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 four of a five-part series.

…continued from part three.

This is part four of a five-part series. Image by <a href="https://www.freepik.com/free-photo/3d-rendering-ventilation-system_22894116.htm#query=ventilation&position=1&from_view=search&track=sph&uuid=8f99f303-f3b1-4c76-a3aa-446576ca6f16">Freepik</a>

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

Balancing energy efficiency and indoor air quality

The duo echoes the sentiment that energy efficiency and indoor air quality are not inherently conflicting priorities. They advocate for a dynamic approach that responds to real-time conditions, promoting the idea that energy efficiency and optimal indoor air quality can be allies rather than adversaries. The conversation underscores the need for operational flexibility and adaptive controls to achieve the delicate balance between energy efficiency and ventilation effectiveness.

The dialogue shifts to the critical role of building controls in ensuring optimal system functionality. Andy reflects on his experiences in the ‘80s, where manual controls, including an outdoor air intake knob, were prevalent. The conversation highlights the evolution of controls from manual to digital, underscoring the ongoing importance of human interaction in maintaining these systems. McNulty and Persily explore the challenges of highly advanced control schemes and emphasise the significance of simplicity and reliability, especially in the context of long-term building sustainability.

The conversation takes a turn as CO2 sensors become the focal point. Persily emphasises that CO2 sensors are tools and must be used with a nuanced understanding of their limitations. He refers to a paper he wrote in 1997 that aimed to clarify the interpretation of CO2 readings in indoor spaces. As consumer-grade sensors become more prevalent, McNulty and Persily discuss the potential for misinterpretations and the need for education on proper usage. They touch upon factors like the proximity of the sensor to exhaled air and the importance of comparing readings to meaningful benchmarks.

Navigating CO2 calculations with ease

McNulty applauds the convenience of a CO2 calculator that handles complex calculations effortlessly. Persily shares his past struggles attempting manual calculations, emphasising the importance of tools that provide not only steady-state results but also dynamic insights over time. The conversation highlights the significance of understanding occupancy patterns and timing, crucial for accurate interpretations of CO2 readings in diverse spaces.

The discussion takes a turn toward the seasonal variations in ventilation requirements. The duo underscores the importance of not fixating solely on minimum ventilation rates but considering dynamic conditions throughout the year. CO2 sensors enter the spotlight as they delve into the misconceptions associated with readings and the need for education on proper usage.

The conversation shifts gears to the post-construction phase, where buildings often face neglect once the keys are turned over. McNulty sheds light on the challenges faced by building operators, highlighting the lack of regulations and the myriad of issues demanding their attention. The dialogue touches on the importance of raising awareness among building owners about the correlation between good indoor air quality and occupant satisfaction.

McNulty tackles the question of existing buildings, shedding light on the regulatory gaps and the limited attention given post-construction. Persily emphasises the technical feasibility of fixing buildings and shares insights into ongoing efforts to integrate ventilation assessments into building performance standards. The conversation offers a glimpse of hope, suggesting that a majority of existing buildings can be improved with strategic, cost-effective measures.

The discussion concludes by acknowledging the often-overlooked role of building operators. They share anecdotes about conscientious operators who strive to maintain optimal indoor conditions. The dialogue underscores the importance of recognising their expertise and the need for focused attention on indoor air quality issues.

Building insights from the ground up

The conversation continues with a simple yet profound truth: studying blueprints and conducting simulations can only reveal so much. The real treasure trove of information lies in direct communication with the people within the building—be it occupants or operators. Persily shares an anecdote from an ’80s-era building plagued by a mysterious issue. The resolution only came when, due to a schedule change, the night-time operator filled in during the day, revealing a hidden routine that no one on the day shift knew about.

McNulty and Persily reminisce about their experiences navigating the complex terrain of building interiors. From gaining access with a coveted master key to the perils of reaching into suspended ceilings, they highlight the importance of hands-on exploration. The anecdote about finding a doughnut box above a suspended ceiling adds a touch of humour to the challenges faced by those dedicated to solving building mysteries.

Continued in part five…


Live webinar on ASHRAE website.