Ask the Experts with Drew Morrison of Slipstream

Published 10/14/2021
By Christian Weeks
enVerid Ask The Expert: Drew Morrison of Slipstream

enVerid Ask The Expert: Drew Morrison of Slipstream

enVerid CEO Christian Weeks catches up with Drew Morrison, energy engineer at Slipstream, in our latest “Ask the Experts” blog.

This 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 more efficiently and cost effectively.

CW:  Drew, it was great to meet up with you in Chicago and learn more about the important work Slipstream is doing. Why don’t you start by telling us about Slipstream and what you do?

Drew Morrison, Slipstream - photo credit Rope Line Media
Drew Morrison, energy engineer, Slipstream – photo credit: Rope Line Media

DMSlipstream is an independent nonprofit organization based in Madison, Wisconsin. Our mission is to accelerate climate solutions for everyone. We look for ways to save energy and reduce GHG emissions. A major focus is ensuring that the benefits of energy savings accrue to all people, including disadvantaged and underserved communities.

I am an energy engineer at Slipstream with a degree in mechanical engineering. One of my roles is to analyze real word applications of innovative technologies to assess how they reduce energy usage.

CW:  We first crossed paths following your independent assessment of an installation of Sorbent Ventilation Technology at 155 North Wacker, an office tower in Chicago. How did you get involved in this project?

DM:  In 2018 ComEd, the utility serving Chicago and much of Northern Illinois, was looking for new ways to improve HVAC energy efficiency in their service territory. ComEd had heard about Sorbent Ventilation Technology and engaged Slipstream to perform an independent assessment of the energy savings and air quality benefits of the systems installed at 155 North Wacker. I was intrigued by the technology from the start because of its potential to save energy and address indoor air quality, and I was lucky to have the opportunity to work on this project with ComEd.

CW: The challenge of achieving good indoor air quality energy efficiently is coming up a lot these days due to COVID-19 and the heighted focus on decarbonizing buildings. Why are goals related to indoor air quality and energy efficiency often at odds with each other?

155 North Wacker Drive, Chicago - photo credit, Rope Line Media
155 North Wacker Drive, Chicago – photo credit: Rope Line Media

DM: Historically, there has been a tug of war between indoor air quality and energy efficiency, and the building world has long considered these objectives to be mutually exclusive. In fact, during the 1970’s to improve energy efficiency, engineers focused on tighter building envelopes and lower ventilation rates. This led to Sick Building Syndrome because high levels of contaminants built up in buildings and negatively impacted occupants’ health.

One of the responses to Sick Building Syndrome was to increase ventilation rates. As the old saying goes, “dilution is the solution to pollution.” But here in Chicago, cooling and dehumidifying hot outside air in the summer and heating cold outside air in the winter to maintain comfort in buildings is very energy intensive.

The other challenge with dilution ventilation is that outside air is not always “fresh”. In fact, Chicago is one of three of the biggest cities in the U.S. that do not meet the WHO’s latest limits for air pollution from fossil fuels. Many national and local studies have highlighted that our outside air contains high levels of pollution from cars, airplanes and increasingly from wildfires, and no amount of exposure to these pollutants is safe. These studies also show that people of color are over three times more likely than white people to be breathing the most polluted air. So, this issue of pollution is a health and equity issue.

CW:  OK, so tell us about your assessment of the project at 155 North Wacker and your findings. Did the project show that we can reduce outside air volumes without negatively impacting indoor air quality?

DM:  Yes, detailed measurement and verification of both energy and IAQ metrics at 155 North Wacker over many months confirmed that sorbent air cleaning can substitute for outdoor air ventilation, leading to energy savings. In fact, we were able to show that offsetting 40% of the outside air requirement with cleaned indoor air allowed for a 25% reduction in peak cooling demand.

155 North Wacker entrance, Chicago - photo credit, Rope Line Media
155 North Wacker – photo credit: Rope Line Media

We also measured indoor air quality (both CO2 and VOCs) to evaluate the impact of replacing 40% of the outside air with cleaned indoor air. IAQ measurements were taken in three office spaces with different occupancy profiles using monitors which trended IAQ data to get a continuous picture of contaminant levels. We also installed a monitor in an outdoor air intake to control for variations in outdoor air contaminant concentrations. In addition, we took spot air quality samples at all three locations to obtain information on levels of specific VOC compounds. The results showed that the sorbent air cleaning technology was able to maintain IAQ levels similar to the before air cleaning scenario even with much lower outside air ventilation.

CW:  That is a pretty good result in terms of energy savings and IAQ. Did you also measure the impact in terms of reducing carbon emissions?

DM:  Our study for ComEd did not calculate greenhouse gas emission reductions from the energy savings, but we have since done the math using the EPA’s Greenhouse Gas Equivalencies Calculator, and the 136,000 kWh of electricity saved on this project is equivalent to eliminating almost 100 metric tons of carbon dioxide equivalent every year, which is the same as eliminating the CO2 emissions from consuming 10,000 gallons of gasoline every year. If we extrapolate this result to the entire Chicago market, the potential reduction of CO2 emissions is the equivalent of eliminating emissions from consuming 24 million gallons of gasoline every year – and that’s just Chicago.

CW:  Impressive. It sounds like we need to get to work deploying this technology in more buildings. Where can people learn more about this project and sorbent air cleaning technology?

DM:  People who want to learn more about sorbent air cleaning technology and the results of our study of the 155 North Wacker project can take a free course we developed called Adsorbent Air Cleaning – A New Way to Think About Ventilation. The course describes sorbent ventilation technology and provides additional details on the results of our study. As an added bonus, the course also qualifies for AIA, GBCI, and WI PE continuing education credits. You can also read about the 155 North Wacker project in Chief Engineer, the official publication of the Chief Engineers Association of Chicagoland (see pg. 38), and in REJournals, which recently published an article called How to keep your building Class A about the project at 155 North Wacker.

CW: Thanks so much Drew for the great conversation and for the work you are doing at Slipstream to advance a carbon-free future.

Learn more about Sorbent Ventilation Technology

Christian Weeks

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