Ask the Experts with TLC Engineering Solutions’ Cory Duggin

The “Ask the Experts” blog series features conversations with mechanical engineers, architects, IAQ authorities and other built environment thought leaders about their first-hand insights into how to deliver better indoor air quality (IAQ) more energy efficiently and cost effectively.

In this installment, I catch up with Cory Duggin, a Principal in the PEAK Institute at TLC Engineering Solutions. Cory is active in USGBC and ASHRAE, and is a member of Consulting-Specifying Engineers Editorial Advisory Board. Cory’s designs are award winning. Most recently, an IAQ and energy adaptive reuse project he helped design for the Southwest Florida Collaboratory earned an Honorable Mention in the ASHRAE 2021 Technology Awards. You can read more about that application here.

In today’s discussion we focus on an innovative design for IAQ and energy savings in a new college dormitory.

CW: Cory, congratulations on a terrific design for the University of Miami Centennial Village dorms, the first dormitory in the U.S. to be registered for both LEED V4 Gold and WELL Version 2 Pilot Gold. Please tell us about the design goals as it relates to IAQ and what shaped them?

CD: The University of Miami really latched onto the concept of high IAQ enhancing the learning/living environment of their students and the downstream benefits this would deliver for the university. The university saw an enhanced IAQ design as a way to reduce stress for students and improve their outcomes. What better way to attract students than by providing an optimal environment in which they could live and learn. Since this is a dorm, we have the ability to affect the quality of a student’s sleeping environment, which directly impacts their cognitive function in the classroom. This resulted in setting a goal for lower than the ASHRAE 62.1 Ventilation Rate Procedure (VRP) design concentration of CO₂ based on the results of the Harvard TH Chan School of Public Health COGfx study, which found participants’ cognitive function test scores doubled in indoor environments with improved indoor environmental quality.

CW: It’s interesting to hear how the University of Miami applied the COGfx study findings to a dormitory setting. Let’s now talk about the energy side of the equation. Cooling large volumes of outside air in steamy Miami is very energy intensive. Was this also a consideration in your design? Were you able to achieve both high IAQ and energy efficiency goals?

CD: We were, but it required some tradeoffs. The traditional method for achieving good air quality in buildings is by providing ventilation, also known as outside air, to dilute the contaminants. To maintain comfortable interior conditions, we have to cool and dehumidify the ventilation air, which is expensive in the tropical South Florida climate. Given the high cost of conditioning ventilation air, over ventilating the building was not found to be a cost-effective way to hit our IAQ goals, so we moved away from the traditional ventilation design approach using the VRP and instead used the ASHRAE 62.1 Indoor Air Quality Procedure (IAQP) to find the right balance between ventilation air and cleaned indoor air using enVerid’s HLR air cleaning modules. This approach allowed us to achieve our enhanced IAQ goals while saving energy by reducing conditioned ventilation air by 25%.

CW: Maintaining low CO₂ concentrations with more cleaned air and less ventilation air is innovative. Please elaborate on how sorbent air cleaning in combination with the IAQP enabled you to achieve an enhanced IAQ design more energy efficiently.

CD: It was really interesting to go through the different possible scenarios of ventilation and number of HLR module combinations. We started with a goal of 600 ppm CO₂ peak, but after using our energy model to quantify the energy cost of this option, we realized how much more ventilation and air cleaning would be required to approach ambient CO₂ levels of ≈400 ppm. So, we analyzed a few scenarios with different ventilation rates and number of air cleaning modules and determined that 750 ppm of CO₂ at peak gave us the most cost-effective solution to hitting our enhanced IAQ goals while still saving energy by cleaning indoor air and reducing ventilation below the ASHRAE 62.1 VRP minimum.

CW: ASHRAE recently published Addendum aa to Standard 62.1, which simplifies the application of the IAQ Procedure. Do you think Addendum aa will help broaden adoption of the IAQ Procedure and encourage more engineers to pursue a sustainable IAQ approach in their building designs?

CD: I was really excited to see ASHRAE publish Addendum aa because it brings clarity to a methodology in ASHRAE 62.1 that has seemed too daunting for some engineers to even attempt. Now it is clear what contaminants have to be included in the calculations and what the minimum design limits should be. Because the VRP is a prescriptive ventilation calculation, most engineers have no idea what the resulting concentration of contaminants will be. Having the contaminant design limits spelled out in an ASHRAE standard sets the bar for minimum air quality, which I hope will lead to more consistency across projects.

CW: Thanks Cory, and congratulations on your design. Sounds like you may have another award winner in the works!

For more information on Addendum aa to ASHRAE Standard 62.1, read our recent blog post.