Image Credit: Christoph Schulte, architect
More Musings of an Energy Nerd
UPDATED on April 16, 2015
More and more designers of high-performance homes are buzzing about a superinsulation standard developed in Germany, the Passivhaus standard. The standard has been promoted for almost two decades by the Passivhaus Institut, a private research and consulting center in Darmstadt, Germany.
The institute was founded in 1996 by a German physicist, Dr. Wolfgang Feist. Feist drew his inspiration from groundbreaking superinsulated houses built in Canada and the U.S., including the Lo-Cal house developed by researchers at the University of Illinois in 1976, the Saskatchewan Conservation House completed in 1977, and the Gene Leger house built in 1977 in Pepperell, Massachusetts. Aiming to refine North American design principles for use in Europe, Feist built his first Passivhaus prototype in 1990-1991.
Feist later obtained funding for a major Passivhaus research project called CEPHEUS (Cost-Efficient Passive Houses as European Standards). Conducted from 1997 to 2002, the CEPHEUS project sent researchers to gather data on 221 superinsulated housing units at 14 locations in five countries (Austria, France, Germany, Sweden, and Switzerland).
The standard sets a strict bar
The Passivhaus standard is a residential construction standard requiring very low levels of air leakage, very high levels of insulation, and windows with a very low U-factor. To meet the standard, a house needs:
- an infiltration rate no greater than 0.60 AC/H @ 50 Pascals,
- a maximum annual heating energy use of 15 kWh per square meter (4,755 Btu per square foot),
- a maximum annual cooling energy use of 15 kWh per square meter (1.39 kWh per square foot), and
- maximum source energy use for all purposes of 120 kWh per square meter (11.1 kWh per square foot).
The standard recommends, but does not require, a maximum design heating load of 10 watts per square meter and windows with a maximum U-factor of 0.14.
The Passivhaus airtightness standard of 0.6 AC/H @ 50 Pa is particularly strict. It makes the Canadian…
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54 Comments
Thank You Martin.. nice report
Martin,
As you may have noticed..I am very interested in Passivhaus.
I don't think that I will be building to the Passivhaus standards anytime in the very near future...but wow what a concept.
Just think if we (USA) could strive for Half of the Passivhaus standard...what a difference.
Our energy codes and high performance goals are way too low.
We don't even have a standard for airtightness.
I think that there is something fundamentally different about the German mindset.
We (USA) say things like "build tight" .. the Germans say "Airtight"
We say "minimize thermal bridging" .. they say "Thermal Bridge free"
We worry over "diminishing returns" and they figure out where the weak links are and fix it.
Just look at the latest FHB article(July) about sprayfoam....
http://www.taunton.com/finehomebuilding/how-to/articles/choosing-spray-foam-insulation-what-you-need-to-know.aspx?ac=fp
One of the Experts gives the impression that an R-17 wall is a high performance wall for a hot-humid or mixed climate.
In North Texas the Energy code only calls for an r-13 wall .. so R-17 is high performance?
I bought into the diminishing return on r-value argument myself until I took a closer look at Passivhaus and then analyzed where the weakness was in my personal home(wall r-value).
I was asking the wrong questions... I would consider what would happen if I added an inch or two of rigid insualtion instead of considering what would happen if I doubled my wall r-value.
Michael Chandler has the right idea .. ignore the diminishing return and add it if you need it.
Yes, the FHB article is disappointing
John,
You're right that the FHB article is disappointing. Particularly egregious is the misleading graph on page 35, purporting to teach us about the "efficiency" of open-cell and closed-cell spray polyurethane foam. The y-axis of the graph is meaningless -- there is no such thing as the "efficiency" of insulation. The caption is wildly misleading: "As the thickness of the insulation increases for both open-cell and closed-cell foam, the insulating value of each diminishes drastically." No! Actually, as the thickness of the insulation increases, the insulating value of the insulation does not diminish -- it INCREASES. The only thing that diminishes is the energy saved per dollar invested in insulation.
Finally — my rant is winding down — the phenomenon applies to all types of insulation, not just spray polyurethane foam. The only reason this phenomenon is emphasized by spray foam salespeople is that their product is so expensive that they need a complicated sales pitch to justify the typically low R-values they sell.
FHB article...final thoughts
FHB is the best magazine ever ...but I have to say that I am dissapointed with the illustrations in the same article.
Either the magazine artist did not portray the architect's wall section correctly or the Architect does not have a good understanding of thermal bridging.
(hint look at the top plate)
Now back to Passivhaus...
Grateful for the discussion / further thoughts
Martin,
I commend you for attempting to clarify the foundations of Passivhaus and would like to extend the discussion and attempt further clarification. Passivhaus(PH) is not a term to be tossed around lightly. It requires study and thought. As Katrin has suggested, "Be ready to let go of many of the ideas that you have relied on as a designer or builder" (and as John Brooks suggests, coming to terms with the fact that we have too often been asking the "wrong questions"). That said, I would also quote energy consultant Marc Rosenbaum's description of its premises as "radically simple".
First, it is important to recall what you have stated elsewhere, that the Passivhaus standard intends to provide housing that can accommodate a living standard on the order of what might be required by the imperatives of climate change and the calculations provided by those who advocate the 2000 Watt Society. For anyone contemplating a PH Project, honoring those imperatives are the table stakes.
The PH standard is uncompromising in its requirements to meet the challenging goals you have just listed - and for this reason: anything less is not going to be enough. There is a reason we need DEEP Energy Reduction(DER). And as Linda Wiggington has reiterated with the Thousand Home Challenge - incremental progress (Energy Star et al) channels our limited resources toward half measures that will become embedded in our housing for what looks to be an increasingly vulnerable generation(or two if we make it) - more work to undo later (like dressing for Delaware and ending up in Maine).
SO PH is DER benchmark load driven - and regardless of climate - so the focus on wall section strategies too quickly confuses the real driver of PH decision making: The Passive House Planning Package (PHPP) and achieving verification according to its model. PHPP is rigorous, comprehensive, exacting, precise, and to be used effectively requires a nine day training regimen or the services of a certified consultant - possessing the software will not provide the insight necessary to use it.
Its fundmental equations very carefully sum transmission and ventilation losses against solar and internal (free)gains to produce a heat demand within the bounds of 4.75Kbtu/sf/yr. Glazing is controlled to produce net gains without overheating. Ground conditions and thermal bridges, along with the stringent ACH standard, and the careful design of high performance balanced ventilation with heat exchange are all conditions(among many others) that are quantified to deliver verifiable results. Decades of experience in Germany confirm the accuracy of the stringent modeling (more than can be said of too many US modeling claims).
Every condition in the building's design gets (and deserves) scrutiny. Accurate determination of the building thermal boundary dimensions can literally make or break a project. A recent Minnesota project failed because they decided to add roof dimension to accommodate deeper insulation, not realizing that the volumetric increase tilted their PHPP result just over the threshold: no verification for this otherwise worthy project (or so I'm told). Even that SF denominator is made more challenging by the standard of German space determinations which excludes stairways and derates closets and utility spaces by 60%.
I share this as a novice in the midst of the training. Eyes wide open and brain deeply engaged. I share this to ward off what I already see at work - the barest understanding of PH being discussed knowingly, as if, after the briefest exposure we all knew and understood what it is and what it requires. We don't! We all have a lot to learn and should be extraordinarily grateful and supportive of Katrin Klingenberg for her dedication to teaching and sharing PH with and for us.
I'm glad that GBA is making an effort to add some depth to that understanding. In time, I hope we can look to a cadre of designers and builders who we can rightly say are masters of the form. For now though, we're all students and should walk humbly in that role.
Thanks for your perspective
James,
I honor your commitment and detailed study, and I'm grateful to you for sharing your comments.
I'd like to add a corollary to Marc Rosenbaum's perception that Passivhaus ideas are "radically simple." Here's the corollary: don't worry too much about screwing things up. Assuming that a builder pays attention to air sealing, doubles or triples the usual U.S. levels of insulation, specs good windows, avoids overglazing the south and west facades, pays attention to the roof overhang on the south side, and includes a good mechanical ventilation system, you're not really going to screw up. A slight increase in roof area may result in "failing" the Passivhaus standard, but it doesn't result in a bad building. It just results in an excellent building that didn't quite meet the strict Passivhaus standard.
Superinsulation techniques have been continuously used by a small cadre of US and Canadian builders for the last 30 years. The ideas aren't new; the principles are well established. So builders shouldn't be afraid to jump in and design better homes.
Taking issue with "jumping in"
Martin,
On the one hand I hear you - I'm sure that Minnesota house is miles beyond most - a true low load DER building that Dr. Feist would tip his hat to (excellent and enlightening interview you did with him - Thanks!).
On the other hand, we need to value the rigor of PH and its demands on our attention to what we can too easily dismiss as quibbling, especially when PH standards are taken as shorthand for thicker walls, better windows, etc. and the resulting notion that we "get it" and can just "jump in".
A key principle of PH is the "energy balance", and if there is not a discipline to carefully quantify the many details that are required to produce that balance we run the risk of producing low load fiascos (not all those super insulated ventures produced comfortable and long lived buildings). I recall Mark Kelley once warning me that passive solar could be a "dog that bites" - gentle most of the time but...
As Lstiburek recalls in his recent podcast/blog about dealing with rain - we need to be really, really, really good at details that less efficient buildings (those with higher drying potential in his case) were more forgiving of. Being really, really, really, good means to me becoming much more sensitive, and consequently much better informed about and capable of modeling the resulting interactions than we needed to be when BTUs could resolve those issues cheaply (this is all about the transition from cheap energy right?). My sense is that the lower the loads get, the more careful we are required to be.
So rather than say, "don't worry about screwing things up," I think we need to acknowledge that this is going to require most of us to buckle down and recognize that we have a thing or two to learn about the sensitivity of the dynamics in low load buildings, then begin learning how they are measured and paying careful attention to all of the parts and their systemic interactions. That's why we're here reading your blog and thinking together about how this all works isn't it?
That and to be grateful for the extraordinary work that Dr. Feist built on the foundation provided by those super insulating pioneers and the few who continued to plow that ground. I really found it curious to hear in your interview with him that, despite the 15,000 or so PH projects in Europe, he felt that US designers were more interested than his native colleagues in PH practices. I guess the grass is always greener...
Jamie
Hungry for Passivhaus
Jamie,
Thank you for stepping up.
I admit that I have a very limited knowledge of Passivhaus.....
A random education from skipping around the english language weblinks.
I would eventually like to take the "whole program".
Meanwhile... I am very interested to learn more about your experience and where you are in the "midst of training"?
PH rigor
I would like to chime in with Martin, and I speak as someone who has been to passivhaus conferences and owns PHPP. I worry that the novelty and media attention being given to Passivhaus is conflating a technical building practice with some sort of mystical training. It's just not that esoteric or arcane, or always even appropriate for all situations and climates.
The proof is that there wouldn't have been 15,000 projects built without an underlying simplicity, replicability and accessibility of the knowledge. I think every contractor on this board could build a passivhaus right now with no other new tools than a blower door and a PHPP consultant. WIth multi-unit, townhouse style construction, it gets even easier.
Also, PHPP is just well validated energy modeling software. Complex, intimidating and requires training to use well, sure, (training I don't have, by the way) but you don't need to be building a passivhaus to find value in PHPP. It is also just as effective at modeling non-PH, low energy or even high energy buildings.
It calculates heating and cooling loads, can help size equipment, optimize glazing, just like other energy modeling software.
The need for Deep Energy Reduction is real and urgent, and PH might be the most economical method to get there for most US climates, but as someone who often builds in a very cold place with lots of cheap firewood, it's not always the best way to travel.
Thanks
Jesse,
Thanks. Another vote for "radical simplicity."
More PHPP
Oh, meant something to emphasize about PHPP as software. The fascinating thing for me has been seeing people much smarter and more experienced than me quickly gravitating to PHPP as their modeling software of choice.
It is gaining respect as more accurate than anything else in wide-spread use for modeling low-energy buildings and some of their unique aspects (including slab to ground issues, and the inherent thermal lag of well insulated buildings). It has good validation, many built examples behind it, and being Excel based, all the equations and inner workings are exposed to the user, which seems to build trust in its efficacy as well.
Jesse Thompson
http://www.kaplanthompson.com/
Jamie, I could have not said it any better
This is a very well written post, Jamie, thank you. "Radical Simplicity" is one of the hardest things to achieve. It is a mistake to believe that it is easy. It looks easy, the main strategies are simple enough, we have known it all along...that does not explain why we have then not been able to create buildings to that level of optimization everywhere. Oh, we didn't think it was worth it, it does not make sense, diminishing returns, too much firewood, too cold climate, only works in the German climate, not economically feasible, there are many excuses to have to admit that this quality simplicity is currently out of reach for most of us, not impossible to attain, but it will take effort, very worthwhile effort nonetheless.
Most high performance builders fail exactly where there is no PHPP to guide them in their optimization process. It is as far as I know the only modeling tool that has specialized in really low load homes and in optimizing the relevant factors. All other programs at those levels are hopelessly overestimating the loads. It is a delicate creature, the Passive House, and yes, if not done right, it can melt away in no time and that would give the effort a really bad name. We simply can't afford that to happen again. That research experiment with a lot of guess work was conducted in the 80s and one of the reasons that those superinsulated buildings did not fly was because many of them did develop severe moisture problems in wall systems and indoors and overheated. Superinsulated wall systems become complex issues (complex not as in difficult but as in differentiated and integrated). Certainly if one wants to move through all different climates using different wall types and yes, the principles hold true in all climates. Those that added mechanical ventilation with heat recovery in the 80's many times ended up creating a net energy loss because the equipment was not efficient enough (and still isn't, with a few exceptions, on the North American market). Without a good optimization tool the "jump right in" designer is bound to get stuck in the zone before the actual economic benefit occurs, before the thing happens that makes PH so ingenious: the elimination of the conventional furnace, and the opportunity to provide all space conditioning through the steady low flow ventilation system. Most of the really good high performing buildings that just miss Passive House Standard are more expensive to build and save less energy than a building built to Passive House Standard. That does not make any sense. Why settle for that? The difference between getting there and almost getting there is to be able to build the project within 10% additional upfront cost and experienced designers as those in Germany, they now get the additional cost down to around 3-5%. This is due to experience (not components, which help), due to learning how to optimize and learning a new design principle. The Minnesota building that was mentioned had an additional 17% upfront cost due to a still sizable mechanical system. Same just happened to a building we were consulting on and where the architect did not think much of integrated design. Remaining rooted in a linear way of thinking will not get a builder or designer to achieve the Standard.
Ps.:
Passive House is a paradigm shift
What I know about Vermont
Katrin,
Thanks very much for your post. I really appreciate the fact that you have taken the time to address these issues.
Here in Vermont, since the early 1990s, builders of superinsulated homes have settled on a fairly standard method of construction:
* Double 2x4 walls with a total thickness of about 12 inches, filled with dense-packed cellulose.
* Cold, uninsulated attics with R-40 to R-60 of cellulose on the attic floor.
* An HRV with dedicated ventilation ductwork.
* Triple-glazed Accurate Dorwin or Thermotech casement windows.
* Not too much glazing; a properly sized overhang on the south side of the house to shade south-facing windows during the summer.
Among those who have been involved with houses like this are Andy Shapiro, David Hansen, and Robert Riversong. There are many others as well. These are good, simple, houses. They are robust. They work well. They don't have mold and moisture problems. They aren't Passivhaus buildings, though.
These are the examples that lead me to the conclusion that builders should not be afraid of jumping in and building good buildings.
When it comes to houses from the 1980s that developed moisture problems in walls: Katrin, please give examples. I think this is somewhat of an urban myth. The houses that developed moisture problems in the 1980s were not the superinsulated houses. They were not, for the most part, houses with impeccable air barriers. They were not the houses built by people who read Ned Nissons's book, Superinsulated Houses. They weren't R-2000 houses in Canada. They weren't houses built by Steve Lentz in Wisconsin. They were sloppily built houses by builders who didn't know what they were doing. Plenty of R-2000 houses have been opened up over they years; they're doing fine. The walls are dry.
Anyone reading the GBA Web site — anyone familiar with the Building Science Corp. Web site or Lstiburek's books — should be able to build walls that won't develop moisture problems.
Finally, when it comes to cost-effectiveness, we are all struggling with these issues. It's a complicated subject. Your houses in Urbana are great examples. Other Passivhaus buildings — including the Waldsee Biohaus — are certainly not paragons of cost-effectiveness. Any time you end up with details requiring 14 or 16 inches of rigid foam under the slab, the cost-effectiveness argument is going to get hot and heavy. However, I will hold up the cost-effectiveness of the Vermont houses I describe in this post against any Passivhaus building I've heard about.
Don't forget us southerners!
Hello everyone - I find the Passive House concepts quite fascinating, and encourage the advancement of the concepts. However, as far as I can tell, the designs are still primarily cold climate oriented. In a discussion with Katrin at ACI, she indicated that they are working on a hot humid model, but that the details are not yet resolved. While I certainly don't advocate underinsulating walls or windows, we do need to consider where to spend our money. I don't believe that there is much, if any, value in R40 walls and triple glazed windows in hot and moderate climates where the Delta T from inside to outside is rarely over 30 degrees. It seems to me that in different climates we should be stressing some different approaches.
HRV's
Don't forget that we use ERV's down here, not HRV's
Carl, you're right
Passivhaus concepts definitely arose in central Europe, where builders were trying to reduce space heating costs and were advocating houses without any air conditioning. The movement was inspired by houses in Saskatchewan, Massachusetts, and Illinois.
Wolfgang Feist is aware that Passivhaus needs to do a better job at providing recommendations for builders in hot climates. Indeed, this aspect of Passivhaus is still evolving.
Hot climate homes need to be built differently from cold-climate homes. (Obviously, you already know that, Carl.) What matters in a hot climate?
1. It's better not to insulate under a slab on grade.
2. Windows need to have a very low SHGC. Triple glazing doesn't make much sense.
3. Hot-climate builders need to pay attention to keeping windows in the shade, and reducing glazing ratios.
4. Deep attic insulation still makes sense, because attics get very hot.
Finally, Carl, are you aware that the preference for ERVs in hot climates (instead of HRVs) is based on an urban myth, not research? You may be interested in reading "ERVs Don't Reduce Indoor Humidity in Hot, Humid Climates," an article I wrote for the May 2008 issue of Energy Design Update.
Delta-T Swing Kool-aide
Carl,
I think that you have bought into the Peter Pfeiffer logic.
I believe that Delta-T swing is not very relevant.
What if the Delta-T swing was only 20 degrees?... but it was 90 degrees outside night and day?
Does that mean that the laws of physics no longer apply?
I know that we (Mixed/Hot/Humid) folks may not need R-40 walls as much as the extreme climate folks... But R-17 ???
Thanks to internal heat gains and solar gain.. we mixed climate people may do OK in the winter with an R-17 wall...
But what about summer? the internal loads are working against us and we will be expending energy just to combat the internal loads and the solar loads.
That's when the extra r-value makes sense!!!
More wall insulation because of internal loads?
John,
I was following your argument in favor of high-R walls in hot climates until I got to your discussion of internal loads. Say what? Wall and ceiling insulation can't help a problem with internal loads. In fact, in extreme cases — computer server rooms, for example, where AC struggles to counteract internal loads — you want less wall insulation, not more.
Heat moves from more to less
If you maintain your home at 70 degrees and it is 90 outside...
It would be wise to reduce or slow down the heat flux...
With higher r-value
Glad I stirred things up
Martin - I actually rarely use or recommend ERV's, I prefer to bring in air through the HVAC return plenum and live with the minor energy penalty. Thanks for the backup on triple glazed windows - there is really no point to spend the money on them in moderate climates, and the high SHGC is good in keeping heat out, but shading is much better. Glass can only do so much.
John - Interesting that you say I have "bought into" the Peter Pfeiffer logic, as I have just started designing my own house with him. While R-17 is on the low side, in moderate climates there just isn't enough heat loss and gain to justify framing extra thick walls and piling on insulation at the level of R40. I'm in favor of something in the range of R22-25, using a combination of spray foam and foam board on the outside for a thermal break. My feeling is that air sealing the entire house is the most critical to control heat gain and loss as well as humidity gain and loss, both of which will keep the house more comfortable. In moderate climates, wall insulation is much less important than air sealing and roof and floor insulation. And don't forget window orientation and shading - no matter how much you insulate, if your windows bring in too much sun, the building will overheat when it gets hot out.
Moving on to a different, but related subject, I am becoming very disillusioned with spraying insulation into existing wall cavities, due to the fact that it tends to retain moisture, particularly where there isn't an effective WRB, causing rot where it often didn't exist before. In moderate climates, I would not recommend insulating existing walls, rather expend the effort and money on careful air sealing. In cold climates, I think we need to consider carefully how to deal with bulk moisture before we insulate old walls.
paradigm shift ... new metrics
Carl,
I'll have what Katrina's having.
An HRV and High r-value may not have a significant impact on an ordinary (or even Energy Star) home.
But if you do the whole Passivhaus enchilada ...then HRV and superinsulation make sense....
"in Sweden and Roma"
in Vermont and North Texas
sorry...I meant Katrin
sorry about the typo
Katrin, Katrina...Architect, Hurricane, whatever
I don't disagree with what she is doing, I just don't think it has been determined that it is the best answer for moderate, and especially humid, climates yet. I like the idea of building a house that doesn't need a central heating and cooling system and look forward to living in one someday, but I would like someone else to go through the learning curve rather than me. I would love to see an analysis of energy usage vs. embodied energy over the live of a building, in different climates, of course, for extra thick walls vs. standard thickness - taking into account all the materials used in the assemblies. This is a little above my pay grade, but I think it would be a good exercise.
Hot Humid Low-Energy
There is a good information about preliminary research on low-energy building techniques in hot/humid climates in the PHIUS book, Homes for a Changing Climate: http://www.passivehouse.us/passiveHouse/PassiveHouseBook.html
The project under conversation is the Lakeland Zero-Energy by the Florida Solar Energy Center, there's extensive documentation of their techniques at this link: http://fsec.ucf.edu/en/research/buildings/zero_energy/lakeland/index.htm
Going to a 36" overhang was more important than increasing wall insulation, keeping the exterior walls shaded from any direct sun was key. White roof was also top on the list, as was as much tile floor as possible to create a natural heat sink. They also worked hard at shifting the cooling load off peak hours using the PV and thermal mass. R-40 wasn't high on their strategy list.
Jesse Thompson
http://www.kaplanthompson.com/
Not So Low Energy Home
Jesse,
I don't think the example home that you posted is a good example of a low-energy home for a hot humid climate.
At best it is a Not So High Energy home with some PV tacked on.
The light colored roof and the generous overhangs are very good strategies .. but some of the other specs really fall short.
John, I have to agree with you
Here's what jumped out at me about the Lakeland near-zero-energy home: its air leakage is 4.9 AC/H at 50 Pascals. The researchers noted that "much of the leakage to the outside appears to be from the 30 recessed lighting cans in the ceiling."
Back to the drawing board, I guess.
Martin - Nice Catch on the Recessed Lights
I missed that gem on the 30 recessed lights in my quick review of the FSEC website on their project. While that is certainly a big problem, it doesn't negate the value of the rest of the research, which does appear to support different details in warmer climates such as overhangs and light colored roof in lieu of super insulated walls. Let the fussing continue.
High Performing Home
Carl,
You are almost there....
You are already building a Peter Pfeiffer Home.
Peter Designs a high performing Home.
Peter knows very well how to design for hot and humid.
Shading Overhangs and a deep respect for the Sun.
Now see what happens if you look at your weakest links....
How are those remaining BTU's getting in and out?
*Wall R-value
*Intentional Air Changes
*Unintentional Air Changes
*Thermal Bridges
*Windows
*Slab Edge
Why not fix those problems and then think about PV or wind?
Does it really matter what the payback is if those are the problems?
Not So Low Energy Home
It's a bit bizarre to discount the research the Florida project highlights because they didn't concentrate enough on air-sealing. I'm sure they're working on that for the next one.
One of the significant issues that the Passivhaus research has highlighted is the importance of room surface temperature and human comfort. It's one of the major reason they have such stringent specifications for window selection, to ensure that people will be comfortable sitting next to their windows in winter without a local heat source warming the walls.
So, hot humid climates. Obviously, if you have mechanical cooling, you need air control, therefore air-tight houses with good ventilation. But comfort is a range, not an absolute, and a house with cold air but hot radiant surface temps can still be uncomfortable, especially when you don't have nighttime cooling that could stop steady heat flow through the walls, even with good insulation.
And in any case, if you are living in Florida, I would hope you would be there at least party for the nice weather. There's a lot to be said for living in an open breezy house with a giant umbrella over the top of it as opposed to a sealed up walk-in cooler baking in the sun. Perhaps the best thing is the walk-in cooler with the umbrella over the top...
Jesse Thompson
http://www.kaplanthompson.com/
Super Insulation sounds wasteful
Carl,
why does appropriate insulation have to be in leiu of overhangs and light colored roofs?
I can imagine a house that has all three.
And nobody said r-40 ... r-40 is not the prescription for all climates.
Thanks Jesse
One more vote for seriously studying Passivhaus concepts and applying that knowledge.
There are some very tall shoulders over there (Europe) that we can stand on.
They are applying what Dr. Lstiburek has been telling us.
Passive House as the way forward
Thanks Martin for helping to raise awareness and continue the dialogue around PassiveHouse.
In introducing the PassiveHouse concept to people, I have referred to it as being “Elegantly Simple”. Good design should actively work towards removing complexity which, well, makes things complicated!
Good design should be elegant! Among other definitions 'elegance' can be defined as...
A quality of neatness and ingenious simplicity in the solution of a problem (especially in science or mathematics); "the simplicity and elegance of his invention"
http://wordnetweb.princeton.edu/perl/webwn?s=elegance
PassiveHouse is Elegant!
Also, Malcolm Isaacs (http://www.flickr.com/photos/malcolmi) who has been busy giving presentations around Ottawa to government, green building, and community groups has described the PassiveHouse approach as being the “evolutionary end-point” of energy efficient building.
The ambitious energy-efficiency goal of PassiveHouse means that the design tool has to be very good. Passive House doesn’t work if a designer is lazy and over sizes the heating mechanicals. A designer can, but what makes Passive House work economically is the substantial reduction in capital cost for mechanical systems that stems from meeting its heat and cooling load objectives.
The Passive House Planning Package (PHPP) (http://www.passivehouse.us/passiveHouse/DesignTools.html) is the tool by which a designer can accurately and repeatedly design PassiveHouses. The Passive House concept and the PHPP together will foster the paradigm shift that Katrin indicated in her comment.
I have no doubt that there are many small builders and architects out there building super-efficient buildings using a variety of design tools. But unfortunately these buildings are few and far between in North America.
It’s pretty safe to say that anyone reading GBA is committed to building energy efficient buildings; and that this commitment is based on concerns about sustainability and the environment.
Also, I believe that everyone reading Martin’s post shares the goal that every house built in North America, whether they be production built by a developer, or a custom home, should be as energy efficient and comfortable as a PassiveHouse.
How do we get there! Passive House is the approach that merits our serious consideration.
Developers, who build the vast majority of houses, will always argue that it is too expensive to build an energy efficient house. Aside from the fact that I think that argument is a red-herring since our houses are twice as big and filled with half as many people as our parents’ homes, nevertheless we must continue to address their argument. Passive House allows us to compare apples to apples, it allows us to refine our building practices, and it allows us to iteratively improve a building’s energy efficiency at the design stage where it's the most cost effective.
If we build enough PassiveHouses and constantly refine our design and building skills to the point that PassiveHouses compete with the cost of a production built home then the builder/developers will be too embarrassed to argue that it is too expensive to build an energy-efficient and comfortable home.
The experience in Germany already indicates that Passive Houses can be built almost as cost effectively as those built to the existing standard of energy efficiency. Given the head start that the Passive House Institute has given us in North America it shouldn't take too long for a committed group of green builders to prove that PassiveHouses can be built cost effectively here as well.
P.S. I haven't built or designed a PassiveHouse! I recently built a major addition on to my very small house, which had no choice but to come along for a major renovation as well. I took what most people would consider a green approach to the work and did my best to reduce the amount of energy the house would need to heat the home. I have a 3 1/2 ton heat pump which my geoexchange contractor remarked was very small for a house my size. I have a four hundred foot bore hole, around nine hundred feet of 1 1/2" geothermal polyethylene pipe to and from the bore hole, there is a 60 gallon storage tank, 1500' of 1/2" pex-al-pex, 1000' of pex, and four radiant hydronic distribution manifolds, and the sytem requires three circulators. And Warmboard!
The design of the radiant system was derived from John Siegenthaler's excellent articles and textbook on radiant hydronics, so in many respects it is a relatively simple system.
But unsurprisingly, I found it extremely complicated to design and implement this energy-efficient heating system to make up for the heat the house loses.
Which is why I think PassiveHouse is so elegant.
As a comparison, Malcolm Isaacs 'almost' PassiveHouse which is in the same area as my house, has a 100 amp panel. I have a 60 amp breaker for the heat pump in a 200 amp panel, and the lights dim when it starts up!
High Performance Home with Climate Appropriate Details
John - I've been building and renovating high performance homes for almost 10 years now, and I have learned a thing or two. I don't claim to know that much about cold climate building, but I have figured out quite a bit about how to build in the mixed humid climate where I live. Regarding your suggestions as to improve the envelope:
*Wall R-value - As I said, R22-25, about as much as you need in my climate
*Intentional Air Changes - will not vent to Ashrae 62.2, use natural ventilation for most purposes, plus outside air intakes into return plenum
*Unintentional Air Changes - minimal ~ACHnat <.1
*Thermal Bridges - virtually none
*Windows - Excellent SHGC and U factors
*Slab Edge - No slab, sealed and insulated crawlspace
Virtually no wind available in GA, solar potential is limited due to large trees, and costs are still prohibitive even with tax credits. Better off minimizing load and buying green power from local utility. I have heard some excellent cases for not doing distributed solar on individual homes due to footprint of manufacturing, maintenance and cleaning, lifespan of equipment, to name a few. Not fully convinced, but willing to consider other options.
Not sure exactly where you are headed with your comments, but I try to be open to others ideas while sticking to what I know works from my experience.
Thanks for an exellent post, Andrew
As we debate whether it's necessary for American builders to adopt every aspect of the German Passivhaus standard, let's remain open and positive. Europeans have much to learn from the best North American builders, and vice-versa. We should all keep our ears open, continue experimenting, and try to learn.
As the former editor of Energy Design Update, I know that a dedicated group of North American builders have (largely unheralded) been quietly building excellent low-energy buildings here for the last 30 years. In the late 1990s and early part of this century, however, European builders became the innovators. They have certain advantages now, including access to much better windows and access to sophisticated HVAC systems that we can't buy yet.
Nevertheless, European Passivhaus buildings aren't cheap. Europeans pay staggering sums for their HVAC equipment -- including their HRVs, air-source heat pumps, and solar thermal equipment. The equipment is beautiful, designed to last 40 years or more, but it isn't cheap.
Moreover, the Passivhaus standard has a huge Achilles' heel: it is based on energy use per square meter. As a result, there really isn't any penalty to building very large homes. The rarely discussed secret: a very small home that DOESN'T meet the Passivhaus standard will often use less energy than a large Passivhaus home.
One last point: all of us, on both sides of the Atlantic, are struggling with a stark truth: a high percentage of our new buildings are using more energy than the modeling suggests they should. The biggest culprit: escalating plug loads from TVs, satellite receivers, set-top boxes, electronic device chargers, computers, and extra refrigerators. Many clients are promised low energy bills, but end up with houses that use more energy than they expect. However, the builder isn't really to blame -- unless he or she failed to discuss these issues with the clients.
One study of the energy use of Passivhaus buildings is Jurgen Schneiders' report, "CEPHEUS: Measurement Results From More Than 100 Dwelling Units In Passive Houses." Among his findings:
* Actual air leakage rates in the eleven studied projects ranged from 0.30 Ac/h to 11 ac/h.
* Only one out of 11 monitored projects achieved the Passivhaus goal of 15 kWh/square meter per year; the average space heat consumption before normalization was 24.8 kWh/square meter per year.
That study was performed years ago, and Passivhaus building performance has since improved. Later studies have shown that newer buildings are achieving better results. But let's all stay humble. We all have a lot to learn, and monitoring studies often show that our performance falls short of our stated goals.
Again, many thanks to everyone participating in this important discussion.
Carl... I respect you
Carl,
I have two heroes here in Texas... Jim Sargent(GBA Advisor) and Peter Pfeiffer.
I even hired Peter to consult on the design of my personal Home.
I admit that I do not know exactly how you build your homes.
I based my comment on your comment from another blog:
"I concur with my good friend Peter's assessment of wall R value in moderate climates."
Here is a Peter Pfeiffer quote concerning wall R-value in Texas:
"once you hit about r-13, you're really reaching a point of diminishing returns"
I should not assume that your homes have the same weakness as my home.
I only encourage you to take an even closer look at Passivhaus.
I thought that I had built a "high performing home" (HERS 51)
Jim Sargent toured my home and then enlightened me about Passivhaus.
That's when I started digging into PassivHaus.
I realized that I was "almost there" and I realized what the weak points were in my home.
If we take care of the Unintentional air changes by setting our airtightness goals higher...then I believe that we (includung Mixed and Hot/Humid)can then take best advantage of the Intentional Air changes by using an HRV
I am not so sure that most of us are doing enough concerning thermal bridging.
I have not seen many details here in the US that I would consider "Thermal Bridge Free"
Carl.. I am on your side
Say what?
Martin... I guess I still don't get your computer room analogy.
Was this done in a cold climate or a hot climate?
Are you saying that because of internal loads that we would be better off with less insulation during the cooling season?
Or are you saying that internal loads are irrelevant?
Let's see if I have this right
John,
I may have this wrong, but bear with me. Let's consider two small sheds. In both cases, it's 90 degrees outside. Let's say both sheds have R-20 floor, wall, and ceiling insulation.
1. Case 1: an empty room.
2. Case 2: a room full of server computers that generate a constant 24-hour-per day thermal load of 4,000 watts.
If the sheds are not air conditioned, doubling the insulation to R-40 will make the Case 2 shed hotter inside, not cooler.
If the sheds are air conditioned to 70 degrees, then doubling the insulation makes sense, because there is a 20-degree delta-T between the conditioned interior and the exterior. So I'll admit that my point was mistaken.
Here's what I was driving at: in a house without mechanical cooling, internal heat loads during the summer lower the delta-T between the interior and the exterior, they don't raise the delta-T. However, the use of mechanical cooling means that the delta-T will be the same regardless of the loads. But high internal heat loads really just affect air conditioner sizing. They don't have anything to do with envelope R-value. The only factor that envelope R-value addresses is the delta-T, which is greater when the outside temperature is greater — but is unaffected by internal loads.
Summer R-value in a Hot or Mixed Climate
Martin, Let me try to clarify my point.
My point is that in a hot or mixed climate...
additional R-value can have more "merit" in the Summer.
Imagine a well designed home in winter...airtight...HRV etc... such that it is insulated just enough for the internal loads(Humans,Pets & Appliances) and solar gains to heat the house....The house has just enough R-value for winter conditions.
Now consider the same house in summer... Internal loads have not changed ...
there are still some solar gains and now conductive gains instead of cunductive loss.
Adding more R-value will further reduce the conductive gains and therefore the Energy required to cool the house.
Maybe it is better to say that the mixed climate does not need as much r-value in the winter because solar gains and internal gains are offssetting part or all of the conductive losses.
Lets match our enegy performance goals to meet our CO2 reduction
I have been curiously following this discussion. It seems to me that we need to take a closer look at what the goals are and what the means are to achieve these overarching goals.
Nobody questions the achievements of the early pioneers, the current building science leaders and high performance home builders. Anybody, who has pursued this field with the commitment and rigor as those who have deserves the greatest respect. It took a deep conviction not to leave this path for 30 years when politics and public opinion did not value conservation at all. The people you are mentioning, I have no doubt that they know their building science and that they build well performing homes. By PH standard, those homes in Vermont are still using twice or more energy than a Passive House. Where do we really need to be to match the crisis?
You asked for examples of building failures. Personally, I only have examples out of the present and they are of the worst kind. In essence, these design teams were trying to build a Passive House without understanding the basic design principles. They built a super insulated, airtight building which then had dramatic condensation, mold growth and building failure in just a couple years. They did have people on the design staff (mechanical engineers)that should have known better. Not sure if they read Joe's books..... I also spoke with a fellow out on the Vineyard a while ago who just moved into a high performing home there. He came to me after a work shop and wanted advice. He told me that his windows were dripping wet, mold was growing and he did not know what to do, the builder was unresponsive. I asked him if he had a balanced ventilation system and he said he only had a whole house fan. Those stories are real and far from urban myth and that is just the most obvious mistake one can make.
Big picture goals: I recently saw a headline that stated "Matching the energy goals to meet the crisis". We now have an amazing chance (and this may be the last one) to seriously get our energy consumption and related co2 emissions back on track to meet the crisis. PH not economically feasible? If one makes the effort and zooms out and looks at the big picture, there is no doubt in my mind that PH is the cheapest solution to meet our goals as a society (other than back to the tents). Just go through the numbers. Look at your options, on how you would provide enough renewable energy (carbon-free)to meet our current energy needs (not counting the projected 60% increase with India and China coming onto the market). Wind? Solar? CO2 scrubbers? There is no economy in the world that can pay for enough of those to reach our carbon-emission goals. The low energy homes are a good first step but we can go further (and they cost more if we do a life cycle analysis, as I stated in my post above).
Our tools to achieve this very ambitious goal: Physics and math, no more guess work here. Wolfgang Feist was not only inspired by Ted Nisson and William Shurcliff (and other around the world), he further refined and engineered the underlying concepts, concepts that are based in physics and if applied, will work in every climate.
Martin, there cannot be a discussion if all of the Passive House principles should be applied or not. That is missing the point of Passive House. Passive House is a performance standard rooted in concepts of physics and our design limits in terms of co2 reduction goals. It is not a check list. If we don't conserve energy to about the level that PH prescribes, we will have to face the consequences. And I personally have come to the conclusion, that PH levels of conservation are really the upper limit we can afford and that they should be tightened beyond where they are now.
One more note: You mentioned the CEPHEUS project to make a point about PHs using more energy than modeled. That particular research project looks at measurements including user behavior and I am not sure which data you have, but the graphs from this project that I have show a mean measured energy consumption of 16.9 kWh/sqm yr over 200 projects. I like to see any other study or modeling tool that can produce results close to the CEPHEUS results. Mission accomplished, performance goals met, as far as I can tell.
PS.: I had an interesting find modeling a project in Louisiana. The PHPP was recomending some insulation in the slab because the ground temperature would warm up to a point that it started to contribute to the cooling load. Together with the losses during the brief cold days the balance was better with under-slab insulation.
P.p.s.: The Lakeland House in "Homes for a Changing Climate" was approaching the discussion of high performance buildings in a hot climate and in many ways does not align with PH criteria. There was no claim made that it was a Passive House.
Thanks!
Katrin,
Thanks for all of the good information provided in your recent comment.
Your stories about tightly built homes with dripping windows is a timely reminder of the importance of good mechanical ventilation. Readers interested in more information on the topic may wish to check out
https://www.greenbuildingadvisor.com/blogs/dept/musings/desiging-good-ventilation-system
Concerning the essential point that new homes need to be built to standards that respond to the seriousness of our current climate crisis: I couldn't agree more. We all owe a debt of thanks to Passivhaus activists who are providing details that are appropriate for the serious challenges ahead. Certainly our path forward will depend much more heavily on conservation than on renewable energy generation.
I'm intrigued by your report of the value of subslab insulation in Louisiana. I'm sure that I'm not the only person hoping to see more building science research on this important topic. We all need to know the climate factors that affect whether subslab insulation makes sense in hot climates — and, if subslab insulation makes sense everywhere, how thick the insulation should be.
PH opportunities
What a passionate discussion!
First, I'd like to parry a blow. Jesse, I am your PH consultant, and I am not, as you write, a "new tool."
Now that that's taken care of, I'd like to draw attention to what I see as most useful about the PH approach. I've only been at this work for 12 years, but I've never seen or heard of any design approach that is as well put together. It is rigorous and transparent in its calculation methodology to such an extent that features typically overlooked, such as the length of the cold air ducts running between ERV and outside, wall to roof connections, length of window frame, spacer, and installation, etc are accurately accounted for. It gives a more sensitive level of feedback in optimizing design than any tool (I trust the software won't be insulted by my calling it that) I've ever used.
It is also extremely accurate. I've asked the big boys in Germany, and they bow to Feist's handiwork in transposing the best dynamic thermal simulation software in the world into a simple MS Excel worksheet. PH is verified as more accurate in field measurements than all of the other European low-energy standards (even Swissy!). This is really important when we are talking about the low levels of heating energy demand we are trying to achieve - it's a whole new ball game. It's also really useful when one wants to capitalize on the extremely long time constant of a SI house. PHPP calculates peak heating load based on the coldest DAY, not coldest hour, or 99.6% hour, etc. This means that it even takes useful solar gain into account, FOR THE PEAK LOAD CALCULATION. This is how passive houses can be built with no more than $300 duct heaters in the main OA duct serving as the heating system.
PH also shows us what's possible - that this can be done, economically; and it gives us a good reference point. George Carlin said that when you're driving, everyone slower than you is an idiot and everyone faster is a maniac. Well, now the nerdiest of us finally have a maniac to complain about.
No, I don't see PH as the solution for all situations. The PH heating standard came about as the logical extension of a cost optimization exercise. It went like this: you're in Darmstadt. You make a house. You insulate it so well that you can meet its peak load with a $300 duct heater in the main OA duct. How much heating energy does it demand annually? Answer: about 15 kWh/m2a.
And we do find in different climates that the ratio between peak load and annual demand is not fixed, and the whole logic goes entirely out the window when we resort to other heating/cooling configurations. Although I still agree with Kat that we can and should be in this ballpark.
But most of all, it is so useful for us to feast on this wealth of information. Jesse put it right that 15,000 units exist because this problem has been so well packaged.
But Jesse, I don't think it is easy. I and others are working very, very hard to get a solid footing with the more subtle aspects. It is successful in producing energy efficient buildings because it is simple and transparent, and rigorous in its logic, but it is not at all easy.
Ultra Low Energy Buildings ....Presentation
Here is a link to a presentation by Katrin
http://www.istc.illinois.edu/about/SustainabilitySeminar20081028.cfm
I hope that others will continue to add more PassivHaus related links to Martin's Blog
another passive house under construction
Folks might be interested in a passive house currently taking shape in Utah: http://www.ourpassivehouse.org/
Tool Time
A note on GBA's forum design, it's far too difficult to notice new posts to old threads. Apparently I called a friend a "tool" to the entire Internet several weeks ago, and just noticed it now...
Thermal Bridge Free? and Climate Data
My question is for a PH consultant:
How do you define and verify "Thermal Bridge Free"?
Does your current climate data(used with PHPP) include a location with a similar climate to Dallas,Texas?
R-Value in Hot/Dry Climates
I would agree with John that a high R-value is necessary even in hot/mixed climates. Living in the Phoenix area where temperatures regularly rise to 110 F during the day and can sustain in the mid-80s through the night, the need for a high R-value is imperative. While the PH standards may have been primarily designed for cold climates, the principles can be applied to hot/dry climates, I would believe. In either situation, you are trying to maintain an indoor temperature that is substantially different from an outdoor temperature.
Cold climate - 60F indoor / 20F outdoor - 40F difference
Hot climate - 70F indoor / 110F outdoor - 40F difference
Shouldn't the same concepts apply?
A roundup of Passivhaus articles
For a good list of Passivhaus articles available on the Web, check out http://www.passivehouseca.org/media .
Another useful resource
Here's a manual on building superinsulated walls. While it is written with Alaskan builders in mind, builders in milder climates will find much useful material here. The handbook quotes Thorsten Chlupp, among others.
http://www.cchrc.org/App_Content/files/Northern_Fundamentals_REMOTE.pdf
Translating German Web Pages
I just realized that I do not have to learn German!
By using a translator like Google .. We can read the German Versions of the Web Pages
Which offer more info
http://translate.google.com/translate?prev=hp&hl=en&js=y&u=http%3A%2F%2Fwww.passivhaustagung.de%2FPassivhaus_D%2FPassivhaus_Verzeichnis.html&sl=de&tl=en&history_state0=
Remote Wall .. In More Detail
http://sustainable.cchrc.org/docs/REMOTE_Manual.pdf
Lots of interesting thoughts in this recently published "Manual"
They even prescribe a slight upward angle for the fasteners that secure the strapping....The caption mentions that it improves the structural connection.
Although not mentioned I would think this would also be wise just in case of a leak near the fastener..the penetration would drain to the outside.
Old Balloon Frame
I have been reading through this discussion with interest and wonder what other posters and especially Katrin Klingenberg would think of our modestly insulated, completely incorrectly orientated (To the South in the Southern Hemisphere)balloon framed cottage. We own the next door plot of land and wish to build on it. At present we burn more than 20 cubic metres of Tasmanian hardwood a year over a nine month period. Needless to say our air quality inside the dwelling is not the best and we would hate to waste money on another inefficient building. Could a Passivhaus be our answer? Our latitude is 41 degrees south in Tasmania and we are close to 400 metres above sea level.
20 cubic meters of hardwood
For North American readers,
Robin's firewood consumption (20 cubic meters) is equal to 5.5 cords.
Thank you Martin, I have often
Thank you Martin, I have often wondered what a cord of wood is. So roughly 4 cubic metres or around 148 cubic feet?
What's a cord?
A cord of wood is 128 cubic feet. The traditional manner of stacking wood called for cords to be stacked in piles 4 feet deep, 8 feet long, and 8 feet high. In the U.S., standard firewood lengths are 16 inches and 24 inches; a 4-ft. deep stack contains either two rows of 24-in. wood or three rows of 16-in. wood.
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