In Part I of PHistory, we looked at the development of passive house’s foundation principles in North America, tracing back to work done in the 1970s and 1980s. The future for passive building was bright back then, but in the United States, conservation and energy issues were put on the back burner.
In the early 90s, physicist Wolfgang Feist picked up where the North Americans left off and continued research and development in Europe. He built on the work of Shurcliff and others to further codify the influence of highly improved envelope components on the minimization of the heat load in low energy buildings for his research project in Kranichstein, Germany. He then set out to make the case to the German scientific community and to the government that these principles could achieve much greater energy reductions than the low-energy homes (approx. 22 kBTU/sqft yr [70 kWh/sqm yr]) being promoted at the time.
Feist’s research facilitated many of the critical improvements predicted by Shurcliff: triple pane window with gas fillings, thermally broken spacers and frames, highly efficient heat exchangers, compact space conditioning systems and smart vapor retarders are among the most significant ones. Such improved passive house components soon became available on the European market at reasonable costs.
When Feist applied these principles and improved technologies in Germany in the 90s he also applied the very similar guiding energy metrics and boundary conditions defined earlier in the USA. He went on to apply the passive house boundary conditions to a swiss energy balancing model which resulted in the development of the PHPP – the first simplified static spreadsheet-based energy calculator and design tool for passive houses. He found that designing a building in the Central European climate to meet the 1W/sqft peak load resulted in an approximate annual heating demand of 15 kWh/sqm yr (4.75 kBTU/sqm yr), slightly lower than Shurcliff’s 15% limit for the annual heating demand in cold climates. That figure became the defining energy metric for the standard. The metric quickly became successful across Europe and is now considered by many to be the world’s leading standard in energy efficient construction today.
I became aware of the European flavor of passivhaus in 1993 while studying architecture at the Technische Universitaet of Berlin. I eventually landed in the United States to study for my Masters of architecture at Ball State. After some time in the United States—and taking heed of the growing science around climate change—I was motivated to test the principles here in the States. In 2002, I broke ground on the first home using the European metrics and design tools for passive houses, at that time still only available in the German language .
Smith House—completed in 2003 in Urbana, Ill.—has served its purpose well. It proved that the fundamental principles pioneered in the 1970s and 1980s in North America, and refined in Europe, worked. But not without some great effort and problem solving.
Since then it’s been gratifying to see the rekindled interest in passive building principles back here in North America. Our annual conference has grown from a few dozen committed visionaries to hundreds of building professionals and dozens of exhibitors. We have put passive building back on the map—now recognized by the U.S. DOE via its Challenge Home program and by RESNET via our PHIUS+ Certification program.
Thanks to the visionary—and courageous—pioneers of our day, projects have been completed in all U.S. climates (except the subtropical southern Florida region)
But we think we’re just at the beginning of an explosion in passive building.
The collective experience has shown that—as Shurcliff predicted—the general principles hold true in all climates, but also that the standard as formulated for Europe would benefit from refinement that takes into account the substantial climate zone variation in North America. For example, in very cold climates (Fairbanks, Alaska) home designs tend to require cost prohibitive overinsulation with walls of 3 feet thick, while in the warm regions of California comparatively very little insulation (between 3-5 inches) is required to meet the current standard–actually leaving further, cost-effective efficiency untapped.
This suggests it might be productive to adjust the standard–relaxing it somewhat in the North (as Shurcliff’s original limit already suggests) and tightening it in the South for North America.
For that reason, the PHIUS Technical Committee has begun work on refining the standard for North American climate zones. The committee is drawing on the now substantial body of data drawn from the growing number of finished projects and the growing body of monitored data we’ve accumulated over the past 10 years.
We think that with these tweaks, passive building—after a promising start and a disappointing lull, will fulfill its promise and become the mainstream design and performance market standard in North America.