William P. Bahnfleth, Ph.D., P.E.
(Accepting In-Person & Virtual Presentation Requests)
Department of Architectural Engineering
The Pennsylvania State University
1426 South Pugh Street
University Park, PA 16801
United States
(814) 863-2076
Region: III
Honorarium: None

William Bahnfleth is a professor of architectural engineering at the Pennsylvania State University (Penn State) in University Park, PA. Previously, he was a Senior Consultant for ZBA, Inc. in Cincinnati, OH and a Principal Investigator at the U.S. Army Construction Engineering Research Laboratory in Champaign, IL. He holds a doctorate in Mechanical Engineering from the University of Illinois and is a registered professional engineer. At Penn State, Dr. Bahnfleth teaches undergraduate courses in HVAC fundamentals and design and graduate courses in chilled water systems and indoor air quality His research interests cover a wide variety of topics including chilled water systems, thermal energy storage, and indoor air quality with a focus on control of bioaerosols. He is the author or co-author of more than 180 technical papers and articles and 15 books and book chapters.

Dr. Bahnfleth is a fellow of ASHRAE, the American Society of Mechanical Engineers (ASME) and the International Society for Indoor Air Quality and Climate (ISIAQ). He served ASHRAE as Society President in 2013-14 and chaired the ASHRAE Epidemic Task Force. He is the recipient of many ASHRAE awards, including the Exceptional Service Award, the E.K. Campbell Award of Merit for teaching, the Donald Bahnfleth Environmental Health Award, the Louise and Bill Holladay Distinguished Fellow Award, the Andrew T. Boggs Service Award, and the F. Paul Anderson Award, ASHRAE’s highest individual honor. He is also a recipient of the Penn State Engineering Alumni Society’s World-Class Engineering Faculty Award and a Distinguished Alumnus of the University of Illinois Department of Mechanical Science and Engineering.

Integrating Indoor Air Quality and Energy Efficiency in Buildings

Buildings are one of the largest energy end use sectors in countries around the globe. Concerns for the availability of energy supplies and the impact of energy use on the environment are driving a worldwide focus on energy end use reduction. In this push for dramatic changes in the energy use intensity of the building sector, it is essential that the fundamental importance of indoor environmental quality, particularly indoor air quality, not be lost. This presentation addresses: 1) the significance of indoor air quality in terms of its impact on health and productivity and associated costs; 2) the inseparable linkage between indoor air quality and building energy demands, including examples of efficient technologies for maintaining good indoor air quality; and 3) the need for an approach to building research, design, and operation that recognizes this connection.

Fundamentals of Ultraviolet Germicidal Irradiation for Air and Surface Disinfection

Germicidal radiation produced by low pressure mercury vapor lamps and other sources is seeing increasing application both for air disinfection and for control of biological growth on surface.  This presentation provides an overview of the fundamentals of ultraviolet germicidal irradiation (UVGI) including principles of operation, component characteristics, system types, applications, and published evidence of effectiveness.

Variable Primary Flow Chilled Water Systems

Variable primary flow is being adopted in chilled water system design with increasing frequency as a lower cost, more efficient alternative to primary/secondary design that is not as susceptible to low delta T syndrome.  Subtopics include a review of variable primary flow and primary/secondary system types; causes and effects of low delta T syndrome and potential remedies; design considerations for variable primary flow, and, comparisons of variable primary flow and primary/secondary flow taken from case study and research literature.

Thermal Energy Storage in the Era of Sustainability

During the 1980s and 1990s, cool thermal energy storage (TES) was a key technology in US utility demand-side management (DSM) programs.  Interest in TES declined steeply as incentives disappeared during utility deregulation.  Today, the focus of design has shifted from energy cost savings toward sustainability and it is reasonable to ask whether TES has anything to offer in this environment.  This presentation will review the essentials of cool thermal energy storage and examine its relevance to sustainable design.  Specific issues examined will include the impact of TES on site and source energy consumption, the economic case for TES without the incentives of the DSM era and the role of TES in achieving net zero energy buildings and communities.

HVAC and Risk from Airborne Hazards

Interest in protection of building occupants from airborne chemical and biological agents was strongly stimulated by several terrorist incidents early in the 21st century. The discussion generated by these incidents brought to the forefront the concept of formal risk assessment for airborne hazards, which few building designers or owners undertake. Over time, the discussion of HVAC security has declined without significant changes having been made to either design requirements or procedures, yet the issue remains and is more important than is generally acknowledged, since accidental exposures have the potential to be just as harmful as intentional ones. This presentation provides an overview of the key issues relating to protection of building occupants from chemical and biological releases including: HVAC system and building characteristics that affect exposure, the spectrum of available countermeasures and their characteristics, risk assessment processes, and metrics for describing the level of risk and degree of improvement achieved by a risk reduction strategy.

HVAC and Airborne Infectious Diseases

Concern regarding the risk of airborne infectious disease transmission indoors is increasing. HVAC designers and building operators need to understand how infectious diseases are transmitted, how HVAC system characteristics affect probability of infection, and what HVAC-based infection risk mitigation measures are available. These topics are presented and discussed using a variety of ASHRAE resources including position documents, standards, and best practices guidance. Pertinent results from research on transmission and control are summarized. General recommendations for reducing risk are provided and key knowledge gaps are identified.

Rewards and Risks of Smart Systems - Are We Smart Enough for a Smart World?
The picture of the future painted in research papers and popular media is of a highly connected world in which information is shared and used to make optimal control decisions from the scale of individual devices to building systems, communities, and power grids, generically referred to as “smart”. This Internet of Things – devices capable of communicating with one another and participating in transactions to optimize utilization of energy and other resources is already on the shelf in the form of smart thermostats, lighting controls, home security systems, personal fitness monitors and others - and major efforts to develop the means to manage smart infrastructure are developing. This is the promise of smart systems – a world transformed for the better to an extent comparable to the difference between the pre and post Internet cyber world. However, there are major obstacles to be overcome in the march towards realizing this vision, including issues of standardization, reliability, security, and privacy. Some are fundamentally technical issues, while others raise deep questions about the nature of civilization in the future. The mere existence of highly connected systems creates the possibility for failure modes and vulnerability to malicious attacks on a scale not previously experienced. Privacy, already eroded by the development of the Internet, may be further diminished when even more aspects of individual behavior may be obtained and used by others. This presentation will present both sides of the expected smart new world – the potential benefits as well as the risks, with particular emphasis on systems that relate to control of indoor environment and building energy use.
Embracing Uncertainty
The widely repeated adage that “the only certain things in life are death and taxes” suggest a popular awareness of the uncertain nature of our world. However, in both personal and professional life, uncertainty is ignored or poorly understood, almost always with adverse consequences. In some cases, conclusions based on very limited and uncertain data or analysis are accepted uncritically, as in the case of the parade of science-based nutrition fads that come and go. In others, the sowing of doubt with conflicting or confounding findings can delay action unnecessarily for years, as exemplified by the drawn out debate over the health effects of smoking. A third class of problems results from treatment of processes involving significant uncertainty as if they were deterministic, for example, life cycle cost projections. All of these pathologies manifest themselves in the design, construction, and operation of buildings as well as in the development of related policy and standards. The results are waste, unmet expectations, unhappy occupants, and in some cases, health and safety impacts. In this presentation, examples of faulty decision making associated with misunderstood uncertainty are discussed and a case is made for a greater emphasis on characterizing uncertainty in building research and the use of statistical methods in building design.
Engineering Controls for Airborne Infection Transmission – Technologies and Application Issues
This presentation considers issues related to use of engineering controls for airborne infection transmission. Available and emerging technologies are discussed, including ventilation, mechanical filtration, germicidal ultraviolet light, and others. An approach to application based on equivalent clean air delivery rate is proposed. Factors impacting application, including building and HVAC system type, cost and energy use will be addressed. Recent research on emerging technologies and remaining knowledge gaps will be summarized.
Understanding and Applying ASHRAE’s Core Recommendations for Mitigating Aerosol Infection Risk
The key elements of ASHRAE’s COVID-19 risk mitigation guidance are summarized in its Core Recommendations. The Core Recommendations outline an approach to risk mitigation using engineering controls that is effective, flexible, and sustainable that is also applicable to other airborne diseases. This presentation provides an overview of the Core Recommendations, including the rationale for each, and summarizes ASHRAE’s Building Readiness guidance, which was developed to support their implementation.
ASHRAE Standard 241-Control of Infectious Aerosols
ASHRAE, through its Epidemic Task Force, provided timely leadership in responding to the COVID19 pandemic from March 2020 through June 2022. At the request of the White House, ASHRAE undertook its own project Warp Speed to build on that expertise for the future. In December 2022, the ASHRAE Board committed to quickly writing a standard to make buildings more resilient against infectious aerosols ahead of the next epidemic. In only four months the project committee created and won approval for ASHRAE Standard 241-2023. In this Lecture a member of the 241 project committee will provide a summary of the standard including its purpose, scope, and key requirements with supporting background.