10th Annual NAPHC – best party of the year, maybe ever…

Wow – was that a successful conference! It has been a week and I am still processing it all. Chicago was unlike any other conference — things did not slow down in the office after it was all over, they rather accelerated. It indeed appears we have reached a tipping point.

From more than one person I heard that it seemed that the quality of work, detailing expertise and technical knowledge, size of projects and complexity of building types had reached a new high. And, compared to the early years, we were not just talking theory and intentions—but what people had done! Really impressive.

LEFT: Dr. Hartwig Künzel giving the Day 2 Keynote -- RIGHT: Sebastian Moreno-Vacca participating in the Architects' Hootenanny (L-R: T.McDonlad, T.Smith, J.Moskovitz, Sebastian, ?)

LEFT: Dr. Hartwig Künzel giving the Day 2 Keynote — RIGHT: Sebastian Moreno-Vacca participating in the Architects’ Hootenanny including (l-r): T.McDonald, T.Smith, J.Moskovitz, Sebastian, C.Hawbecker)

New modeling tools such as WUFI Passive (Technical keynote Hartwig Künzel, day two) are making building science interrelationships more visible and intuitively understandable. WUFI Passive is enabling CPHCs to optimize designs using “hygrothermal mass” (ever heard of that?) to optimize humidity loads and even to inform design decisions overall (as Sebastian Moreno-Vacca illustrated in his session) to create a unique architectural language! How cool is that! Science, heat fluxes and thermal dynamics begin to shape architectural form.

Dirk Lohan, Principal, Lohan Anderson -- Welcomes conference attendees to Chicago

Dirk Lohan, Principal, Lohan Anderson — Welcomes conference attendees to Chicago

Dirk Lohan—Mies Vander Rohe’s grandson, and an extremely accomplished architect in his own right—hinted at this development during his welcoming remarks.

“I believe that we will begin to see as beautiful what also is energy-conscious,” said Lohan.

Supported by the John D. and Catherine T. MacArthur Foundation

But maybe the most significant news is the explosive development in the multifamily affordable housing sector. It is seeing significant growth, interest and pilot developments going up in many places of the country. Thanks to the support from the John D. and Catherine T. MacArthur Foundation, we were able to make this our core topic for the conference and will be able to actively provide support to the affordable development community.

The pre-conference sessions included a daylong affordable housing Hootenanny that brought together successful affordable, multifamily housing project teams together who generously shared lessons learned and experience. Four different project teams presented during an intense full day. The morning and afternoon presentations drew full rooms of affordable housing developers who soaked up the information and had terrific, incisive questions

The same teams presented again during the core conference breakouts in a more condensed form for those who were unable to attend the hootenanny. In addition, there were more presentations on even bigger size affordable projects in progress:

  • A 101 unit affordable development in New York now under construction in the Rockaways (Steve Bluestone, Bluestone Org.)
  • A planned affordable retrofit of a 24 story historical brick building in Chicago (Doug Farr, Tony Holub from Farr and Assoc.), the Lawson House.
  • 24 story residence hall under construction in NYC (Matt Herman, BuroHappold)
L-R: Steve Bluestone presenting with Lisa White, Doug Farr, Matthew Herman

L-R: Steve Bluestone presenting with Lisa White, Doug Farr, Matthew Herman

Really amazing stuff.

Katherine Swenson

Katherine Swenson, Vice President, National Design Initiatives for Enterprise Community Partners — Day 1 Opening Keynote

Of course this growth has been fueled by forward-looking programs that recognize that energy efficient homes make so much sense for affordable housing developers/owners and dwellers. Katie Swenson from the Enterprise Foundation was a breath of fresh air–dynamic, positive, and motivating opening keynote. She explained that in her and her organization’s eyes energy is a critical part in assuring not just housing for people—but healthy housing! “Health is the new green,” she said, and of course passive housing delivers here with excellent comfort, indoor air quality and the added bonus of resiliency when the power goes out. Katie announced that the Green Communities criteria had just included PHIUS+ 2015 certification as one of the highest energy point options.

Other affordable housing agencies also have made a move: the Pennsylvania Housing Finance Agency (PHFA) awarded bonus points in its last round of selecting projects for Low Income Housing Tax Credits. More recently the New York State Homes & Community Renewal (HCR) effort was mentioned in a release regarding energy efficiency measures from the White House. Those agencies now directly encourage passive building standards in their RFPs. Remarkable!

Sam Rashkin, U.S. D.O.E. -- Closing Plenary Keynote

Sam Rashkin, U.S. D.O.E. — Closing Plenary Keynote

On the other coast. Seattle just amended their multifamily building code to allow additional floor area ration (FAR) for projects that meet the PHIUS+ 2015 criteria. That’s a significant incentive for developers.

Things are cookin’!

The core conference, as usual, was chock full of goodness. There were examples of how the new PHIUS+ 2015 climate specific passive building standards helped to optimize costs both here in North America (presentations by Chicago’s Tom Bassett-Dilley, Dan Whitmore, and) and internationally (Günther Gantolier from Italy). There were nuts-and-bolts presentations on wall assembly solutions (Tom Bassett-Dilley again), air and water barrier best practices (Marcus and Keith). And, the Builders Hootenanny—led by Hammer & Hand’s Sam Hagerman, focused on component challenges such as sourcing airtight FDA approved doors for commercial construction.

The U.S. DOE’s Sam Rashkin closed the conference with an unexpected message: he suggested that we needed to rename a few things to facilitate behavioral change. He posited that ZERH, LEED, PHIUS and other green building programs are essentially fossil fuel use rehab centers trying to rehabilitate an addicted nation and to show how it can be done differently. He received a standing ovation.

A few more comments on pre-conference workshops – three WUFI Passive classes drew almost 80 people and they all were super happy throughout the two days! Who would have thought! Happy people energy modeling!

LEFT: Marc Rosenbaum's lecture on Renewables -- RIGHT: Joe Lstiburek on Multifamily Building Science & HVAC

LEFT: Marc Rosenbaum’s lecture on Renewables — RIGHT: Joe Lstiburek on Multifamily Building Science & HVAC

Marc Rosenbaum single-handedly won first place in registering the most people for his class to connect passive principles with renewables to get to positive energy buildings (the logical next step).

Joe Lstiburek placed a close second (sorry Joe) and did a phenomenal job in covering ventilation concerns in large multifamily buildings. Rachel Wagner showed the most awesome cold climate details that I have ever seen. Galen Staengl took folks on a spin to design multifamily and commercial mechanical systems.

And Gary Klein topped it all off by reminding us that without efficient hot water systems design in multifamily, no cigar!

Thanks to all presenters and keynotes! You made this an excellent and memorable event.

I have not even mentioned the first North American Passive Building Project Awards—the entries were just beautiful projects—check out the winners here. I must mention the overall Best Project winner of 2015, as I believe this is pivotal: Orchards at Orenco. What a beautiful project, the largest fully certified PHIUS+ project in the country to date, a game-changer, underlining affordable multifamily projects on the rise.

I’m extremely happy that the Best Projects winners for young CPHC/architects was a tie, and both winners are women! Congrats to Barbara Gehrung and Tessa Smith! Go girls, you are the next generation of leaders!

L-R: Best Overall Project: Orchards at Orenco; Best Project by CPHC under 35 (tie): Island Passive House, Tessa Smith; Best Project by CPHC under 35 (tie): ECOMod South, Barbara Gehrung

L-R: Best Overall Project: Orchards at Orenco; Best Project by CPHC under 35 (tie): Island Passive House, Tessa Smith; Best Project by CPHC under 35 (tie): ECOMod South, Barbara Gehrung

One last note on a thing: Passive building people know how to party while devouring the most challenging, inspiring energy science, details, philosophies (Jevons paradox – Zack Semke’s fascinating lunch keynote) from the field.

And the architectural boat tour on Saturday to top it all off was almost surreal. When we were all out on Lake Michigan and the fireworks went off over the magnificent skyline, I thought, “that’s how we roll :).” Plus, the docent from the Chicago Architecture Foundation was a font of information, and even long-time Chicagoans learned a lot along the way. If you weren’t there, you missed the best passive building party of the year, maybe ever. (But we’ll try to top it, promise.)

Finally, for the crew that just can’t get enough, the Passive Projects Tour on Sunday was, as always, an enormous hit. Tom Bassett-Dilley and Brandon Weiss put together an array of completed and in-progress projects that generated a buzz at every stop. Thanks to Tom and Brandon and to PHA-Chicago for all your help!




Passive house history (PHistory) Part I–North American roots

In 2002, when I set out to build my own passive house as a proof of concept, I eventually selected a site in Urbana, Ill. I had was working in Chicago at the time, but Urbana made sense for several reasons: it offered affordable land, the city and its citizens have a progressive history in terms of environmental issues, and it is home to the University of Illinois at Urbana-Champaign (UIUC) and all the resources that a research institution offers.

What I’ve learned since then is that pioneering work at UIUC decades ago actually helped spawn what we now refer to as passive house. It’s a fascinating history, and one worth sharing here. To all the pioneers out there—weigh in with additions and clarifications. I hope you enjoy!


Passive house describes a set of design principles and defined boundary conditions that—if applied holistically—lead to a building that remains comfortable with only minimal active heating or cooling during extreme climate conditions. The specific boundary conditions determine the design of the thermal envelope. Minimized mechanical systems result from specific space conditioning energy consumption and peak loads: quantitative, measurable performance-based energy metrics for homes and buildings.

The underlying passive principles were pioneered and formulated in the United States and Canada in the 1970s and 80s following the oil embargo and resulting energy crisis of 1973. By 1986 the noted physicist William Shurcliff was able to summarize what at the time he considered a mature and widely adopted technology. He described the five main principles of superinsulation also known then as passive housing in his article int the 1986 Energy Review”:

a) thick insulation
b) airtight construction
c) prevention of moisture migration into cold regions within the walls, and other regions where much condensation could occur
d) optimum sizing of window areas
e) a steady supply of fresh air

He goes on to describe in detail the necessary components: triple pane windows, heat recovery ventilators, thermal bridge free and airtightness design strategies, vapor retarders, a small wood stove as a heat source for the entire house etc.

In essence, what Shurcliff termed “Superinsulation” was essentially identical to passive house as we know it today.

Council Notes–the University of Illinois’ Small Homes Council periodical–featured the Low-Cal house back in 1981. Plans and energy modeling details were published in a standalone paper years earlier.


Where it started: Back to the future

Urbana, Illinois. The same Urbana that—by Kismet—is today home of PHIUS. In the early 1970s, a group of engineers and architects at the University of Illinois Small Homes Council (now knows as the Building Research Council) began experimenting with highly insulated envelope components. The group included included Wayne Schick (who coined the term superinsulation), W.S. Harris, R.A. Jones and S. Konzo. Their research culminated in the concept of the Lo-Cal (for low-calorie) house in 1976. (You can still buy original publications about Lo-Cal by the Council and Schick  here. And Building Science Corporation’s Joe Lstiburek writes about it here.) Lo-Cal was projected to save 60% in energy consumption compared the most efficient design promoted at the time by the Department of Energy.

A young architect working with the Council at the time, Mike McCulley, built four Lo-Cal houses in Urbana and Champaign. The Council monitored and evaluated them for performance, and these projects gained some attention from press outlets around the country.

An article about one of McCulley’s Lo-Cal houses appeared in the 1982 Louisville Courier-Journal. (Click to enlarge)

This Illinois group’s ideas greatly influenced a Canadian group of engineers working on the Saskatchewan Energy Conservation House (well chronicled in 2009 by Martin Holladay in Green Building Advisor–“Forgotten Pioneers of Energy Efficiency). They succeeded in reducing losses and peak loads even further. The peak load of the Conservation House in this extremely cold climate was designed to be approximately 1.5 W/sqft, equivalent to the best peak loads we are seeing in today’s passive houses in similar climates.


The concepts gained momentum in both countries, spawning prototypes and buzz at building conferences.  The press and the public took notice. The term superinsulation was evolving as the most commonly used label for this set of principles in a growing North American high performance building community.

In 1980 William Shurcliff published one of the first books on the topic, called “Superinsulation and Double Envelope Houses.” Shurcliff, an accomplished physicist who took up the subject after his retirement from Harvard, went on to publish many books on the passive solar and superinsulation concepts in the late 1970s and early 1980s. In fact, Shurcliff appears to be the first to have labeled the new concepts “passive house” in his 1982 self-published book “The Saunders-Shrewsbury House” [Shurcliff, 1982]. It describes direct-gain and indirect gain passive houses. Later in a 1986 article he states that “a superinsulated house is really a special type of a direct-gain passive solar house.”

Because many architects and builders felt that superinsulation was too narrow a term, passive housing started to be commonly used interchangeably with “superinsulation.

Regardless of labels, Shurcliff states that by the mid/late 80s there were tens of thousands of homes built in the United States and Canada (as many as in Europe today!) to these design specifications. By 1982 a movement had formed. Thousands of building professionals were traveling to conferences taking training to learn the techniques. Construction of such homes was growing “explosively” as Shurcliff puts it in one of his early books in 1980 (Superinsulated Homes and Air-to-Air Heat Exchangers). The Canadian government offered free builders trainings. Widely read magazines sprung up, amongst them the still today well known and respected Energy Design Update.


Shurcliff defined a superinsulated house as follows: “…a) receives only a modest amount of solar energy […], and b) is so well-insulated and so airtight that, throughout most of the winter, it is kept warm solely by the modest amount of solar energy received through the windows and by intrinsic heat, that is, heat from miscellaneous sources within the house. Little auxiliary heat is needed: less that 15% as much as is required in typical houses of comparable size built before 1974.”

He further explained: “The 15% limit on auxiliary heat […] was chosen because a house that conforms to this limit can get through the winter fairly tolerably even if auxiliary heat is cut off entirely. Specifically, the house will never cool down to 32 F. […] In summary, the basic strategy of superinsulation is to make the house so well-insulated and airtight – so conserving of heat – that it is kept warm almost entirely by heat that is received informally and is free.” (2)

What’s striking is that the 15% maximum limit cited for the annual heating demand compared to standard construction at the time is very close to the energy metric that defines today’s passive house criteria: 4.75 kBTU/sqft yr!

To explain: Comparing current contemporary home energy consumption for heating to the energy consumption of a home built in 1970 one finds that the reduction in heating energy consumption from 1975 to 2006 is approximately 17% (see DOE graph). In 2005 a typical home in the state of NY consumed approximately [34.76 kBTU/sqft yr] according to the EIA for heating. Increasing this energy consumption by approximately 20% (MEC-IECC Graph) results in 41.71 kBTU/sqft yr for a home built in 1974 (before the MEC took effect). 15% of that total value equals 6.25 kWh/sqm yr, (19.7 kWh/sqm yr) an energy metric limit very close to the current Central European passive house metric of 4.75 kBTU/sqft yr which was codified in the late 80s to early 90s.

Note that most passive houses at the time were built in quite a bit colder climates of the US and Canada. The colder climate boundary conditions are likely reflected in this slightly higher annual heating demand limit (as a direct result of greater peaks).  Peak load then as it is today was understood to be the determining factor. Another curious historic trace of those early superinsulation experiences describing very low load homes similar to the European secondary passive house standard peak load threshold of 10 W/sqm exists in the International Energy Conservation Code (IECC). The current International Energy Conservation Code (IECC) still recognizes extremely low load homes, defining them as homes with a peak load equal or smaller than 1 W/sqft (10 W/sqm) for heating in section 101.5.2 [International Code Council, 2012] effectively exempting them from having to have a conventional auxiliary heating system. The code assumes in this case that the intrinsic heat sources are equal to the tiny peak losses aka no need for additional heat. According to the Code Council the IECC is the successor of the first 1975 Model Energy Code (MEC), from which this definition was originally adopted!

Shurcliff goes on to describe the performance of such houses in winter:

“1. The typical annual heat requirement on the auxiliary heating system is so small that the annual cost is almost negligible compared to the main household expenses […] 2. The occupants benefit from the absence of drafts, cold floors, and cold spots near windows. 3. Because the south windows are of modest size, little or no sunny-day overheating occurs. 4. Anxiety as to possible failure of the auxiliary heating system is minimal because the rate of cool-down is so low (a fraction of a degree per hour) that the house can easily ride through a 24-hour period with no auxiliary-heat-input. 5. Thanks to the use of an air-to-air heat exchanger, humidity tends to remain in the desirable 40-60% range and there is a steady inflow of fresh air (at, typically, 50-150 CFM, or about half a house volume of fresh air per hour). 6. Little outdoor noise penetrates the house.”

He also notes that the orientation of the house is not critical to the concept. He says that the house can have almost any orientation, unlike only passive solar-heated designs that had to be oriented within 25 degrees of south.


The technology matured and the market began to follow. Energy Design Update published an entire edition in 1987 as a consumer guide devoted solely  to the many air-to–air heat exchangers. The Canadians appear to have taken the technology lead in the 1980s. Shurcliff credits Harold Orr’s construction type from the Division of Building Research of the Canadian National Research Council to be the most widespread type being built in North America.

In 1984 young J.W. Lstiburek and J.K Lischkoff publish a book called “A New Approach to Affordable Low Energy House Construction,” further advancing various aspects of passive housing and related sciences. The “Superinsulated Home Book” by Ned Nissen and Gautum Dutt published in 1985 is the most advanced construction and detailing book in the industry at the time. The book even presented a detailed chapter on the theory of energy balancing and sample calculations for low load homes, explaining how to balance losses and gains to arrive at a design with an extremely low balance point temperature.

In 1988 Shurcliff concluded in his book “Superinsulated Houses and Air-To-Air Heat Exchangers” [Shurcliff, 1988] that this type of energy efficient home construction is here to stay and that one might see some further improvements in window technologies, vapor retarders, more efficient heat exchangers and compact minimized mechanical systems, “…but that there is no need to wait for such refinements. Superinsulation is already a mature and well proven technology.”

That was 1988, and the future of superinsulation/passive housing in the United States was bright, but…

See the passive house history Part II





The standard: Less energy, less pollution, more comfort.

I’ve been on the road a lot lately but let me thank you again for your thoughtful contributions and the

Solar radiation exposure is one factor that differs dramatically between Germany and the US. (National Renewable Energy Laboratory, European Commission)

healthy debate sparked by my first blog post, “15kwh is Dead, Long Live 15kwh.” In the post I put forth PHIUS’ plans to modify the passive house standard to address the specific climate and market needs of the North American market. A quick summary of the changes and their value:

  • Modifications will be based on the first and only large-scale analysis of passive house buildings in the United States and Canada – the 100+ buildings certified/under review by PHIUS.
  • They will address the substantive and reasonable critiques (such as the small-home penalty) of leading building scientists in North America like John Straube, Marc Rosenbaum, and Martin Holladay.
  • They will safeguard the high quality for which passive house is known by acknowledging

    View Marc Rosenbaum's presentation on passive house in the United States from the 2011 North American Passive House Conference

    fundamental differences (e.g., building in high-humidity zones presents unique quality challenges).

  • Modifications will calibrate envelope improvements more precisely for each climate and will be more cost effective than the one-size-fits-all approach. They will improve cost effectiveness in colder climates while maintaining comfort and quality of the envelope. And they will actually tighten the standard in climates where there is opportunity for more stringent targets.

The post touched off a great deal of constructive discussion and supportive comments – many folks expressing support for an idea they believe was long overdue.

Understandably, the prospect of change also caused some angst. Recently, a petition was circulated asking folks to sign-on in support of maintaining a single numerical standard associated with the term passive house. I fully understand the response – years ago, I might have signed on myself. But since then, based on the collective experience of passive house consultants who have designed and constructed projects across the continent, it’s become clear that adaptation is critical.

It’s also become clear that we at PHIUS need to get better at explaining the rationale for the modifications that we’re proposing and how they will help propel the market forward while maintaining the core principles of passive house.

To that end, I’d like to respond to some of the concerns and ensuing discussion around the petition mentioned earlier.

Let’s start with a sentiment expressed in a Green Building Advisor article related to the petition topic:  It was expressed that the “beauty of the standard is its purity.”  Purity implies uniformity, and my intended point is that 15kwh is not a universal truth, and therefore not practical for all climate regions.  The rigor of passive house is universal.  In the US, 15kwh is rigorous and practical in the Pacific Northwest  but hat’s not the case in most of the other North American climate zones.

By the same token, in some areas of the United States – Southern California, for example – it’s technically and economically practical to do better than 15kwh.  And it’s worth reiterating: adjusting the standard will allow us to do away with the small-house penalty (that being that it’s actually easier to achieve 15kwh in a larger structure than a small one, thereby presenting an incentive to build larger).

As mentioned in the first blog post, other parts of the world have already concluded that 15kwh is not universal. This is really not a new development.

More important, is the suggestion that modifying the standard creates market confusion. Three points argue against this being a concern:

1. Passive house is not a brand. Passive house is a generic term for structures that require little or no actively generated energy for heating and cooling. Put another way: “Passive house” is the equivalent to “hybrid automobile.” Car manufacturers now make their versions with their brands.

2. Passive house applies to the principles and practices – which are universal – required to build passive structures. Many of them — superinsulation, airtightness, energy recovery ventilation, managing solar gain — originated in the United States and Canada. They don’t belong to anyone. They are not brands. And they are available to all designers and builders who want to learn to apply them. They remain intact and powerful regardless of any number.

3. As more competitors arrive in a growing market wishing to offer passive house products clear branding of different passive house products (different trainings, quality assurance protocols or standard variations) is important to avoid confusion in the market place. PHIUS has differentiated its product by creating the PHIUS+ program.

Market size is a bigger concern. Passive house has come a long, long way in the past several years. But the market is still tiny. The imperative is to grow the market. And it will not grow if we adhere to a standard that isn’t practical in large swaths of the continent.

By making the standard applicable across the continent, and teaching professionals how to make passive house work where they work, we can help passive house principles go mainstream here in North America. We can make passive house principle best practice. And that will achieve all of our ultimate goals: Less energy, less pollution, more comfort. All thanks to passive house.