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Musings of an Energy Nerd

Redefining Passivhaus

The Passive House Institute U.S. takes a stab at developing new passive house standards for North America

The committee charged with developing new passive house standards for North America ran energy simulations that modeled a variety of envelope measures for homes in a great variety of climates. Each yellow dot on the map shows a location that was simulated in the study.
Image Credit: Images #1 and #3: Building America

In January 2012, Katrin Klingenberg, the founder of the Passive House Institute U.S. (PHIUS), announced that her organization would develop a new passive house standard for North America — a standard that differed from the Passivhaus standard developed in Darmstadt, Germany.

Writing in her blog in 2012, Klingenberg explained that “it’s time to allow for a modification process to the rigid annual heating and cooling requirement of less or equal to 15 kWh/m²•yr… for the North American continent’s more extreme climates… This idea that we need to adapt the standard to various regions has taken root around the world from domestic energy experts like Martin Holladay, Alex Wilson, and Marc Rosenbaum and to Passive House groups from other countries, like the Swedes.”

Almost two years later, Klingenberg made another announcement: the work required to develop the new standard would be partly funded by U.S. taxpayers (through the Department of Energy), and one of the contracts for the required study would be awarded to the Building Science Corporation of Westford, Massachusetts.

A few weeks ago, Klingenberg’s first goal was reached when the DOE-funded paper (“Climate-Specific Passive Building Standards”) was published. The report has three authors: Betsy Pettit (from Building Science Corporation), Graham Wright (from PHIUS), and Katrin Klingenberg.

In effect, the paper is a draft for a proposed new passive house standard. PHIUS is now inviting the public to comment on the draft standard; after the public comments are reviewed, the standard may be modified before being adopted by PHIUS.

What is a passive house?

A few years ago, PHIUS cut the umbilical cord linking it to Germany. Since then, the U.S. organization has no longer been bound by the German definition of a “Passivhaus.” Because if its recent independence, PHIUS now has a chance to ask an…

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  1. EthanFahy | | #1

    Another standard, another chance to post this gem:
    As someone interested in having a home built someday I enjoy following the progression of these standards and ideas, but amid the flurry of figures I tend toward throwing my hands up and just demanding a pretty good house.


  2. user-1119494 | | #2

    Head-scratcher, indeed
    Excellent post, Martin.

    I applaud the PHIUS for allowing PV! With it getting cheaper and cheaper, one can oversize systems to gain 90% or 95% of energy from that source, dumping excess into heating or cooling the moderate thermal mass of the house while the sun shines, sidestepping the source-energy penalty.

    One might sidestep uncertainty about future energy costs by assuming all being electricity at $0.15/ as that seems to be a close approximation for PV and other. It is hard to imagine that low prices (coal in Wyoming, for example) will not rise and high prices (Hawaii) moderate as cheap PV lets folks defect from expensive power.

    That said, it IS hard to figure out just what one gains by going with the PHIUS standards. They claim "Comfort. Quality. Efficiency. Resiliency. Affordability. Now." but one can easily show that none of these are really addressed in a spherically defensible way and one ends up with a "standard" that pretty much simply provides an expensive plaque and not much more compared to a net zero or PG house.

    That said, it is hard to imagine a solid standard that would fit the PH moniker. Perhaps it could be a house that "remains liveable" even if power goes out for a week in the worst part of the year, but it needs a simple, attractive, and all-around sensible definition... that remains sensible in practice. I hope they can do it, but sometimes you need to stop tweaking your spaghetti-code and start fresh.

  3. user-2453173 | | #3

    $/kWh for PV
    Dustin, not sure where you're located, but generally PV's cost for energy is a lot less than $0.15/kWh.

    "...$0.15/ as that seems to be a close approximation for PV and other..."

    A very small system can come in at $0.15/kWh with no economies of scale behind it. But your average residential PV system (5-6kW) comes in at $0.10/kWh or less depending on your specific details. I don't have a chart saying what the average $/kWh is for utility power in each state, but i believe that is lower than the Utility in the majority of the US.

    I calculate cost/kWh using the 25yr performance warranty held by almost all PV module manufacturers. If you want to define it differently, then maybe you're $0.15/kWh is accurate. Also if you finance the array, it affects the cost as well.

  4. stuccofirst | | #4

    A ceiling height of 6.6 ft. is 6 feet 7inches and 3/16ths roughly. 3.3 ft. is 3 feet 3 inches and 5/8th if you round it to .625. converting decimals to inches gets hairy.

  5. vensonata | | #5

    Reply to Daniel Young
    Pv cost per kwh. It's good to say how we get the price per kwh from pv, then anybody can use the math. Here is one way. An easy average production from a one kwh pv array fixed optimal angle is about 1500 kwh per year( in Arizona 1800). Though pv warranty is 25 years, they will last and produce much longer with only minor loss, however I will use 30 years times 1500kwh per year as 45,000 kwh production lifetime( very conservative). Each dollar per watt installed is equivalent to 2.2cents per kwh lifetime.( (1000 divided by 45,000) $1000 per kwh installed gives you electricity at 2.2cents kwh. But we are not done yet...don't celebrate. The rest of the system has a lifetime too. Wires and racking have even longer than 30 year lifespans...great! Now inverters are necessary, oh, oh. Inverters will cost you 30cents per watt and have a lifespan of 15 years. So a 1 kw inverter $300. You need two in 30 years so $600. So add 1.3 cents per kwh. Now we have 2.2 plus 1.3 = 3.5 cents plus another $1500 for labor and cost of racking and wiring. 3.3 cents kwh. Grand total 6.8 cents per kwh. Guaranteed for thirty years. So my calculation work out to $3.50 per watt installed at average 1500 kwh per year production for thirty years. That is a fantastic rate for electricity. By the way $3.50 is possible these days but on the low end.
    I should add a new thought. Micro inverters are now warranted for 25 years...the life of the panel, so the formula is easier to give all parts of the system a 30 year lifespan and soon installed rates on larger systems of say 5 to 10 kwh will be $3watt. At that rate 6.6cents per kwh...nothing competes with that. Note that I am estimating the pv panel price at $1 watt. You can get them as low as 85 cents now!

  6. Expert Member

    I agree. Carl Seville's recent blog about city ordinances mandating compliance with one of a range of "green" standards makes your cartoon even more poignant. Given the difference between the aims of programmes like Leed and Passive House I just wonder what, beyond a feel good factor, such rules are meant to achieve?

  7. ErgoDesk | | #7

    Findings frome Mold Growing fron the Breath of Cave Visitors
    "The cave located at Santillana del Mar, in the Cantabria region, was closed in 2002 after damages had been reported to its polychrome prehistoric paintings from the carbon dioxide in the breath of the large number of visitors."

    RE: More on airtightness
    The PHIUS paper repeats a problematic claim made by Wolfgang Feist — namely, that “The airtightness requirement comes from consideration of building durability and mold risk.”

  8. vensonata | | #8

    The bottom line is kwh sq ft
    Passivhaus allows what I consider an extravagant amount of total energy use per sq meter. 110 kwh per year. While they are impressive in their heating allowance, the bottom line is total energy used. Our house is about 30% more in heating demand than passivhaus standard per year (although we are in a 9000 heating degree day zone) but 70% less overall than passivhaus total energy allowable. Specifically the house is 1000 sq meters (10,000 sq ft) and uses 35,000kwh per year total. That does not even count the fact that 97% of electricity is provided by PV (we are off grid). We do not do without anything but we have thought through everything carefully. So this raises a major question mark about the whole vision of passivhaus. Although, don't get me wrong, many things I have done have been inspired by passivhaus ideas...but there is much more to explore. GBA and the Passive house group are a very canny and bright bunch of people, keep it up.

  9. jackofalltrades777 | | #9

    A Great Start
    I believe the PHIUS movement is a great start to help push for a higher energy level in US homes. While we have the 2012 IBC and it's related energy codes, the Passive House goes above and beyond and in the end it will make for more energy efficient homes. If there is no "goal" or standard to attain for, people will usually not respond and build homes like they did 20 years ago.

    I know PH has it detractors and those who like to mock it and it's always frustrating to see the Green Building movement always fighting with itself. That phenomena can be seen here on GBA with people arguing about what is green and what isn't green. Everyone has their bias, that is a reality of being human. No matter what title or position they hold, they are bias to one way of building and hold to their own definition of what constitutes "green".

    I believe the PH movement will gain ground in the USA and the PHIUS is leading the way.

  10. Aaron Birkland | | #10

    Active, Passive, and Tunneling through the ____ barrier.
    This article does a good job in explaining that both passivhaus standards are well-specified lines in the sand for building a house with unusually low energy consumption, but that these lines don't necessarily define the operating conditions that enable any specific observable phenomenon in occupant comfort, cost optimization, or energy usage.

    In my mind, it would be most logocal to tie a standard with 'passiv' in its name to some desirable 'passive' phenomenon. The article mentions that the German standard 'tunnels through the coat barrier' by eliminating the he need for an expensive hydronic heating system, but says there isn't an equivalent barrier in North America. Isn't there?

    Wouldn't the point at which a house no longer needs a distribution system for heating or cooling be a neat place to define a standard around? Such a point would be reached when a house can maintain comfort (say a maximum ∆T between living spaces, or something else that is quantifiable) using only a maximum of one point-source heating or cooling appliance per unit living area (story?). One could argue that relying completely on the conduction, convection, or radiation that naturally occurs in response to introducing a so gle heat source or sink makes sense to call 'passiv'.

    In facy, now I wish a house designed in such a way (with attention to room by room loads, and satisfying heat from a single point source per floor) had a name

  11. GBA Editor
    Martin Holladay | | #11

    Response to Aaron Birkland
    You have proposed a new standard -- let's call it the "one point-source heating appliance only" standard.

    It's a perfectly reasonable standard, but lots and lots of homes comply with it -- including almost every leaky log cabin in Alaska equipped with a wood stove, as well as my own leaky, poorly insulated home (also equipped with a wood stove).

  12. Aaron Birkland | | #12

    response to Martin

    I have a shed in the middle of a field that is net zero. May I blog about it :).

    In all seriousness, the "tunnelling through the cost barrier" section of the article doesn't quite make sense in relation to your response. It is asserted in the article that one (claimed) benefit of the passivhaus standard is that it renders hydronic heating systems commonplace in Europe unnecessary. Your comment implies that lots and lots of houses do not need to distribute heat and cooling, even leaky ones in severe climates. If this is true, then that implies that there really is no barrier to tunnel through (i.e. the hydronic systems that the PH was rendering unnecessary were never necessary in the first place.

    Are you indeed saying that the "tunneling through the cost barrier" is a unicorn, because the this barrier never existed in the first place? That being able to heat and/or cool a home so that all living space is is within a small ∆T from one another using single point-source per floor is generally unremarkable?

    For that matter, could Carter Scott have built significantly worse homes, and still maintained the same degree of comfort with just two ductless minisplits?

  13. GBA Editor
    Martin Holladay | | #13

    Response to Aaron Birkland
    The point of my response is that it's tricky to write a standard. If you want to create a new standard, the "one point-source heating appliance only" standard, you may be surprised to find how many leaky buildings comply with your new standard.

    You issue you raise is complicated, and is often discussed on GBA. The following points are true:

    1. It can be argued that most European hydronic heating systems are, indeed, unnecessary. There are lots of ways to heat a house.

    2. Comfort expectations vary widely, so many families are perfectly happy with a single point-source heater. Other families have members who complain about room-to-room temperature differences.

    3. Tight, well-insulated homes with high-performance windows are less likely to have comfort complaints, or to suffer from large room-to-room temperature differences, than leaky, poorly insulated homes.

    4. Most building codes require the installation of a heating system that keeps every room in the house at a comfortable temperature. It's up to the local code inspector to determine how to enforce this provision, but it raises questions for some homes with a single point-source heater.

    When I compared the idea of "tunneling through the cost barrier" to a unicorn, this is what I meant:

    1. Most Passivhaus buildings in North America have relatively expensive HVAC systems. Many include Zehnder HRVs that cost between $5,000 and $7,000 to install, as well as a heating system and/or a cooling system. (To take a handy example, GBA is now running a construction blog by Alexi Arango. The HVAC equipment for his 1,000-square-foot Passivhaus residence cost $19,224. Plenty of contractors who build conventional tract housing can install all of the HVAC equipment needed for a single-family ranch house for much less than that.)

    2. Wolfgang Feist chose the word "Passivhaus" deliberately, to imply that these buildings don't require active heating equipment. Moreover, he has made statements that imply that Passivhaus buildings don't need heating systems. In fact, every Passivhaus building in the U.S. includes a heating system.

    These observations are mine, but (as my article notes) the PHIUS committee expressed similar observations. The report states, “In North America, ‘tunneling through the cost barrier’ was not achieved. Unlike Germany, there is not such a clear breakpoint where an expensive baseline boiler and hydronic distribution system (the typical heating system in Europe) can be eliminated for great savings.”

  14. AntonioO | | #14

    Tunneling and Cost
    I wonder if you might comment on how much of the "tunneling through the cost barrier" is attributable to the differences in soft and hard costs for the U.S. and E.U. Oftentimes it seems that the cost structures for many aspects of home building are vastly different. For example, it boggles my mind to hear posters like Alexi Arango report that his PH Euro windows were imported for less money than none-PH offerings of well regarded American brands. Thoughts?

  15. GBA Editor
    Martin Holladay | | #15

    Response to Antonio Oliver
    Of course the very high cost of hydronic heating systems in Germany -- perhaps the most expensive residential heating systems in the world -- affects the idea of "tunneling through the cost barrier."

    I have no doubt that when a German Passivhaus designer reduces the design heating load to the point that the hydronic heating system can be replaced with a less expensive heating system (often an air-source heat pump or electric resistance heat distributed by ductwork), significant HVAC equipment savings are possible.

    In the U.S., there are many possible ways to design a heating system. Often, designers make mistakes. Sometimes, American architects or engineers specify a $40,000 ground-source heat pump -- so if a Passivhaus designer can convince the engineer that this specification is stupid, of course savings can be made.

    However, in a broad area of the U.S., a standard heating and cooling system consists of a split-system air-source heat pump connected to forced-air ductwork. When the return-air plenum is connected to a central-fan-integrated supply ventilation system (simple and cheap), this approach provides heating, cooling, and ventilation at an almost unbeatable price.

    Another inexpensive option is an exhaust-only ventilation system (that is, a Panasonic bath fan on a timer) and one ductless minisplit.This type of system can be installed in a Passivhaus -- although it rarely is, because Passivhaus designers almost always insist on installing an HRV -- but it is more often installed in a simple house that doesn't meet the Passivhaus standard.

    A conventional house can have a well-designed, inexpensive HVAC system, or it can have an extravagant, poorly designed system. While poorly designed HVAC systems for Passivhaus buildings are rarer, they certainly exist.

    To sum up, in the U.S., the average Passivhaus building does not have an HVAC system with a lower cost than a typical forced-air heating and cooling system with central-fan-integrated supply ventilation.

  16. AntonioO | | #16

    Thanks, Martin
    Thanks for expanding. To make a final comment though, maybe I got the wrong take-away, but I was persuaded by an article recently (maybe here on GBA) that it's too easy to bungle ventilation integration into your central A/C ducts. The inference from me was that perhaps one is better off paying the extra money to keep it separate regardless of how energy efficient the house is. H, V, and A/C instead of HVAC seems to come to mind for some reason also, not that most people could afford to separate all three.

  17. dankolbert | | #17

    Don't know whether to laugh or cry
    Can't wait to read KK's response.

    On a related note, as I've told you privately, Eric Werling of DOE recently presented up here in Maine - I was impressed by their Net Zero Ready program. He and Sam Rashkin went over from EPA, where they worked on Energy Star, and set up this more encompassing and ambitious rating system. I think it may be the Pretty Good House.

  18. Expert Member
    MALCOLM TAYLOR | | #18

    Reply to Dan Kolbert
    That's good news! Any chance someone could do a blog on what their programme entails?

  19. dankolbert | | #19

    Zero Energy Ready Home
    I believe Martin is on it. They have a good website as well.

  20. Expert Member
    MALCOLM TAYLOR | | #20

    And again...
    Thanks Dan

  21. GBA Editor
    Martin Holladay | | #21

    Response to Antonio Oliver (Comment #16)
    You wrote, "I was persuaded by an article recently (maybe here on GBA) that it's too easy to bungle ventilation integration into your central A/C ducts. The inference from me was that perhaps one is better off paying the extra money to keep it separate."

    I agree that separate ventilation ducts are a good idea. They aren't required by code, and many homes without separate ventilation ducts work just fine, but the best possible ventilation system (at least in a cold climate) includes an HRV with dedicated ductwork.

    That said, I would never say that installing the best possible ventilation system "tunnels through the cost barrier" and results in savings. The fact is, most above-code measures (including a good mechanical ventilation system) cost more than the systems installed in code-minimum houses. There is no shame in that. If we want to build high-performance homes, we probably need to explain to home buyers why the added costs are worth it.

  22. Ken Levenson | | #22

    A response regarding airtightness
    We've written a blog post regarding the airtightness aspects of the report called "BSC & PHIUS Passive Building Report Not Airtight" with references and links back to your post here. I hope it is useful to the conversation.
    - Ken

  23. GBA Editor
    Martin Holladay | | #23

    Response to Ken Levenson
    Thanks for the link to your blog.

    To clarify my position: I am not arguing in favor of PHIUS's proposal for changing the airtightness limit for Passivhaus buildings. Rather, I am questioning Wolfgang Feist's explanation for the airtightness limit.

    Your position -- that it makes sense to aim for an airtightness target that can reasonably be achieved -- is defensible, and makes more sense than arguing that 0.6 ach50 is necessary to avoid moisture problems, mold, and rot.

  24. Ken Levenson | | #24

    Response to Martin
    Hi Martin,
    Yes, understood regarding your position. I just think that PHI's position has more to do with buildability. - that if PHI thought .2ACH was reasonable they'd argue that .2 was necessary to avoid mold/rot... And like the earlier "eliminating a heating system" miscommunications, it appears to be more a matter of being lost in translation.
    - Ken

  25. GBA Editor
    Martin Holladay | | #25

    Response to Ken Levenson
    Wolfgang Fiest has often repeated his idea that 0.6 ach50 is necessary to avoid condensation problems. Although many Americans insist that these statements are "a matter of being lost in translation," I disagree. Feist's command of English is pretty good, and when I have asked Feist follow-up questions attempting to clarify the issue, he has stuck to his guns.

    Here's what he said in one of my interviews with him:

    Feist: "If you have air flow through the structure, humid air flowing through the construction, you can get condensation. That is the most important reason it has to be airtight, to avoid problems due to structural damage from moisture. The structural damage problem is the reason why the airtightness requirement is a separate number. That was one of the experiences in very early superinsulated houses — there were often problems, structural problems, from condensation."

    [Dr. Feist turns to me and asks me for confirmation. I agree.]

    MH: "But it is still possible to have condensation problems in a building that is perfectly airtight. That’s what happened in Juneau, Alaska. Convective loops brought warm, humid air in contact with cold sheathing, and there was rot — even when there was no exfiltration."

    Dr. Feist: "It is always a good idea to have it as airtight as possible. From a technical point of view, having a figure of .6 ACH or its equivalent in metric units will give you a good guarantee that you don’t have damage from infiltration or exfiltration."
    __ _ _ __

    There are three issues here that Feist has muddled:

    1. There is no evidence that buildings with air leakage rates of 1.0 ach50 or 2.0 ach50 have problems with condensation.

    2. Problems with condensation can happen even when there is no exfiltration or infiltration.

    3. Some types of walls (for example, ICF walls) can tolerate lots of condensation without damage.

    In short, there is no basis for Feist's statement that 0.6 ach50 is necessary to prevent condensation.

  26. Ken Levenson | | #26

    In response to Martin
    You're talking past each other..... The Germans talk about airtightness inboard of the insulation - so if you have airtightness in this way there can be no contact with cold surfaces and you are guaranteed no problems. Again, the the .6 it is a buildable limit they are positing. For renovation they make the limit 1.0ACH - the physics and risks are the same.... So to take both at face value there is an internal contradiction....unless there is something else going go as tight as you reasonably can be expected to. Then there is no contradiction etc, etc...

  27. dankolbert | | #27

    So we should treat Feist's writing as less of a diktat and more as a zen koan?

  28. jinmtvt | | #28

    Dr. Feist
    has manifested his hard position on different levels, many times now. This is one of the reason why PHIUS had to work on a modified standard.

    Why would dr. Feist change his position on airtightness ?

    I also disagree ( with my limited knowledge and intuition ) that this airtightness target indicates a condensation proof building, but, one has to admit that pushing for a specific, moderately severe 0.6ACH, obliges the designer/builder to do as best as they can to reach the target.

    In that, it seems to attain its goal, and we've seen many examples of teams surpassing this measure within acceptable efforts.

  29. GBA Editor
    Martin Holladay | | #29

    Response to Ken Levenson (Comment #26)
    I think that the record clearly shows that both the Passivhaus Institut and PHIUS have taken the position that the purpose of the Passivhaus airtightness target is to limit condensation and mold.

    From a technical point of view, this position is difficult to defend, and for the life of me I have no idea why both organizations continue to try to defend it.

    It would seem to me that a much more defensible position would be that very tight buildings perform better and save energy compared to leaky buildings, and to establish an airtightness target that can reasonably (and cost-effectively) be achieved on a job site.

  30. GBA Editor
    Martin Holladay | | #30

    Response to Dan Kolbert (Comment #27)
    Not quite. The Zen approach is more useful for interpreting the Pretty Good House concept.

    "What is the sound of a house with more cfm of exfiltrating air than infiltrating air?"

    You guys in Maine have all winter to come up with a few more such koans.

  31. dankolbert | | #31

    We'll work on it
    We're meeting tonight. Maybe guided meditations.

    "Inhale and think of your make up air. Exhale and think about your mechanical ventilation."

  32. Ken Levenson | | #32

    Response to Martin
    Not sure why you're repeating yourself - at risk of doing same: Yes, extreme airtightness is driven by "First, do no harm" principle. And yes, PHI has declared .6ach for new construction AND 1.0ach for retrofits - reasonable and cost effective. We think that is the case, while others may disagree. (I think this is all pretty well spelled out in our blog post.)

  33. wjrobinson | | #33

    Dogs... look at all the
    Dogs... look at all the shapes and sizes and... cats... domestic anyway.... color changes...that's about it. Raining cats and dogs... PH... PHIUS........ and .... pee you, comes to mind.... now give me a PGH and I get pretty darn excited..... gotta go pee now... you know the puppy... that can't hold it...upon greeting the love of it's life. PGH.... for me.

    Sorry, just have a hard time explaining myself in peer review format and word. Too boring for such a short life on this planet.




    Start the nationwide cheer

    Who's on the plaque committee for PGH? If we can have one person per committee with full dictatorial rights, I'm in.

  34. anderslewendal | | #34

    opportunity cost/PHIUS
    Martin: Excellent article. I think you nailed it on all accounts. I hope the PHIUS staff and supporters take seriously your recommendation at the very end of the article:

    For the net-zero-energy designer, an envelope measure makes sense if the value of the energy saved by the measure exceeds the value of the energy saved by a PV system that costs as much as the envelope measure under consideration.

    All energy performance improvements should be guided by this measure. Although I believe the current PHIUS protocol goes well beyond the cost optimum point I am building a new custom PHIUS based home in Zone 6. I'll let you know how the costs compare to the annual savings in a year or so.

  35. GBA Editor
    Martin Holladay | | #35

    Response to Anders Lewendal
    Thanks for your comments.

    If you want to write a guest blog for GBA in about a year, sharing your experience building a home to the PHIUS standard, we'd be interested in publishing it. Keep track of your costs, and keep track of your energy use and budget.

  36. anderslewendal | | #36

    response to Martin
    Thanks. I plan to keep track of actual costs compared to achieving an Energy Star Home which is our basic level. Since my client is not bringing in natural gas to the house we will install PV to achieve net zero. Should be easy to get actual energy use for a full year. I am happy to share my spreadsheet when we are done.

  37. Expert Member
    MALCOLM TAYLOR | | #37

    Looking forward to reading about it.

  38. mikekeesee | | #38

    Passivhaus Controversy
    Martin once again brings clarity to the Passivhaus controversy. In particular, his comments on whether the market will accept Passivhaus, even the new "American" definition of Passivhaus, is the most important question to ask. Here's my take on Passivhaus. I spent 22 years trying to persuade national production (and local custom) home builders to build energy efficient homes and adopt new business practices as the manager of a utility new construction program. In brief, it wasn't easy and most builders resisted incorporating energy efficiency into their new home products (and still do). Without changes to California's Title-24 building code, I doubt that my efforts which included providing generous cash incentives and free training would've gone nearly as far as they have. And as far as Title-24 has come, it is still far short of Passivhaus, German or American.

    The problem I had (and have) with Passivhaus was that it represented an ideal "standard" that as Martin explains does not recognize market conditions and more importantly the American home building business culture. As an ideal standard, I appreciate Passivhaus for setting the bar for what can be achieved, especially from a research point of view. But that's where Passivhaus falls short. As an unattainable standard for the overwhelming majority of home builders (and incomprehensible standard for home owners), it will have little or no influence on how homes are built. This important fact is especially relevant for areas without stringent building codes, which is the majority of the country. Getting bog down on definitions is something of a pointless exercise if the intended audiences - home builders and owners - ignore it.

    The most pressing home building issue that needs urgent attention is radically transforming the home building industry's culture and building practices, not coming up with a new foreign, obtuse, difficult to implement, costly standard. In my experience, the one thing that caught the attention of both builders and owners was the Zero Energy Home (ZEH), and by zero energy I mean it's simplest, easiest definition- a home (building) that uses as much energy as it produces (or a zero, annual utility bill for homeowners). Both builders and owners instantly grasped what ZEH meant and were enthusiastic about it. The problem was in building a ZEH, and so long as builders continue their current practice of basing their business on out dated building techniques, such as in field assembly, and low-cost subcontractors ZEH was hardly cost-effective, especially from a low cost production business model. The advent of low cost PV is something of a game changer but still represents what I'd call an "old school" approach to improving home performance; that is, a "technological" solution - let's just slap on a new (costly) "technology" on to improve the home's performance rather than use design and improved business practices to gain efficiencies.

    This business approach to ZEH can be seen in the best of the Japanese production home builders, like Sekisui House. Sekisui and others are true production home builders that employ continuous quality improvement in the manufacture of homes, controlling all aspects of home building. Sekisui and others have been building ZEHs for several years for arguably the most discerning consumer in the world, the Japanese home owner, and they offer many lessons on how home building can be improved in the USA. I believe that the key, therefore, to wide scale adoption of ZEH is changing builder business models to a practice that builds homes utilizing continuous quality improvement techniques.

    But more importantly, wide scale, rapid adoption of ZEH is critical if we want to dramatically reduce the energy use and its environmental impacts of the residential sector, particularly contributions to greeenhouse gas emissions. As Martin points out, Passivhaus still requires energy to operate. And, the market will never accept Passivhaus as a building standard.

    To sum up then, Passivhaus, American or German, represents in my mind an important research standard that demonstrates the technological limits of home performance. It's not a standard that will work in the America home building market or appeal to home owners. ZEH is a building concept with wide spread appeal to both home builders and owners with tremendous potential for lower residential energy use and its associated environmental impacts, although poorly implemented in the USA. ZEH is best achieved by home builders who employ state-of-the-art technologies and use modern continuous quality improvement techniques to advance design and lower costs. It's critical that we devote our limited resources on assisting the home building industry change how it builds houses, but deploying another standard, one that's confusing and almost impossible to achieve is not the best way to make this change.

  39. user-1084434 | | #39

    The purpose of a "passive house" standard
    Thank you to Martin and all the commenters here. I haven't read the whole draft report but I hope to get to it.

    In a world of proliferating green building standards, I think "Passive House" should claim relevance by being a restrictive standard that focuses almost exclusively on building envelope. To me a "passive (passiv) house" should be a house with the best "reasonable" envelope. It may also be net-zero, LEED Platinum, Energy Star, HERS 50, etc, but isn't necessarily any of those things. It probably has to go beyond the "pretty good house" measures. In places with really cheap electricity (green or not) it should probably be uneconomical.

    I'm basing this on an understanding of envelope performance that might be flawed, however. I'm assuming that at some point, additional thermal control stops making sense at any energy price, and that point isn't too far from what the current passive house standards demand. At a certain point the embodied energy of the insulation (and/or the structure that supports it) exceeds the energy it can save in heating and cooling. At some point air sealing hits diminishing technical returns. If the "leak" you're hunting down during construction will spill less conditioned air over several years than a slightly damaged window gasket, or a door left open to get the groceries in, is it not a waste of effort?

    I don't have numbers to back this up (RTFR! I hear you scream), but I'm assuming at some level of thermal performance, the 15 year energy use of a house starts to get extremely sensitive to assumptions in the modelling program. I don't know how close a top of the line passive house is to that point, but if the descriptions of some European examples are honest, we must be getting close.

    Just my thoughts for now. If I had to sum up in a sentence, I'd say PHIUS should avoid being too pragmatic, I think there's a place for a cutting edge standard.

  40. wjrobinson | | #40

    Michael Keesee you have the
    Michael Keesee you have the best post I have seen in a long time.

    Net zero could be a one sentence energy code. It could be easily mandated by selling someone net zero electricity for a set price and if you go over you pay ten times as much or what ever the environmental people say the real value including pollution that energy should cost.

    And let the free market the builders you refer to figure out how to get there and how to learn to do as your Japanese have started to do.

    One simple rule and the free market. That's how the X Prize works so well. Put out the challenge and let games begin. That excites me as a builder. And so I fully agree with you. I just don't want to see another 800 pages added to the code books, so there I also fully disagree with you if that is what you think is missing as you implied by saying much of the country is lacking strong codes and strong enforcement.

    Make a meter that has your set allowance programmed in. Make an inside panel and smart phone app to keep the owners informed. And let the owners decide how to get to stay net zero or pay to play outside the rules automatically. No need to write a book of new regs and no inspectors and no payroll and administration and retirement and health care... I see this costing billions if tree huggers or school teachers implement this or dollars if it were my program or a builder were in charge.

    And even more important, when oil is down like now and the economy is decent, rules can jump up.

    And twice as important. Set up a timeline that every year via your homes age,it has to comply so that all existing homes are "net zero metered" (the name of the new aj plan) by 2035. 5% of the oldest homes go net zero annually. start with homes built from the years 0-1600, then 1600-1650.... analyze the home, set the new meter, and in one year it turns on the new netzero allocation program and you're on your own. Apply for energy stamps to a pool of private donators for material, money and labor via a net zero kickstarter restartingnetzero site.

    You all are smarter than me.... take my lead with this post and make something happen. Make is simple. Use the free market ideas. Keep the code pages down! I think one line is enough. That is my X prize challenge.

  41. Bronwyn Barry | | #41

    Michael Keesee
    I think your point regarding the need to transform our building industry is well taken and where most of us agree. How we affect that transformation is where we lack consensus. Despite your misgivings about Passivhaus/Passive House (and respectfully a number of totally erroneous statements regarding the standard) I believe that Passive House provides both the tools and the methodology that our industry so sorely needs to both transform itself and simultaneously reach the mythical 'NZE' goal many aspire to, but have no idea how to get there. (In as much as that is possible for what I'm guessing is around 1/3 of our built environment.)

    I'll respond to you more comprehensively off-line, since it looks like this thread is almost dead. I'd like to share a growing data set of Passive House projects in California that I think may surprise you, or at least make you reconsider your viewpoint. I've also just started four new projects this year, all driven by clients requesting Passive House (or at least an approximation, which I'm now calling 'Progressive House.') It's an exciting time to be working in this field and even more interesting to be focused on what you rightly refer to as 'a cutting edge standard.'

  42. GBA Editor
    Martin Holladay | | #42

    Response to Bronwyn Barry
    Thanks very much for your comments. I can assure you, this thread is not "almost dead." (It's solar thermal that is almost dead -- not online communication.) The conversation here is only dead when readers like you decide to take the conversation off-line.

    If you are willing to share aspects of the Michael Keesee / Bronwyn Barry dialog by posting your comments here, all GBA readers would be grateful. Thanks.

  43. Tom_Bassett_Dilley | | #43

    zeroing in
    I think PHIUS and NZERH are heading the same direction and will eventually converge: it makes sense to invest as much as is reasonable in passive measures (insulation, airtightness, passive solar) so that you can use a cost-optimum amount of PV to get to zero. To that extent, you prioritize Passive, or better said, you figure that amount out first, then figure out your PV.

    So how are you going to figure out that "reasonable passive measures?" Rule of thumb? IECC? Now imagine you're going to try to tell the US/Canada--from Key West through Edmonton to Fairbanks--what is the definition of "reasonable" for passive measures...kind of a lot to figure out there. I don't think many people are going to run out and get BeOpt and spend hours finding the cost-optimum, but that was what PHIUS did, using over 100 climate data sets, though they took it just beyond optimum--I think it's like a future-proofing idea, since energy rates will increase. Perfect? No. Helpful? Yeah, very.

    Having built a PHIUS+ certified house and designed a few others, including a few to the proposed adapted standard, I can say that the proposed standard is definitely easier to reach, closer to IECC, and, in the world of high-quality custom residences, not that big a deal if a good designer and builder are involved. It won't be for production builders or those who don't want to mess around with modeling, and if those wind up Pretty Good, that's not bad. Even better if they are NZER--but they should check to see if they can get to NZ using their rooftops for PV in extreme climates.

  44. Superpod | | #44

    Passive House standard and non European countries (Superpod)
    Fascinating thank you! I have been wondering about the PHI/PHIUS split details. From the perspective of another non-European country (Australia) the challenges of the PH Standard are many. 99% of the design and building industry has not heard of ... repeat. ... never heard of ... the PH Standard.

    I built a certified passive house and learnt what this means in all its glory.

    Barriers include lack of components, lack of services, lack of understanding, Oh yes, and that means cost. I agree that for area where elec is cheap AND would add where the climate is mild, AND in a country that has a handful of passive houses, if any, PH can seem prohibitive.

    But it is only cost prohibitive if your only equation is cost of building envelope vs cost of power.

    I think we need to raise the other features and benefits of PH more. And make it easier to construct. And think of other ways of compromising without compromising.

    I therefore made my building system a replicable building product to the PH Standard, with new connection details etc. (company Superpod, website

    Very very easy to build, and fast. Anyone can do it with a little training.

    So adding speed to PH benefits helps. That can make it a cost saving if you have larger projects including high rise.

    And it has low maintenance components that don't need painting. Ongoing maintenance costs are reduced.

    It is steel therefore robust.

    The comfort benefits of complying with PH Standard are blowing us all away. Everyone who walks in the door wants one. In a climate (Melbourne Australia) where temperatures bounce around even in a day between 38 and 10 degrees, who wouldn't want consistent relaxing fresh but stable temperature air inside? The effect on the psyche is truly remarkable. Put a dollar value on that!

    Barriers to entry for PH include an obsession with windows here, which means imported windows, because triple glazed high qual windows virtually don't exist here. people also like fireplaces or wood stoves.

    Finally, I have decided that to offer the product to those who can't afford a whole PH, we will have a PH core, with a sunroom annex - the annex will be usable for comfortable days, or when you want a wood fire stove. It can have single glazing and be cheap and poor insulation etc. Could even be just corrugated iron!

    That is compromise without compromise.

    One more thing, I would like to see PHS adopted and adapted around the world without country-specific variable standards. It is hard enough without people trying new measuring methods. I say let's stick to one method but find other creative solutions to cost barriers and expand the debate about PH benefits.

    (oh yeah, like that other little benefit, climate change improvements from reduced carbon emissions... but who in the building industry, government or customer base really cares about that?)

    Our building system can be done anywhere as the products are readily available (apart from windows!). This is my attempt to promulgate the established standard for low energy use in building design across country borders.

  45. GBA Editor
    Martin Holladay | | #45

    Response to Fiona McKenzie
    Your comments imply that most builders in Melbourne can't build a house with even indoor temperatures. That's surprising.

    You wrote, "Who wouldn't want consistent relaxing fresh but stable temperature air inside?" I agree that stable indoor temperatures are usually desired. But they aren't that hard to achieve.

    A good builder should be able to deliver that. What you need is a fairly airtight envelope with decent insulation, and a well-designed HVAC system. You certainly don't need a Passivhaus to achieve that -- although I don't doubt that a well-designed Passivhaus can provide it.

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