Phius Certification Manager Al Mitchell utilizes energy modeling tools to examine the future of building construction through the lens of passive building.
For those of you who have talked to me, you may know that I have been working through graduate school part time while working at Phius full time. I started both work and school during the COVID-19 pandemic, and when my wife Anna would come home after work I would just brain-dump on her.
I sought further schooling to give myself a social setting to discuss all of my building science research ideas with like-minded colleagues, and to further develop the skills necessary to push the envelope (pun intended) in research into passive buildings. With the birth of my son this past January, I took advantage of paternal leave to spend time and grow with my family, and to wrap up my dissertation. This month I am sending out my dissertation book for signatures from my committee, and the transition away from late nights working on school after work has left my mind swirling; where are we headed now?
When people ask me “what do you do for work” I usually answer with “energy modeling,” but further development from research at school and growth at Phius has changed that answer to “I am a building scientist.” Energy modeling, or as I prefer to call it now “building performance simulation,” is just a vehicle for me to test and explore ideas without the added cost and time delay of building and monitoring a building to know if the idea truly works. The technical validation and backup to our claims are critical to the success of Phius and the promulgation of passive building.
If you have seen a Phius 101 presentation or gone through training in the last few years, you have likely seen the above slide. When I have led these presentations in the past, I have mistakenly called these “secondary” or “tertiary” benefits of passive building, but after further research, I think these are truly the primary benefits of what we do here at Phius. The new-ish Phius REVIVE 2024 protocol is driven by these benefits first, with energy savings and carbon emission reduction as the secondary benefits, and I think this is the right framing of passive building in general.
As we look toward the future, the changing environment and long-term resilience and durability become more critical for us to consider.
To demonstrate this need, I took the Pacific Northwest National Laboratory (PNNL) single-family prototype home, a 2,100 sf, 3-bed, 2-story home designed to represent the generalized geometry of American single-family homes1, and evaluated for long-term performance.
I utilized REVIVEcalc v24.3.0, and ran a batch of simulations based on actual weather data from 2000 through 2024, and then Representative Concentration Pathway (RCP) 4.5 future projections from the future climate model from Argonne National Laboratory (ANL). Unlike previously available future projections in which typical weather conditions have been shifted up based on IPCC reports, these future projections come from a physics-based model with weather data for years 2045-2054 and 2085-20942. To me, these files represent the best future projection freely available for building performance simulation.
With identical mechanical systems, ERV and heat pump, we see an average EUI of 14.8 kBtu/sf yr for the Phius version of the home, and 23.0 kBtu/sf yr for the IECC 2021 case. This represents a 35.3% drop in annual energy consumption. More importantly, the standard deviation of the Phius home EUIs is 0.627, while the IECC 2021 home is 3.46. This means the Phius home is less sensitive to variability in the climate, with the super insulated and airtight envelope decoupling the building from the exterior environment. Long-term energy use is more predictable and consistent year over year ensuring the long term affordability as mentioned. The above graph shows this with the stable consumption of the blue Phius line, while the orange IECC 2021 line varies drastically over time.
From the resilience perspective, the results are more alarming. The warming of the climate still maintains a cold snap period in the ANL climate model, but the overheating risk becomes more prevalent over time.
The statistics on the weather data at the end of the century show my beloved 5A Chicago shifting towards 3B, where the summer survivability becomes more significant. Using REVIVEcalc, I simulated a summertime outage during the statistical extreme week (no morphing on the weather data as these are actual weather files, not the typical meteorological year (TMY) data currently used in the REVIVE protocol).
The above graph shows the comparison of hours in the danger or extreme danger ranges of the National Oceanic and Atmospheric Administration (NOAA) heat index metric3. The IECC cases all have significant hours with heat index in Danger during the extreme week of past weather years, while the Phius cases show less overheating risk. The latter half of the century in the future climate models show the first significant increase in danger hours in the Phius homes, so there is more research to be done on optimizing our passive measures for this risk.
So where is this all headed? I firmly believe that the most sustainable buildings we can construct today are passive buildings. This is not just the nature of my employment – the data supports it. When we move away from the focus on simply just energy savings, the other benefits of passive buildings can help make our case for building better, while still resulting in the energy and carbon savings we are hoping for.
We at Phius are committed to continuing on in this research, developing better guidance and tools for practitioners everywhere to build better. I personally hope to continue to be around to push the built environment along for the betterment of everyone.
As a note on the future of what we are up to a Phius, we have an R&D hootenany at Phius Con in Milwaukee this October, scheduled for the end of the conference, bring all your great ideas and be heard.
