Ask the Experts: DLR Group’s Nathan Kegel, High Performance Design Leader

In this installment of enVerid’s Ask the Experts blog series, I catch up with Nathan Kegel, High Performance Design Leader at DLR Group. Nathan and his team of “Zero Heroes” won the “Lowdown Showdown” design challenge at ASHRAE’s Building Performance Analysis Conference and Simbuild in September for their design for a new K-5 school in Albuquerque, NM. Their compelling approach has attracted a great deal of attention.

The goal of the design challenge was “to minimize carbon emissions, related to both operation and construction materials, while providing exceptional indoor environmental quality and creating a structure that is both adaptable and durable.”

CW: Nathan, congratulations to your team on winning the ASHRAE “Lowdown Showdown” design challenge. We were glad to see that exceptional indoor air quality was one of the key goals of the design along with an emphasis on reducing the carbon emissions associated with building operation systems. Interestingly, the two goals are often in conflict with each another. Can you walk me through how you approached this design challenge?

NK: The traditional approach to improving indoor air quality (IAQ) is to simply introduce more outdoor air (OA). This can be described as “the solution to pollution is dilution” approach. The challenge with increased OA is an increase in both heating and cooling energy in most climates and building types – and certainly in this school.

The energy and carbon constraints drove us to look for alternate solutions to achieve good IAQ that would also allow us to reduce OA. Improved particle filtration was an obvious need for better IAQ, but standard filters don’t remove gaseous contaminants like volatile organic compounds (VOCs) and therefore cannot be used to reduce OA.

In search of a solution that also addressed gaseous contaminants, the team reached out to enVerid to learn more about its sorbent filtration and for help calculating the reduction in total OA that could be achieved according to ASHRAE’s IAQ Procedure by adding sorbent filtration to the design.

What we found attractive about enVerid’s sorbent filtration is that it uses filtration to remove gaseous contaminants from the airstream without “adding” anything to the air. We also like that performance for all the relevant contaminants has been established according to the ASHRAE 145.2 test procedure.

CW:  You specified a dedicated outside air system (DOAS) with MERV 13 particle filters and enVerid sorbent filters and calculated OA rates using the ASHRAE Standard 62.1-2022 Indoor Air Quality Procedure (IAQP). What did you find attractive about this design from an IAQ and energy use perspective?  

NK: This was this team’s first foray into using the IAQP methodology. We had reduced the energy consumption with passive design strategies (improving the thermal envelope, reducing internal gains from lights and equipment, siting the building to optimize passive solar heating) and needed to continue to reduce the peak heating and cooling load along with heating and cooling energy. Integrating sorbent filtration and using the IAQP to reduce OA was the next place to look.

What we found is that by introducing sorbent filtration with the IAQP, we could reduce OA by 46%, which resulted in an additional 23% energy savings and a 50% reduction in peak heating and cooling loads while delivering the same or better IAQ than if we had used the Ventilation Rate Procedure. We used MERV-13 filters because they achieve really good particulate removal without adding fan energy to the system – which would have increased energy consumption.  Reducing the total OA reduced the size of the PV array needed which helps keep the cost of zero carbon down.

CW: Your design was attentive to climate resilience issues, acknowledging that the school might be used as a community shelter in emergency situations such as wildfires which are occurring more frequently in New Mexico. Can you speak to how this sensitivity informed your design choices? 

NK: One of the unique features of our design is a passive night-flush strategy which allows windows to open during unoccupied hours to let heat passively escape and recharge the thermal mass.  However, when we reviewed the air quality index (AQI) over time, we found there were already significant periods of time where the outdoor air quality might prohibit this night-flush from happening due to poor outdoor air quality, particularly from increasing wildfires which are a primary concern for the region. Growing concerns about outdoor air quality was another reason why having an active air filtration strategy for both particulate and gaseous contaminants was really a necessity to ensure climate resiliency.

CW: enVerid and six other leading IAQ and energy efficiency organizations recently published a white paper on how to achieve sustainable IAQ using a “clean first” approach.  Your design reflects many of the recommendations outlined in the paper. Had you read the paper before you did your design? Do you have any feedback on the “clean first” approach?

NK: We were so excited to see the “Clean First” white paper after we submitted our design because it reinforced the importance of so many of our design choices!  For example, several members of the design team are WELL AP and RESET certified, and so we had applied that knowledge to go beyond the minimum of CO₂ monitoring in this design, which is in line with the recommendations in the paper.

The section of the white paper that we especially like is the section on Step 1: Define IAQ Goals.  There are many ways to measure IAQ, but without defining specific IAQ targets, there is no way to know how well you’re performing. 1,000 PPM CO₂ may be what the sensor records, but is that what you want the sensor to read? The paper does a nice job of discussing the pros and cons of different IAQ metrics and recommends specific metrics and targets for enhanced IAQ.

CW: Thank you, Nathan. We look forward to seeing DLR Group implement key findings from this compelling design into your future projects.

For more on DLR Group’s winning design, review their Summary and Poster.

To read more about how you can employ the 4-step Clean First approach to achieve Sustainable IAQ, read the white paper.