Re-opening buildings post pandemic


Re-commissioning a large office building after it has been sitting idle for several months requires a strategic approach.

By Simon Blake

As governments get a handle on dealing with the COVID-19 pandemic and commercial buildings begin to re-open after three months of being largely dormant, mechanical contractors and maintenance staff will play a key role in ensuring that these buildings are safe.

In some ways it’s simple. Just ensure the indoor air quality (IAQ) and the water quality is as good as it can be. But at the same time, contractors have to be careful. They need to follow the rules that governments and other authorities establish to avoid liability, among other things.

“You can’t be out there telling people that this works or that works. You can’t just sell something that you think works. You have to sell something that (a recognized authority) says works,” remarked Gord Cooke, president of Building Knowledge Canada Inc., Cambridge, Ont. “The big thing is not to make claims that you can’t substantiate.”

On May 29 Martin Luymes, vice president, government and stakeholder relations for the Heating, Refrigeration and Air Conditioning Institute of Canada (HRAI), met with Health Canada officials to “explore the role for the HVAC/R sector in COVID-19 mitigation.”

Did HVAC systems contribute to the spread of COVID-19? “Nobody wants to say categorically that they play no role,” said Luymes. “To date, most technical experts in the scientific community have said that there’s a minimal chance of HVAC playing a role in the spread of the virus, but they’re not saying there’s no chance, and that is research that is ongoing.”

ASHRAE has also stated that it’s low risk, but the possibility can’t be ruled out. It cannot be ignored, however, that a study published in February showed that nine diners at a restaurant in Wuhan, China contracted the virus from an asymptomatic COVID-19 carrier sitting near an air conditioning vent.

Airflow at the furnace is checked with a TruFlow airflow grid that slips into the filter opening.

“I don’t necessarily think that this study is representative of transmission risk. However, it is important to be mindful of air flow patterns, especially if they are strong and create a jet stream for droplets,” infectious disease expert Dr. Amesh Adalja, senior scholar at the Johns Hopkins Center for Health Security, told Health Magazine.

Cleaning the HVAC system

HVAC contractors have control over two key areas – fresh air ventilation and humidity levels. “These are the two parameters that seem to be of interest to the powers that be,” remarked Cooke.

The U.S. Centers for Disease Control and Prevention (CDC), a division of the U.S. Dept. of Health and Human Services, recommends keeping humidity levels below 50 percent to minimize the growth of mould during and after a prolonged shutdown. Sources of moisture need to be addressed quickly.

The building’s use is also a determining factor. In Ontario, for example, the  Royal College of Dental Surgeons has dictated that dental operating rooms require a specific number of air exchanges per hour (ACH).

The College recommends that “dentists should consult an HVAC professional to assess the existing HVAC system and calculate the actual ACH for the dental practice.” The question is, are HVAC contractors ready and able to do this?

“We had close to a dozen calls from dentists wondering what they can do and, of course, they are all looking for one simple (piece of equipment) that they can throw in. But when you look at the air change rate, it really is pretty significant and it comes down to flushing out the room between patients,” said Cooke.

And if the dentist wants to bring in the next patient within three minutes, they will need about 50 air changes per hour. With half an hour between patients, they only need three.

As with so many things, the contractor has to manage expectations. “Every dentist goes, ‘well, of course, I want the next patient in within three minutes, so give me 50 air changes,’” noted Cooke. That would require a commercial sized HRV in every room – obviously not possible.

Solutions, or not

The HVAC contractor needs the right instruments to measure airflow accurately, something many lack, remarked Cooke. “They have equipment to measure temperatures, they have equipment to measure pressure and refrigerant, but very few have equipment, other than some little vane anemometer that they wave around over a grill, that has the ability to measure air flow.”

There are two options; either partner with an air balancing contractor or a company like Cooke’s or purchase the equipment and develop the expertise to use it.

A Building Knowledge Canada technician checks airflow at a register with a flow hood.

“If you want to measure ventilation off a rooftop heat/cooling unit you need an anemometer. If you want to measure airflow out of a grill you need a flow hood (balometer).”

Flow hoods are used to test airflow at the registers in residential applications. Total flow at the furnace is best measured with a product like the TruFlow Grid from the Energy Conservatory in Minneapolis, which fits in a standard furnace filter slot.

There are a number of devices that have been suggested to prevent the spread of COVID-19. Ultra-violet lamps have long been used for coil, duct and water disinfection and have proven effective against most viruses and bacteria. The problem with COVID-19 is that it is so new that there is little, if any, science to say that UV is an effective solution, although common sense suggests it should be.

That’s not good enough for the authorities. Health Canada is taking a cautious approach in recommending certain types of equipment, as is ASHRAE, said Luymes. “The minister’s staff noted that the government prefers to take guidance from peer-reviewed research. That also means not recommending anything that hasn’t been proven through proper testing.”

ICI spaces

In institutional, commercial and industrial (ICI) buildings, ASHRAE recommends creating a strategic plan prior to opening the building. “Review HVAC programming to provide flushing two hours before and two hours post occupancies. This includes operating the exhaust fans as well as opening the outside air dampers.” There is considerable information on the ASHRAE COVID-19 Resources webpage at

The CDC recommends that contractors and maintenance personnel ensure that cooling towers are clean and well maintained and that shut-down and start-up procedures are conducted according to the manufacturer’s instructions and industry best practices. Each tower and basin must be free of visible slime, debris and biofilm before start-up. Considerable information is available on the website of the Cooling Technology Institute (CTI) at

The CDC also advises that, for buildings that have been closed for a prolonged period, a routine HVAC operation and maintenance program for the building should be established to guide re-commissioning.

Initial HVAC system checks should be weekly, with the frequency of checks reduced as time goes on and the system starts operating normally. These should include inspection and maintenance of HVAC components, calibration of HVAC system controls and HVAC testing and balancing.

Plumbing and piping reboot

The big danger in a building’s water system when it sits idle for a prolonged period is not COVID-19, but Legionella that can form in stagnant water. Reuters News Agency reported that insurers are watching to ensure that building owners have Legionnaires’ disease safeguards in place as buildings are re-opened.

Like the HVAC system, the CDC recommends the development of a comprehensive water management program for the building. There is considerable information at

In re-opening the building, the CDC recommends thoroughly flushing the hot and cold water systems through all points of use. “The purpose of building flushing is to replace all water within building piping with fresh water.” That’s pretty straightforward!

The CDC also notes that water using machines, such as ice-makers, may require additional steps including disposing of old ice so that the machine, after cleaning, can regenerate new ice from freshwater. There are many other steps for things like hot tubs, decorative fountains, etc.

Design changes expected

In the long-term, the experience with COVID-19 will likely result in design changes for ventilation and other mechanical systems going forward. Things like individual unit ventilation systems for multi-unit buildings will become more prevalent.

“Certain technologies will come to the forefront, and not because they deal with COVID-19, but because people will suddenly have a sensitivity around air movement in buildings and dealing with potential (outbreaks). If it’s not this virus, then maybe the next one. One of the positives about this, if there is a positive, is that there’s a higher awareness of indoor air quality. People are starting to ask questions that they didn’t used to ask, like why aren’t all these things in the building code?” said Luymes.

“There are rules and standards that we can apply, but we typically don’t do it because they are seen by builders as too expensive,” he added. With so many people working at home, there’s a much higher IAQ awareness.

“That’s where our industry can actually play a role and sell more of its specialized products. Now, it’s more likely that people will be asking for these things and the industry should be ready to offer solutions,” said Luymes.


HRAI COVID reopening training program

The Heating, Refrigeration and Air Conditioning Institute of Canada (HRAI) has developed an online training program for re-opening buildings and HVAC businesses following the COVID-19 shutdown. Created at the request of Fortis BC, it is designed to help contractors get back to work.

Originally aimed primarily at safety, HRAI asked instructor Gord Cooke, president of Building Knowledge Canada Inc., Cambridge, Ont., to go beyond that and talk about HVAC technologies and what they can and can’t do. “We don’t want contractors out there either missing opportunities or saying the wrong thing,” said Martin Luymes, HRAI vice president.

“On the residential side, do what we’ve always known to be right,” said Cooke. “There is good evidence that if people are living in healthy air, their immune system is better able to handle challenges, so if you do get a virus, wouldn’t it be best if your air is in really good shape so your lungs don’t have to work as hard? That’s what we’re going to encourage contractors to do. Improve the baseline – good ventilation, good humidity control, good dust control.”

The six-hour course is primarily aimed at residential contractors. Large commercial is a different matter, added Luymes. “We tell people to go check the ASHRAE guidelines, which are evolving.” A course aimed at the more complex needs of the commercial market may be developed if there is demand from the industry.

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