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New Passive Building Standards for North America

Why the European Passivhaus standard isn’t appropriate for North American climates

Image 1 of 3
This map shows that the space conditioning needs of buildings in the U.S. are significantly different from those in central Europe. Guide to abbreviations: HHD=High Heating Degree, MHD=Medium Heating Degree, MCD=Medium Cooling Degree, LCD=Low Cooling Degree.
Image Credit: Image #1: Global Buildings Performance Network
This map shows that the space conditioning needs of buildings in the U.S. are significantly different from those in central Europe. Guide to abbreviations: HHD=High Heating Degree, MHD=Medium Heating Degree, MCD=Medium Cooling Degree, LCD=Low Cooling Degree.
Image Credit: Image #1: Global Buildings Performance Network
These graphs were produced by WUFI Passive software. The upper graph shows indoor temperature at a Passivhaus in Illinois from February 1-10, when outdoor temperatures were below freezing. The overheating is evidence of the design's over-reliance on south glazing. The lower graph shows the operation of the heating and cooling systems during the same period. On some days, space heating and space cooling were necessary on the same day for the occupants to stay comfortable.
Image Credit: Image #2: PHIUS
The Smith house was completed in 2003.
Image Credit: Image #3: Martin Holladay

By August of 2011, eight years had passed since we completed the Smith House, the first home in the United States to be built to the European Passivhaus standard. Those eight years were heady and full: We founded the national non-profit Passive House Institute U.S. (PHIUS). We created a Certified Passive House Consultant (CPHC) training curriculum and delivered trainings to hundreds of professionals from coast to coast.

Those pioneering professionals began building their own projects from coast to coast, and from north to south, in all U.S. climate zones save for Florida. Because PHIUS had a good deal of practical experience building its own projects, because it provided training and certification (at the time under the auspices of the German Passivhaus Institut), PHIUS was quite naturally closely involved with nearly all of these projects.

And that’s when we — PHIUS and CPHCs and builders across the United States — began collectively to learn the limitations of the European Passivhaus metric in varied climate zones outside of Central Europe.

Some buildings were overinsulated and overglazed

To be sure, the concept of a single, relatively easily understood, internationally applicable energy metric for heating and cooling was (and is) enormously attractive. And in Central Europe the metrics have been well verified and tested.

But between consulting on some projects and certifying and reviewing many others, we learned that the concept of a single Holy Grail standard for North America’s varied climates is just too good to be true.

In practice, designers have arguably been forced into non-optimal decisions and designs in pursuit of the European 15 kWh/m²•year metric. For example, in the colder climates they tended to seriously overinsulate — with diminishing returns in the outer layers — and tended to overglaze (with expensive high-performance windows, no less). The projects relied heavily on solar gain to make the energy balance work.

With some exceptions (e.g., the Pacific Northwest), the North American continent has design temperatures that are much more challenging than central Europe. It gets significantly colder during the winter, even while the number of heating degree days (HDDs) on an annual basis can look very similar to those in Europe. Madison, Wisconsin, is a perfect example: It has a colder design temperature than Oslo, Norway, while its HDDs are almost 2,000 lower than Oslo’s.

An overreliance on solar gain

Although design temperatures are colder, there is generally very good solar potential in North America. Therefore designers in the U.S. and Canada tried to compensate by becoming essentially “solar Passivhauses” to get closer to the target, which in return caused overheating and comfort issues. (The passive solar movement learned those lessons in the 1970s. Ironically, those lessons were the ones that led to the development of the original passive house concept that deemphasized solar and reemphasized insulation.)

Let’s face it: the annual heating demand of 15 kWh/m²•year was a result of meeting 10 W/m2 peak load in a specific climate, the European climate, with less extreme design temperatures — which as a bonus also allowed “supply air heating only” — the flagship core definition of a Passivhaus as established by the Passivhaus Institut (PHI).

The specific relationship of annual demand and peak load in the European climate has led to the characteristic definition of the standard. Yet, the relationship of annual heating demand and peak load is not a strong one, and is very different on the North American continent. This is likely the reason why the pioneers in the 1970s and 1980s had identified generally similar peak loads as energy targets but paid little attention to limit their peaks to “supply air only,” because they could not get there, and comfort was still assured with slightly higher peak loads and greater annual demands.

Solutions that weren’t cost-effective

Overinsulation and overglazing both resulted in overspending beyond cost effectiveness, seriously challenging the claim that 15 kWh/m²•year is somewhat magically the cost optimum/sweet spot between demand and supply everywhere in the world. (See many earlier articles by Martin Holladay questioning the 16-inch-thick subslab insulation of early Passivhaus projects and the discussions that followed.)

Conversely, in warmer and milder climates (a prime example being California), the target of 15 kWh/m²•year is actually too high, allowing projects to leave significant cost-effective energy savings on the table. In extreme hot and humid climates like Florida, we learned that energy targets for cooling were simply unattainable.

It appeared that the European standard had simply mirrored the heating demand of 15 kWh/m²•year for cooling without verifying it in hot climates. In practice, insulation does not yield the dramatic return in energy savings in cooling-dominated climates as it does in heating climates; in fact too much insulation can increase the cooling load.

PHPP problems in hot, humid climates

These issues also manifested in the Passive House Planning Package (PHPP). Because PHPP is a massive Excel spreadsheet, users can “look under the hood,” which makes it a nice teaching and learning tool. But while well validated for heating-dominated climates, the tool proved inaccurate when we consulted on the LeBois House in Lafayette, Louisiana.

The project was intended to be a proof-of-concept project in the Lafayette climate, and to demonstrate that designers could confidently use PHPP in hot and humid climates. The project plan included monitoring for two years after it was inhabited. During that period it became clear that in PHPP, cooling demand and sensible peak algorithms were off by a large margin. Moreover, we learned that latent loads really need to be accounted for in the standard (they were not at the time).

The project was performing significantly better on the sensible cooling demand side than PHPP had predicted, by about 30%*, but worse on the peak — a situation that makes system sizing difficult. On the other hand, RESNET’s energy modeling tool REMRate predicted the actual performance almost spot on.

Overall, the project was a huge success. We proved that hot climate passive principles do apply, resulting in superior comfort and significant energy savings.

In California, PV beats passive house

But this project was another example of an overarching conclusion: the original German standard and tool were inadequate when applied in climates other than the cool, moderate, heating-dominated baseline climate. Results did not support the one-size-fits-all standard concept.

In cold climates, unreasonably high investment costs led people to abandon the concept, and uptake in northern cold climates remains to this day insignificant. In warmer climates like coastal California, a European passive house is easily beaten by a house with a photovoltaic system, because the standard does not go far enough and does not harvest enough through conservation to make it a financial slam dunk.

Standards are tools that help us to quantify, measure against and meet certain goals we have agreed upon. It’s only logical that they need to be updated and refined as economics, materials and other conditions change and as we learn more. It is an evolutionary process.

Standards should evolve, informed by feedback loops, or they become a hindrance, not a help. We can’t blindly trust: we need to verify and validate to assure that our models remain applicable.

Developing new passive house standards for North America

In 2011, the PHIUS Technical Committee, a volunteer body based on modified consensus and comprised of international building science experts and North American passive house practitioners, embarked on the plan to identify a methodology to generate new passive standards for all climate zones. The tech committee has identified four foundational principles that the standard should follow:

  1. 1. Being biased towards conservation by constraining the envelope design through definition of annual heating and cooling demands and peak loads per climate that must be met using passive measures first. The climate-specific annual demand thresholds should pay back the investment and peak load thresholds should assure comfort.
  2. 2. Meeting a total primary energy maximum per person for all energy uses in a building. This is essentially the equivalent to a carbon limit, responding very directly to the amount of carbon savings that need to be achieved in the building sector to stabilize the climate.
  3. 3. An airtightness requirement assuring building envelope durability, verified by climate and measured in air leakage per square foot of envelope area.
  4. 4. Cost-effectiveness using national average costs for materials and energy.

The sweet spot or characteristic energy use intensity (EUI) is then defined as the optimum design between demand and supply, or more specifically, between conservation and generation.

Lower PV prices have changed the conversation

In a sustainable world we must look at zero energy as our goal. We are no longer only trying to justify the cost-effectiveness of a certain level of stand-alone conservation, we are trying to justify the optimal combination of both, conservation and generation, to reach zero energy.

The energy supply would be expected to come from renewable sources; for buildings this would most likely come from photovoltaic (PV) systems. The cost for these systems has come down dramatically over the past few years. This changes the conversation significantly. Figuring that zero is our goal, the cost of PV has a significant impact on where the optimum lies. Now zero has indeed realistically become our new target; positive energy is next. That alone is reason to redo the calculations and refine the standards.

In 2013 we pitched the idea of refining the standard depending on climate and cost to Building Science Corporation in Westford, Massachusetts. They liked the idea and submitted a research proposal with PHIUS as an industry partner under their DOE Building America contract to define passive standards by climate zone according to U.S. cost data. The calculations are being done using the energy modeling tool WUFI Passive (developed by the Fraunhofer Institute for Building Physics, Owens Corning, and PHIUS) and the energy and cost optimizer BEopt (developed by the National Renewable Energy Laboratory).

A one-hundred-year payback period is unrealistic

The effort is running calculations for all climates for a typical single-family home, with carefully chosen and defined design constraints and energy baseline features, first in BEopt. All baseline decisions were carefully conceived and evaluated by the PHIUS tech committee. In the process, it became clear that the European case for cost effectiveness of the 15 kWh/m²•year standard is based on a 100-year lifecycle period for a single-family end townhouse.

The tech committee found this to be an unrealistic value for a North American economic feasibility assessment of conservation measures. One hundred years might be accurate in an ultimately sustainable energy economy, but we are not there yet. The measures need to be cost-effective in the old economy as we are transitioning to the new. Consequently, the tech committee opted to use 30 years instead of 100.

The committee also settled on using a detached, average size single-family home — the predominant housing type in North America. The detached home is also arguably a worst-case scenario to use as a benchmark; any other building type, larger or attached, will perform better.

European internal load assumptions don’t work for North America

In reviewing base assumptions for the model, the tech committee also decided that the internal loads currently assumed in the European model are far from realistic. While the committee agreed that the defaults for internal loads should be stringent compared to the current national average use of miscellaneous electrical loads, they also acknowledged that the current European defaults are only one-seventh of the actual current internal load average in the United States. This leads to a significant mismatch of what is assumed and what happens in reality.

Corrected higher initial internal loads in turn impact heating and cooling demand criteria on an annual basis, and have an impact on where those demand criteria need to be defined when setting standards.

As of this writing, the standard adaptation test plan is almost complete and the parameters and the methodology for the study have been decided. As the project progresses, the dynamic modeling side of WUFI Passive will be used to verify hygrothermal wall assembly performance by climate and to assure that the comfort criteria by zone are maintained when annual heating or cooling demands are slightly increased or reduced.

Preliminary results are looking very promising. PHIUS is already accepting projects under a pilot certification program.

As the work has moved forward, questions have arisen as to how granular these new standards should be. The final format is still an open question. Originally, a zone-based standard model was envisioned, but it is also possible that the study will result in the development of an equation that accurately calculates the respective heating, cooling demand and peak loads by location.

The new climate specific standards findings are scheduled to be presented for the first time during the Ninth Annual North American Passive House Conference in San Francisco, September 12-13, 2014.

* Because of the limitations in PHPP discovered in the field, PHIUS partnered in 2011 with Fraunhofer Institute for Building Physics and Owens Corning to collaborate on a new passive design tool that would appropriately predict energy performance for passive buildings in all climates. We now use WUFI Passive, capable of static (similar to PHPP) as well as a more detailed dynamic simulation to assess whole building energy performance, comfort conditions, hygrothermal performances of envelope assemblies, and hygric interaction of the enclosure and the living space.

Katrin Klingenberg is the co-founder and executive director of the Passive House Institute U.S. (PHIUS). She has spoken and published on passive building topics nationally and internationally, holds a masters degree in architecture, and is a licensed architect in Germany.


  1. Mike Eliason | | #1

    dumb dumb dumb
    and some revisionist history/wishful thinking.

    a. single family houses as basis is the worst idea possible. hey, let's lock in sprawl and high surface area to volume ratios! let's continue to focus on the issues that got us where we are in the first place! (burt's bees) lipstick on a pig!

    b. it's not the 'european passive house standard' - maybe PHIUS should get its head out of the sand. jakarta's not in europe! neither is mexico! or south korea! or china! the PHI is working with groups in asia, the middle east, north america, australia/NZ - and in process, making solid inroads for product manufacturers and building relationships. guess we missed that boat.

    c. this is some stellar leadership. i wonder how many people were drummed out to get to this point? PHIUS is being trounced by uptake in the UK and other locations. in large part because of the focus on single family housing. so shortsighted. so dumb.

  2. jinmtvt | | #2

    I'm sorry to pop your bubble, but i would never personally consider living in a house attached to someone's else house. Maybe you come from town , but alot of north america residents don't and love it that way.

    In fact, i'd probably go as remote as possible from others if i did not have children :p
    but that's another story

    Single family/owner house is something that will need to stay and work with.

  3. Expert Member

    Sounds Eminently Sensible
    Since Passive House seemed unwilling or unable to make the necessary adaptations its nice to see someone doing it for them.
    Also nice to see Mike Eliason chime in with his unique brand of curt rudeness. I do wonder why if, as he says, single houses are such a non-starter his website features so many as illustrations of his designs?

  4. jinmtvt | | #4

    a few humble comments ...
    Hallo Katrin ! :)

    - How are you/we going to implement PH standards when all we see are ( mostly ) 500 000$+ single family projects ?? What is the % of USA homes being built higher than codes in the recent years?
    Most projects we are fortunate to be presented with here, are completely overwhelming budget wise with very expensive installations and appliances.
    If it is to ever make a dent in residential buildings, we will need to jump on the low cost solutions soon else we won't see much more than "influencial results " for a few decades still.

    - I still would like to be explained the link between PV panels and PH standards.
    Anyone can slap some PV on a house, heck on free land ..what does it have to do with building performance ?? Then it is easy to discuss about "Zero" or positive production, but what about us up north in Canada, or in Alaska where solar efficiency is lower but heating loads are multiples ?
    Again another nice project for architectural designs etc.. , but much harder to justify for low cost housings unless the energy required by the use of the building are ridiculously small.
    ( or your local power is dirty/expensive )

    - lastly, over-insulation... In a heating dominated climate, the more you add insulation the less SHG is required --> thus less windows -> lower loss -> $$$ saved goes toward insulation -> better performance during night time -- > eliminates overheating
    So can we really overinsulate in cold climate ?? I believe now after a few years of learning that the associated labor to install additional insulation , and the "structural" complexity it adds is the limiting factor here in northern north-america.
    Most projects want it all = low loss and superb large view windows, counter productive and very expensive.

    i apologize for my bad english !
    mit freundlichen gruben

  5. jackofalltrades777 | | #5

    Why the negativity?
    There is no doubt that high-performance building envelopes will cost more money. It's like that with any material, appliance and technology. The better the product, the more it will cost. It's always been this way. People are currently building $500k + homes that are nothing more than code minimum homes with expensive granite and finishes. A wiser investment in terms of energy efficiency is a $500k home that uses little to no energy and is well-insulated to curb future heating/cooling costs.

    Reading some of these posts is a trip down curmudgeon lane. The negativity from some people tends to be overboard. Nothing is perfect in life and no green building approach is perfect. Each has its pros and cons and costs are involved.

    If you want to build an earthen ship and live out in the desert off the grid and it makes your life full and enjoyable, congrats and best wishes. If you want to build a $500k Passive House out in the city, congrats and best wishes. If you want to build something in the middle that is a "pretty good house" for $300k, congrats and best wishes.

    Maybe taking on an optimistic approach and not being so negative and condescending towards different green building movements would make the movement better for all. It's like that Saturday Night Live skit with "Debbie Downer", Nobody wanted to be around her and people would avoid her because of her gloom and doom approach to everything in life. Don't be a Debbie Downer!

  6. jinmtvt | | #6

    Peter :
    ever heard of "Critical constructivism "
    or "constructive questioning " .

    We could also all close our eyes and hope for the best!!

    Earthen ship ?? lol

    I think we all understand that more efficient enveloppe is more expensive, problem is that most
    ( i know some have pushed on the right side of things ) do not decide on the right compromises
    ( let's use house size as en example ) and just try to slam more insulation
    on a very large building, with very large windows and then end up driving the project price ridiculously high which hinders the acceptability of efficient buildings for the less fortunates.

    It is superb to witness the current push toward passivhaus derivated standards,
    but at some point , all of this will need to be directed to regular affordable solutions.
    And it will need to happen soon if it is to make any difference in the current ( now ) global warming/energy crisis solution .

    there is not as much merit in building a 300 000$ Ferrari as there is in a super efficient 26 000$ honda accord , although both exist, only the later helps with current global problems.
    that is what i wanted to point out ( not in a negative way .sorry if it reads that way )

  7. ecdunn | | #7

    Oak Ridge National Lab Standards Work!
    The standards set by Oak Ridge National Labs decades ago have always worked well for us here in Flagstaff. I will stick with what works. They are much more cost effective than LEED or Passivehaus.

  8. lutro | | #8

    Interesting information
    Thank you, Katrin, for this snapshot of the roadmap for evolution of the US Passive House PHIUS standard (thoroughly mixing my metaphors). I'm curious about the first graphic, which indicates climate differences between North America and Europe, as well as the rest of the world. While it is hard to be sure from the low-resolution image, the graphic seems to include in the region/category 17 parts of southern New Mexico to northern Florida, and from southern Texas to southern Michigan. While most of this region may need heating, cooling, and dehumidification, as indicated, during the course of the year, there is such diversity in the area covered, that very diverse strategies are needed to address the building issues. Zone 6, if I read the graphic correctly, extends from California to Maine, and from Canada to southern Arizona. Again, the diversity of this region is ignored in the categorization.

    I'm guessing that PHIUS doesn't base its planned calculations on this graphic's general climate zones. Is there another chart or graphic, which reflects more accurately the kinds of climate divisions that PHIUS is aiming for in its standards for North America?

  9. kyeser | | #9

    What's wrong with Hindsight?
    I like the discussion within PHIUS to reevaluate and address what has worked and what hasn't worked. PHIUS is on the front lines of presenting a building of what "could be." Wether or not you subscribe to the metrics put forward by PHI or PHIUS, one has to admit that PHIUS is the 10,000 pound gorilla in room.
    However, I am a builder. I build both custom and spec homes and I have to build a product, especially when it's on a speculation basis, that people both aspire to own and can afford. In Northern NY I have mocked up Passive House assemblies however my projected costs have risen by at least 30% not including my labor. No where near the 10 -15% thrown around often in Passive House discussions.
    There is a lot of "fat" that goes into a Passive House that I just don't know is equitable. The Zenhder guys didn't blink an eye at quoting me $6000+ for my new ERV in in a 1400 s.f. House.
    I like the discussion of adding an affordability criteria to PH.
    As echoed above its great to say you can build this energy stellar building but if the populous can't afford it who cares!

  10. Expert Member
    MALCOLM TAYLOR | | #10

    Reply to Peter L.
    Peter, perhaps some of what you see as negativity may be the result of contributors having different purposes in looking at projects.
    Like you, if I see a friend or someone down the street building a house, I don't critique it's energy efficiency, or cost (unless it's really egregious!), as long as it makes the owners happy.
    However many of us who are building professionals look to projects with the eye towards incorporating their best features. And others may evaluate them as to their effect on larger issues. Those who see housing as being in a bit of a crisis, or at least a transition, may critique them as representing a viable solution, or being part of the problem. Much of criticism is just a collective discussion as to the merits of certain approaches. I don't think that's a bad thing.

  11. albertrooks | | #11

    Looking forward to a formal release

    I've been looking forward to the PHIUS's release of it's new standard. Your cost optimization points are real issues that many struggle with. It remains a tough issue. You can't get the Passivhaus performance for free. It always takes more.

    I'm sure your aware of the new labels coming from PHI announced in Germany this month. I find the new "conservation building" label intriguing.

    As the standard that you are proposing to be revised is PHI's own standard, I'm hoping that you go forward with your efforts offer a standard from PHIUS.

    In the last few years PHIUS has developed significantly. New communication that focuses on the "PHIUS + Passive Building Standard" and a modeling tool to go along with it. I'm eagerly awaiting the proposed standards release and to see it named as something rather than Passive House. You did help create the name Passive House in the market as you introduced us the work and tools of The Passivhaus Institut of Darmstadt Germany.

    Your selection of a name to clearly distinguish the PHIUS standard from "Passive House" would keep PHIUS clear of any suggestions of co-opting someone else's development. Or - adjusting someone else's standard.

    Thanks for your work and contributions. I wish you success.

  12. Alan Abrams | | #12

    PHIUS reappraisal
    having invested great amounts of time (and $$$) pursuing PH training and certification, and having enthusiastically persuaded clients to invest significant sums to comply with this system, it would be easy to feel disillusioned by some of these conclusions--most particularly, that "Overinsulation and overglazing both resulted in overspending beyond cost effectiveness..."

    On the other hand--the training gave me a vastly deeper understanding of building science, and the concept of a house as a system, intimately integrated with its site and climate. Moreover, that Katrin and PHIUS leaders and associates are willing to stand up and say, essentially, we veered off course, but we're still striving to get it right--is a testament to their integrity.

    when you live out on the bleeding edge, you can expect to get wounded from time to time, even with your own sword. When it happens, its time to suck it up, learn your lessons, and move on ahead.

  13. Marc Rosenbaum | | #13

    Also looking forward to the release
    It's hard to comment without specifics, but the core thinking that is embodied in the foundational principles are pretty sound. I'm not sure about how much cost-effectiveness should be related to the current price of natural gas, but otherwise these principles should lead to guidelines that make more sense than the standard we have been using from PHI. I'm particularly pleased to see that one of the principles is primary energy per person, not per sq ft. What I call 'resource equity' gives an ethical basis to the standard which I fully support - it's saying, this is your carbon allocation, use it as wisely as possible. In any case, I hope the new standard will represent sound guidance as we ask the question, where does the next dollar invested save the most carbon? Many of us didn't think it was in the twelfth inch of insulation under a basement slab, and it seems PHIUS agrees. Thanks to all whose efforts lead us to this point.

  14. Expert Member
    ARMANDO COBO | | #14

    Why all the hate?
    I don’t see much of a practical use for the PHI or PHIUS as their programs are very constrictive and expensive in my opinion. Having said that, I believe is important for members of our industry that want to push the envelope (no pun intended) to the highest they can, and as long as they and their clients want to spend the money, more power to them.
    To me there’s no difference than an astronaut reaching for the moon, or someone spending $1M in a car just to drive faster than everyone else, or some nutjob who gets its kicks by free diving 600ft in an ocean or jumping on a wingsuit from a cliff.
    Sometimes succeeding a challenge that few have achieved is just what some folks need, until then, it's just plain hard to get it!

  15. Expert Member
    MALCOLM TAYLOR | | #15

    I completely agree. Clients put money into all sorts of things and deciding to spend it on more energy efficiency is great to see. Where the "hate" comes in for me is in proponents saying it is the way rather than one way to a viable solution for how we should build. You se that in the schism between the two branches of the movement. The other problem is that they aren't generally honest about the costs. Spend all the money you want upgrading to Passive House standards but don't say it doesn't cost a lot more.

  16. dankolbert | | #16

    Some faint praise
    I have a lot of respect for all the important work done by Katrin, but as someone who has always been a PH agnostic, I have to confess that the "revisions" presented here seem so blindingly obvious that it brings into question the wisdom of the entire methodology.

  17. user-944275 | | #17

    PHI should take note
    This is a no-brainer and I applaud the PHIUS technical committee for their work. Anyone who has been truly in the trenches designing and modeling Passive Houses over the past 6 years knows that there has been some degree of shoe-horning a central European energy consumption standard into many North American "climate shoes", which led to more than a bit of chaos and confusion. The points that Katrin makes above have become self-evident for experienced designers and I am looking forward to the release of the new proposed standard. In short, it seems that PHIUS is making the standard smarter, more accurate, and more relevant to my projects. The PHI would do well to follow their lead.

  18. GBA Editor
    Martin Holladay | | #18

    Contrasting responses
    To some engineers, designers, and builders -- including Alan Abrams, Marc Rosenbaum, Dan Kolbert, and Dave Brach -- Katrin Klingenberg's suggested revisions are a step in the right direction (or are "blindingly obvious").

    To other observers, including Ken Levenson, Klingenberg's approach represents an undesirable attempt to "loosen" Dr. Feist's standard.

    In my view, the widening gulf between the benefits of a 3-kW photovoltaic array and the last 6 inches of a 12-inch-thick layer of subslab rigid foam make Ken Levenson's contention that Dr. Feist's standard "provides unparalleled performance affordably" harder and harder to defend.

  19. Ken Levenson | | #19

    A (very) long comment
    PHIUS’ ambition to propose a new low-energy standard is impressive. I was initially trained by PHIUS and while NY Passive House is estranged from PHIUS, I happily work with many PHIUS practitioners including former and current PHIUS board members. I’m a member of the PHAUS VT chapter and participate in PHAUS events.

    The competition of ideas drives innovation and I welcome the announcement of the new PHIUS standard – and hope my comments can be constructive and help make PHIUS’ standard clearer and stronger. (Apologies for the length.)

    To build credibility PHIUS should refrain from falsely characterizing the Passive House standard as a Central European standard. The standard does not refer to any particular climate or geographical region – it is global. Yes, it originated in Germany and was validated there first. Since then it has successfully spread around the world, is being validated as a global standard and is practiced as a global standard. Like many other standards the idea of starting local, and then as validated applying universally is not unique to Passive House.

    Many are understandably confused and think PHIUS is proposing to change the Passive House standard. It would help differentiate its new standard if PHIUS would be clearer on this point: PHIUS is not proposing to change the Passive House standard. PHIUS cannot change the Passive House standard. Admittedly, I’m stating the obvious: PHIUS is proposing a new standard. Of course it would be clearer if PHIUS came up with a new name as Albert Rooks suggests. The Living Building Challenge is not named LEED. And Pepsi is not named Coca-Cola. If PHIUS is going to make a better new standard, please make a better new name as well.

    It would be more effective to not focus on anachronistic problems. When the PHPP was first used in hot and humid climates the latent load issue was acknowledged and discussed. PHI then ran a series of studies to scientifically validate PHPP adjustments. Those adjustments were then integrated into the next PHPP upgrade. The certification criteria was also adjusted to specifically address dehumidification. Today Passive Houses are successfully being designed and built with the PHPP in climates that have significant dehumidification requirements, from New York City to Shanghai – and the hot and humid American South is no exception.

    Regarding internal loads, one simply adjusts the default loads to actual projected usage. For a middle ground default of a global standard the European norms would seem a very logical. In the presentation at the last PHIUS conference in Pittsburgh, Graham Wright, the Technical Committee chair, effectively showed that any proposed adjustments to internal load defaults cause as many problems as they purport to resolve, while there was apparently no consensus on the Technical Committee about this issue. It’ll be interesting to see what the consensus has now become.

    Financial arguments about 100 year life cycles and PV are not so convincing in the face of ample evidence that efficiency pays for itself. Adam Cohen, member of the PHIUS Technical Committee has repeatedly shown the economic viability of Passive House – and we look forward to his presentation on the subject on June 17th at our conference in NYC. ( ) And study after study, most recently reported on GBA just last week, with one by Lawrence Berkeley National Laboratory and another by The American Council for an Energy Efficient Economy ( ) – show that efficiency measures cost less than renewable power measures.

    (Where PV becomes interesting is not in the cost argument but in the NZEB framework & primary energy profile/climate impacts – and here PHI is developing a comprehensive recalculation of primary energy and certification integration with two new standards. Wolfgang Feist will be presenting the new framework Sept 22nd at the NAPHN conference in Portland Maine, ( ))

    PHIUS’ economic argument appears to be that because of the added costs, the uptake in Passive House in the US has been lackluster – and that to increase the uptake it needs to be “cost optimized” based on local climate and construction costs, based on the detached single family house. Three quick points:

    First: Choosing a single building type, and the detached single family home no-less, to optimize a standard for many building types doesn’t seem robust.

    Second: The cost logic of Passive House where a fully integrated design can provide unparalleled performance affordably is real but is also dependent on functioning marketplaces, where the needed products and trained professionals are readily available. Let’s keep the rigorous standard and push the marketplace to mature to support it, rather than weaken the standard to suit an immature market. High expectations drive innovation, from the moon shot, to our personal computers. Yes, first adopters suffer, or as Alan Abrams rightly says, the bleeding-edge bleeds, mistakes are made - and we are all better off for it.

    Third: For an ambitious building standard to be widely adopted it needs to be in the building code, and short of that market penetration will be marginal at best. Energy Star New Homes is fair evidence of the problem. As PHIUS board member Allison Bailes described its decline on his blog ( ) - he writes: “…ENERGY STAR is dying because they forgot what their role was. ENERGY STAR used to be an entry-level energy efficiency program. Home builders generally didn't have to stretch too far, or pay too much, to meet the requirements and get that ENERGY STAR label. They abandoned that role with Version 3.”

    The automotive industry fought the mandatory installation of seat belts as being cost prohibitive (seat belts!) – that’s what entrenched interests do. How far does PHIUS need to water down its standards to make them acceptable to industry? Let’s not go there. Instead let’s change the market conditions and let’s change the codes.

    On the opposite end of the spectrum, in places like Brussels and Aachen, we see, after specific efforts to develop the high performance marketplace, building codes being enacted that are adaptations of Passive House - as I reported in GBA recently ( ). There will be political compromise as codes evolve. It’s more sensible to approach that political debate with a maturing marketplace that’s capable of delivering the strongest standards possible.

    PHIUS, while it wants to make low-energy building affordable by loosening the construction standards, is on the other hand, adding great amounts of complexity and work into the certification process. PHIUS’ PHIUS+ protocol includes elements of RESNET and the DOE Challenge Home program. Is it possible that the added work of PHIUS’ expanded certification requirements cost more than that extra inch of insulation? Like Energy Star builders, PHIUS practitioners are facing an escalating list of certification requirements and costs.

    Adding further complexity and cost is the use of WUFI Passive for certification. WUFI is complicated. WUFI can be very useful to provide specific risk assessments but it doesn't seem logical to stick entire buildings in it. Joe Lstiburek, of Building Science Corp, which is reportedly developing the new standard with PHIUS, has been derisive of WUFI, paraphrased on GBA ( ): “Joe said that if you need to use WUFI, you've done something wrong.” The same may generally be said for the dynamic simulations of WUFI Passive.

    Lastly I hope PHIUS’ ambition doesn’t rush it to release its new standard. Graham Wright’s presentation in Pittsburgh demonstrated that there was no consensus on the Technical Committee for many of the proposals. Two and half years ago PHIUS took a stand to differentiate itself and announced it wasn’t going to accept projects with closed cell spray foam insulation for certification. PHIUS then had to disavow its new requirement. And last year, BAYER, a big producer of closed cell spray foam, was the major sponsor of the PHIUS conference in Pittsburgh.

    I wish PHIUS the best of luck in developing a clearer and better, new and different standard and look forward to seeing it released.

  20. Indigo Ruth-Davis | | #20

    turning away from PHIUS
    Great comments Ken.
    In Vermont, many in the Passive House community are turning away from PHIUS certification due to the added issues associated with combining with the DOE challenge homes.
    I think climate based standards will seal the deal. Tellingly Fine Homebuilding's best energy smart home, a Passive House, was certified by PHI, not PHIUS as well.

    Even if Martin and others are right about it just being to darn hard around here to build Passive Houses, a climate based standard is by definition not the Passive House standard.
    When speaking of PV, the issue of the life cycle of the PV isn't always discussed. Output does start decreasing after 25 years or so (so I've heard) while insulation lasts for as long as the house lasts, in Vermont we are living in many 100-150 year old houses.

  21. jinmtvt | | #21

    Althought i agree that insulation is key in cold climates,
    even for a young apprentice as myself it is very easy to understand why a single standard with an inflexible energy goal designed for/around a specific climate cannot be the best compromise for every other climate.

    Following a "leader" blindingly is often a sign of a religion, and religion doesn't go well with scientific approach.

    There is also the case here that alot of efforts seem to go into setting standards and rules,
    but not that much into finding technical/product solutions.

    If adding the last 2" of insulation does not make much economical sense, it is because there is not a cheap enough way to do it. Limits are always set (almost ) by budget.

  22. Bigeorge80 | | #22

    SIP panel problems
    I would like to talk to Mr Ted Clinton about my roof panels on a home I built in 1997. his comments made on SIPs in an article Green Advisor published July 1911 is of great to me. thanks.

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