Ask the Experts with Anil Giri of Global Engineering Solutions: Delivering Superior Indoor Air Quality Energy Efficiently

The “Ask the Experts” 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.

In this installment, I catch up with Anil Giri, director of mechanical engineering at Global Engineering Solutions (GES), a Salas-O’Brien company, to discuss the mechanical design for the new Solomon Solis-Cohen elementary school in Philadelphia, which set out to deliver great indoor air quality (IAQ) energy efficiently.

CW: Anil, thanks for talking with me. Let’s start by discussing the new Solomon Solis-Cohen elementary school project and the goals relating to energy efficiency and IAQ.

AG: Solis-Cohen, which opened in the fall of 2021, is the largest school in Philadelphia serving 1,400 students in a two-story 140,000 ft² building. It is also the first construction project in the district’s $5 billion school revitalization plan, which gave us a great opportunity to establish a blueprint for future new school construction projects in Philadelphia.

For the design, the district wanted to optimize the total lifecycle cost for the school while also maximizing energy efficiency and LEED® points under the Indoor Environmental Quality (IEQ) credit category. The other important goal was to deliver great indoor air quality as this has been shown to improve student test scores

CW: I love talking about projects that have energy efficiency and IAQ goals because traditionally energy efficiency and IAQ have been at odds with each other because we have relied on more outside air to improve IAQ. How did you address this tension on this project?

AG: The Solis-Cohen project is a great example of how IAQ and energy efficiency can go hand in hand.

In most buildings, HVAC consumes roughly 40% of a building’s energy, so reducing ventilation rates is key to improving energy efficiency. Reducing ventilation rates in climates like Philadelphia also helps with humidity control. The key is reducing outside air without negatively impacting indoor air quality or safety. This can be done using direct source control measures such as high efficiency particle filters for PM2.5 and SARS-CoV-2 and sorbent filters for CO₂ generated by people and volatile organic compounds (VOCs) from the space. Using these air cleaning technologies, it is possible to replace a portion of the outside air with cleaned indoor air, which is more energy efficient than relying only on outside air to achieve good IAQ.

CW: OK, so we can achieve good IAQ energy efficiently by substituting some of the outside air with cleaned indoor air. For Solis-Cohen how much outside air were you able to offset with air cleaning?

AG: For Solis-Cohen we were able to go from around 50,000 CFM of outside air using ASHRAE’s Ventilation Rate Procedure and no air cleaning to around 20,000 CFM using the ASHRAE’s IAQ Procedure with air cleaning. This is a 60% reduction in minimum outside air under the code.

CW: A 60% reduction in outside air is very significant. Were you able to translate this into first cost savings and ongoing energy savings?

AG: Yes: because of the reduction in required outside air, we were able to reduce the cooling and heating coil load and the chiller and boiler plant sizes. This downsizing has a ripple effect: because of the lower flow rate for the pumps, we were also able to reduce the pipe size. From the cooling load reductions alone, we realized $135,000 in first cost savings by reducing 180 tons of peak cooling load.

We were also able to save first costs by eliminating the need for energy recovery. Depending on the exact system size, energy recovery systems are generally required when your outside airflow is greater than 30% of the total supply airflow. Since we were able to reduce outside air to 10-20%% of the total supply airflow, energy recovery was no longer needed, which led to additional first cost savings.

CW: And what about ongoing energy savings?

AG: Reducing the outside air requirement by 60% did also deliver ongoing energy saving and helped us earn more LEED points.

Our IAQ Procedure design is expected to reduce annual energy use by 241,422 kWh, which will save the district over $725,000 in utility costs over 20 years. This design also helped us earn additional LEED points in the Energy and Atmosphere credit area and by applying LEED pilot credit EQpc124, which can be used to earn up to 7 points for doing an IAQ Procedure design.

CW: OK, so your IAQ Procedure design resulted in first cost savings and ongoing energy savings and more LEED points. And you were able to do all this without negatively impacting IAQ?

AG: That’s right. Using enVerid’s Sorbent Ventilation Technology we were able to replace increased outdoor air with cleaned indoor air. This is because the Sorbent Ventilation Technology is capturing all the gaseous contaminants including CO₂ and VOCs that would otherwise have needed to be addressed with more energy intensive dilution ventilation.

CW: And in your design you are using particle filters for COVID-19, correct?

AG: We designed Solis-Cohen before the COVID-19 pandemic, but it was designed with high MERV filters for particles, so it was future-proofed for COVID-19.

The latest ASHRAE Core Recommendations for COVID-19 are based on the concept that ventilation, filtration, and air cleaners can be used flexibly to achieve exposure reduction goals subject to constraints that may include comfort, energy use, and costs.

For ventilation, the Core Recommendations say to provide at least required minimum outdoor airflow rates for ventilation as specified by applicable codes and standards, use combinations of filters and air cleaners that achieve MERV 13 or better levels of performance for recirculated air, and deploy control options, including standalone filters and air cleaners, that provide desired exposure reduction while minimizing associated energy penalties.

This is exactly what we designed for Solis-Cohen even before we knew about the pandemic using the IAQ Procedure for code minimum ventilation, MERV 13 filters for particles, and sorbent filters for gaseous contaminants.

CW: Not surprisingly, you were ahead of the curve. Nicely done.

Last question: Solis-Cohen was one of your first projects using the IAQ Procedure with Sorbent Ventilation Technology to improve energy efficiency and IAQ cost effectively and to increase LEED points. Will you use this approach again for future projects?

AG: For sure. In fact, we recently finished designing another new middle school using the same approach and we are now working on an outdoor education center where we are also using the approach we developed for Solis-Cohen. We are incorporating the Solis-Cohen design approach for energy efficiency and IAQ on numerous projects as we speak.

CW: Thank you, Anil, for making time to have this conversation with me.

To learn more about this project, read our Solomon Solis-Cohen case study.