Tom Bassett-Dilley reflects on his 2025 PhiusCon opening keynote — how TBDA’s growth paralleled Phius’s evolution, and where high-performance design goes next.

I was honored to be asked to kick off 2025 PhiusCon with the opening plenary keynote. After I accepted the task, I swallowed hard and had that thought I’m sure many in similar positions have had, like what the heck am I going to say that’s important, interesting, or engaging enough?! After some soul-searching I realized that while just talking about me or TBDA wasn’t enough, the fact that our growth as a firm has paralleled the amazing growth and development of Phius, and that in fact we’ve fed off of each other, is a good story.

Once Upon a Time

My dad was a biochemist studying photosynthesis (the OG solar power). What I realized after watching 40+ years of his research work was that individual scientists are like cells in the big organism of knowledge–their discoveries build on the work that preceded them, and most of them make contributions whose significance will only become clear in hindsight. What makes their work meaningful is not the assessment of significance, but the collective pursuit of knowledge.

Figure 1. Diagrammatic representation of a plant cell. From Plant Physiology, by L. Taiz and E. Zeiger, Sinauer Associates Inc. Copyright by Sinauer Associates.

This parallels what my colleagues and I in the high-performance world of building are doing, each of us figuring out what it means to take conservation-based design seriously in our climate and culture. The Phius keynote was a chance for me to step back and look at the progress we’ve all made, and it felt like a full-circle moment.

Figuring Out Phius

When I first became aware of contemporary Passive design in 2010, it was apparent that attention to air barrier design, insulation continuity, window quality, and proper ventilation needed to be much more rigorous than I realized–they needed to be brought to the fore in design. Shortly thereafter I took Phius training, saw early inspiring projects by GoLogic and Katrin Klingenberg, and soon got my first Phius certified project, an ICF house in River Forest, IL. The hunger for knowledge about these projects brought hundreds of people to our jobsite tours, Phius Alliance meetings, and the GreenBuilt Home Tour, put on by Illinois Green Alliance. We were the early pioneers in metro Chicago, with the region’s first projects certified in 2013, 2015, and 2016, with many more following after. We took the solutions, successes, and challenges to Phius Conferences each year to share in the wonderfully open-source environment that is passive design and building in the US.

Phius develops

About the time we were hitting our stride with passive building design and certification, a big change came as Phius broke with PHI (the German originator of the Passivhaus standard); their objective was to better address the climate- and building culture-specific issues present in the US. In doing so, Phius evolved the standard to be based on the climate specific to each project. Seems obvious, but apparently Germany’s system, geared for Europe’s continental climate, wasn’t interested in expanding to cover the diversity of the US. But now, from Key West to Tucson to Fairbanks, the Phius standard covers a nearly global range of climate conditions, so designers could figure out the best strategy for their particular climate. Continuing this brilliant thinking, they also continue to evolve the Phius standard metrics to take into account the role of renewable energy (rooftop solar especially) and lessons learned from implementation in various climates. We found that our projects became easier to certify in this difficult Chicago climate, with better “tuning” to the climate through glazing, orientation, and shading.

The Ripple Effect

The “Phius effect” meant that we couldn’t go back to designing buildings with leaky, minimally insulated buildings–knowledge is power, and it also brings responsibility. Over the years we’ve had many non-Phius projects that may have been certified as LEED or Zero Energy Ready Home, but didn’t pursue Phius, but since CPHC training, all of these projects benefited from our knowledge of passive design. This has had a great ripple effect throughout the industry: beyond how firms like TBDA have leveled up, previously obscure terms and concepts like air barrier continuity, continuous insulation, energy recovery ventilation, and thermal bridging became commonly heard in seminars, online articles, and building industry publications. Yes, advancement is possible, and is happening! 

What about existing buildings?

Retrofitting existing buildings for modern use and aesthetics is an important part of maintaining our built environment. Importantly, retrofits allow us to incorporate energy efficiency, improved air quality, and resilience while modernizing the design and maintaining the huge amounts of embodied energy and cultural significance of existing buildings. Instead of spending energy tearing the old down and using new materials (which are often less durable than historic materials), we can bring old buildings up to modern standards. Our Fair Oaks house, Phius Zero Historic retrofit, and Carroll Center are a few examples of this approach from our portfolio.

Where do we go from here?

Most of us in the sustainable design and construction world recognize that we have created many solutions to reducing or eliminating net operational energy from buildings–we have designed numerous annual net zero projects even here in our challenging Chicago climate. Our next frontier is reducing the embodied energy from buildings. Straw, hemp, cork, wood fiber and structure, and clay-based finishes are some of the materials getting attention for their ability to lock up carbon for their life spans. Our goal is to design buildings that store more carbon than they use; we haven’t been able to do it yet due to concrete and glass, but we’re making progress.

We’re all part of this

In closing, I reminded the Phius audience that all of us in that room, all of us in the industry are like cells in the big organism that is working for a built environment in harmony with nature. Here we are in the Summer of 2026 with massive wildfires in France and Spain and Canada, and we know we have to keep accelerating progress. Like the research scientists, we don’t necessarily understand how our work may have an impact, but what’s important is that we move in the direction we believe is best. Against the headwinds of greed and political idiocy we’re currently witnessing in the US, we do our best and let time and chance play their parts.