naturally aspirated hot water tank in the basement. /6
Figure: plot based on physics

Mechanical pressures: It depends. Nearly all MURBs use corridor positive pressurization with fresh air to make up air exhausted from suites from kitchen and washrooms. Typically these flows are not balanced between units at all. /7
Figure: CMHC 2017 agency.coop/media/747/down…

The implications are that in cold climates in winter, there are significant amounts of uncontrolled air movement between suites, sometimes substantially more than the intentional air supplied by mechanical systems. /8
Figure: Fitzgerald & Bohac, 2012 slideshare.net/mnceeInEx/mf-s…

*IF* any centralized exhaust fan is off, there is a potential for direct connection to other units with flows driven by wind, stack, and remaining mechanical pressures. /9
Figure: Center for Energy and Environment multifamily ventilation assessment 2016 cards.commerce.state.mn.us/CARDS/security…

In Ontario alone there have been outbreaks reported in the news of MURBs in London, Sudbury, North Bay, Collingwood. All of these had significant numbers, all were in winter. There are likely many more, but health units aren't aware of them because they are overwhelmed... /10

Dr. Alex Summers: A heavy load of case area-wide and the ability to notice trends contributed to delay. "It wasn’t until we had a few weeks of seeing this common address pop up multiple times, that we were able to see that trend and declare outbreak" /11 london.ctvnews.ca/why-did-it-tak…

So what can those in mid-rise and higher apartments do?
⛔️DO NOT cover up exhaust vents, or block the suite door, they exhaust stale air and provide fresh air!
✅Check with toilet paper for this necessary air movement out of and into the suite. /12

✅Look for areas of uncontrolled leakage entering the suite from other suites. Pipe penetrations are common. /13
Figure: slideshare.net/mnceeInEx/mf-s…

Pandemic or not, if kitchen & washroom exhaust fans are not functioning (toilet paper not sticking to the grill) or worse, slight air movement into the apartment, bring it to management's attention immediately.
/14

Remember, #COVIDisAirborne.
Properly functioning mechanical systems help.
Portable HEPA air cleaners will provided lasting indoor air quality benefits.
Open your windows a crack.
Wear a tight-fitting quality respirator outside your home.
Don't panic: Be aware of shared air. /15

Whoops, forgot the figure. You want central exhaust fans to be operating. If not, there's potentially direct connection to other suites.

https://twitter.com/DavidElfstrom/status/1379814623004798976?s=20

Looking to other cold climates, 26 infected at an apartment in Norway
"I have no idea how I have been infected, because I have not mixed with anyone. I have almost only been to the store"
h/t @Lisbethsindag
nrk.no/sorlandet/smit…

Another outbreak. @cityofhamilton please engage engineers & building scientists ASAP to help stamp this out. globalnews.ca/news/7833640/c…

"While Rebecca Towers is the only apartment [in Hamilton] to see an outbreak so far, Richardson said there may have been smaller ones in buildings that the city couldn't detect with their systems". 10 new cases today. cbc.ca/news/canada/ha…

Tacking this on. Start looking for clusters in apartment buildings and you just might find them.

https://twitter.com/JoeyColeman/status/1391836560748949504?s=19

Streetlight effect again. "City staff admit they do not have a system in place to track outbreaks in residential buildings, as they do for workplaces. The city should immediately establish a system to track case counts in apartment buildings" thespec.com/opinion/contri…

Here's a list of apartment building outbreaks in Ontario from news reports. Many health units do not report them, or aren't looking for them, and are overwhelmed.
Link to Google Sheet: docs.google.com/spreadsheets/d…

How to do it: ONE person tests positive for variant, entire apartment block locked down & tested. 10% infected (19 of 189 people). I think they should move those infected off-site to individual air-gapped accommodation to prevent additional infection. dailymail.co.uk/news/article-9…

Singapore. "Although the four units with confirmed cases are in the same stack, (vertically aligned), MOH said its initial assessment is airborne transmission highly unlikely." No reason given. Maybe they need a building sci engineer? HT @drkristenkc straitstimes.com/singapore/heal…

If it can happen between adjacent apartments outdoors then it can happen between adjacent apartments indoors driven through unsealed penetrations by zonal pressure differentials

https://twitter.com/linseymarr/status/1399108640183828481?s=19

An excellent thread by @markegilmore filled with photos and observations about how we might be sharing air between units, or be exposed to contaminated air from drainage systems in apartment buildings. Thank you Mark!!

https://twitter.com/markegilmore/status/1403564633424809985?s=19