Coronavirus and the air conditioned nightmare – Treehugger

What happens when it gets really hot and the AC is blasting on full?

In much of the United States, the malls and restaurants are reopening to the public. Some of those states get really hot in the summertime. Sarah Goodyear, a writer and host on The War On Cars, posted an interesting tweet:

Recent research indicates that large droplets from sneezing can travel much further than 2 meters, even if there are no air movements. Small particles (

They have been studying the problem in Canada too. Professor Brian Fleck told the National Post that "this has been on peoples radar for quite a while. Somebody on a different floor sneezes The particle can stay airborne long enough to go all the way through the system and then pop out in somebody elses office."

There are various ways that the risk can be lessened, including use of filters that catch a greater number of those particles, and drawing more fresh air into a system... But each of those changes carries a cost. Adding more fresh air can require additional heat or air conditioning. Heavier filters means more energy is needed to push the air through them.

But it doesn't get as hot in Canada as it does in Arizona. Engineer and Professor Ted Kesik told TreeHugger that "we shall be greatly challenged retrofitting our existing buildings to eliminate dilution ventilation systems." This is especially a challenge in the heat of a southern summer, where the difference between inside and outside air can be 40F in Arizona or Texas. In the Southeast, there is also a lot of humidity with the heat. That's why the air is recirculated; the amount of energy needed to condition a mall's worth of outside air would be ridiculously high.

ASHRAE, the American Society of Heating, Refrigerating, and Air-Conditioning Engineers, had a look at the issue of the coronavirus and issued a statement in late April:

Transmission of SARS-CoV-2 through the air is sufficiently likely that airborne exposure to the virus should be controlled. Changes to building operations, including the operation of heating, ventilating, and air-conditioning systems, can reduce airborne exposures.

They issued technical guidelines in a position document on infectious aerosols:

Infectious aerosols can be disseminated through buildings by pathways that include air distribution systems and interzone airflows. Various strategies have been found to be effective at controlling transmission, including optimized airflow patterns, directional airflow, zone pressurization, dilution ventilation, in-room air-cleaning systems, general exhaust ventilation, personalized ventilation, local exhaust ventilation at the source, central system filtration, UVGI, and controlling indoor temperature and relative humidity. Design engineers can make an essential contribution to reducing infectious aerosol transmission through the application of these strategies.

That's fine, the engineers know what to do with new buildings. But what about existing ones? Here, they make some recommendations, and I try to add an explanation in italics.

All of these modifications are expensive, either in equipment or operating costs. All of these building owners and tenants have been bleeding money in the last few months. All of the companies making this equipment are going through the crisis, too. In short, it is probably safe to say it's not gonna happen, at least in the short term.

I have tried to get comments from engineers and experts, but the only one I have received so far is, "Yikes, I think that is a problem." I will add more comments as I receive them.

But I do believe that Sarah Goodyear has raised an interesting point. In my limited experience in Arizona in summer (two weeks in Scottsdale in July), I rarely saw anyone outside. And it's not even summer yet, but as one shopper in Arizona told NBC News after the mall opened, "We hit all the museums and this place because its hot."

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Coronavirus and the air conditioned nightmare - Treehugger