How Clark Nexsen is approaching COVID-19 engineering challenges

Bill Stingl is a mechanical department leader at Clark Nexsen, a CFE Media content partner. His experience ranges from energy usage development and analysis to innovative HVAC/plumbing design for many project types including cleanroom and laboratory, industrial, classroom and commercial.

He responded virtually to a host of questions on the engineering challenges faced by consultants.

Have building owners or clients approached you to assist with changes or updates to their building to help protect against COVID-19? What services can you offer?

Bill Stingl: Yes, so far we have had an existing client ask us to provide design costs to expand the current design to include ultraviolet-C lamps for a coil cleaning only setup to airborne virus inactivation setup. It is my understanding there is published documentation from ASHRAE that provides technical guidance, which includes the use of UV lighting to inhibit spreading of airborne viruses. I have some concern that although this could provide some benefit, not all air in a building moves through the airstream of an air-handling system, especially those older buildings, which are not properly air balanced. But clients may find issues with the cost/benefit of this type of approach.

As an aside, on the residential level, I would recommend that homeowners take a look at what the filtration limitations are for their particular HVAC system and then use the best possible filter system they can for that system to be able to take out smaller particulates.

What test-and-balance or air balancing challenges have you encountered? What unique challenges are you solving?

Bill Stingl: Much like in cleanroom design, in order for buildings to significantly benefit from HVAC control against germs/bacteria, we must assure that as much of the air as possible can be managed within the mechanical air systems.

We do this through:

• Building positive pressurization, avoiding leakage from the outside.
• Sound duct design (controlling duct leakage classifications).
• Higher air circulation rates (air-changes/hour).
• Better/higher levels of filtration and decontamination at the air handling units, (i.e., 85%, 90%, HEPA, UV, etc.).
• Regular duct cleaning maintenance recommendation.

The ASHRAE Position Document on Infectious Aerosols states, “Even the most robust HVAC system cannot control all airflows and completely prevent dissemination of an infectious aerosol or disease transmission by droplets or aerosols. An HVAC system’s impact will depend on source location, strength of the source, distribution of the released aerosol, droplet size, air distribution, temperature, relative humidity and filtration” (ASHRAE, 2020). We must understand the benefits and limitations that all buildings have. It is our job as engineers to educate building owners of the challenges they may face as well as provide them with the cost-effective strategies and solutions.

To accomplish dissemination of infectious airbornes can be rather costly, especially in older existing buildings, but there are opportunities. We do have a much better chance at implementation in new buildings and in fact some of the listed items, such as positive building pressurization are already required for buildings with regular occupancies.

From an engineering standpoint, what other markets or building sectors do you anticipate will grow due to the changes occurring due to the coronavirus? Is there a new engineering sector you plan to focus on to meet these needs?

Bill Stingl: I imagine we will see an increase in the science and technology market, particularly public health projects and laboratories as funding should be robust for these types of projects in response to COVID-19. For public projects, it takes a while for the process of determinations and funding to be completed. But there should be an increased emphasis on public health projects.

The coronavirus has required several facility managers to remotely control all aspects of their building systems (lighting, HVAC, etc.). What building automation or controls projects are you working on to meet these needs? How will this impact future design?

Bill Stingl: Almost all of our projects require the ability to remote access the control systems, some through client servers, but most through the web. All the building management system manufacturers have web access systems.

What might other engineers/building professionals need to know when tackling COVID-19 projects?

Bill Stingl: Biosafety level 3 and 4 lab standards will need to be implemented for COVID-19 related projects.

Proper management of indoor air has always been of paramount importance, from a high level of indoor air quality to energy efficient design. Moving forward there will be challenges attaining these goals. There will be sacrifices in one area to benefit in the other. We will have to look at more innovative ways to minimize potential negative impact.

It’s very helpful to look at how we develop clean rooms where the standards start very high. Filtration and air changes are still the primary sources to get the indoor air quality to the level that’s needed for those types of containments. In order to increase the filtration and get the particulate count down to where you need it to be in BSL 3 and BSL 4 environments, you’ve got to pass that air as many times as you can within an hour across that filter so the air volume is increased.

UV is supplemental. It doesn’t do it all. It’s a combination of things and the ASHRAE paper referenced drives into that on a higher level and points out all the other publications that are out there — that we already have and use in hospitals and cleanroom environments. All that information applies to COVID-19 related projects, but it comes at a cost.

It should also be noted that medical professionals are learning about the virus on nearly a daily basis, and new strategies will evolve as knowledge about COVID-19 continues to grow.

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