The Quintessential Passive House

Sunken Yaodong village in the Chinese Loess Plateau

I recently went through Passive House training with the Passive House Institute US (PHIUS). Passive House is an excellent, superb, and really very good standard for building. If you aren't familiar, it's a method of design that creates a super efficient building, so efficient in fact that in certain climates, no active heating or cooling may be required at all to maintain comfortable indoor conditions. How is this possible, you ask? Through a series of simple and well-considered principles of design, listed here in no particular order:

• superinsulation

• airtightness

• high-performance glazing

• shading and daylighting

• thermal-bridge-free detailing

• balanced ventilation & heat recovery

As the name implies, nearly all of these are passive strategies, a favorite among builders of all cultures for most of human history. In other words, it's getting back to the good ol' basics of environmental control. It's efficient, it's resilient, it's affordable, and it's feasible. What's not to like?

Alas, when it comes to criticism, my past self always has something to say. During my college years, I recall harboring a mild suspicion for Passive House. I believe this is because I developed a strong aversion to a different building certification, the LEED rating system, which I despise to this day*. To my undergraduate brain, Passive House fell into the same category of rating system that sacrifices 'design' for 'metrics'. Somehow, these had always been two forces at odds with one another throughout my education. There never seemed to be a way to bridge the chasm between the technical data of my building science courses and the intuitive design process of the studio. They simply had nothing to say to each other. When a building science professor would bring up insulation R-values during a review, I would suppress a scoff. When a studio instructor would suggest showing mechanical ducts, I would internally roll my eyes. "Let's stop wasting time and get back to the real stuff," I would think to myself.

Reflecting on those times now, I see that there was indeed a missing link in the curriculum that failed to string together these two worlds**, however there was nevertheless profound truth in what was being said—I was simply too young, too arrogant, and too inexperienced to hear it. As a result I did not begin to really appreciate building performance issues until I had worked a while in professional practice, and later again during my passive house training.

As noted earlier, the passive strategies embodied in passive house design were first employed by local builders of the past. Without question, vernacular buildings are the original passive houses. I highly recommend the book Architecture without Architects by Bernard Rudofsky, it's essentially a picture book with captions documenting the amazing myriad of forms expressed in the vernacular all around the world.

Vernacular architecture does exactly what we have collectively forgotten how to do in the last few centuries—making high performance architecture on a modest budget (and no electricity!). The vernacular embodies the virtues of passive design out of necessity—a poor farming family did what they could with what was within reach. Not only do vernacular buildings passively manage light, heat, moisture, and air, they also use locally sourced, low or negative-carbon materials, employ skilled craftsmanship, perpetuate generational construction knowledge, make use of localized supply chains, and support local economies. Basically, all of the 'radical' sustainability ideas that have been gaining traction in recent years within the architecture establishment were no-brainers back in the day because regardless of whether or not you had a brain that thought otherwise, it was the only option.

Today we look at vernacular buildings and say, "what a lovely and quaint place! Why can't we make buildings like this anymore!" when in truth the architecture was generated not so much from a conscious decision to create a preconceived form (as we understand architecture now) as from a place of functional and logistical necessity. And now we find ourselves stuck with a different set of logistics, one which prioritizes economies of scale, global supply chains, and image marketability. I don't mean to suggest that there is no artistry in the vernacular, of course there is abundant artistry involved, as a brief perusal of Rudofsky's book would make abundantly clear. It is, however, a different kind of artistry - one carefully tuned over generations, rather than eureka'd one night in a bathtub.

Though the industry may move toward more passive and low-carbon strategies, there are aspects of the vernacular process that we politely ignore because the implications are too offensive to consider. Local supply chains are great until you visit the produce aisle in the dead of winter, for example. And local materials are great until your artistic vision is squashed because the only cladding material available for 100 miles is yellow brick. In truth, I'm not convinced a piecemeal approach to sustainability can get us there - I think there will need to be significant shifts in how we approach design, even before pencil is put to paper (or cursor to screen ?), but my intuition says there is untapped wisdom yet in the vernacular. When it comes to arriving back at the source of passive design, we still have a long way to go.

Footnotes:

*My biggest issue with LEED is that the award is based on simulated building performance and not on measured post-occupancy data—a building may simulate well under ideal conditions, but if the detailing and construction quality are less than ideal the actual energy performance can be quite poor, in particular due to poor air sealing of the building envelope. This is why Passive House requires blower door testing, to measure the actual built airtightness of the enclosure. Few people are aware that airtightness can make a huge difference in a building's energy performance, and can also have profound impacts on building durability in terms of moisture control (humidity issues, condensation, mold, rot).

**We of course did not hear much of anything in school about Louis Kahn's obsession with integrating mechanical systems into his buildings—Salk Institute, Kimbell Art Museum, and the Yale Art Gallery being just a few examples where the architectural form was significantly influenced (dare I say ..driven?) by the mechanical ventilation strategy for the spaces. A good architect makes systems disappear, a great architect finds opportunity in them. It took me a long time to recognize the fact that architecture that engages MEP as a design problem does not have to resemble the Pompidou Center. Perhaps I will return to this issue in a later post.