A recent episode of the ASHRAE podcast titled ‘Ventilation in Theory vs. Ventilation in Practice’, featured ASHRAE members Megan McNulty and Andy Persily – two seasoned professionals in the field of mechanical engineering and ventilation. This is part one of a five-part series.

This is part one of a five-part series. Image supplied by <a href="https://www.freepik.com/free-photo/close-up-ventilation-system_25777536.htm#query=ventilation&position=13&from_view=search&track=sph&uuid=728f04f6-64c2-46b6-a334-11bb34483814">Freepik</a>

This is part one of a five-part series. Image supplied by Freepik

The panellists engaged in a conversation that delved into the world of building airflow, airtightness, and indoor air quality. With decades of combined experience, they shared their personal journeys into the realm of ventilation, shedding light on the challenges and misconceptions surrounding ASHRAE standards.

The conversation kicks off with Persily, a mechanical engineer at the National Institute of Standards and Technology for over four decades, recounting his entry into the world of ventilation. Initially focused on measuring building airtightness and infiltration rates, Persily’s trajectory took an unexpected turn when he discovered discrepancies between measured ventilation rates and design values. This revelation sparked his deep dive into ventilation, a journey that would eventually lead him to become a recognised expert in the field.

McNulty, an engineer, shared her own path into ventilation during her early career. Assigned to support LEED certifications for existing buildings, she found herself grappling with the challenge of applying ASHRAE standard 62.1 to buildings with complex histories and configurations. Her interest in understanding the trends and history of ventilation was piqued, leading her to McNulty’s research on the evolution of ASHRAE standards.

Exploring the history and evolution of ASHRAE Standard 62.1

The conversation takes a historical turn as McNulty prompts Persily to share insights into the origins of ASHRAE standard 62.1. Persily provides a condensed history, referencing a recent ASHRAE journal column that touches on the controversy surrounding the 1989 publication of the standard. The committee formed in 1992, in which he served, faced the task of determining appropriate ventilation rates.

With a wealth of scientific research dating back to the 1930s, the committee examined studies on how people perceive body odour in different spaces based on ventilation rates. Drawing on a variety of research, including studies in offices and chambers, the committee engaged in extensive debates to establish the table of ventilation rates present in the standard today. Notably, the rates cover a diverse range of space types, from offices to schools and conference rooms.

Dispelling misconceptions

Persily emphasises that despite misconceptions, health considerations were a primary focus during the standard-setting process. The committee even debated the amount of air necessary to control airborne infectious disease transmission, highlighting the thorough and comprehensive approach taken in developing the ventilation rates.

As Persily recounts the history of his involvement with ASHRAE standards, he shares a humorous anecdote about the dynamics of leadership within the committee. Steve Taylor, a friend and colleague, found himself unexpectedly appointed as chair. In a twist of fate, Taylor approached Persily before a meeting, revealing that he had been tasked with selecting a vice-chair. Persily, perhaps unknowingly, agreed to take on the role. Little did he and Taylor realise that this decision would later lead to Persily assuming the position of chair, marking the unpredictable nature of volunteer commitments within professional organisations.

Continued in part two…


Live webinar on ASHRAE website.