Image Credit: Martin Holladay
More Musings of an Energy Nerd
Last weekend I attended the Fourth Annual North American Passive House Conference in Champaign-Urbana, Ill. The conference offered a great opportunity to learn more about the Passivhaus standard and to discuss low-energy buildings with an experienced group of architects, engineers, and builders.
Among the most valuable sessions offered at the conference:
- David White provided an introduction to the Passive House Planning Package, the software tool for determining whether a house meets the Passivhaus standard’s strict maximum annual heating budget of 15 kWh/square meter.
- Stephen Thwaites explained the differences between the European and American methods for determining a window’s U-factor.
- Marc Rosenbaum shared his approach to designing HVAC systems for low-energy buildings.
The Passivhaus advocates I met at the conference are responsible for some of the best new buildings in the country — buildings with extraordinarily low energy budgets. These exemplary buildings can inspire all designers of low-energy buildings to sharpen their pencils.
Unfortunately, the launch of the Passivhaus movement in North America hasn’t been particularly smooth. Some Passivhaus advocates have reacted defensively to legitimate technical questions from knowledgeable American builders. On the other side, the chance for fruitful dialogue has been hampered by a few Passivhaus critics who have adopted an unnecessarily adversarial tone. Fortunately, these bumps are only public relations problems; they shouldn’t seriously detract from the great accomplishments that Passivhaus builders have achieved.
Clearing Up Misconceptions
In my opinion, the Passivhaus movement in North America needs to do a better job at disassociating its message from a package of misconceptions. It’s important to emphasize the core strength of Passivhaus — namely, the fact that PHPP software provides a sophisticated method for designing and constructing buildings that use very low levels of energy — and to clearly separate this message from a collection of red herrings…
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32 Comments
Wood Stove in Passivhaus?
Did anyone at the conference come up with a product which would be suitable as a wood stove in a passivhause?
In my design, I have a need for about 3KW of heat in winter. All Wood stoves I found would overheat the house, But in VT, Heating with wood from the property is the "greenest" method.
Thanks, Martin
Thank you for this informative article. You've reduced the mis-information coefficient (same units in IP and SI)! A couple of thoughts:
- I don't think there is much disagreement on the net zero home goal of most cost-effective path. What I think needs to be factored in to that discussion is that PV systems degrade over time - inverters have a lifespan and the output drops from PV panels. Assuming that the system you just bought will make the same output over time without any further investment skews the result.
- I would really like the PH standard, and indeed any discussion of resource use, to include the issue of equity across cultures and species. A 6,000 sf PH isn't what we're aiming for. Amen.
Lastly - I wish you would write a bit about Gunter Lang's keynote, and the amazing range of building types and scales he showed being built in Austria as PHs. He told us 1 in 4 new homes were built to the PH standard there, if I understood correctly.
PV degradation and Günter Lang
Marc,
Thanks. I agree that PV arrays are less durable than sub-slab foam. As I wrote in my August 21 blog, "PV equipment and heat-pumps have a shorter life, and require more maintenance, than sub-slab insulation. In fact, this point may be enough to convince some builders to choose 14 inches of foam over a PV array. It’s a defensible position, but it’s one that should only be made after considering the fact that the homeowners would get more bang for their buck from a PV array than from the last 10 inches of foam."
I hope to be able to report more in future blogs about the proceedings at the conference, including a discussion of Günter Lang's keynote address. As an American, it was disconcerting to hear Lang repeat the old canard about Passivhaus buildings not needing a heating system, and it was unnecessary to hear him explain that Passivhaus ventilation systems provide high levels of indoor air quality. (But maybe I'm too sensitive on these issues.) But once he got beyond these red herrings, his presentation of a variety of case studies from Austria was, indeed, inspiring.
Heating with a wood stove
Steve,
Heating with wood is an art as much as a science. You're right that a wood stove can easily produce too much heat (especially in a Passivhaus), forcing occupants to open the windows.
I suggest:
- Buy a small stove with a small firebox.
- Buy 12-inch or 16-inch firewood, not 24-inch firewood. Split it fine.
- Practice making small fires.
- Don't light a fire until the house is several degrees colder than your preferred indoor temperature.
Practice makes perfect.
Wood Heat
What about a masonry heater, seems like a solution to overheating in a well insulated home.
Thoughts
Hi Martin,
Thanks for the great post. I have a few thoughts.
Red herring one – it has been my understanding that the U value standard is for occupant comfort, and I’ve come across examples in my own work where double glazing would suffice to meet PH standard. ASHRAE and European guidelines both allow 5 K temperature difference between coldest and warmest surface, but the 3 K PH adopts is based on Feist’s claim that ASHRAE and the Europeans resorted to 5 K because, despite thermal comfort research findings, 5 K was all they could achieve. Passive Houses are sensitive to this because the glass surface cannot be warmed as with a radiator or forced air grill. I agree with you that comfort is relative, though; and I don’t object to a cold window surface. It was a romance of my childhood to wake up on a snowy morning and press my nose to the glass, my spirit venturing out ahead of my body.
I don’t think that windows are unfairly portrayed by NFRC vs CEN. Recent inquiries I’ve made on Window 5 (as has Stephen Thwaits) indicate that for triple glazing with ½” gaps, the U-value is within 1% by NFRC/CEN methods, with NFRC looking better, not worse! Unless you are referring to frame size – this is also complicated because of installation details – what if the German window frame is substantially overinsulated with a lager rough opening? What is the installation thermal bridge?
Red herring two: I may be presumptuous here, but after working for a German company, I look for linguistic confusion. I had thought that Gunter Lang was referring to conventional heating systems. I think there has historically been some miscommunication about this. Doesn’t the term “Passive” refer to the history – Bo Adamson’s research on better comfort for buildings in China that have no heating?
Herring three: I would submit that PH may offer fresher air. The ventiation rates are higher than 62.2, although they match 62.2 quite closely when 62.2’s allowance for air leakage is taken into account. To me this implies less dirt/mold from cracks, as well as a more consistent fresh air rate across a wide range of outdoor temperature and wind speed. This is especially important for humidity – the coldest and windiest days are the driest.
Herring five: If one takes heat recovery as a given, then I am finding substantial cost savings. In a 30-unit project in Brooklyn, we’re dropping from the conventional 64 tons AC plus heating system, to 24 tons of reversible split. Note that it hasn’t been built yet, but a cost estimate found a net savings in mechanical, including heat recovery ventilation, compared to conventional.
I think a lot of this hinges on comfort standard. I’d personally be happy with a point source, but for the masses forced distribution seems to be the rule, even for SI houses that Marc is doing. Amen that Zehnder is expensive, but so is the Euro, and so is shipping. We need to start making our own, and making them just as well if not better. We did it with the fridge (although the fridge needs to step up again to non-halocarbon world standard).
I appreciate a lot that you raise this point: a lot of qualities of PH are often taken to be unique to PH itself – superinsulation, air tightness, mechanical ventilation. My clients gravitate to the notion that it’s all or nothing, that one can’t have a durable building with great air quality without having a PH.
I also appreciate your question about net-zero and PH. The PH standard sets in essence a rule of thumb – the building must achieve a certain standard of performance independant of generation. Note, however, that the most stringent number is the heating demand, not the primary energy – the latter is not so hard when one uses the (prescribed for certification) default values for DHW use, plug loads, etc. PH also assigns a PE value of 0.7 to PV, i.e. that 0.7 units of fossil fuel are used for every unit of electrical output on a life cycle balance. That roughly matches the energy payback numbers I’ve heard tossed around here in the US. I think it’s a mistake to think of a kWh of PV as a direct offset of site kWh.
In general, I appreciate the 15 kWh heating energy demand target when I consider it in the context of other energy demands, the potential for those demands to go down in coming decades, the relative importance of heating to other energy demands, the passive survivability aspect of a good envelope, and high envelope retrofit costs. But I agree that the standard shouldn’t be taken on faith and that we should work openly with it. However, I so, so, so highly advocate the PHPP for this purpose! I believe, though I’m not sure, that almost all parts of the PHPP will work well with a somewhat higher heating energy demand, not sure how high (this and other questions I hope to answer post haste).
To note: A recent LBNL study by Parker found that the Smith house, when given a hypothetical PV array, was, climate adjusted, among the two or three most cost-effective net-zero houses in the study. And the study did not penalize PV for its embodied energy, while the Smith house had a comparatively small PV system. My suspicion is that we are going to find that increased insulation is in many cases cheaper than we now think. Regarding sub-slab insulation, this is also a mystery to me. In one project, it’s been the cheapest way to crank out those last few tenths of a kWh, after going to the practical limit above grade. But the PH details I see in general don’t seem to go that thick.
I don’t think that the PH standard enforces the limit of 50 m2 per person anywhere, although the software enacts a “soft” enforcement, in all places, of certain per-person energy demands (including outdoor air) calculated directly from the floor area – this feeds into the heating and PE demands, so it helps to somewhat level the playing field. The PHI has told us that they just can’t prevent gargantuan Passive Houses that, although they were calculated for ten people, in fact house only two. The trick is that because Germans in general live in smaller spaces, and because they have a much more uniform level of wealth than we, such houses are exceptional enough not to be a problem. Not so for us, and I fully agree that this needs our careful attention. I also am quite excited about small houses – I think that if people can go back to 1950 shares, the technical potential is great. At that size, a fresh air heating system is allotted closer to 15 W/m2.
Great comments, David
David,
Thanks for you excellent analysis. A few points:
1. You've had more experience modeling different windows with PHPP than I have, so I bow to your experience. But I understand from Stephen Thwaites' presentation that there are several anomalies that arise due to the way that U-factor is calculated by European standards and PHPP: (a) In theory, a window that was mostly frame, with a tiny square of glass in the center, could still meet Passivhaus certification because the certification doesn't really consider the SHGC of the entire window -- just the glazing chosen, no matter how small the glazing; (b) As a result of this, Canadian fiberglass windows don't get as much credit in the Passivhaus certification process for their solar-gain potential as they should.
2. Concerning the fact that Germans often use the term "heating system" to mean "a boiler connected to a hydronic distribution system" whereas Americans use the term "heating system" to mean "a heater, furnace, stove, boiler, or heat pump used for space heating purposes" — I agree with you, the linguistic confusion exists. All the more reason for the U.S. Passivhaus movement to "do a better job at disassociating its message from a package of misconceptions," as I propose.
Frankly, whatever the details of Bo Adamson's contract with the Chinese government, Dr. Feist has emphasized the "houses without heating systems" angle for public relations purposes. No engineer would reach the conclusion that these are houses without heating systems.
3. I think that the possibility that the very slight difference in ventilation rates between ASHRAE 62.2 and Passivhaus recommendations results in fresher air in a Passivhaus is a stretch. I think any difference in design parameters would be quickly overwhelmed by differences in system operation due to occupant behavior. If any IAQ study finds the result you are implying, based on testing in occupied houses, and comparing Passivhaus buildings to Building America homes, then I'll concede the point.
4. I'll happily concede that equipment savings are possible in superinsulated multifamily buildings compared to multifamily buildings without superinsulation. But the savings don't exist for single-family homes. Once you get down to specifying the smallest available equipment — and that's what those of us involved with well insulated buildings have been specifying for 25 years — it's hard to go any smaller, even with Passivhaus.
Thanks again, David, for your comments.
Overheating
Doug,
Actually, masonry heaters are MORE, not less, prone to causing overheating than a small wood stove.
Here's the way a masonry heater is used: in the morning, the homeowner looks at the thermometer and listens to the weather report and tries to decide if it's going to be a cold day. If the homeowner concludes it's going to be cold enough to require a fire, then the homeowner builds a roaring big hot fire in the masonry heater. The roaring big hot fire heats up the bricks and stone and mortar and tile and concrete surrounding the firebox, and those masonry materials stay warm for the next 12 hours.
If the homeowner guessed wrong, and has misread the weather — for example, if the clouds blow away and the sun comes out — the house will overheat.
Overheating
I have some experience heating with a wood stove, when a fire is going it is too hot in the house. A masonry heater would temper the heat and distribute it over a long time period. The more even temperature inside the home would make for greater comfort and in theory use firewood more efficiently.
Granted, a PH or superinsulated home does not require much supplemental heat, but there is heat loss and a savvy fire builder could get close to offsetting the loss with wood heat. I would encourage the use of onsite wood as a heat source, this is sustainable.
Wood heat, passive houses, and ventilation
I've lived with wood heat for the past 30 years, but it's not at all clear to me how one would efficiently heat a structure with an ultra-tight envelope. (All the wood-heated houses I've lived in have been leaky, some of them spectacularly so.) Presumably there's a need for some sort of dedicated combustion air inlet adjacent to the stove or heater that can be hermetically sealed when there's no fire? And presumably a way to seal the flue in an airtight manner when there's no fire going? Where might one find the hardware to accomplish those things? Maybe you just open a window for inlet air, but I'm not clear how you seal the flue.
Also, it would seem that air flow through the heater would short-circuit the ventilation system both while the system is actively operating and as one waits for it to cool down enough to shut it down. No doubt there are good answers to all this but I've never heard them discussed.
PHPP Comparison
How would you compare the PHPP software to those of RESNET like Rem Rate or Treat?
Wood heat and superinsulation
After running a few numbers it appears that a masonry heater would not be suitable for a very well insulated home, you could not build a fire small enough.. Some of the new age pellet stoves might be a fit as you could trickle in just enough wood pellets to offset the heat loss.
More for Martin
Hi Martin,
Thank you for your helpful comments.
1. I need to tease apart two issues: U-value versus overall energy performance. The PH recommendation for U-value is not energy based, but rather comfort based. It is intended to provide adequately warm interior surface temperature at design point, i.e. dark outside and cold. Therefore it’s about U-value only, not SHGC. The overall energy performance of the window has no requirement at all; however PHPP does an excellent job of accounting for window losses and useful solar gains in terms of meeting the 15 kWh heating demand target. It even discounts excessive gains that would overheat the space and would need to be vented, based on a curve-fit to extensive parametric studies done in support of the software. So the Canadian fiberglass windows do get as much credit in PHPP as they should.
2. Point well taken, thank you.
3. By this I reference the BSC example house – 50 cfm ducted, 40 cfm assumed leakage; versus around 80 cfm ducted and 10 cfm leakage in the PH. I’d opt for the PH because of dirty, moldy cracks as well as highly variable flow rates through those cracks.
4. I agree. My smallest project is heated mostly by a hydronic duct heater tied to a DHW solar storage tank. The parts is around $500, but the labor... However I think that if we were mass-producing these things they could be very cheap. Even the exhaust air heat pumps that some of the European PH’s use are simple – about the same type and size as the compressor on a refrigerator.
Wood stoves and air leakage
Jon,
I agree that manufacturers have not yet developed equipment to address air leakage in wood heated homes. Two big problem areas:
- Wood stove flue dampers aren't airtight. This may be deliberate, because of the possibility that a smoldering fire can produce carbon monoxide.
- The clean-out doors installed at the base of masonry chimneys aren't airtight. Even if the flue damper were airtight, a lot of air leaks continuously through the clean-out door and up the chimney.
Cost optimum path
Thanks Martin for providing a nice space for discussion. You set a nice tone with this posting. It is great to see you consistently trying to provide a constructive discussion of Passivhaus.
I have followed the discussion regarding cost effectiveness of the Passivhaus standard and the way I currently interpret this discussion is that if one is building in climate zone 4 or 5 the project should nearly be cost optimum as regards to energy conservation to production following Passivhaus. But if one builds in zone six up following Passivhaus may not be the lowest cost path. I am asking because it would seem to be a complete waste of time to bother modeling a project in PHPP and BEopt in zones 4 and 5 but may be worth the effort if one is building farther up North (depending on how one feels about recurring costs in energy production equipment)? Is this a fair assumption?
Interesting question
Kyle,
You raise a very interesting question. Your question cannot be answered using PHPP alone because PHPP never compares the cost-effectiveness of envelope options with PV. While BEopt does make such a comparison, the use of BEopt is limited (for now) to the use of NREL researchers.
As far as I know, the best method for answering the question requires the energy modeler to do a little bit of old-fashioned trial-and-error construction cost estimating. I believe it's necessary to narrow down your design to a few logical options -- for example, R-15 slab, R-20 walls, and R-40 ceiling insulation might be Option 1, and R-40 slab, R-40 walls, and R-60 ceiling might be Option 2. These two options are costed out — a laborious but necessary step.
You also look at the energy budgets of the two homes using PHPP.
Everybody knows that PV costs about $7 a watt, although there is some variation from location to location, and the price is dropping. A 1-kW PV system will produce 970 kWh/year in Seattle, and 1,176 kWh/year in Chicago, and 1,664 kWh/year in Las Vegas. (For more cities, visit http://www.pvwatts.org).
You can add PV to the roof of the cheaper option (Option 1) to see if thinner insulation plus PV is cheaper than thicker insulation (Option 2).
I don't know if there is a rule as simple as the one you propose: "if one is building in climate zone 4 or 5 the project should nearly be cost optimum as regards to energy conservation to production following Passivhaus." My guess is the answer will vary by location and will be more complicated than your simple rule of thumb.
Comments on Clearing Up
Comments on Clearing Up Misconceptions
Being an advocate of the passive house, I would be happy to help clear up misconceptions. However, the “red herrings” noted in Martin Holladay’s article might actually perpetuate some misconceptions.
Number 1 notes the low U windows are for the comfort of the occupants. In my reading of German literature and also in attending the last Passive House conference in Frankfurt, (as well as three US conferences) I thought the emphasis was on saving energy. (As a side note, I think we need to be careful in saying these red herrings came from Germany).
Relative to number 2, you quoted Marc and David as saying “In almost all cases, Passive Houses do have heating systems.” Was that for Germany or the US? If this is the case for 20,000 passive houses in Europe it is more significant that a dozen houses in the US.
Relative to number 3, it is noted that Passive Houses have fresh air ventilation systems. I don’t think passive house advocates have ever said that no other buildings include these – they simply note that they are basic to passive houses.
Number 4 says that space heating should be delivered through the ventilation system. I am not sure if this is a rule in the PHPP or conjecture.
Number 5 says that the mechanical cost for passive houses is less than the ordinary mechanical costs. Presumably this comes from Germany and I guess we would have to compare the costs of German ordinary mechanical systems.
Martin says these red herrings originated in Europe and are rarely promulgated by North American Passivhaus advocates. Is this really so? Is it possible interviewers of Wolfgang may have misunderstood? I may have missed some of these in my trip to Europe but certainly they were not on posters on the walls nor are they in specs discussed there.
Do we really need to separate the N.A. approach from its European roots, such roots from my review of PH history, founded from the roots of the American and Canadian super insulated homes of a few decades back? It seems the core of the Passive House is the algorithms found in the PHPP. I think that admitting that Passivhaus buildings have heating systems (rather than need heating systems) is a statement of fact about these kinds of houses and not so much an admission. As far as costs, everything I have read or heard about the passive house in Germany or the US, acknowledges that the houses cost more to build – ranging from 5% to 15%. I agree the passive house strength is the low level of energy use and that’s where the emphasis should be placed.
Martin asks two “Legitimate Questions” which he says passive house advocates should answer, one being to resolve the “the zero-energy-home approach — a design method that stops making envelope improvements when software has determined that a photovoltaic (PV) array would meet the home’s energy needs more cheaply than adding additional insulation”. Do we need to resolve this? There are two approaches to saving energy and a builder can decide which one he or she wishers to follow. It would be interesting to compare some real life cost-effective comparisons between envelope measures and PV, using today’s retail prices for both, not knowing the future of government subsidies. I think if today’s non subsidized PV costs showed a significant advantage, Wolfgang might alter his views.
His second question is – why has the Passivhaus movement in the U.S. decided to ignore an important element of the Passivhaus standard — namely, the maximum house size limit of 50 square meters per person? As part of the movement, I didn’t decide to ignore it – I didn’t even know it existed. I had heard of it as a recommendation but not a requirement.
I certainly agree that a ”per-person energy budget is a fairer way to address the world’s climate crisis than a per-square-meter energy budget, so the house size issue cannot be avoided for long.” Well said. And the next statement - that it makes sense to build a very small house even if the house fails to meet the per-square-meter budget of the Passivhaus standard - is certainly a good recommendation. In the US this is as likely to succeed as banning guns control. Americans are not yet ready to be told they can’t waste space. But this is not necessarily a responsibility of the German passive standard. I think this is the job of politicians who determine the code rather than rating systems. Having a fairly new and tiny movement suddenly take on such huge political issues could do more harm than good.
I appreciate this and all such articles. The recent dialogue of pros and cons is extremely valuable and, as Martin said, very intense differences are simply public relations issues. His identification of some of these issues and providing the space to debate them is commendable.
Pat Murphy
More information on European red herrings
Pat,
Thanks for your post. I'll try to provide context for my discussion of European red herrings.
1. Concerning window U-factors, my source is Dr. Wolfgang Feist. In December 2007, when I interviewed him for Energy Design Update, I asked, "Can you explain the Passivhaus Institut’s window performance specification, which seems very stringent to some North American designers?" Dr. Feist answered, "The window specification depends on the climate. In Central Europe, we need an R-7 [U-0.14] window. You would not need the same window in Florida or California. The reason for the number which we now use in Europe is the comfort of the occupants. It is a functional definition. During the winter, the coldest surface temperature in the room will be the window. If you don’t have a radiator in your room, the difference between the surface temperature of the window and the mean surface temperature of the room should not be more than 3 degrees Celsius; that’s for comfort reasons."
2. As far as I know, virtually all Passivhaus buildings in Europe and North America include heating systems. Many German and Austrian buildings are heated with an electrical resistance heater or an air-source heat pump; the heat is often distributed through ventilation ductwork. Every time I read a new article about a European case study house, I have found mention of such a heating system. I have challenged readers of my blog to suggest examples of Passivhaus buildings without heating systems -- I suspect that it's possible to build one in Spain or Italy -- and so far no one has been able to point to one.
3. You're right that some Passivhaus advocates acknowledge that non-Passivhaus buildings can be well-ventilated. But at the recent Illinois conference, the keynote speaker seemed to feel that good ventilation systems were a key asset of Passivhaus buildings. He even said that most schools lack ventilation systems. That may be true in Austria, but it hasn't been true for schools built in the U.S. for a long time -- probably decades.
4. My source on the question of delivering heat through ventilation ducts was Dr. Feist, who told me, "As long as you build a house in a way that you can use the heat-recovery ventilation system -- a system that you need anyway for indoor air requirements -- to provide the heat and cooling, it can be considered a Passivhaus. Since you need a house to be tight, you need a supply of fresh air. If you need that anyhow, the idea is to do everything else -- the heating and cooling and dehumidification -- with the ventilation system."
You speculate that I may have misunderstood some points made in an interview with Dr. Feist. I will admit that his answers were at times vague, and even (concerning one or two points) contradictory. But I feel confident that I did not misunderstand him.
On cost-effectiveness comparisons
Pat,
You wrote, "I think if today’s non subsidized PV costs showed a significant advantage, Wolfgang might alter his views."
Well, I feel that John Straube has demonstrated, and Marc Rosenbaum and David White have confirmed, that unsubsidized PV arrays are cheaper than sub-slab foam insulation beyond, say, 6 inches. So it would be great to hear from Dr. Feist, assuming that your suspicion that he "might alter his views" is accurate.
On establishing an energy standard
Pat,
You wrote, "Americans are not yet ready to be told they can’t waste space. But this is not necessarily a responsibility of the German passive standard. ... Having a fairly new and tiny movement suddenly take on such huge political issues could do more harm than good."
Well, we're in a climate crisis. Ed Mazria is sending out his e-mails every week, trying to get the architectural community to wake up. Bill McKibben is trying to motivate all of us to demonstrate in the streets, as the clock is ticking toward Armaggedon. I think that the Passivhaus standard, and Energy Star, and ASHRAE, and the building codes, ARE responsible for establishing appropriate energy budgets in response to this crisis. These are precisely the groups that should shoulder this responsibility. To establish a new energy standard for homes, as Passivhaus has done, and to ignore house size is, in fact, irresponsible, in light of the global crisis.
But that's just an opinion. I'm merely responding to your opinion that it is NOT the responsibility of standard-setting organizations to address house size. I propose it is.
If I Was Passive House, I Would Pick Up and Go Home
I've been learning about Passive House concepts and ideas since way before I ever saw any mention of them on Green Building Advisor. Ever since there has been mention of it on GBA, there has been constant nitpicking and time and effort wasted in trying to find fault with the concepts.
I have read everything, including Martin's raid on the Passive House blog a while back to lure readers over to GBA to read about the faults with Passive House. Martin, the entire lengthy criticism you have written about Passive House concepts, and nitpicking over exactly what Feist has said, and trying to make recommendations into gospel, doesn't amount to a hill of beans. I don't know exactly what your driving force is, but it's related to money, pride, arrogance, standing in the "industry," or to all four. Lately, you have backed off and recognized the value of Passive House concepts, but I believe, based on having read everything, that it's only because you finally recognized how ridiculous you have been, and are currently trying to ease out of the past with pride. But, as just one example, you continue to bring up the issue of whether or not the "standard" calls for a mechanical heating system in a Passive House. Who cares! ? Anybody with any building sense knows that if your climate gets at all cold, and if the resident insists on the 65F+ comfort level, you had BETTER have some sort of back up mechanical heating system---period---but that doesn't mean it gets used much, if at all. Even on the US Passive House website it says: "The Passive House concept represents today's highest energy standard with the promise of slashing the heating energy consumption of buildings by an amazing 90%." It doesn't say NO heating system. And, so what if it hasn't always said that?
America gives up its arrogance very reluctantly. The only reason it has paid any attention at all to Passive House is because reality is finally setting in...slowly. It's not just reality as related to "global warming," but reality as related to the fact that we have been living orders of magnitude more lavishly than any king in the history of man for far too long. Although it's been known for thousands of years that only so many kings can be sustained, that fact has been ignored. Now, there is uncontrolled human population and more and more around the world are trying to become kings--but reality is catching up.
Stop nitpicking and really struggling to find fault with Passive House "Standard." It's never going to be perfect, and the continued nitpicking is a manifestation of pride and arrogance. "How dare a foreign country (once again) beat us at a game that really started 'over here' in the first place." If anyone knows about the Wright Brothers, then the US building industry is to Passive House as the French were to the invention of the airplane. They know it's coming, but cannot accept that the credit is not theirs. Maybe Passive House should go home to Germany, and leave the U.S. to continue plummeting toward becoming a communist third-world country (yeah, you might have to think a little, but that's what has been happening).
Clarifications
Rick,
Thanks for posting.
I'm sorry to hear that you interpret my reporting as nitpicking. I think the technical issues under discussion are worthy of debate. Concerning your speculation that my reporting is "related to money, pride, arrogance, standing in the 'industry,' " I suppose it's worth mentioning that I receive a journalist's salary for my reporting, and am probably guilty of having such human emotions as pride and arrogance, for which I sincerely repent. I'm not quite sure which industry I'm enrolled in, however.
Those who know me well will probably smile at your guess that I am motivated by outrage along the lines of "How dare a foreign country (once again) beat us." I am happy to stipulate that the Europeans (especially the Swedes, Germans, and Austrians) have consistently done a better job at addressing residential energy efficiency and our global climate crisis than Americans. I grew up overseas, attended primary school in French, and have struggled as an adult to fully identify with American culture. None of these facts, however, is relevant to my ethical obligation as a journalist to avoid favoritism or nationalism in my reporting. Anyone who has read my reporting in EDU knows that I haven't shown any particular favoritism to flawed American energy-efficiency programs, including Energy Star.
In my reporting, I have consistently praised the exemplary accomplishments of European Passivhaus builders since February 2002, when I reported with admiration on Hans Eek's Passivhaus project in Lindas, Sweden.
Once again, I'll repeat what I wrote above: "Even those who don’t adopt the Passivhaus standard should acknowledge the accomplishments of Passivhaus builders and extend them a helping hand. All of us who believe in building energy-efficient homes are working toward the same goal. The Passivhaus movement is gaining momentum, and I wish them the best of luck."
Passive House Crosses the Atlantic
Martin,
I am new to your blog, but I appreciate what I have read so far for its fairness and decency (and that’s saying a lot, given that most of the blog world consists of rants and raves).
I think that some of your “red herrings” and points in this discussion are not necessarily the result of misunderstandings or faulty German to English translations or whatever. They are an inevitable result of a bunch of nerds getting together to exchange ideas. Let’s face it, at some point, when fields of study become very specialized, the cognoscenti will discuss ever finer questions of doctrine. Angels on the head of a pin and suchlike, and the big picture tends to be forgotten.
The one basic definition of a Passive House is the 15 kW/sq.m/yr. energy for heating and cooling figure. And that is it. Any discussion beyond that is basically one of doctrine.
The question of limiting house size is interesting but in a way irrelevant in this country. Lets face it, in our political climate it just isn’t happening. We can talk about it, maybe let the idea germinate out there, but right now we have to do something about all those houses being built as we speak. And it is here that I think the Passive House has to deal with its most serious criticism, recently brought up by John Straube on his Building Science Insight: that the standard is too severe. If I may quote him (from an e-mail he sent me):
""The perfect is the enemy of the good"… You want to jump to the right answer immediately. I am being more pragmatic: I want a standard that is very significant in energy, and that can be widely deployed in all parts of the country by which I will measure success in terms of a multiplication of the number of houses times energy savings."
In other words, we need a standard that can make a real difference now, today. Straube argues that the Building America standard fits the requirement because it is more economical and it is buildable by Average Joe Contractor. I think he has a point and I’m not sure I have an answer, other than that the Passive House is without a doubt the direction of the future.
I also agree with you that the Passive House movement has to seriously consider its relation to the Zero Energy approach. After all, isn’t that what all of this is, fundamentally, all about?
Wood Stove in Passive House
I am also struggling with the need for a small efficeint wood stove in a cold climate with lots of wood available versus the leakage that is introduced with a wood stove (24/7).
I am considering a Jøtul F 100 Nordic QT "the Jøtul F 100 Nordic QT, continues our tradition of clean-burn woodburning design and innovation. . . . this stove is the perfect space heater for cottages, camps & smaller living areas."
How does Germany deal with wood stoves in Passive Houses? The seem to be the leader in lots of equipment related to energy efficiency.
Bruce
Wood stove in a Passivhaus?
Bruce,
Mark Siddall recently answered a similar question on the Passive House bulletin board. He wrote, in part:
"This paper has a little study on wood burning heating systems: Re-inventing air heating: Convenient and comfortable within the frame of the Passive House concept, Energy and Buildings Feist, 2005. In this paper Feist reported that there were no suitable wood burners for PassivHaus projects. With a wood burning stove in a PassivHaus the danger of overheating the room is quite high as it is hard to control the output. Stoves using wood chips or pellets are more suited to use in a PH as the output can be more readily controlled. Stoves have to be equipped with an room air independent air supply, and flue gas removal i.e. some sort of balanced flue.
Austrian bio-mass burners are reported to be amongst the best as I understand and Okofen are at the front of the pack. Not cheap but of high quality as I understand. Have a look at
http://www.organicenergy.co.uk/content/index.php and click on the Okofen image.
For a review of the Okofen range that Organic Energy stock see
http://www.housebuildersupdate.co.uk/2006/12/pellet-boilers-okefen-examined.html
Okofen Presnetation at European Bioenergy Business Forum 2006
http://www.aebiom.org/IMG/pdf/Ordner.pdf
There are concerns about emission from residential boilers fired with wood logs and wood pellets. For more on this see:
http://www.vtwoodsmoke.org/pdf/Johansson03.pdf
http://www.vtwoodsmoke.org/pdf/Olsson05.pdf
http://www.uku.fi/laitokset/ifk/PAVA_raportti2007.pdf "
Hope this information helps.
Inhibition of mold growth and IAQ in air tight envelopes
Thank you Martin for an interesting blog!
Has there been much penetration of the Passivhaus concept in the colder areas of Europe: Norway, Sweden, Finland, or Russia? Even with an adequately sized HRV with humidity monitor and air filtration system are there technical solutions for the inhibition of mold growth when the annual temperature range is +35C to -47, as in our historical climate?
With the exponential growth of asthma in Europe and N. America it would seem that in promoting air tight envelopes we should be equal champions of all products & finishes that do not compromise IAQ with the eventual goal of convincing builders and the public that this issue has a solution.
Scandanavian countries
Russ,
Yes, many builders in Scandanavia have adopted the Passivhaus standard. (For more information, you may be interested in reading "Passive Houses In Sweden," by Ulla Janson. The English is quaint but charming; my favorite line is, "The proud carpenters with straight backs are priceless as advertisers for building passive houses.")
I'm not sure why you are worried about mold. Mold needs moisture to grow; where are you worried about mold occuring? In a Passivhaus building, interior surfaces should be at a very uniform temperature, within a few degrees of room temperature, so there are few, if any, opportunities for condensation.
Cost-effectiveness comparisons
Martin,
Thank you for sharing so much useful information and drawing in all the well informed contributors.
I am currently working to determine when the cost effectiveness of insulation is overtaken by pv for my new construction in the Lower Hudson Valley NY. Could you post links to the Straub, Rosenbaum and/or White findings? Thank you!
Previous blogs
Lillian,
Here's a list of previous blogs on these topics:
1. I interviewed John Straube on the topic of whether sub-slab foam might cost more than PV in "Can Foam Insulation Be Too Thick?"
2. We ran a Pro/Con series in which John Straube's views on Passivhaus standard were countered by a response from Marc Rosenbaum and David White.
3. John Straube's article is titled "Comparing Passivhaus Standard Homes to Other Low-Energy Homes."
4. The response from Marc Rosenbaum and David White is called "In Defense of the Passive House Standard."
why wood STOVES?
I'm new here, but I don't understand the discussions of wood stoves. Are "stoves" a thing of the past? Surely anyone thinking of installing wood heat is thinking of a wood BOILER, no? Stoves are dinosaurs, aren't they? Cheap, sure, but no efficient in any way I know of. With all the good boilers around, and their successful marriage to radiant floor heat, who would install a wood stove in a new house? If you are not familiar w/ wood boilers, check of hearth.com, Tarm, Garn, etc, boilers. Did I miss something? j
Wood boilers
J. Klingel,
I disagree that wood boilers are the best way to heat with wood. Boilers have the following disadvantages:
1. Because the firebox of a boiler is surrounded by water, it's challenging to burn wood at a high enough temperature for efficient combustion. The most efficient way to burn wood is very hot. Water tends to cool the firebox.
2. Wood boilers require electricity. In a power outage, a wood boiler will not keep your house warm.
3. Wood boilers with hydronic heat distribution systems cost much more than a wood stove.
4. In a Passivhaus building, especially, a full hydronic heat distribution system makes little sense. Passivhaus buildings don't need much heat, so a small wood stove would usually be sufficient.
Wood Stove in Passive House - Bruce
Bruce
Most pellet stoves have a minimum amount of time they need to run before they can shut off. That magic number is 40 minutes for most units. A pellet stove running for 40 minutes would generate a tremendous amount of heat and would overheat a Passive House. You may want to look into some other options like alcohol fire places.
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