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Green Architects' Lounge

Passive House: After Hours

After the Boston syposium is over and the PowerPoint is put away, it's time to go out for dinner with Dr. Feist and Katrin Klingenberg to get some inside information on the future of the Passivhaus standard

Charley's Saloon on Newbury St. In Boston. Our dining location.

I left Maine with a plan. I had already corresponded with Dr. Wolfgang Feist (founder of the Passivhaus Instiut) and Katrin Klingenberg (head of PHIUS, Passive House Institute U.S.) and asked if I might be able to interview them for Green Building Advisor and the Green Architects’ Lounge. Both had indicated a willingness to do so, but the schedule for the event at the Boston Architectural College on October 23 was pretty full and they really didn’t know if there would be time.

So I had decided that after joining up with Martin Holladay for the small group conversation prior to symposium, I’d try to steal some time between the meeting and the symposium. Failing that, I would attempt to pull them aside afterward for a quiet interview or even better, take them out for a drink and record a short interview on location.

As you can imagine, there was a shortage of spare time to steal away during the event. So I was thrilled when I was included in the small party of six for dinner afterward. Our mission was to find a nice quiet place to dine, drink, chat and record an interview.

It turns out there’s no such place on Newbury St. in Boston. So, an audio recording of the dinner interview exists, but I’m afraid the background noise is too distracting and makes for an annoying aural experience (unless you really enjoy the chiming of flatware, background music, background conversations from neighboring tables, and the loudest fajita ever ordered). Perhaps if we find an audio editing genius, who enjoys donating their free time, the Green Architect’s Lounge will release it as a bonus later. Until then, the transcript will have to do.

Engaging and delightful

It was a beautiful autumn evening. We walked a few blocks to our restaurant, chatting about some of the evening’s events and how the Boston Architectural College building might be perfect for a deep-energy retrofit (possibly Passivhaus?). In attendance were Dr. Wolfgang Feist; Katrin Klingenberg; Declan Keefe of Placetailor; John B. Clancy (or “J.B.”) of Albert, Righter & Tittmann Architects; Mark Anstey of J.P Design; and myself.

I found all to be most engaging and delightful, Dr. Feist in particular. After hours of discussion on the topic (and being seven hours ahead of all of us) he was still just as kind and eager to talk about Passivhaus as though his day was just beginning. In fact I thank them all for participating and ignoring the microphone on the table as we happily talked about politics (omitted, for obvious reasons), architecture, and some finer details of the Passive House system.

If you are new to the Passive House concept, I urge you to visit a few of the links on this page prior to continuing. It will help you quite a bit, as this conversation does not cover the basics (like, “What is a Passive House?”).

A toast, to my dinner guests and you, fine reader.

Varying climates

Briley: Using the same study that you used to come up with these [passive house] standards, could you theoretically do that same study for our six different climate zones and come up with six different sets of standards?

Dr. Feist: You may be surprised; this has already been done.

Briley: I am surprised! … and I see Katrin is smiling like crazy.

Dr. Feist: It’s not yet published, but we have a project financed by the German Environmental Foundation, and they asked us to do these studies in six different climate zones worldwide.

Briley: Worldwide?

Dr. Feist: Yes, including China, but not tropical climates. … Siberia, Dubai (one of the toughest climates in the world).

Briley: Right, and the buildings probably have to be all glass…

Dr. Feist: …Ha, they now even have a big hall where they can go skiing in the middle of the desert. But seriously, it is a really tough climate. It also turns out that the main [Passivhaus] principels can be used everywhere. There are only a few climates — like Lisboa in Portugal — where the conditions are so good that you don’t need any heating or cooling anyway, so you don’t really have to do a lot to meet the standard.

Klingenberg: Like San Diego.

Dr. Feist: And then there are parts, say, in Antarctica, where it is extremely tough to do anything.

Briley: Did you develop a standard for Antarctica?

Dr. Feist: No, we did not. Though there were some crazy guys in Belgium who have already built a Passivhaus polar research station. It’s already there. But I don’t care about this climate. It’s kind of like northern Sweden; if you say you can’t build a Passivhaus there, well, then I could live with that.

The PHPP spreadsheet and thermal mass

Briley: So Dr. Feist, there must have been a moment long ago where you said, “I know what I’ll do: I’ll open up an Excel spreadsheet, and I’ll work out these formulas.” Is that how it went down?

Dr. Feist: No, it was completely different. When we started the first project, there was nothing like that, so we had to use simulation software where we simulated every nail to get the right values, and it didn’t turn out so well. It’s interesting. There was another American involved in that. It was Amory Lovins [of the Rocky Mountain Institute]. I showed him the simulations and the measurement, and after an hour of conversation he said, “Well, Wolfgang, you are completely wrong.” [Laughter around the table.]

I was completely shocked. My belief was that the first Passivhaus project was just a research project. He said, “No, you are wrong. This is not a research project – this is the solution.” And he also told us, “You have to simplify and create a tool that is easy to handle.”

So that is the point where we started to think about how to simplify the concept and how we arrived at these simple three standards, on the one hand, and on the other, to see if we could reduce the complexity of the simulation to focus on the real important parts. Of course, thermal mass is also important, to have that in the simulation makes it much more complicated. If you want to include thermal mass, you can’t be satisfied with just the envelope, you have to use the whole structure, and that makes it much more complicated to bring these data all into the program. So we decided to simplify it to a simple almost envelope-only system.

Briley: So does the Passive House Planning Package take thermal mass into account at all?

Dr. Feist: It does, but you estimate the thermal mass, by looking at how many areas are filled with masonry or timber, and you account for those and calculate a good guess, for thermal mass. Because the influence of thermal mass isn’t so high – this is still good enough compared with the accuracy of other inputs.

The PHPP: Passive House Planning Package

Briley: Do you think there’s going to be any development in the PHPP software? Right now it’s a spreadsheet, a very elaborate spreadsheet. I’m just now getting my feet wet and starting to use it myself. I started off thinking “Ah, Excel! I can do this.”

Dr. Feist: It’s easy, no? That’s the reason we did it this way. Well, there are two reasons: one is that anyone can use it, and the second is that it’s open. You can see every algorithm which I think is important. It’s also easy if you want to add something. There have been other discussions about having other programs besides the spreadsheet, but I think we will always keep the spreadsheet.

Briley: Are you prepared to see other people run away with the spreadsheet and adding on other complex things?

Klingenberg: Good luck with that. [Chuckles around the table.]

Dr. Feist: I think we should never stop thinking about development. I like to have feedback and it’s good to give that feedback back to the community. That’s why we’ve started Passipedia, because it’s very important to share knowledge. [Dr.Feist was referring to their new Web site,, that acts as a warehouse for user knowledge on all subjects relating to the Passivhaus standard.]

Anstey: There’s a gentleman who spoke up at the meeting today who mentioned that he worked on AutoCad, and I was wondering if someone has tied together a CAD system and the PHPP spreadsheet.

Keefe: Revit would be great for this.

Dr. Feist: Have you heard of SketchUp? There’s already a draft that uses SketchUp to input the geometric data into the spreadsheet because inputting the basic data into the cells is fun, but dealing with all of the geometric data is tough work.

Klingenberg: So it’s like you put the information on both of them…?

Dr. Feist: You make a sketch, then you hit the button and you get your areas and volumes for PHPP.

Klingenberg: Do you know when this is going to be available?

Dr. Feist: There’s already a draft, so maybe we’ll try to get it in the next draft of the PHPP. Or maybe we’ll create a separate tool. I think that would be very interesting for architects.

Briley: It would! Because it’s hard to input the information if it’s not a rectangle, or a box.

Dr. Feist: The other thing is you get to change and choose components. Because that’s lots of fun, isn’t it?

Briley: Oh yeah, lots of fun [light sarcasm]. I do that in my spare time when I’m not doing stuff like this.

Keefe: One of the guys I work with is working on the same thing for Revit, where there’s a file within Revit that has all the geometric data. We’re trying to get from Revit into PHPP.

Klingenberg: There’s another person in Chicago that’s already done it. It’s probably something we should really talk about, because there are some other platforms, some other design tools… I think Laura will show you some of her design students have built a platform through Grasshopper that connects the Rhino software with PHPP. It’s pretty cool, they can pull a corner of the building and it updates the data automatically.

Dr. Feist: That’s good! Even as a tool for teaching!

Klingenberg: Yeah, it’s perfect. And for designers! Designers don’t want to deal with numbers. So they just pull on the corner of their building and…

Dr. Feist: …and it gives you a feeling of what they are doing. Cool.

Anstey: And for shading. Like Fred’s building where there are a lot of different shading conditions for all the different windows. SketchUp models shading. It tells you at any time whether the window is fully shaded or partially shaded… If we had to input that, sort of analog, then it would take us forever. Not that we need to get to that level of precision, but it would be really great to let SketchUp tell the model, “That window is 45% shaded, this window is 22% shaded” — because it changes so much.

Dr. Feist: You know there are sheets for shading. And as it turns out, this is really important, much more than people think. That’s one of the reasons why some of the old passive solar concepts didn’t work, because they very often didn’t look at shading.

Well, that’s interesting that you had the same opinion on this [development of the software] because that’s very high on our list.

Passivhaus commercial buildings

Briley: So Katrin, you mentioned that you were dabbling with the idea of coming out with a passive house standard for commercial or institutional building types?

Klingenberg: We’re not developing a new standard; it’s basically the same standard. We’re going by the same certification. But there are a lot of inquiries we’re getting right now, especially from governments. We really want to do this for commercial buildings, for our governmental buildings, and for our schools and for retrofits.

Dr. Feist: We’ve done research on offices and schools and so on, and I think this is not so different in Europe as in the U.S. But they do have different boundary conditions than residential buildings (these schools and offices), so the calculation process has changed a little bit, so we definitely know how to do this. The interesting thing is that if you change the purpose of a building then the criteria will change.

Briley: It WILL change?

Dr. Feist: It will change. For swimming pools, for example. They normally have incredibly high [energy] consumption — like ten times that of an ordinary building.

Briley: And hospitals…

Dr. Feist: Yes, hospitals. That might be next. What we have learned is that we can’t do that from a theoretical point of view. You have to work through all of these calculations and then come up with a recommendation.

Briley: You mean like one number for energy consumption?

Dr. Feist: Maybe three or four. But you can come up with a performance standard that will be different from a dwelling.

Klingenberg: We’re getting busy implementing the first schools, and maybe by the time we’re ready for the hospitals, you guys [to Fiest] will have it all worked out [with a laugh].

Dr. Feist: [With a laugh, to Katrin] Keep away from hospitals for the moment.

Heating, cooling, AND primary energy use

J.B. If a building is below the total energy demand standard but is somehow not able to meet the heating demand, is that a bad building?

Dr. Feist: No, It’s not a bad building, but it’s not a Passivhaus. You could be using an expensive heating system, and that’s the problem. The heating requirement, 4,755 Btu per square foot… if you start changing that number, then soon you start changing other numbers, and where do you stop? That’s the first reason. The second is, we want to have an incentive for the development of better components. I think that’s a good idea to have.

J.B. I’m in complete agreement in holding the line. I guess I was wondering if one line needs to be held, do both lines need to be held, since the primary energy consumption includes the heating demand?

Dr. Feist: To be honest on that, I really think that the heating demand and cooling demand is more important, because that represents the structure of the building. The thing that would last for a hundred years…

J.B. Because [in the future] you could always change to more efficient light bulbs…

Dr. Feist: …And the systems could change several times over the life of the building, and the amount of the primary energy depends on the supply system. So we put in the primary number because what we don’t want is an efficient Passivhaus that then uses electric resistance heating.

Briley: That makes it clear, because there are a lot of people out there who think the primary energy standard should be the only standard.

Dr. Feist: I don’t agree with that. We had that in Germany. In Germany the code is on primary energy. That has a lot of difficulty. For example if you have a poorly insulated building and you heat it with wood chips, it will get a good number, but this is not a solution that everybody can do. The other question to address with the primary energy, is how to account for cogeneration.

Briley: So you keep the heating and cooling load in there because it directly relates to the building, whereas the primary energy is really focused on the energy coming into the building — which over time could be a variable.

Integrating Passivhaus and LEED

Briley: There seems to be this misconception out there that it’s Passivhaus versus LEED — that you have to pick one or the other. Isn’t that a false choice?

Klingenberg: Definitely false.

Anstey: They seem ripe for synergy.

Briley: It’s like LEED covers this huge spectrum of “green,” while Passivhaus is focused on just energy.

J.B. It’s how they [LEED] cover it. What they cover is fine, but if they’d give you values that are quantifiable and not just a point…

Briley: Right, it’s binary. Point, or no point.

Anstey: It’s like in the earlier versions of LEED when they give you a point for a bike rack…

Briley: I’ve gotten that point before!

Anstey: …So, I think they have a learning curve, and that’s fine.

Briley: Yeah, like with LEED for Homes, we complain because in Maine we’re a water-rich state. And there are a lot of points I can get for an awesome irrigation system that I don’t need.

J.B. You could not irrigate at all.

Anstey: That’s one point.

J.B. [laughing] But if you do irrigate you can get 10!

Briley: [To Katrin] Well, it’s very nice to hear that you guys are chatting [LEED and Passivhaus].

Klingenberg: It’s a very fine line. I can’t say much more about it. We’re also talking to Sam Rashkin at the Energy Star department, which is doing better.

Briley: Can you at least give us an impression on how it’s going with the LEED folks?

Klingenberg: I think it’s going really well. I think I expressed that today at the symposium. It’s amazing. There’s an awakening that is happening that would have been unimaginable a year ago.

Is there a size bias?

Briley: Katrin, you mentioned that the compactness of a building relates to the efficiency of a building, which we all conceptually understand. But when you’re sizing standards by the square foot, is there an advantage given to larger buildings?

Dr. Feist: Yes, there is, but with respect to usable area… We only count the usable area, we don’t count the ‘brute’ area because that might create wasteful space and that’s what we don’t want. So we only count usable spaces, and this gives us the right relation. So it makes bigger buildings less expensive than the smaller ones, and I agree with that.

Briley: You mean to make buildings more compact, not necessarily bigger.

Dr. Feist: If you do just a single-family home, that is not true, because if you make it bigger it will just make the home more expensive and you’re not going to just make something bigger to get better square foot numbers. That won’t happen.

What we’ve already defined, but it’s not yet published, is something for smaller buildings. I think if you have a smaller amount of area per person, we don’t want to punish that. So you will be able to choose a per area value or a per person value. I think we should not bring up these social discussions of limiting the size of homes, especially in America.

Briley: Because it’s easy to make someone shut down and say, “Well, then I’m not interested, because I want my space.”

Feist: Yeah.

Anstey: You also don’t know what a house is going to be used for in 20 years time. Because there are plenty of examples of huge mansions that are now multi-unit condos. If you did the PHPP on them 100 years ago, they’d be massive, but now you’ve got 40 people in them. As it’s all about the envelope…

Dr. Feist: [Very pleased] That’s the argument to be used!

J.B. And what we found interesting today is we heard that Passivhaus is easier with multi-unit buildings. Well, 1) I don’t think that’s true, and 2) obviously with a larger building with a better envelope-to-volume ratio, yes it is easier. But, that should be an incentive to build multi-unit buildings. It would be really difficult to do it as a single-family detached, but if you get a benefit for joining walls and floors and ceilings then…

Dr. Feist: This is pushing us in this direction. We had the same thing. I had a very serious discussion with the German government. Why not have the same requirement for ALL buildings, say 40 kwh per square meter, because that would be tougher for single-family homes than for multi-unit buildings.


  1. Brian O' Hanlon | | #1

    Thanks for the interview
    Will look forward to having a read later on.

  2. homedesign | | #2

    Thank You Mr. Briley
    2 thumbs up

  3. Christopher Briley | | #3

    It was truly my pleasure,
    It was truly my pleasure, John.

  4. Kevin Dickson | | #4

    Multi vs. Single Family
    I'm interested in the energy advantage that multifamily buildings seem to be getting.

    The back of my envelope is only showing an energy savings of $8-$15/month to share walls with my neighbor. In a rowhouse form, there's very little savings during construction, because firecodes essentially require two walls between units.

    I don't think that's enough for the average person who would also have to forfeit windows on two out of four walls. And folks who always envisioned living in a detached single family home wouldn't even consider sharing the ceiling and/or floor with others.

    So although energy efficiency may be steering us toward attached housing, it's a direction that today's consumer will refuse to go.

  5. mike eliason | | #5

    back of envelope calcs might be off...

    the construction costs/sf of passive house projects shooting for MFH are less expensive than SFH, typically, as windows don't have to be as good and less insulation is needed.

    energy savings of passivhaus MFH projects are considerably higher over code-minimum MFH projects.

    the 'american dream' - which was never sustainable - doesn't matter. issues of affordability, livability, rising energy costs, jobs, etc. will push people back into cities (e.g. - like the rest of the world) and require significant density improvements to single family neighborhoods. Rowhouses, townhouses etc. are a great option and can be just as enjoyable to live in as a single family house. btw, you can have light on more than 2 sides of a rowhouse (stagger the houses, lightwells, etc)

  6. Wolfgang Feist | | #6

    mfh versus sfh
    Well: We can do both - the affordable multifamily houses and the sfh. Yes, the efforts for a passive single family home are somewhat higher (but the savings are, too). That can clearly be seen by the Thousends of examples which have been built - but it's possible and it's ecnomic.What is needed, are solutions. These are available. Let us just use them.

  7. A non mouse | | #7

    cities are not the answer... populations need to stop growing...
    cities haven higher costs than towns. Less people is smarter. Religions want to dominate by asking their followers to have as many kids as come along... more kids... and they can outnumber the next religion.

    Why do people foolishly think unlimited population growth for centuries to come is smart.... acceptable.

    Population is problem number one.

    New passive homes in like number 1000 on a list of priorities.

    Reconstructing all existing living quarters and lowering property based services costs (taxes) is becoming very urgent.

    Staggered row houses so we can all have ten kids each? Rediculous solution.Have one child and get fixed. That is the best way one can contribute to a better future for all of us.
    a non mouse

  8. Christopher Briley | | #8

    of mice and men...
    Rather than tackle that tangled web of reason and seriously sidetrack this blog, I will simply ask that we keep comments focused on the topic at hand, or at least, on green building in general. (Even if it ranks 1000 on some peoples lists of priorities.)


  9. a non mouse | | #9

    Chris... think a bit longer about my post...
    The simplest solution to mankind ruining Earth is to reduce mankind. Reducing the number of new births is possible, easy, and already being tried and it is working! China by edict, and in all countries that have equalized women with education and careers giving them something to enjoy about life rather be a mom to a baseball team size family.

    The passive house chat is nice but it should shift to existing housing stock now and by government intervention via taxing up the cost of fossil juice.
    A non mouse

    (I do think you are a cool dude Chris, would share some ipa's anytime)

  10. Christopher Briley | | #10

    to non mouse
    Fine, I'll address it.

    I am an architect and not a politician, sociologist, or obstetrician. Managing population control (however important that may be) is far outside my sphere of influence. Like others who visit this website, I'm always eager to learn about better, smarter ways to go about my job and help my clients (especially those who share my passion for sustainability). The passivhaus principles are very exciting to me because of their tight focus on the energy consumption of a building. It, it is not trying to address the entirety of green building, sustainable buildings, or global sustainability. (By the way, it can also be applied to existing buildings and their renovations.) Thus, I’d like to keep the subject matter of this blog somewhat focused on that. Please understand, I’m not being dismissive of your ideas, I’m being dismissive of their place on this blog.
    (I’m sure I’d likewise enjoy sharing an IPA with you)


  11. Steve El | | #11

    Exactly why is the single family home the american dream?
    Chris I realize you're an architect, not a sociologist or psychologist. I'd be very interested in some clinical research probing the question why people desire single family homes over multifamily units. If people were subjected to different marketing (ie that hypes multifamily housing) would that inculcate consumer demand for such housing? Or does the single family home appeal to some part of us on a hardwired basis?

    My hypothesis is that the demand for one over the other is directly proportional to the type of advertising and other images one is subjected to. But that's just my guess. Opinions are great, studies are better.

    Thanks for an interesting piece.

    Steve El

  12. user-869687 | | #12

    Desirability of single family
    I think many people assume that attached housing means hearing the neighbors through shared walls or floors. This is based on experience living in rental apartments with poor soundproofing, and it's something to address through marketing (after addressing the problem through design). Aside from that, the most likely selling point for detached housing is price per square foot, which is usually much lower (so you get more house for the dollar). This trumps other concerns so long as people aren't worried about transportation costs (living in low-density neighborhoods) or heating / cooling costs.

    I do think it's possible to market the benefits of multifamily or attached single family housing, especially as energy costs rise and traffic gets increasingly worse. There's no question that the excesses of suburbia are needless and possible to leave behind, if the alternative saves money and avoids hours wasted in traffic. This is a recurring theme in articles and news spots about infill development--young couple moves into a townhouse and they comment how it's relatively small but certainly livable, and look at all the destinations that are within walking distance. It's even possible that people could begin to dislike the wastefulness of typical suburban homes as PH gains notoriety.

  13. GBA Editor
    Martin Holladay | | #13

    Honesty requires a truthful tally of pluses and minuses
    Single-family homes have pluses as well as minuses: the ability to alter the home to suit one's needs, regardless of neighbors' opinions -- subject to zoning and other regulations, of course; and a certain amount of privacy, depending on the distance from neighbors.

    Multifamily housing has a different set of pluses: these often include proximity to shopping, cultural amenities, jobs, and public transportation. However, minuses include a loss of privacy and a greater need to negotiate with neighbors.

  14. user-869687 | | #14

    More issues for attached houses
    Many of the concerns folks may have about attached housing types can be addressed through design, including soundproofing and visual privacy (to some extent). But you do lose the ability to add on, when the original building volume maxes out the zoning envelope. Another factor is that attached housing generally gets built together, for example five townhouses in a row. That means there's no going to an architect to design a single townhouse, and instead a developer will make design decisions.

    On the other hand there are places where townhouses are built singly with brick walls against the lot line. This isn't typical in new construction for cost reasons, but it makes the city interesting when there's a unique building elevation every 20 horizontal feet--Amsterdam is an example. Speaking of which, the Dutch seem minimally concerned about privacy, and you can walk down the sidewalk in the evening and see what people are having for dinner.

  15. Anders Lewendal | | #15

    Chris, thanks for the discussion. Does the German gov't provide subsidies for passive houses? If yes, how much. Have they evaluated the diminishing returns on insulation in their homes? I am interested in what the 2012 IECC might propose as the most efficient wall insulation package or a new standard wall system for the US.

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