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Building Science

From Superinsulation to Passive House, With a Trip Across the Pond

A bit of history and a look at where the Passive House movement stands in North America

Image 1 of 2
The Lo-Cal House in Urbana, Illinois was one of the first superinsulated houses.
Image Credit: Small Homes Council-Buildings Research Council, Univ. of Illinois
The Lo-Cal House in Urbana, Illinois was one of the first superinsulated houses.
Image Credit: Small Homes Council-Buildings Research Council, Univ. of Illinois
Wall section showing double-stud construction in the Lo-Cal House
Image Credit: Small Homes Council-Buildings Research Council, Univ. of Illinois

In 2002, Katrin Klingenberg introduced the Passivhaus program to North America when she built the Smith House in Urbana, Illinois. She had come to the U.S. from Germany, where she studied architecture and got involved with Passivhaus. But is this really where it all began?

Of course it’s not. The Passivhaus program, promulgated by the Passivhaus Institut in Germany, formalized the requirements but was building on earlier work, much of it from North America. Even the term “passive house” has American origins.

Here are three of the early superinsulated houses in North America:

  • Illinois Lo-Cal House, 1976. Lo-Cal here is short for low calorie, as in low energy. That’s a sketch of it above and a vertical wall section below. Notice the double-stud walls and triple pane windows. This was the beginning of superinsulated houses.
  • Saskatchewan Conservation House, 1977. Another superinsulated house, this one with R-40 walls, R-60 roof, triple-pane windows, and low levels of air leakage.
  • Leger House, 1977. And a third, this one in Massachusetts.

But were they “passive houses”?

William Shurcliff was a Harvard physicist who worked on the Manhattan Project in World War II, helped stop supersonic passenger planes in the 1960s, and took a big interest in passive solar and superinsulated building in the 1970s and ’80s.

In 1979, he put out a press release praising the characteristics and benefits of superinsulated houses. He described the thick insulation (“Not just thick, but clever and thorough”), the airtightness, the lack of a need for thermal mass and large, south-facing windows, and the ease of controlling temperature and humidity.

He concluded his press release with this: “What name should be given to this new system? Superinsulated passive? Super-save passive? Mini-need passive? Micro-load passive? I lean toward ‘micro-load passive.’ Whatever it is called, it has (I predict) a big future.”

Martin Holladay resurfaced this piece of superinsulation/passive house history in his 2009 article, Forgotten Pioneers of Energy Efficiency on Green Building Advisor and republished nearly the entire piece. Go to his article to read that and more on this topic.

The evolution of passive house

Shurcliff’s preferred term, “micro-load passive,” didn’t catch on, but the passive part did. Those “forgotten pioneers” also pushed another piece of the passive house concept. They understood that airtightness and energy efficiency were important. That meant quantifying the goals, setting limits for annual and peak loads.

Dr. Wolfgang Feist, a German physicist, and Dr. Bo Adamson from Sweden took those early ideas and created the Passivhaus program. In their program, certification required hitting an annual load at or below 4.75 thousand BTU per square foot per year or a peak load of 3.17 thousand BTU/h per square foot. They also have to achieve an airtightness of 0.6 ach50 or less and a primary energy of 38,000 BTU per square foot per year.

That’s what Klingenberg learned in Germany and brought with her to the U.S. Those numbers worked great in Germany, but not so well in all parts of the U.S. There were problems with the amount of insulation required in really cold climates like Minnesota and with cooling and dehumidification in places like Kentucky and Louisiana.

So the Passive House Institute U.S. (PHIUS), of which I’m a board member, developed new climate-specific passive house standards. Instead of one set of numbers for every place in the world, we have numbers that came out of a lot of work by Building Science Corporation and others on what numbers are supported by the science for different climates in North America.

PHIUS also has a rigorous quality assurance program called PHIUS+ Rater, using HERS raters to verify homes going for certification.

The split between PHIUS and PHI

Unfortunately, relations between PHIUS and PHI came to an end a few years ago. I wasn’t involved at the time and don’t know all the details, but now there are two separate groups promoting passive house in North America. The North American Passive House Network (NAPHN) was created after the split between PHIUS and PHI. That group promotes the German standard. Passive House Institute U.S. has gone its own way, with a variation of the German standard.

Both groups have their own conferences. I attended the NAPHN conference in New York City last month. It was well attended (with about 500 attendees) and had a good trade show. I got to see some old friends and meet some people in real life for the first time. (Hello, Terry!) There were also quite a few people there whom I know from PHIUS conferences.

In September, PHIUS will host its 10th anniversary North American Passive House Conference. It’s in Philadelphia, and I’ll be giving a presentation there on a topic that’s gotten me in trouble once already this year. The title is The Global Warming Impact of Insulation Revisited. Joe Lstiburek will be there again, of course, as will Marc Rosenbaum and a bunch of other smart people. (And if you register by July 18, you can be there, too, and get the early bird rate.)

What’s next?

There you have it. Forty years of evolution of the passive house concept in North America, including a trip across the pond and back. Where it goes from here remains to be seen. There’s some confusion in the marketplace because of having two groups and two different certification paths. (I’ll write more about that in a future article.) Naturally, since I’m on the PHIUS board, I have a bias. I think anyone going for passive certification on a project should go through PHIUS’s climate-specific standards and PHIUS+ quality assurance.

A lot of others do, too, because PHIUS has more than a million square feet of buildings certified and pre-certified. When you add the projects that have been submitted but aren’t yet pre-certified, that number jumps to about 2.5 million square feet. The big driver isn’t single-family detached homes, though. It’s big multifamily projects.

Come to the 10th anniversary North American Passive House Conference in Philly to learn more about passive house. Will I see you there?

Allison Bailes of Decatur, Georgia, is a speaker, writer, building science consultant, and the author of the Energy Vanguard Blog. Check out his in-depth course, Mastering Building Science at Heatspring Learning Institute, and follow him on Twitter at @EnergyVanguard.

18 Comments

  1. Anders Lewendal | | #1

    PHI
    Allison: Thanks for the article on Passive Homes. I just completed a Passive home project for a client in zone 6 in Montana. Our ACH at 50 was point 35. They did not use any offsite heat or PV's during this last winter. The south facing windows and thermal mass in the floor worked as designed. I am quite sure we meet the PHI requirements but do not intend to certify. The architect thought it would cost about $5K.

    You might consider including some of these homes that can document meeting the PHI protocol but do not certify. They make good stories and add to the square footage of Passive homes in American.

  2. Charlie Sullivan | | #2

    Offsite heat
    Anders,

    I'm not sure exactly what you mean by "did not use any offsite heat" My guess is that the supplemental heat beyond parasitic heating and solar gain was a wood stove, using wood grown on site, or perhaps using wood scraps left over from the construction project.

    In any case, congratulations on what sounds like excellent performance.

  3. Expert Member
    Michael Maines | | #3

    Names Matter
    There is enough confusion among consumers (and some professionals) between passive solar and Passive House/Passivhaus, that it is truly unfortunate the U.S. offshoot chose to keep the name while developing their own standard. They should have chosen a different name for their program instead of piggybacking a new approach on the international standard that everyone else in the world uses.

  4. Anders Lewendal | | #4

    PHI
    Charlie: Sorry, I should be more specific. I was surprised to hear that my clients never turned on their mini split. They do have a preheat loop under the slab for the ERV but I don't think it was on. Natural gas is available to the site but they chose not to bring it in. No wood heat. The house is super efficient and comfortable.

    I think PHI should have a couple more categories like Passive75. The protocol is very useful but the cost to going 100% is a little beyond diminishing returns. I talked to my clients about that and they chose to go all the way. A 75% or 80% PHI would be a very efficient home. The final cost of the project was about 15% above building a qualifying home for the federal $2K tax credit. I have completed over 20 of those.

  5. GBA Editor
    Martin Holladay | | #5

    Response to Anders Lewendal
    Anders,
    There is a name for a "75% or 80% passive house." It's called a "pretty good house."

  6. Lloyd Alter | | #6

    I was glad to see you again
    I was glad to see you again at the NAPHN conference in NYC, and was honoured to moderate the panel discussion that was, I believe, the first time the two camps were on the same stage. As a Canadian who has always been troubled by the idea of American exceptionalism, I have never accepted that your climate is somehow different than you will find between China and Sweden, and I rather like the idea of everyone in the world working together to one standard. But hey, you and Liberia and Myanmar cannot even accept the metric system so I should not be surprised. And the real takeaway from the New York NAPHN conference was that it was clear that the similarities in approach outweighed the differences. There is real work to be done, and I hope that this issue will go away soon.

  7. GBA Editor
    Allison A. Bailes III, PhD | | #7

    Response to Anders Lewendal & Martin Holladay
    As Martin said, going most of the way there is pretty much the idea of the Pretty Good House. It's not the same as Passive House, however, because there's certification or modeling or verification required. So it might be pretty good. Or maybe not. I think third party certification does add to the value because then you know what you have (or should).

    You can search GBA for article about the Pretty Good House. I believe Michael Maines, another commenter here, wrote the first one if I recall correctly. I wrote one or two also.

  8. GBA Editor
    Allison A. Bailes III, PhD | | #8

    Response to michael maines
    Michael, you may know this already but not everyone else in the world uses the same standard for passive house. Belgium is one country that has modified the German standard to suit their needs.

    But you raise an interesting question about what is it exactly that distinguishes passive house from other programs. I think Dr. Shurcliff and the other superinsulation pioneers set the stage when they focused on airtightness, peak loads, and annual loads. Feist and Adamson took the work further. PHIUS has taken the European PH standard a step further.

    But it's still passive house. We have the same focus on airtightness, peak and annual loads, primary energy, and thermal bridging. What we've done is acknowledge the folly of saying that one set of numbers will be cost effective everywhere on the planet. We've also added some sorely needed verification and quality assurance.

    But the PHIUS standard is still passive house.

  9. GBA Editor
    Allison A. Bailes III, PhD | | #9

    Response to Lloyd Alter
    It was great seeing you, too. And now that I read your comment again, I see that my response about the Pretty Good House is nearly identical to yours. Glad to see we agree there.

    The PHPP spreadsheet, as I understand, had to modified for it to work in places like China. It's also been modified to work better in North America. There are two components to this issue. One is that earlier versions of PHPP led to failures. Another is that the original idea is that the thresholds, 4.75 kBTU/sf/yr for example, are cost effective everywhere is ludicrous. This isn't American exceptionalism. This is mathematics.

    Regarding similarities, yes, I agree that when you step back and look at the bigger picture, PHI and PHIUS are both passive house programs with a lot of similarities. But the differences are significant. To name another one, the PHIUS standard uses more realistic numbers for plug loads and appliances. It's easier to meet primary energy targets with the PHI standard because you're not really including everything that real people use in real houses.

    It's interesting that you criticize the US for not being on the metric system when Canada isn't fully on it either. In fact, you've even expressed fondness for the old units. Here's what you wrote in a comment in an article I wrote four years ago: "While I am completely comfortable in Metric now, and while it is so much easier doing architectural drawings, Imperial is in fact much more human, much more loving, part of our being and not a dispassionate cold science." (Here's the link: http://ow.ly/qMPzN.)

    Why don't you come to the PHIUS conference in Philly and find out more about the new standard and what's really happening in the program?

  10. Stephen Sheehy | | #10

    Certification
    How about this: You build your house and present verifiable data as showing how much energy the house used over a year or two. Wouldn't that be more meaningful than meeting PH criteria ahead of time?

  11. Expert Member
    Malcolm Taylor | | #11

    Stephen
    Then you bump into the problem that occupant behaviour can trump the efficiency of a house's construction. We could leave all new houses vacant for a year while we monitor them, or we could just not worry too much about it, sit back and enjoy watching the fratricidal bickering of the pre-certifiers.

  12. GBA Editor
    Allison A. Bailes III, PhD | | #12

    Response to stephen sheehy
    Actual operational data are great! But how does that help someone who's designing and building a new home? You have to have a way to model what you expect to get ahead of time and you need verification and quality assurance. And then you need to monitor the operational data and give final certification based on actual performance.

    Yes, we need operational labels, but we do still need asset labels, too. (Here's an article I wrote that explains those terms: http://ow.ly/BznZr.)

  13. Stephen Sheehy | | #13

    Occupant behavior
    Isn't actual energy use the only meaningful measure? Modeling is great, but measuring actual energy use will tell us whether the model is accurate. To be sure, the same house with different occupants might have somewhat different energy consumption. But in my Pretty Good House, we pretty much set the thermostats at 70° and leave them alone. I don't think other occupants would do anything much different.
    To respond to Allison's point, if every house reported actual energy data, it wouldn't take long before a designer could incorporate that data into a design and be more accurate than simply using a model.

    As I understand the situation, you can get certified without demonstrating actual energy use. Are there any actual PH performance measurements other than airtightness?

  14. Expert Member
    Malcolm Taylor | | #14

    Stephen
    The owners of the last house I built keep two fair-sized windows open year round. it's very likely they would do the same if they bought your place, and I don't see how i could extract any meaningful data on the house's efficiency with them as residents.

    Perhaps I am showing my own prejudices, but after we have agreed on some general rules of thumb as to what building assemblies to use in a given climate, whether they come from modelling or post-occupancy data, that's good enough for me. Incorporate them into the local building code and provide good enforcement. Continue to fine tune them based on the work of building scientists and amend them periodically.

    I think the history of medicine may provide a good analogy. The most dramatic and far-reaching improvements in longevity, the eradication of diseases and the general well-being of populations came from very simple public health initiatives, not bringing an intense focus of consultants on individual cases. We need the equivalent of that in our industry. Subjecting each project to an array of consultants, modellers and accredit-ors is aways going to consign energy efficient houses to a boutique niche.

  15. Charlie Sullivan | | #15

    Houses vs. people
    I think there should be separate certification systems for buildings and for occupants. I nominate Martin to be the first one to be officially certified as a pretty good person, but there might be problems with certification of passive people--anyone who truly qualified would never get around to actually filing the paperwork to get certified.

  16. Stephen Sheehy | | #16

    Malcolm
    I think we are generally in agreement. Here in Maine, we're all too cheap to leave windows open in January. I.suppose one could accumulate data on a thousand houses, throw out the hundred highest and lowest and get pretty good info.
    Your medical analogy is a good one.

  17. Expert Member
    Malcolm Taylor | | #17

    Charlie
    I'll vote for you!

  18. GBA Editor
    Martin Holladay | | #18

    Response to Malcolm Taylor
    Malcolm,
    I'd like to highlight what you wrote -- one of the best comments posted in GBA in quite a while. Hear, hear!

    "After we have agreed on some general rules of thumb as to what building assemblies to use in a given climate, whether they come from modelling or post-occupancy data, that's good enough for me. Incorporate them into the local building code and provide good enforcement. Continue to fine tune them based on the work of building scientists and amend them periodically.

    "I think the history of medicine may provide a good analogy. The most dramatic and far-reaching improvements in longevity, the eradication of diseases and the general well-being of populations came from very simple public health initiatives, not bringing an intense focus of consultants on individual cases. We need the equivalent of that in our industry. Subjecting each project to an array of consultants, modellers and accredit-ors is aways going to consign energy efficient houses to a boutique niche."

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