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April 7, 2023

William P. Bahnfleth Explores the Development of ASHRAE Standard 241 for IAQ

Sustainable IAQ: Expert Insights - Episode 1
William P. Bahnfleth, Ph.D., P.E.

Guest Bio

William Bahnfleth is Professor of Architectural Engineering at the Pennsylvania State University, where he teaches classes in fundamentals and design of heating, ventilation and air-conditioning systems and conducts research on a variety of areas, principally energy efficient control of bioaerosols. He is the author or coauthor of nearly 200 scientific and technical publications. He has held prior positions as a senior consultant for ZBA, Inc. and as a principal investigator for the US Army Construction Engineering Research Laboratory. He holds BS, MS, and PhD degrees in Mechanical Engineering from the University of Illinois at Urbana-Champaign and is a distinguished alumnus of the Department of Mechanical Science and Engineering. Dr. Bahnfleth is a Registered Professional Engineer and a fellow of the American Society of Heating, Refrigerating, and Air-Conditioning Engineers (ASHRAE), the American Society of Mechanical Engineers (ASME), and the International Society for Indoor Air Quality and Climate (ISIAQ).


Design, Performance, and Operation

A key aspect of ASHRAE Standard 241 is its focus on both design and operation, as well as the inclusion of prescriptive or performance-based alternative paths. By considering these elements, the standard simultaneously addresses the needs of existing buildings and ensures that future constructions effectively mitigate indoor air quality risks. Moreover, the performance-based approach empowers users to tailor the requirements to their specific needs, fostering a more user-friendly and adaptable environment. During the conversation, William P. Bahnfleth stresses the importance of integrating design and operation in creating a more thorough and reliable standard. By offering a performance-based alternative path, the standard promotes flexibility and adaptability, allowing users to establish their own risk tolerance based on their unique circumstances. This holistic approach aims to provide building professionals with a viable path towards improved indoor air quality.

Intersection with Other Standards

ASHRAE Standard 241 is intended to work in conjunction with existing standards such as 62.1, 62.2, and 170, rather than replacing or overshadowing them. The goal is to build upon these previous regulations and improve their effectiveness by incorporating the additional requirements and guidelines outlined in Standard 241. This approach seeks to enhance overall indoor air quality compliance and performance in the building industry. William P. Bahnfleth expresses his hopes that Standard 241 will not only strengthen existing regulations but also contribute to the evolution of national indoor air quality model standards. By reinforcing and refining the current standards, Standard 241 is poised to make a significant impact on the building industry, promoting improved, safer indoor environments.

Committee Progress and Milestones

The development of ASHRAE Standard 241 is a collective effort, with a diverse group of experts coming together to address various aspects of indoor air quality. The committee comprises professionals from various fields, including airborne transmission, air movement, public health, consulting engineers, and building owners and maintainers. Dividing the work into specialized groups allows for a more efficient and collaborative process, ultimately resulting in a comprehensive and effective standard. William P. Bahnfleth discusses the progress of the committee during the podcast, detailing the creation of multiple working groups focusing on distinct aspects such as risk assessment, air distribution, air cleaning, commissioning, operation and maintenance, residential buildings, and healthcare buildings. The formation of these specialized groups ensures that each component of the standard is meticulously examined and optimized to establish a robust framework for indoor air quality management.

Testing, Verification, Documentation, Commissioning, and Periodic Recommissioning

Establishing comprehensive standards for indoor air quality management requires a rigorous process of testing, verification, documentation, commissioning, and periodic recommissioning. By implementing these steps, ASHRAE ensures that buildings are operating as intended and achieving the desired level of indoor air quality. Additionally, the ongoing process of periodic recommissioning ensures the continued effectiveness and efficiency of the implemented strategies. William P. Bahnfleth emphasizes the importance of these steps during the episode, stressing their vital role in ensuring successful implementation and adherence to desired outcomes. By meticulously testing and verifying the results, ASHRAE Standard 241 stands as a valuable and reliable resource for building professionals navigating the challenges of maintaining optimal indoor air quality in a rapidly evolving landscape.

The Urgency of Developing Standard 241

With the COVID-19 pandemic placing a spotlight on the importance of indoor air quality, the development of ASHRAE Standard 241 has become a significant priority. Recognizing the crucial role that mitigating indoor air pathogens plays in maintaining a safe and healthy environment, the timeline for the creation of the standard has been expedited. The goal of this faster approach is to establish a comprehensive framework for professionals in the building industry, helping guide and equip them with the necessary tools and strategies for reducing the risk of infection in a post-pandemic world. In the podcast, William P. Bahnfleth highlights the close collaboration between ASHRAE and the government, emphasizing how this collective effort is driving the speedy development of Standard 241. He believes that this sense of urgency is vital to providing a stable foundation that enables businesses to operate more safely and efficiently, ultimately contributing to public health and economic recovery.



ASHRAE emphasized the standard will include: Design & Operation, Alternative Paths, & Testing. Why were these 3 called out so explicitly?

00:00:06:15 - 00:00:27:03
William P. Bahnfleth, Ph.D., P.E.
I think in the short term, prescriptive is what we're going to focus on. But when we're considering infection risk, there are so many factors that go into determining what acceptable risk is that I think we would like to have a standard that allows users to determine what their own risk tolerance is and to develop requirements that are based on those.

00:00:27:03 - 00:00:49:06
William P. Bahnfleth, Ph.D., P.E.
That's one aspect of performance versus prescriptive. The other is a prescriptive standard might say you must use outdoor air to achieve your target or you must use a certain type of equipment. And something that we learned in the Epidemic Task Force was that there was a real advantage to allowing flexibility on the part of the user to meet their goals.

00:00:49:06 - 00:01:20:07
William P. Bahnfleth, Ph.D., P.E.
So in one climate, more outdoor area might be a really good solution to reducing exposure indoors. But in another one where the climate is extreme, that might be a very expensive way of doing it. So to that extent we'd like to have performance objectives in terms of the equivalent outdoor air requirements that can be met with technologies that will help the owners achieve other goals like energy goals and first cost and operating cost goals.

00:01:20:09 - 00:01:47:07
William P. Bahnfleth, Ph.D., P.E.
Well, design versus operation writing standards for design typically applies to the next building or two, in addition to a building or to a major renovation. And what percentage of the building stock is new every year? It's a single digit percentage that's new. So that's one reason for going beyond design to operation so that you have a standard that will say something about what existing buildings should, should do.

00:01:47:07 - 00:02:19:01
William P. Bahnfleth, Ph.D., P.E.
And the other reason for having Operation called out specifically is that we know that no matter how well designed buildings may be, they fail in operation. We've seen that in many contexts before. If systems are not even doing what they were supposed to, it's kind of a futile goal to make them even better.

There are a number of existing IAQ standards and a lot of potential overlap with 241. How do you see 241 intersecting with the other standards?

Ultimately, what we want is not a standalone national infection risk mitigation standard.

00:02:19:01 - 00:02:56:01
William P. Bahnfleth, Ph.D., P.E.
At least that's my personal view. But what we really need are national indoor air quality model standards. And so my hope is that 60 to 1, 60 to 2 with upgrades, with amendments based on to 41 can become those standards eventually, as we've seen what happens in the energy arena, when you have national model standards like the IPCC and 90.1, I'm hopeful that if we had a similar situation for indoor air quality, that we would see more consistent and widespread progress than we've seen over the last 50 years or so.

00:02:56:03 - 00:03:25:19
William P. Bahnfleth, Ph.D., P.E.
The relationship currently to the other standard, 60 to 1, 62 to 170 is there. We're going to write the standard essentially on top of them. So requirements in two $0.41 will assume that the minimum standard that applies for air quality is being met though if you have a nonresidential non and health care building of an office building or something of that sort, compliance with 60 to 1 is kind of taken as is given as the baseline.

00:03:25:19 - 00:03:52:02
William P. Bahnfleth, Ph.D., P.E.
And so we're working on how would you go beyond that and a little bit in the way that maybe one 89.1 goes beyond 90.1 for energy and 62.1 for air quality, but the big question is how will those standards ultimately change? Because those are the ones that are referenced in in codes and other similar documents, especially 60 to 1 that is basis for ventilation rates in the main model code.

00:03:52:02 - 00:04:28:10
William P. Bahnfleth, Ph.D., P.E.
And that's not really within the scope of the 241 committee. But we have participation on the committee from people who are very involved in on 62, one, 62, two and 170, and it's one of our activities we will be discussing with them how we might move some of the to 41 requirements into those standards. What you need to understand is that if you're going to change those ANSI standards to include provisions that deal with infection risk mitigation, you actually have to change the title purpose and scope of the standard to say that that is something that is included.

00:04:28:10 - 00:05:00:18
William P. Bahnfleth, Ph.D., P.E.
So how that will happen, I can't really say yet. I can imagine a process that might start with Addenda. So you could have affirmative in penned appendices for these standards. That would be information that could be used by a user of the standard if they wanted to include requirements in their design that would address infection risk. The big leap is going from informative appendices to actual standard content, and that will proceed by the normal ANSI process.

How is the Committee’s work progressing? What is the intent of this first version?

00:05:00:18 - 00:05:26:08
William P. Bahnfleth, Ph.D., P.E.
I think I want to emphasize that because we're trying to take on really an unprecedented task in a short period of time. A combination of two things, really difficult problem and much less time than you would really like to have to do it. We're thinking already down the road to what else will need to be done once we get the first version out.

00:05:26:14 - 00:05:51:13
William P. Bahnfleth, Ph.D., P.E.
The intent is certainly the first version is a meaningful contribution to the industry that will help us do the things that need to be done. But there are certainly going to be ways in which it can be expanded and enhanced beyond what we're targeting in the first version.

Standard 241 will be code-enforceable. How do you foresee it being integrated into building code? How would you like to see it integrated?

Let me start by saying that there's a big difference between enforceable and enforced.

00:05:51:13 - 00:06:08:10
William P. Bahnfleth, Ph.D., P.E.
So we can write a standard in code language that if there was a jurisdiction that wanted to adopt it, it would say things in a way that is consistent with what you need to have in a code, not, you know, you. It would be nice if you did or you should or could do it has to say this is what you shall do, what you need to do.

00:06:08:10 - 00:06:37:04
William P. Bahnfleth, Ph.D., P.E.
So we're taking care of that. The next question is how will authorities adopted the construction codes that we talk about so much really stop at design so that they regulate how the building is designed and after that, in most cases, there's no further regulation. So I think the ultimate successful adoption of standards like this is when the authorities put in place a structure that that addresses operation as well as design.

00:06:37:04 - 00:06:58:14
William P. Bahnfleth, Ph.D., P.E.
But that's different entities. You know, the design standard relates to the owner and how much they have to pay for a building and to the professionals and how they have to design the system. Now we're dealing with who is the tenant or the later owner of the building and do they have to periodically evaluate and report how their building is operating?

00:06:58:14 - 00:07:24:03
William P. Bahnfleth, Ph.D., P.E.
And so that's a more of a policy making issue that is really out of ashtrays hands. But we hope that we will write something that is viewed as providing a feasible path to an acceptable to most level of regulation. I would make the analogy to energy. We used to have the same situation for energy, build the building and then what happens afterwards?

00:07:24:03 - 00:07:57:10
William P. Bahnfleth, Ph.D., P.E.
Who knows? But we're seeing more and more requirements to report building energy use, and that is moving in the direction of some degree of regulation and enforcement. That if your building isn't up to standards, you may at some point, if you don't improve it, have to pay a penalty. Yeah, I'm not saying I want to see people paying penalties for not meeting an operational standard, but ultimately that is the best insurance that those things will actually happen.

Can you comment on why the timeline is so fast? Why is the rapid standard development so important?

00:07:57:12 - 00:08:25:12
William P. Bahnfleth, Ph.D., P.E.
It's much shorter than the normal standard development process, which often takes several years. Three years, four years can be even longer than that. So obviously the urgency is tied in part to what the government would like to see. They would like to have be able to say that there are standards available that will help to reduce risk of infection transmission in buildings as we come out of the COVID restrictions that we've had for several years.

00:08:25:12 - 00:08:56:12
William P. Bahnfleth, Ph.D., P.E.
So when all of that is lifted, I think there is a desire to know that we have learned something from the experience that we've put in place, protections that will help ensure that it doesn't happen again.

What prompted ASHRAE to commit to developing Standard 241 for IAQ pathogen mitigation? And why now?

A real driver for doing it now and for having a short timeline is the relationship that developed between ESRI and the government and specifically the White House during the current administration.

00:08:56:12 - 00:09:41:00
William P. Bahnfleth, Ph.D., P.E.
So the White House recognized the importance of indoor air quality and came out in the first part of last year with the Clean Air and Buildings Challenge. And we had already had some discussions going on with the COVID task force in the White House about standards. And in November, the White House had some meetings with ESRI leadership, and that led to ESRI agreeing to develop on a fairly tight timeline, a standard that would address infection, risk mitigation in buildings, kind of in support of the White House's programs.

How is the committee attacking such a complex topic that extends beyond ASHRAE’s traditional focus on mechanical engineering and HVAC systems?

00:09:41:02 - 00:10:09:12
William P. Bahnfleth, Ph.D., P.E.
One of the key things in any consensus standard effort, which this is, is to get a committee that is sufficiently diverse in all respects. So we have experts that cover the whole range of things that we need to be concerned about. We've got researchers who study airborne transmission, who study air movement in buildings. We have public health experts, we have consulting engineers who design buildings and commissioned buildings.

00:10:09:12 - 00:10:33:02
William P. Bahnfleth, Ph.D., P.E.
And we even have those who own and maintain buildings. So we set up a group that can address all of the areas that we had defined as important. And we've broken the committee up into a number of working groups and put clusters of expertise in each of them. So risk assessment, air distribution, air cleaning, commissioning operation and maintenance, residential buildings and health care buildings.

00:10:33:02 - 00:10:52:04
William P. Bahnfleth, Ph.D., P.E.
So the reason for having those two occupancy specific groups is that those are the two types of occupancy where we actually expect to have occupants who are infected with some disease, who need to be cared for or isolated, and also protecting others who are not infected in the same buildings.