Image Credit: Martin Holladay
More Musings of an Energy Nerd
For years, the English-language website of the Passivhaus Institut in Germany provided this definition: “A passive house is a building in which a comfortable interior climate can be maintained without active heating and cooling systems. The house heats and cools itself, hence ‘passive.’”
The idea of a house that “heats and cools itself” has a certain PR value, of course. The only problem is that it doesn’t exist. Excluding a few buildings in areas with a very mild climate (for example, in San Diego or Honolulu), no one has yet managed to build a house that heats and cools itself. That’s why Passivhaus buildings always need an active heating system, an active cooling system, or both.
The chickens come home to roost
Until recently, most of the people complaining about exaggerations from the Passivhaus Institut were cynics and curmudgeons like me. Now, however, even Passivhaus fans have begun grumbling about the fallout from the false claim that Passivhaus buildings don’t need heating or cooling systems.
The myth is responsible for a great many misunderstandings — misunderstandings that can in some cases lead to bad building designs.
“Beware the Passivhaus Kool Aid”
Allen Gilliland is the founder of One Sky Homes, a design/build firm in San Jose, California. His company specializes in Passivhaus construction, and Gilliland designs all of his projects’ HVAC systems. In a recent PowerPoint presentation that he shared with a monthly meeting of a group called Passive House California, Gilliland expressed his frustration with the idea that a Passivhaus building “heats and cools itself.” In one of his slides, Gilliland warned, “Beware the Passivhaus Kool Aid: Hyperbole, careless references, and hearsay are everywhere.”
It is often said that a building with a low rate of air leakage and above-average amounts of insulation is inherently more…
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64 Comments
Duh +1... And what about moisture control issues?
It appears to me that any time I read about Passivhaus I only hear about heating and cooling. Last weekend, we had a slumber party for my son, and were amazed with how much more "humid" the house became with 10 additional 12 year olds running around the house. And even though we live in a 50 year old house and did an energy retrofit a couple years ago, our home is probably "breathing" at around 25 times the PH standard.
I am certain that if we had somehow miraculously achieved the Passivhaus standard, we would have been screwed if we didn't have some form of mechanical moisture control. For a good portion of the year, the outside air here is probably either too moist or too heavily pollinated to mix into the home without electrical/mechanical assistance.
In 2013, I just can't imagine a house being built in this part of the country (Mid Atlantic) without some form of H-VAC system. Given the expense of PH, it's "sort of" like buying a high-end electric car and being persuaded you can do without air conditioning because it will reduce your car's efficiency.
Damn Occupants!
I too applaud Evans & Rue. We can build all sorts of wonderful things, but occupancy trumps all, and can either simplify or complicate, save or squander.
Perhaps I am a bit naive
But given the amount of money being thrown into these projects... Is it a bit odd to think someone might have thought of just throwing a small inline fantech fan or equivalent, with a nice merv11 or hepa filter inline, with a low air return, pushing air up or around to distributed supply ducts to both balance air temps, and clean the inside air at the same time?
This strikes me as basic as something such as, having windows, or doors in a house.
Response
This was an interesting article, and I’m glad to see some discussion of how to improve Passive Houses’ performance. Although I can’t say I agree with all the criticisms or things stated in this article, I believe that having these open discussions is important. As one of the Evans-Rue homeowners, I’m a huge advocate for Passive House design and look forward to the day when it is commonly used across the U.S. – and we need to continue to tweak and improve the concept to help it move closer to that common usage. The issue of having more even temperatures throughout the home is an important one to consider, and one that I hope will continue to be improved.
That being said, I had to comment about several of Gilliland’s statements about our Passive House in Oregon, because they are inaccurate.
1. He stated that our home suffers from “serious overheating” and that some of that is due to our condensing dryer. He claims: “The homeowners told me, ‘We can’t use our dryer for most of the year because it gets too hot inside.’” We never said that, because it is totally untrue. As my husband, Stuart, said in this article, we only consider the effects of our dryer on the hottest days of the year, which is only about two weeks in our climate. On those days, we do try to avoid doing laundry during the day and do it more at night when our windows are open to let in cooler air. But for the other 90-95% of the year, we use our dryer at all times of day without thinking about it, and without any issues whatsoever. I’m not sure where Gilliland got the idea that we “can’t use our dryer for most of the year.”
Even if what he said were true, and the dryer was an issue for us, his idea that the dryer “needs to get out of your building envelope” doesn’t make sense to me from a convenience perspective. We purposely located our laundry room upstairs right next to all our bedrooms because I didn’t want to constantly lug all my laundry up and down stairs (and with one cloth-diapered toddler in our house and another one on the way, we generate a lot of laundry). I can’t imagine having to drag my dirty clothes outside the main part of my house (into my garage or elsewhere) – it would not be as convenient.
2. Gilliland also said our house has a problem with a noisy ventilation system. I am unsure how he reached this conclusion, because we have always considered one of the high points of our house to be that the system is extremely quiet. In fact, we recently gave a tour of our home to some future homeowners who were considering a Passive House, one of whom was admittedly picky about the noisiness of the system in her current non-Passive home, and both of them marveled at the quietness of our system and how it could barely be heard. Yes, our mechanical room is located inside our home (in the mud room), but our builders insulated the walls around it to keep out noise, and so we also never hear any noise from our ERV, hot water heater, etc. So I would say that we definitely do not have issues with noisy ventilation.
Again, I’m glad to see open discussion on these topics, I just felt the need to add my voice to make sure those discussions are accurate.
Response to John O'Brien
John,
Your suggestion of introducing a mechanism to recirculate indoor air is an interesting one. (You suggested "throwing a small inline Fantech fan ... with a low air return, pushing air up or around to distributed supply ducts to ... balance air temps.")
Of course, most U.S. central heating and cooling systems recirculate air as a matter of course.
In the Passivhaus community, however, one is immediately faced with Dr. Wolfgang Feist's prejudice against recirculated air. One of the definitions of a Passivhaus that has been proposed by the Passivhaus Institut is this one: “A Passive House is a building, for which thermal comfort can be achieved solely by post-heating or post-cooling of the fresh air mass, which is required to achieve sufficient indoor air quality conditions – without the need for additional recirculation of air.”
The idea is that 100% of the air coming out of the fresh air ducts must be exterior air. Passivhaus purists see the recirculation of indoor air as a barbaric American practice.
Response to Sarah Evans
Sarah,
Thanks for posting your comments, and for clarifying the facts regarding the performance of your house.
Great coverage of points
I've worked with Allen and Bronwyn and over time I've really come around to their perspectives. In some sense, before their concern about cooling (especially in Bay Area California climate zones). Prior to learning from Allen, I was more interested in building occupants making a stronger connection that they're living in a sewer of their own waste heat, and that perhaps they need to regulate that better. In other words-- occupants of a Passivhaus (like Sarah and Stuart) are pretty good about 'learning' how to live in their house comfortably.
I've now come to realize that this is an important expectation to make clear. And, I've found that many of my clients like the 'insurance' policy that thinking about an active cooling system provides. The added cost of proper distribution is something that becomes another choice for the homeowners (not a matter of fact).
[BTW-- I hope that someday, there might be a way to showcase on this website a particular example of a reasonably cheap, flexible, and eminently clever HVAC system for a house that Allen designed on with 10 bedrooms (!), where each bedroom is it's own zone with thermal and acoustic privacy from neighboring rooms. ]
People who want to be hands off with their house will always pay a premium price for that. In other words, if they don't want to open windows, then they'll pay for that in any number of ways. After all, window opening is essentially how we turn the (UA) value of a Passivhaus into a conventional house in about 10 seconds.
Adapted for our local environment
Hi Martin,
Thanks for the article on our recent One Sky Homes presentation. As you’ve noted, it’s good for the high performance building (aka ‘Passive House’) community to keep things real by looking at both our successes and failures. Our goal is always to do so in a constructive and respectful manner and your article almost conveys that.
It’s great to hear that the Rue-Evans family has fine-tuned their activities to optimize the comfort of their house. (We already know the Passive House envelope optimized the performance.) While it was never our intention to ‘out’ them on a national forum ~ thanks for that ~ I'm relieved to read that Sarah Evans is able to see this as part of a larger discussion on how to improve the performance of Passive Houses in general.
Given your own particular penchant for hyperbole where Passive House is concerned, I must commend you on your restraint. You managed to hold out all the way until the comments section before slinging two ‘zingers’ at both Dr. Feist and Passive House in general. (“In the Passivhaus community, however, one is immediately faced with Dr. Wolfgang Feist's prejudice against recirculated air.” and “Passivhaus purists see the recirculation of indoor air as a barbaric American practice.”) I take that as a good sign. It must mean that you’re finally warming up to Passive House?
Lastly, I’d like to invite you and any other PH-curious builders and clients to visit us in California at any time. Allen and I are both regular contributors to a very active Passive House California community, for whom this presentation was developed. Their website for meeting info is: http://www.passivehousecal.org. It will also enable you to recognize the context in which much of this mechanical systems design advice was given – a climate zone in which certain pieces of equipment really should not be included within the thermal envelope.
Viva Passive House! Viva Dr. Feist! Viva all the clients, architects and builders willing to seriously address carbon emissions by building and living in these high performance buildings! :)
Response to Bronwyn Barry
Bronwyn,
Thanks for your comments. It seems that the remaining unsettled debate -- in light of your comment that your climate is "a climate zone in which certain pieces of equipment really should not be included within the thermal envelope" -- is whether a clothes dryer belongs indoors or in the garage (or, presumably, on the porch, if the Passivhaus family has moved from automobile transportation to the use of bicycles).
Sarah Evans likes the convenience of an indoor clothes dryer. It seems that you are implying that locating a clothes dryer indoors is a no-no. It will be interesting to see how this debate resolves itself over the next few years.
When I spoke to Allen Gilliland, he explained that turning on a large-screen TV and cooking dinner can raise indoor temperatures by a few degrees, so maybe the TV and the kitchen stove belong on the porch, too -- right beside the clothes dryer. Perhaps your climate is one in which all domestic activities can occur on the porch -- in which case the Passivhaus Institut's dream of a house that heats and cools itself may finally become a reality.
Let a thousand pretty good houses bloom
Ms. Barry writes - "...it’s good for the high performance building (aka ‘Passive House’) community to keep things real by looking at both our successes and failures." Agreed except for the aka part - there are many paths.
I've said it before...
In my AO I simply can't sell discomfort and deprivation, and especially not to clients in a position to shell out the substantial extra $ a PH (or for that matter, LEED Titanium home) requires for both construction and documentation.
I've been a critic of PHs "10% overheating" standard since I first learned of it a couple years ago. Today's root article describes that as 36.5 days. While that is an astoundingly long period of annual discomfort, the reality is likely a bit different. The upward temperature excursion contemplated by the PH standard is likely to occur only during summer afternoons and evenings, say from 3 PM until midnight, in other words, call it 9 hours per day. Applying that reasoning to the 10% standard returns almost 100 DAYS of temperature excursions, effectively the entire summer.
Another troubling aspect of the PH 10% temperature excursion standard is that it is based upon 77*F (25*C). That in itself is OK, assuming decent RH, say below 50%. What is left unsaid is the degree of deviation...is a period of 78*F interior temperature treated the same as a period of 83*F interior...88*F?
I think that PH aficionados, confronted by the reality of inadequate response of their projects to summer's sensible and latent loads, affect a sort of "Stockholm Syndrome" with regard to the characteristics of the project. They declare that they really don't mind that rooms not served by the central minisplit rise into the low 80s, or that they don't mind not being able to cook anything more sophisticated than a bowl of soup, or not being able to do laundry on warm days. Given that stance, the best thing they could do for the environment would be to give up entirely on the PH and instead just camp in tents. That way they can experience all the discomfort and energy savings of a misguided PH project but avoid the trouble, embodied energy and hideous expense.
As to 5*F temperature differences amongst rooms? Clients pay me good money to wring that OUT of their homes, most assuredly NOT to design that in!
Every project should include a room-by-room Manual J calculation and an HVAC plan to meet the latent and sensible loads of each room 99% of the time (NOT 90%). I don't care if the walls are R5 or R50, the windows U 0.5 or 0.05. I'm willing to contemplate any combination of HVAC, HRV, ERV, recirculation, whatever, as long as it has a reasonable chance of attaining temperature setpoint at a reasonable humidity 99% of the time.
I strongly support cost effective measures to reduce HVAC load - I routinely advise clients that I could furnish and install X tons of HVAC for their house as it exists, but I could go with X-1 (and often X-2 or X-3) if they implement load reducing upgrades. If they agree, I set about lining up a project team to implement the reductions, QC the work, and then install the downsized HVAC.
However I will not sacrifice, nor ask clients to sacrifice, comfort at an altar of blind devotion to an arbitrary and capricious standard of home and HVAC design.
Long live Pretty Good Houses!
Response to Curt Kinder
Curt,
Thanks very much for your thoughtful comments. I think that your suggested phrase to describe some Passivhaus homeowners is a useful one -- the "Passivhaus Stockholm Syndrome." Something tells me that I'll have an opportunity to use the phrase in the future.
I had a feeling...
...that might resonate
Not to pile on, but
May I suggest Darmstadt Syndrome?
Response to Curt Kinder
Curt,
Your statement: “I will not sacrifice, nor ask clients to sacrifice, comfort at an altar of blind devotion to an arbitrary and capricious standard of home and HVAC design.” Really puzzles me.
The issue is simple load vs comfort and it appears that you refuse to place any responsibility on your clients. I could understand it when clients demand it, but here you seem to relegate anyone placing comfort over principles as only worthy of living in tents.
That’s a curious attitude to me when this week I read that CO2 is now holding steady above 400ppm: http://www.nytimes.com/2013/05/11/science/earth/carbon-dioxide-level-passes-long-feared-milestone.html?pagewanted=all&_r=0.
Between your clients and the occupants of the Evans-Rue household, the Oregon householders are far better citizens as they accept a wider comfort range. I’m surprised that you would advocate for less occupant participation in the actual, operation of the building. After all, isn’t that the overriding issue and common complaint of all loads (especially plug loads): Lack of occupant engagement???
I understand the professional issue involved, but just because you cant sell your clients on lower loads doesn’t mean that you should make fun of it.
Martin, Dan & Curt
Boys, boys, boys...
Your "syndrome" phase is "cute" regardless of it being based in Stockhom or Darmstadt.
However, before you get too excited with your "new toy" and over use it: If these owners are not self deluding, and that the projects really work...
You just come off as cry babies.
Response to Albert Rooks
Albert Rooks,
I will describe the two camps.
On one side is Allen Gilliland (a Passivhaus fan) and Curt Kinder (a Passivhaus skeptic) who both agree that clients deserve a high level of comfort and room-to-room temperature differences that are as low as possible.
On the other side are Albert Rooks, Sarah Evans, and Stuart Rue (all Passivhaus fans) who are willing to tolerate occasional high temperatures indoors, a wider range of room-to-room temperature differences, and active daily tweaking of drapes and windows, as well as some flexibility is using appliances during the summer.
There is no need to insist that only one of these camps is correct, and the other is wrong. There is more than one way to build a house, and many possible lifestyles. As I wrote in my concluding paragraph, "The common-sense approach adopted by Sarah Evans and Stuart Rue — an approach which occasionally requires them to take active measures to adjust curtains and blinds, and to accept a greater range of indoor temperatures than their more finicky neighbors — shouldn't be dismissed out of hand."
Here's what's important: if a designer is building a house that requires the Evans-Rue level of participation and flexibility, the designer had better inform the homeowners about what they are getting into. Especially if the homeowners are paying a $40,000 premium for Passivhaus features.
Finally, Albert -- concerning your finger-wagging ("boys, boys, boys"): I haven't yet had an opportunity to use the new phrase, "Passivhaus Stockholm Syndrome." All I wrote was, "Something tells me that I'll have an opportunity to use the phrase in the future." Until I use it for the first time, you can't wag your finger at me.
Response to Martin Holladay
Martin,
I don't see where I took issue with your post, or where i said that there is a right way or a wrong way. Again my point was a simple value judgement: I think that it's in all of our interest when occupants accept wider comfort ranges in order to reduce loads. That seems like an obvious environmental benefit. Would you disagree?
My comments were directed at Curt writing: "Given that stance, the best thing they could do for the environment would be to give up entirely on the PH and instead just camp in tents. That way they can experience all the discomfort and energy savings of a misguided PH project but avoid the trouble, embodied energy and hideous expense."
Perhaps that doesn't seem a little strong to you, but it does strike me as belittling. Notice I wrote two times that I understand the professional conflict.
Lastly, the point I was making was not about Passive Houses, It was about occupant involvement. The same issue you have written about many times such as: "There are no net zero houses, just net zero families". Occupant expectation and behavior are a significant load factor as you have pointed out in the past.
And... On the "finger wagging". Perhaps I was premature. My feeling is that you enjoy a good turn or phrase more than most and would be eager to use it. I did say it was a good one:)
Response to Albert Rooks
Albert,
Fair enough. I understand your points, and I agree. Occupant behavior matters -- and conscientious homeowners like Sarah Evan, and Stuart Rue are definitely taking an admirable approach to saving energy.
And my comments about living on a porch (as well, possibly, as Curt's comment about living in tents) were flippant rather than helpful.
Response to Martin Holladay
Martin,
Thanks for the reply, and yes in rereading I can see that Curt's intent was probably aimed at a far worse performing building that I was talking about. (Sorry Curt if I took your position out of context.)
I can see that too many Passive House is a bit extreme on many fronts. Passive House Northwest together with Walsh Construction hosted John Straube recently in Olympia WA. He delivered his HVAC for low load buildings presentation. The same one that you wrote about in https://www.greenbuildingadvisor.com/blogs/dept/musings/choosing-hvac-equipment-energy-efficient-home.
It was a great day and we are really happy that together with Walsh Construction we were able to offer the day for free to 190 attendees.
As you can guess, we went a few friendly rounds on airtightness. Dr Straube maintained that 1.50 ACH 50 was enough for any situation and that 0.6 ACH50 was "arbitrary and wasteful since the resources could be used elsewhere". He stuck to this even though members in the audience kept telling him that 0.6 was now easy. One even kept on with the point that by targeting 0.6 the common results are in the 0.40's.
My point is that these standards and goals are achievable even though our stalwart educators are still holding more lenient targets. I often wonder why the resistance in greater efforts...
The bit about tents was flippant but illustrates my point
I stand by my scorn and disdain for what essentially amounts to a home with an HVAC system designed to fail to meet code 10% or more of of the time. Code in my neck of the woods requires that the HVAC system be able to attain 75*F on a 99% design day. Sound practice dictates we avoid relative humidity above 60% whenever possible. PH awards itself a pass on that.
I strongly suspect, ESPECIALLY in the case of a submarine-airtight, superbly insulated PH-like home, that the energy consumption difference between being comfortable (indoor conditions somewhere inside the ASHRAE square on a psych chart) vs being 5 degrees outside the square is chump change.
There's been lots of controversy over the PH standard of 0.6ACH50. That is one PH standard I, like Joe Lstiburek and others, care not a whit about. While the payback period on the added $ to achieve 0.6 vs say 1.5 might be measured in centuries, that's a fair choice for a design team to make, as long as whoever is cutting checks knows the score. A house will be no less comfortable for it.
I take vehement exception to tying the HVAC team's hands with arbitrary standards and limitations that operate to force the HVAC to fail.
Building codes and sound practice exist to protect not just the first occupant of a home or building, but also FUTURE occupants whose priorities may be much different.
There is nine kinds of hand wringing and sighing about getting bankers, appraisers, and the wider community to place and accept a premium on energy conservation. If a buyer shells out a $40k premium in March for a PH but then learns, come June, that the master bedroom will be no cooler than 82* for the next 80 evenings, that buyer will be pissed off, and at the end of the day, two days max, it won't BE a PH any more because there will be some sort of add-on AC. No one, within or outside the PH or broader home performance community is well served by such outcomes.
My company constructs new and retrofit projects designed to deliver comfort at the minimum possible tonnage consistent with clients budgets and ROI goals. We advocate high SEER HVAC, ducted or not, with particular emphasis on even temperatures and good humidity control. That generally means multi-stage or variable capacity systems with zoning. Our energy conservation work / expertise extends beyond HVAC to insulation, air-sealing, glazing, water heating, lighting, kitchen, laundry, media, even pool filtration pumping.
If a client THEN decides to save EVEN MORE energy via relaxed setpoints, such as 60s winter, 80s summer, they are free, indeed welcome, to do so, but I will not be a party to a project that regularly inflicts those conditions on occupants without their consent.
Shivering / sweating naked, unbathed, and starving in the dark may truly be the best thing for the environment, but I defy anyone to run a business based on that. Religion maybe, commerce no.
Response to Curt Kinder
Curt,
A few years ago I'd agree that 1.5ACH50 was good. However the reality is that we can regularly achieve 30% of that number on new projects.
It really doesn't matter if you have notoriety like Dr Joe or not. Airsealing is just plugging holes. There's nothing to be gained by skipping a few.
Take a look at the attachment. It's a letter dated last Friday from the guys that performed the airsealing work on The Small Planet Workshop. The initial test showed 9.12 ACH50 when we moved into this 20 year old steel building January of this year. It did not cost anymore to get to 1.07ACH 50 than it would have cost to stop at 1.5ACH50. And that's on a 20 year old building constructed without any regard to airsealing and simply using the drywall as the air barrier. For new projects 0.45ACH50 is now the average high range.
I offer the attached letter as proof that blindly sticking to 1.5ACH50 in 2013 is outmoded thinking.
It's too bad your company is not designing HVAC for PH projects as well as your current work. Your team would probably be really good at it. The two projects that you and Martin are evaluating were the first PH projects in the Western United States. I personally know both builders. They are great guy's and did their level best without any other projects to learn from. The comfort standard that is the source of your disdain is simply a relaxed performance range. Your not required to design to the minimum.
It sounds like with your skill, you could design better low load HVAC systems that operate in a tighter performance range than the PH minimum. Well, who wouldn't welcome that?? If you can't reach the load minimums then I guess you've got something to work on. There are many that would appreciate any performance improvements you could bring to a project at similar loads. The building enclosure would help you. It's just got a little more insulation and fewer air leaks.
(Note that the air sealing letter is addressed to WestCoast Associates. WCA is the parent company of The Small Planet Workshop. The work was done on 2000ft2 of wood framed offices with a drop ceiling within a 12000ft2 steel building. Final test results are from this past Friday and include a fully ducted ventilation system ((Zehnder CA 350))
"Plenty of idiots..."
I've learned a great deal from this website and from your writing specifically, Martin. You and GBA give out an incredible amount of information, much of it for free. One of the things I appreciate most is your writing style and the dignity with which you approach your readers.I try to read every article and every answer you give in the Q&A sections. I've never read a single word reflecting a superior attitude, yet you are widely recognized as a leading expert.
When I hear, "There are plenty of idiots who....", the rest is just noise. I don't care what their level of knowledge is, I tune them out. I truly appreciate your depth of knowledge and the humility that comes with it. It's interesting to note how much more engaged your readers are, judging by the number of comments you get, than other writers on this site.
Keep it coming. Thanks again for another great article.
You do realize
He was quoting someone else, right?
Response to David Martin
David,
In case Dan Kolbert's comment was unclear to you: the sentences that bothered you -- “There are plenty of idiots doing the wrong thing, and I think trying to fight that is a waste of good energy. Instead, I’m a big fan of encouraging the other people who are headed in the right direction.” -- were spoken by Bronwyn Barry, not by me.
For many years, David, I worked as a builder and spent every working day on a construction site. I can assure you that phrases like "plenty of idiots do it that way" are fairly common on construction sites. I might even go so far as to say that such a phrase is relatively mild compared to a true job-site epithet.
Bronwyn Barry is not the only construction professional who speaks this way. Joe Lstiburek is famous for the use of the word "idiots," for better or worse.
I agree that respectful language is an ideal we need to aim for. We will all catch more flies with honey than with vinegar. But I think I know Bronwyn well enough to give her a pass on this phrase. Let's just chalk it up to a little straight talk from someone who occasionally hangs out with builders (and building scientists).
truth is a valid defense against libel
A quick search reveals that at least Mississippi, Kentucky, Ohio, and New Mexico, by way of their state constitutions, prohibit idiots from voting.
Ohio: "No idiot, or insane person, shall be entitled to the privileges of an elector. "
I found no mention or prohibition of same engaging in the construction trades.
...or...
"I found no mention or prohibition of same engaging in the construction trades."
...or running for public office. :-)
Climate variation
Passivhaus sure brings out the strangest discussions and accusations.
So far in this conversation we have professionals from Florida (Curt), Bay Area CA (Bronwyn), coastal Washington (Albert) and coastal Maine (Dan) discussing a German energy standard in context of a project in Salem Oregon. If James Morgan and Armando Cobo would pipe up, we would have almost every climate zone in the country covered.
The tone here seems to be that there is something inherently flawed in the Passivhaus standard and practice, especially in the realm of over-heating, but if we just build houses a bit worse than Passivhaus (pretty good?), somehow all these technical issues of mechanical system cost, hours of supplied cooling and occupant comfort standard will go away? What kind of argument is that?
Why are occupants happier in a house with a worse built enclosure? Do buildings with worse enclosures have smarter mechanical designers? Better energy modeling? A lower burden of performance, so they don't get scrutinized in research projects and at conferences so we don't know if they are failing?
The logic doesn't follow. I know several pretty good houses with overheating issues, but they aren't under discussion here, because people aren't analyzing them trying to figure out how to improve their construction practices, improve the buildings they build, and build better houses that do less damage.
The only reason anyone has Passivhaus to beat on here is that the community is actively trying to figure these issues out in public, as part of a fractured and isolated construction micro-business culture working without national funding, in a system with no manufacturers of scale who can implement solutions across the board (like the auto industry, for example).
As well, to claim that Passivhaus practitioners are ignoring this issue is specious at best.
Overheating and summer comfort analyzation is the #1 improvement listed in the current 2013 version of PHPP from PHI europe: http://www.passivehouse-international.org/index.php?page_id=188
It has been a dominant topic of the US PHIUS conferences over the last years, especially relating to the deep south and mid-Atlantic climate zones. Here is discussion back in 2010 on the issue, there are many other examples: http://passivehouse.us/passiveHouse/2010_Passive_House_Conference_Presentations,_November_6_files/2010%20Conference-Lafayette-Dehumidification-Corey%20Saft.pdf
Here is Katrin talking about the same issue in her recent post: http://passivehouse.us/blog/?p=724
All I know is that I hear constant talk about summer comfort, and how to deal with these issues in a smart, low cost way across the board. It's a real and active challenge, and it's certainly not being ignored so that home owners can shiver in silent misery.
Response to Jesse Thompson
Jesse,
The broad range of climate zones represented by GBA readers is one of the strengths of the GBA community. To me, the fact that GBA commenters represent "almost every climate zone in the country" is a good thing, rather than one that necessarily leads to what you call "the strangest discussions."
Thanks for the links, which are certainly appreciated. However, I think that the discussion on this page provides more depth and useful back-and-forth than any of the documents that you linked to.
Your first link goes to a page that announces a new version of PHPP that will include new "validated calculation algorithms for cooling and dehumidification in both hot and hot and humid climates." That will probably be useful for Passivhaus designers who want to avoid overheating problems.
Your second link goes to a PowerPoint presentation on the Passivhaus in Lafayette, Louisiana. (GBA has published two stories on the house in Louisiana: Passivhaus Finds a Home in the Bayou State and Following Up on a Passive House in the Deep South.) Unfortunately, most of the slides in the PowerPoint presentation that you linked to have no words -- just photos.
Finally, the blog by Katrin Klingenberg doesn't directly address any ways for American Passivhaus designers to avoid the overheating problem. She only refers to the problem obliquely, when she writes, "Word is that the PHI significantly improved the cooling demand and latent load algorithms to be more appropriate for hot and humid climates. A new latent demand annual budget had already been included in the overall cooling demand certification criterion for 2012."
You wrote that the Passivhaus community "is actively trying to figure these issues out in public." I'm aware of that; that's why GBA is reporting on one of the discussions (one occurring in a Passivhaus group in California).
Finally, Jesse, you imply that a Passivhaus building is better than a Pretty Good house when you write, "The tone here seems to be that there is something inherently flawed in the Passivhaus standard and practice, especially in the realm of over-heating, but if we just build houses a bit worse than Passivhaus (pretty good?), somehow all these technical issues of mechanical system cost, hours of supplied cooling and occupant comfort standard will go away?"
Here's my defense of a Pretty Good House: a PGH is more likely than a Passivhaus to have a conventional furnace that delivers conditioned air to every room in the house, rather than a single minisplit unit in the living room. As a result, a PGH with a furnace is likely to deliver more uniform comfort conditions than a Passivhaus with just one minisplit. Moreover, the Pretty Good House will almost undoubtedly cost less to build than the Passivhaus.
Regardless of the opinions and outcomes...
I really do want to say that these discussions are really helpful and that Im extremely happy to have the opportunity to read or participate in therm.
Jesse it occurs to me more and more that this is largely where the industry is moving ahead and that these small groups of PH, PGH, Active House are where it's happening. DR's John & Joe need the feedback as much as any of us do. Without a self admitted upstart like me, saying that 1.5ACH is too easy and "step it up!", standards don't get challenged.
It works because we can admit where we fail (as much as I hate to...) and that other professionals will not let us self delude.
The Passive House or (PGH) Stockholm Syndrome must be avoided.
There Martin... I beat you too using your new phrase! :)
We need a divorce - know a good family lawyer in Stockholm?
The PH envelope is a fine standard and its creators are highly skilled crafters and constructors - my hats are off to them. My brother in law has built a small bunch of PHs in Philly with more on the way.
I favor the tightest envelope, bestest windows and mostest insulation an informed client consents to buy. As an AC / heat pump guy, I then want to meet the tiny remaining load with the most efficient HVAC system an informed client consents to buy. We also want the home to have highly efficient water heating, lighting, refrigeration, laundry, media, pool pumping etc.
Insanity rules the roost when client comfort, which should cost pennies per day in these truly awesome enclosures, is sacrificed to comply with capricious HVAC rules.
It's as though my dream car, a 100 mph, 500 mile range, 10 km / kWh EV, came only with bare plywood seats because that's what the English translation of the German specification manual mandated. So arch your back and suck it up! Oh and you're not allowed to recharge it with site-mounted photovoltaic panels...because it says so, right here in appendix 17x...
Homeowners, raise your hand...
I am going to sit next to Sarah at homeowners' table and advocate a practical sustainable lifestyle: my goal as a homeowner is a balanced combo of low energy costs and great comfort and if I have to draw a curtain (or close a shutter, to be truly European...), I am happy to do it. All these minor manips will anyway be better than the truly uncomfortable leaking house I used to live in and where I had to invest in so many toys to correct the discomfort.
I also added a condensing dryer on 2nd floor of new passive house (where are men when you need to carry heavy bedlinen loads up and down?) and I shall be super duper happy to use the generated heat to air dry the rest of my laundry I never put in the dryer...saves energy and clothes!
Coming where I come from, it can only be better and I'll report more in less than a month when living in our newly completed passive house in NY state but I can already tell you how serene I am to see the leaf blowers and not hear them!!! My neighbor is jealous already...
PS1: thank you Martin for being our energy guru
PS2: just test drove the perfect car: TESLA S. Try it: it is hard to resist ;)
If the PH crowd gets ahold of the Tesla...
...look out for plywood seats
(Sorry - just couldn't resist)
I share your pleasure with the serenity of a house that transmits little exterior noise. We are variously buffeted by loud high performance watercraft, low flying military aircraft, and National Guard artillery practice. All are locally described as "the sounds of freedom".
Our ICF / sprayfoam / double pane windowed home prevents most of the above-described uproar from coming indoors.
Feedback loop?
As I've said at least locally, Jesse, the PGH may indeed be a PH in some cases. I haven't followed the internal debates and discussions of PHI or PHIUS. My concern has been precisely what you allude to as a problem here - the one-sized-fits-alledness of it.
Katrin has been apparently warming (that's a clever play on words) to the idea that things are different in the cold north. I'd like to think Martin's questioning has played a role but have no idea if that's true. But from my (very) limited involvement in a couple of PH projects here, I am concerned that designers, builders & owners may not be questioning decisions/alternatives in the way they should.
OTOH, from my (again limited) exposure to PHPP, I think it's fantastic software and I hope it gains wider usage and continues to be tweaked. And I am always happy to hear that there are discussions that may be affecting the model to take into account the experiences of real buildings & their occupants.
You're right that PH is a convenient target because it has a unitary (or, at the moment, binary and counting) identity, just as LEED was before. But it is also to be expected - if you claim as large a crown as PHI has, and look at everything else as "PH Lite," you'd better have your (free-range, cruelty free) ducks in a row.
At our most recent building science discussion group, the topic was energy modeling and monitoring, with a strong emphasis on the latter. If I have any energy left to put into things, that's where it seems to me that we should be putting our efforts - the lived experience of buildings. It's the cart-before-the-horse quality of PH that has always put me off. With the confession that it has never fully occupied my radar screen.
I also need to add that, as you and I have discussed, I'm not sure any single family detached is ever going to solve any of our problems. If any of the standards took size more into account it would also make me feel better about them.
Response to Curt Kinder
Curt,
I don't think we need to call up the divorce lawyers just yet. The Passivhaus community is still getting over its first divorce, and I don't think the children can stand another divorce so soon.
We're all going to have to learn how to get along.
Response to Veronique Leblanc
Veronique,
We look forward to your upcoming report on the comfort levels in your new Passivhaus. Let us know how much fiddling and how many lifestyle adjustments (if any) are required to achieve indoor comfort.
The more reports we receive from Passivhaus owners, the better.
Response to Dan Kolbert
Dan,
Great comments -- I agree. Thumbs up to your statements:
"I am concerned that [Passivhaus] designers, builders & owners may not be questioning decisions/alternatives in the way they should."
"If you claim as large a crown as PHI has, and look at everything else as ‘PH Lite,’ you'd better have your (free-range, cruelty free) ducks in a row."
"If [we] have any energy left to put into things, [monitoring] is where it seems to me that we should be putting our efforts - the lived experience of buildings."
"If any of the standards took size more into account it would also make me feel better about them."
practical experience - from all worlds
We just finished our retirement house in NE mass. using passive concepts, but also using passive solar concepts for underground or earth berm homes which we visited out in the midwest. Combining properly sized overhang (40 inches for latitude of 45 degrees) on all south windows, and super sealing the walls ceiling and foundations, using an ERV (Ultimate air), and a simple electric instant water heater for our embedded radiant floor heat, we have an extremely comfortable home now. Stays lower 70s during the hottest summer heat (90s last fall), and easily stays very comfortably warm in the coldest and windiest winters (very snowy and cold winter this year). I have to do a few changes to the heat source for our radiant floor heat to make it a bit more efficient, but simple logic and looking everywhere, and attention to detail - keep those hired hands away from the sealing of the structure, makes for a great house.
I choose not to get a passive certification since the cost was prohibitive (18k on top of an already designed home). I did attend passive seminars to learn about the concepts, and did attend Earth sheltered seminars and open houses also to learn. Combined the best of all worlds, and listen to logic, and you will end up with a great house. We did.
By the way - about R27 ICF walls, R25 under floor, and R60-70 ceiling blown in.
msd.
Additional comments
I would like to add to the comments I gave Martin.
Allen Gilliland picked a poor example in his search for a badly performing Passive House. Our house is the most comfortable house I have ever lived in. The temperature variations from room to room are very small, the floor isn't cold in the morning (unlike our last house), there are no cold/hot spots in corners or near windows, and the humidity is nearly always within a few degrees of 50%. All of this is done while running our heat pump very little.
During our first 12 months in the house, we spent about $75 on heating, cooling, and heating the water. Total. We did this using simple techniques such as opening windows and drawing curtains. It takes very little effort. But if this effort was somehow too great a burden for us, we have the option of simply running the heat pump more. We are not forced to open windows. We are not forced to run the heat pump. We have decided the balance that works best for us, and recognize that it will be different for others.
One of the benefits to having a high performance home is that when we do run the heat pump, it works very quickly and effectively. Contrary to what Mr. Gilliland reports, we do use our condensing dryer all year. During the summer, we choose to run it during the evenings to take advantage of the cool air venting through the house. We could use the heat pump to move that excess heat outside, but that seems silly when our current practice is so easy. But it's still a valid option.
Nor do we have a "serious overheating" problem. As I told Martin, our practice of using night air to flush out excess heat is limited during a few weeks each year when the outside temperature doesn't drop at night. As a result, we cool using the heat pump. This is not a failure of the house. It is a success that we need to do this so infrequently. It is a success that we can use such simple and easy practices to avoid using our heat pump. It is a success that with such little effort and for such little money I live in the most comfortable house I have ever lived in.
Finally, while I enjoy witty repartee as much as the next person, I think we could all stand to remember that we are on the same side here. We want to build high performance and sustainable buildings that are affordable and comfortable. I am sure that the PH standard can be improved, and we will probably never achieve perfection. We will differ on the best way to achieve our goals, but let us focus our energies on productive discussions. At the very least we can do without insulting phrases like "Passivhaus Stockholm Syndrome."
I seriously question
I seriously question your commitment to witty repartee if you don't find Passivhaus Stockholm Syndrome funny.
But otherwise, yes, one team, one fight, and we're arguing over the margins, not the meat. I'm thrilled that your house is performing so well, and I think Feist, Klingenberg, et al have contributed greatly to our understanding of how to build better houses. And I am going to stop now before I start using the word "but."
If not in the house, where does a solar tank go?
Martin,
Great article and thanks for continuing to focus on the reality of houses in the real world, instead of in models.
I do have to take exception with one thing though; you lump the solar hot water tank together with the condensing dryer and assert a number of times that it is problematic that the tank is in the building envelope and that it contributes to overheating. Where else would you have a hot water tank installed if not in the envelope?
A well insulated domestic hot water tank loses maybe 5-7000 BTU per day or roughly 250 BTU/hr to the mechanical room. That's less than the sensible heat gain from a single occupant so is hardly a smoking gun in any overheating house (ph or otherwise).
Best,
~Fortunat
http://www.revisionenergy.com
"Passive Houses did not overheat in the 80's"
...according to William Shurcliff who already knew about the physics of it all in then and wrote about it extensively:
1. Passive House is a subcategory of a Passive Solar House, a special kind if you will.
2. It does not overheat like its Passive Solar relatives because the design balances limited glazing/gains and insulation according to climate while also employing rigorous airtightness and balanced ventilation systems with heat exchangers.
3. Only a tiny space conditioning system is needed to maintain comfort on "rainy" days, the extreme climate conditions of the year (as tiny as 10 incandescent light bulbs, three friends coming over playing cards and if you are in a warm climate a few buckets of ice).
Nothing new really. The theory is the same.
I think I heard it here on GBA first that passive houses apparently don't heat themselves - I was stunned! They don't heat themselves? Oh these Germans really had me fooled :)
The more interesting question to me is, why the opposite is in fact true of what is being presented here in this usually very informative blog location: firstly, passive houses that have been built around the country tend to all have a small micro-load space conditioning system in them (those who accidentally forgot a system retrofitted one by now, I guarantee you). It indeed seems that the community of designers and builders is quite clear on the fact that passive houses don't heat themselves. Secondly, not only have the homes small systems but they actually work very well contrary to what is being described here and passive houses are widely characterized - backed by measured performance data and many articles in the media - as extremely comfortable (see homeowners testimony). These positive reports are coming from all climate zones where projects have been constructed (probably close to 300+ units now in this country? First certified one in Arizona was recently the center fold of the Wall Street Journal in the Mansion section on Friday May 3rd 2013). Measured data shows that they indeed have the lowest delta in temperatures between rooms amongst all their cousins PGH and all the houses with a big blasting fossil fuel furnace in them. How can it be?
It continuous: people also have started successfully to figure out how to build passive buildings very close to the cost of PGHs and regular construction, builders have gotten into it and with more experience prices have come down! Passive houses affordable now? There has been a learning curve and it appears that designers, technology and micro-load solutions are all clearly maturing.
Not only the topic of overheating but also micro-load integrated systems design including equal distribution and smart duct design has been actively addressed by the community and has been one of the center topics each year at the Annual North American Passive House conference (you should join us again sometime). It will be again in Pittsburgh this year October 16-19 for the 8th conference as there is lots of progress on systems optimization to report. The knowledge base is building and US manufacturers are coming on board.
Specific to the system, there is evidence of convective assist (thermal distribution) when a balanced ventilation system is continuously exchanging air throughout a space at very low flows. It is correct that a heat recovery device will always cool in the winter and always heat in the summer, but only very very little. Heat loss through envelope is so low and exterior surface temps are so warm, no need for a furnace, not even close. Point source and/or ventilation integrated small conditioning sources are sufficient. Various Building America teams have done research on this topic over the past 10 years and essentially they all agree on the underlying physics principles. It works.
The ability to keep these delta's of temperature really small and to minimize the heating and cooling effect of a ventilator to very close to non-existent is critically dependent on the right level of insulation and you guessed it internal heat gains/losses and climate appropriate design decisions including shape of the structure. But also just as important is the right energy design targets and metrics by climate. One does not fit all. Not optimized criteria lead to what already Shurcliff knew better: don't overglaze in sunny USA when chasing the annual heat demand rainbow!
Why only obliquely, what a nice word, addressing the problem of overheating? I am trying to be diplomatic. I know this is funny. But joke aside, there should be no surprise that overheating occurs when one uses a static tool that says 10% overheating is ok. One either needs to use another model to answer those more dynamic questions or be extremely cautious and conservative in how to use the results.
Personally, I don't use that tool anymore. I am" tickled pink" to say it with my friend Lance Wright's words about the advent of WUFI Passive and the ability to dynamically model my projects much more accurately in rather complex climates in North America. I feel less at risk, more confident in the results. They match closer what I have seen happening in the field. Static modeling can only take us so far and looking back I wonder what took me so long to connect the dots...
And that is not so obliquely said also on my blog, maybe you just did not read it all the way to the end.
A view from the EU
As an occasional gate crasher from the EU I'd like to add a couple of points.
1) For me the key thing arising from all of this debate is the need for using appropriate tools for design. No benchmarking system is "complete" (LEED, BREEAM, Passivhaus.) In my experience the greatest thing about the Passivhaus community is its willingness stick with projects after they have been completed and assist occupiers with the bedding in process (with traditional build designers and contractors often walk away). By sticking around this not only helps the client get the most from their home/building but also creates a virtuous feedback-insight-foresight loop. Aspects of this loop are openly discussed at conferences rather than hidden from view either because it it "intellectual property" or because certain aspects of performance have been left wanting. Whilst such feedback behaviour is poorly/not fostered by other benchmarking tools I would welcome a more formalised project by project process for Passivhaus buildings.
In the UK the Usable Buildings Trust has been pioneering the development of Post Occupancy Evaluation. The recent "Soft Landings" programme is a means of trying to make feedback routine. Until recently their emphasis has been upon non-domestic buildings (watch this http://www.carbontrustlive.co.uk/) but they have now managed to move forward work in domestic buildings also.
2) Whilst the Passivhaus standard is based upon limiting overheating to less than 10% good practice is to limit over heating risks to less than 5%. It should be noted that the 10% threshold is not a whimsical figure, rather it is based upon adaptive comfort surveys in free-running buildings (I'm not sure but I don't think that the homes used in the study were Passivhaus homes).
3) Why is there a prediliction for using tumble dryers? What people want are dry clothes within a reasonable time frame. Arguably you don't need a tumble dryer to achieve this. One low energy solution for drying clothes relatively quickly - over night - has been used at a terrace of Passivhaus homes in Kronsberg, Hannover. What they did was adapt a drying cabinet, removing the heating element, and using the volume flow of the air leaving the property to dry the clothes (see final pages of this link: http://www.passivhaustagung.de/zehnte/englisch/texte/PEP-Info1_Passive_Houses_Kronsberg.pdf)
4) Is a drying cabinet needed? Even without the drying cabinet and the higher ac/h, clothes are reported to dry within 12hrs.
...I appreciate that the low energy solutions in items points 4 and 5 may run into certain thresholds (humidity) in certain zones climate within the USA; that's for you people think about. All that I am trying to do is indicate that there are other alternatives that may reduce the risk of overheating.
5) Discussions with Dr Feist have confirmed that the Passivhaus standard was developed BECAUSE buildings with zero heating are not econimically viable. (Why else would you have the 15 kWh/m2.yr threshold?) Passivhaus buildings have always needed heating.
It is fair to say that there have been some translation problems in the past and that a book title such as "CEPHEUS: Living Comfort without Heating" (http://www.amazon.co.uk/Cepheus-Living-Comfort-without-Heating/dp/3211837205) has muddied the water, however it should be noted that the authors were refering to to omission of central heating (as noted on page 13 of the book "Comfortable climate
conditions are achieved without a conventional heating system in a passive house")
What are we designing for?
The hands free home? The autopilot home? The occupant free home?
I make my living in landscape architecture and engineering. Whenever I come into a room and hear the requirement for a "maintenance free landscape", I slowly back out of the room hoping nobody saw me entering... You don't want to engage with the landscape on your property? Why not live in a condo highrise?
Why are we expecting that the occupant of PH or PGH should have the least amount of interaction possible when it comes to controlling comfort? What is next? An app for our ceiling fans so we don't have to remember to turn them on or off? (probably exists already)
I am the first one to admit that behavior is a difficult beast to deal with. Still, I don't understand why we expect technology to solve that problem (occupant behavior) for us. A certain level of short term discomfort is a very effective motivator to adjust or even change behavior (i.e. turn the ceiling fan on or off).
Could it be that we are going about this with a flawed mindset? Should behavior become front and center and at the very least share the stage with technology?
Response to Stuart's Rue's additional comments (#40)
Stuart,
I'm glad to hear that your house is comfortable to live in. I completely understand. I live in a house with single point source heating, and, like you, I'm comfortable.
While I reported on Allen Gilliland's presentation, and interviewed both Gilliland and Bronwyn Barry, I thought that it was important to balance Gilliland's perspective with the perspectives of the homeowners. That's why I interviewed you and quoted from a published interview with Sarah Evans.
I completely agree that we are all on the same side here. The point of this dialogue is to work together to build better houses: houses that use less energy and are as comfortable as we can make them.
Thanks again for sharing your experience with the GBA community.
Response to Fortunat Mueller
Fortunat,
You asked, "If not in the house, where does a solar tank go?" Here is what Allen Gilliland told me when I interviewed him: "All that kind of stuff the creates heat — the condensing dryer, the solar thermal tank — you need to get it it out of your building envelope.”
Presumably, Gilliland would prefer to locate the solar hot water tank in the garage, on the porch, or in an unconditioned vented attic rather than inside the home's thermal envelope. This is one Passivhaus designer's approach to addressing the overheating problem. Not every Passivhaus designer will agree with Gilliland's approach. Obviously, Gilliland's approach helps reduce overheating during the summer, but hurts the performance of the house during the winter.
Stuart Rue, one of the owners of the house in question, agrees with you. When I interviewed him, he said, "The room with the solar tank is not that warm even in summer."
Response to Katrin Klingenberg
Katrin,
Thanks for your thoughtful comments. A few reactions:
1. After spending the last 11 years trying to explain to American readers that a Passivhaus is not the same thing as a passive solar house, I'm not sure that I agree with you that a "Passive House is a subcategory of a Passive Solar House, a special kind if you will." I think that statement muddies the waters rather than clarifies the design issues we are discussing.
2. Concerning overheating: I think the jury is still out on how many U.S. Passivhaus buildings have overheating issues. You report that a Passive House "does not overheat like its Passive Solar relatives." If the house is designed properly, I have no doubt that you are right. The question now is whether some U.S. Passivhaus buildings may be overheating. If so, these examples of buildings with overheating problems would provide useful "lessons learned" to other designers. Gilliland reports, "Everyone is obsessed with keeping heat in, and now everyone is having overheating problems." I suspect that the truth lies somewhere between these two statements -- somewhere between your statement that a Passivhaus "does not overheat" and Gilliland's statement that "everyone is having overheating problems."
3. I'm glad to hear that you were never fooled by the statements from Germany that a Passivhaus building "heats and cools itself."
4. I agree with you that owners of Passivhaus homes are reporting that they are very satisfied with their homes' performance, and that they generally experience a high level of comfort. That's good, and it is exactly what we might expect from a superinsulated home with a very low rate of air leakage.
5. I agree completely with your advice (quoting Shurcliff): "Don't overglaze in sunny USA when chasing the annual heat demand rainbow." I think that discussions like the one occurring on this page are potentially helpful to designers interested in following Shurcliff's (and your) advice.
6. I'd like to respond to your comment that "Why the opposite is in fact true of what is being presented here in this usually very informative blog location." The debate that I reported on is occurring in the Passivhaus community. The PowerPoint presentation made by Allen Gilliland, and the views expressed by Gilliland and Bronwyn Barry, came from a Passivhaus consultant and a Passivhaus builder. I tried to balance Gilliland's presentation and Barry's observations with an interview with a satisfied Passivhaus homeowner. My report is not intended to undermine our shared interest in designing high-performance low-energy homes.
Response to Mark Siddall
Mark,
1. I find it interesting that you report that "the Passivhaus standard is based upon limiting overheating to less than 10%." Bronwyn Barry implied that trainers in the U.S. who advised designers to limit overheating to 10% (using PHPP) were misinformed and were providing bad advice. In any case, your statement that "good practice is to limit over heating risks to less than 5%" shows that designers in the U.K., like designers in the U.S., are waking up to the overheating problem.
2. I agree with you that there are many ways to dry clothes other than the typical American approach of putting the clothes in a clothes dryer. That's why I wrote an article on the topic (Alternatives to Clothes Dryers). However, if Passivhaus designers start insisting that American homeowners can't use a dryer, but instead have to use a clothesline or a drying closet, don't be surprised if there is pushback -- even to the point that some cynics will start reporting that smiling clothesline-using Passivhaus owners are victims of the Passivhaus Stockholm Syndrome.
3. You wrote, "Passivhaus buildings have always needed heating. It is fair to say that there have been some translation problems in the past." I find it amazing that Passivhaus advocates continue to buy the "translation problems" explanation for an obvious PR exaggeration made by an educated, bilingual physicist who clearly understands the meaning of the English phrases "without active heating and cooling systems" and "The house heats and cools itself."
Response to Marcus de la fleur
Marcus,
You wrote, "Why are we expecting that the occupant of PH or PGH should have the least amount of interaction possible when it comes to controlling comfort?"
I am a homeowner who is always interacting with my house -- putting another piece of firewood in the woodstove or opening a window. I get it, and I'm on your side.
However, not every homeowner wants a house that requires this level of interaction. This debate goes back to the 1980s, when many passive solar homes included insulated shutters that were supposed to be closed every evening and opened up every morning. Some (Stockholm-Syndrome-suffering) homeowners jumped right in, enthusiastically enrolling in the shutter-closing and shutter-opening club. However, after a few years, most of these homeowners got tired of the routine. (Many also got tired of looking at stacks of 55-gallon drums filled with water in their living rooms, but that's another story.)
If you design a house that is subject to overheating on sunny days in March, one solution is to tell the homeowner, "Pull the curtains shut and open the windows!" But if the homeowners go off to work at 7:30 a.m., it's hard to predict how sunny it's going to be. When the family returns at 5:30 p.m., it might be 83 degrees F indoors. I'm not exaggerating. Many Americans can't afford to take time off work to babysit their house.
Hats off to Mark Dickerson - post #39
Great move - gather and apply the knowledge from advanced building science (such as LEED and PH), taking care to account for local climate issues, but then disinvite the certificate raj.
$18k buys a whole lot of energy conservation, maybe even enough PV to approach net zero, even if that doesn't count in Stockholm.
During my industrial automation decades, I learned that if someone holding a clipboard with soft hands and wearing an unblemished hardhat was anywhere in sight, the day just became much longer.
[Editor's note: The comments continue on the next page. Click the number 2 below to continue reading.]
PH heating; WUFI Passive
The English-language version of the PHI website that Martin linked to includes 1) a caveat "Please note that the translation is still in progress." 2) a chart showing clearly in red the amount of heating typically required for a Passive House. Hardly an attempt to mislead.
On WUFI Passive, the Fraunhofer Institute had a much different take on the software than Katrin does in her comment. See: http://www.linkedin.com/groups/Fraunhofers-take-on-WUFI-Passive-3647672.S.240402980?qid=6344e553-2487-4f64-a560-77cdffd441a3
Response to Greg Duncan
Greg,
On the question of whether WUFI-Passive will prove to be a "passive modeling tool that is accurate for all climates" (as Katrin Klingenberg predicts) or is a tool that is "not appropriate to rely [on] solely ... when designing a Passive House building as WUFI Passive is not capable of performing the analysis provided by the PHPP and is not intended to replace the PHPP" (as Harold Krause, a representative of the Fraunhofer Institute, evidently maintains) -- let me just say that it does not surprise me that a difference of opinion exists.
For more information on WUFI-Passive, see Makin’ WUFI.
On the other question you bring up -- on whether the misunderstandings introduced by a few unequivocal sentences are the result of a translation error -- I leave it to GBA readers to draw their own conclusions. The sentences in question are these: “A passive house is a building in which a comfortable interior climate can be maintained without active heating and cooling systems. The house heats and cools itself, hence ‘passive.’”
Passive House - understanding?
In Europe the average buyer of Passive homes is sceptical about their claims and usually has under floor heating, which is easily controlled, providing heat tailored to each room and even zones within a room.
The idea is that a Passive home will use 80 to 90% less heating and cooling compared to other local homes.
Passive houses in Europe are intended to be heated most of the year by the sun, and heat generated by peoples bodies and the electrical equipment running in the home, plus a suitable amount of heating or cooling provided by elements integrated into the ventilation system.
Cooling where there is central provision is always going to doubtful, separate provision is the best solution - and of course further units may be added if required. An "as designed" provision is not always the best living solution.
Shade needs to be better understood. The provision of shade within a room, doesn't work, as the shades get very hot and transfer their heat to the room. The best shade is provided externally and European homes deal with their long hot summers by having external roller blinds that are electrically powered, they roll up into a space above the window and may be lowered to any desired position, this system keeps the suns heat outside. As a by product they also provide excellent security when the owners are on holiday.
The ventilation and extra heating/cooling of European homes is provided by in line mechanical ventilation with heat recovery, the overall concept is fresh air heating using ventilation air usually having a dual purpose 800 to 1,500 Watt heating and cooling elements integrated within the supply air duct of the ventilation system, It is fundamental to the design that all the heat required is transported by the normal low air volume required for ventilation.
In Europe most of the heating is electrical resistance, with some hot water. Both of these systems are cheap to fit, easily controlled and it is very easy to have different temperatures in each room or several different temperatures (using UFH) in different parts of the same room.
From the above, it would appear that the Passive idea has been corrupted on its journey from Europe to here.
Response to Roger Anthony
Roger,
All of the information you have written is well understood by the American Passivhaus community. However, simple physics will show you that it is impossible to deliver all heating energy through the ventilation system in colder parts of the U.S. unless you either (a) introduce some recirculation rather than using 100% outdoor air, or (b) deliberately overventilate the building, a strategy that incurs an energy penalty.
That's why virtually all U.S. Passivhaus buildings -- and, believe it or not, a growing number of Passivhaus buildings in Europe -- deliver heat through a different mechanism than via the ventilation ducts.
I have been writing articles on the Passivhaus standard since 2002, and I understand the basics you have described.
It is possible, of course, that "the Passive idea has been corrupted on its journey from Europe to here." I am curious to know two things, however:
1. What aspect of the idea has been corrupted?
2. Which designers and builders have exhibited symptoms of this corruption?
A response to Martin Holladay
Martin,
1) The PHI advocate the <5% overheating threshold (or at least Dr Feist does - it was from him I first heard the recommendation.)
2) It is always up to the client what they want. They are the most critical part of the design team after all. The best design all comes back to addressing practical, functional needs and tackling them appropriately. Occasionally systems come into conflict with one another - clothes drying vs. overheating for example - and appropriate solutions must be found. Providing that the client has an appreciation if the risks then they can do as they please.
3) Translation - you can continue to play that game if you like. Whenever I have spoken to anyone from PHI they have never contended that a Passivhaus is a home without heating; quite the opposite in fact.
WUFI Passive and active cooling
Martin,
Thanks for the link to the WUFI Passive post. I commented there as well.
The current PHI website definition of a Passive House is very clear: http://passiv.de/en/02_informations/01_whatisapassivehouse/01_whatisapassivehouse.htm
Maybe someone there heard your critique?
Response to Greg Duncan
Greg,
I agree with you that the current definition of "passive house" on the Passivhaus Institut website is a vast improvement over the former one. It may have taken many years of badgering by a great many people (including me) who pointed out the inaccuracies of the old definition, but eventually, the definition was changed.
Topping up heating and cooling in Passive House
I think the figures speak for themselves.
There are over three thousand Passive House accredited homes in Europe. And over 30,000 Passive homes spread over 20 countries - including NewenHouse, Viroqua, Wisconsin, energy use 11.4kWh/m3, blower door 0.51 ach @ 50Pa, the BioHaus, near Bemidji, Minnesota The latter is built to the German passive house standard for energy conservation and renewable energy. It uses 85% less energy than a similar home built to Minnesota’s Energy Code.
In Europe Passive houses have been built above the 60th parallel where it is as cold as anywhere. In Sweden homes are built with 13 inches of insulation in the walls and 20 inches in the roof where required to meet Passive house standards.
Kingspan in Ireland have built a certified 5 bedroom Passive house in Ballymun Dublin of 3,230 square feet using SIPs with an annual energy use of 10kWh/m2 and an airtightness of 0.6 m3/h/m2 @ 50Pa. Using a typical Irish scepticism the home is fitted with a pellet burning stove.
The European Union has decided that all new homes built in Europe will be of Passive house standard from 2016 and all new office blocks will be of Passive house standard from 2020. Interestingly office block builders are already constructing to Passive house standard as they realise that none Passive house standard office blocks will be difficult to let in future, because of their high energy requirements.
Obviously the secret to keeping Passive houses warm or cool only using their ventilation system, plus heated towel rails, where fitted, is insulation and lots of it. Plus as Professor Wolfgang Feist said. "Open the windows when you are hot, close them when you are cold." The Professor has lived in one of the first Passive houses built in Darmstadt since 1991. And he points out that the specification hasn't changed at all.
All of the above shows that a great many certified Passive houses have been constructed Worldwide.
Perhaps the people who have failed to do it, should ask around for help?
ps. NewenHouse was reviewed in GreenBuildingAdvisor.
Keeping cool at home and on the Internet
A home and an Internet discussion share the need to get rid of waste heat in an acceptable manner. Generalizations and exaggerations lead to problems in both. An encouraging difference is that while the Internet is probably getting worse, home design and construction is definitely getting better.
Martin begins this article by saying, "The idea of a house that “heats and cools itself” has a certain PR value, of course. The only problem is that it doesn’t exist." However, another recent GBA blog posting describes a house that comes very close, in Dillingham, Alaska (near Fairbanks), with 11,333 HDD. https://www.greenbuildingadvisor.com/blogs/dept/green-building-news/meet-tightest-house-world
I would argue that there is a significant number of homes that come close enough to heating and cooling themselves, to be worthy of attention, investigation, and celebration. These exist in more challenging climates than San Diego. More importantly, the evolution and improvements that GBA is helping to foster will make a good portion of the current debate archaic within a few years. While some are arguing that such houses don't, or can't exist, I think that they are clearly on the horizon for an expanding range of climates. I'm really encouraged by the rapid evolution of good house design, and effective information sharing that is showcased on this site.
Response to Derek Roff
Derek,
I certainly agree that we should be paying attention to (and celebrating) superinsulated houses with very low energy bills. I have been focusing on that topic, both as a matter of personal interest and professionally, since 1979, when I first read about the Gene Leger house in East Pepperell, Massachusetts.
Concerning another one of your points: in the depths of winter, there is absolutely no way that the Alaskan superinsulated house you referred to is going to heat itself. For one thing, there is almost no sun at that time of year. For another thing, the owners will need a lot of electrical appliances and gadgets (and the grid-supplied electricity to keep them running) to keep the interior temperatures above freezing. And finally, the owners have projected that the house will require 35 gallons of fuel oil for space heat every year. I'm sure that you are aware of these facts, but it's important to make a clear distinction between low-energy buildings and buildings that "heat and cool themselves."
As I wrote about a Passivhaus project in 2011, "The heating requirements were very low, raising the question: why exaggerate?"
Finally, Derek, you wrote, "Generalizations and exaggerations lead to problems." I couldn't agree more. I think that it's essential for Passivhaus proponents to understand how much their exaggerations have undermined their credibility. The exaggerations of the Passivhaus movement are especially painful for those of us who have been advocating for the use of superinsulation techniques for many decades.
For a young movement like Passivhaus, credibility is a kind of currency that shouldn't be squandered.
Window shading
Wouldn't it be easy to incorporate some sort physical shading into the window unit? Similar to screens.
I was at the Joshua Chamberlain house yesterday with my daughter's field trip.
They had beautiful wood panels that slid sideways into the walls (like pocket doors).
To keep the indians from shooting arrows into the house.
Why not use this simple idea to shade the window? Maybe like skylights - it could be motorized or man-powered, but IMHO the less mechanicals to break and the more involved the homeowner is the better
Response to Ben Hemberger
Ben,
The type of shading device you describe is routinely installed on new homes in many European countries. The most common such device in Europe is an exterior motorized roll-up metal shutter. This type of shutter is available in the U.S. as well; see the photo below.
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Window shading
I was imagining something a little more attractive, on the interior. I know some folks are using a thin utility cavity throughout the inside between the interior finish and the insulation( disentanglement).
A shade could be slid in and out of this space nicely.
Response to Ben Hemberger
Ben,
I lot of builders did what you suggest in the 1970s. Of course, to exclude solar heat, exterior shutters work much better than interior shades.
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