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Passive House: PHIUS or PHI?

An architect's guide to help you decide which organization should certify your Passive House

Posted on Nov 30 2015 by Christopher Briley

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It happens sometimes. Great people that you admire, respect — even love — just can’t work out their differences with each other. Things may get rough or uncertain at times, but if they truly have everyone’s best interest at heart, they find a way to forge ahead, sometimes on their own path, but ever careful to protect what they’ve built together. I’m talking about divorce… sort of.

If you’re working on a Passive HouseA residential building construction standard requiring very low levels of air leakage, very high levels of insulation, and windows with a very low U-factor. Developed in the early 1990s by Bo Adamson and Wolfgang Feist, the standard is now promoted by the Passivhaus Institut in Darmstadt, Germany. To meet the standard, a home must have 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 W per square meter and windows with a maximum U-factor of 0.14. The Passivhaus standard was developed for buildings in central and northern Europe; efforts are underway to clarify the best techniques to achieve the standard for buildings in hot climates. (or Passivhaus) project, there will come a time when you will have to decide whether to certify your project through PHI (the Passivhaus Institut) or PHIUS (the Passive House Institute U.S.). Before their split in 2011, they were essentially one and the same, where PHIUS was the American “branch” of the European PHI. But due to irreconcilable differences, sadly, our “parents of passive house” got a divorce and now you have to choose which one you will stay with for the holidays.

In this episode, Phil and I decided that we are not going to take sides. In fact, we don’t want to talk about the history of why they split, who’s to blame, or who is more deserving of your love and attention. That’s history, and not productive in helping us move forward toward a world where we all build better buildings. At this point, it's clear that they are separated and not getting back together.

So instead, we'll pour ourselves a stiff drink (goes well with divorce), talk you through your options, and highlight the differences between the two organizations. We ended up putting a lot of focus on the new 2015 PHIUS standards, because with these, for the first time, the metrics for a passive house are different between the two organizations.

It’s almost inevitable that some of the comments on this blog will be geared toward rehashing the past and will be condemning one organization or the other or declaring one superior to the other. But if you find yourself beginning to leave such a comment, I urge you to ask yourself, “Who am I helping with this comment?”

All right, let’s get to it.

The highlights:

Phil's Manhattan. 2 parts bourbon (Woodford's Reserve) , 1 part sweet vermouth (Punt E Mes, Italian for "point and a half") , 2-3 dashes of bitters (Phil's Almond Fig Bitters, or substitute Angostura bitters). Shake in ice, pour in a chilled glass, and garnish with a cherry.

They're just different. One is not better than the other. They are just different. Relax.

A brief history. It all started here in North America during the energy crisis. These methodologies were studied, developed, and perfected in Europe, where the standard was introduced and formalized. Passivhaus was born. An American branch was developed here in the U.S., and then ties were severed leaving two separate entities: an American "brand" and the European original.

The Classic Passivhaus standard. To be a Passivhaus, a building must meet the following criteria:

  • an infiltration rate no greater than 0.60 air changes per hour @ 50 Pascals,
  • a maximum annual heating energy use of 15 kWh per square meter (4,755 BTUBritish thermal unit, the amount of heat required to raise one pound of water (about a pint) one degree Fahrenheit in temperature—about the heat content of one wooden kitchen match. One Btu is equivalent to 0.293 watt-hours or 1,055 joules. 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).

Is the Passivhaus standard appropriate for all climates? The European standard seem arbitrary to us in the United States, but it wasn't developed in a vaccum. The standard was developed based on a specific climate with a specific goal of reducing the energy demand to a point that one only needs to heat the fresh air that one brings into the building. I was extremely ineloquent in the podcast about this, so I will elaborate further here.

The air leakage target in the standard (0.6 ach50) was developed with occupant health and assembly durability foremost in mind. With this amount of air leakage in a building, and assuming a desire to provide 0.3 air changes per hour for said building in the mid-European climate, and assuming that a building has a ceiling height of 8.2 feet, the maximum amount of heat that that ventilation air can provide (assuming that you don't want the air to be so hot that the dust in the air begins to smell scorched) is roughly 4.75 kBTU1,000 Btus per square foot.

The U.S. has many varied climates. So does this "one size fits all" approach make economic and common sense for America? PHIUS believes not. PHI, however, would rather leave the standard in its pure form.

PHIUS 2015 standards. Creating a deep and permanent difference between the organizations, PHIUS has introduced climate-specific passive building standards.

Different modeling software. PHI uses the PHPP (Passive House Planning Package) only. PHIUS accepts the PHPP and WUFI Passive. We talk about the difference.

The "easier standards" myth. There's a common misconception out there that the new PHIUS 2015 standards exist because they are "easier to hit," setting a lower bar for energy performance. This is not universally true at all. Some standards will be tougher, and some will be easier, depending on your climate.

TFA vs. ICFA. The European Passivhaus standard uses TFA (treated floor area) to calculate ventilation volume. The PHIUS 2015 standard uses ICFA (interior calculated floor area). We talk about the difference.

Primary energy. PHIUS has modified the way it counts occupants; occupants equal the number of bedrooms plus one. Sound familiar? That's the same way RESNET calculates occupancy. This is not a coincidence.

PHIUS’s marketing problem. The simple Passivhaus standard is easy to understand, memorize, and hammer home. PHIUS is losing this simplicity. Is it a problem?

WUFI Passive is free. The free version does have its limitations. For example, you can't print out your results and your screen display is watermarked. Also, you can't do hygrothermic analysis.

Goodbye 0.6 ach50, hello 0.05 cfm50. This is PHIUS 2015's attempt at eliminating the "big house bias" of the ach50 metric. The metric is based on shell area instead of building volume.

PHI is changing too. PHPP has a new sketchup plugin. PHI is recognizing renewables with its Passive Plus certification.

Three questions. We asked Katrin Klingenberg and Dr. Feist some questions. We heard back from Katrin and read her answers.

As usual, we end the episode with a song that Phil thinks we should be listening to in studio. This time it's the Mountain Goats with Foreign Object from their album "Beat the Champ." It's excellent.

The bumper music was from Hearts of Oak by the always awesome Ted Leo.

Keep up the great work, everyone, and thanks for tuning in. Cheers!


Chris: Hey everybody, welcome to the Green Architects’ Lounge podcast. I’m your host, Chris Briley.

Phil: And I’m your host, Phil Kaplan. Hey, I’m doing great, Chris! How are you doing?

Chris: I was just going to ask you: How are you doing?

Phil: I beat you to it again.

Chris: I know. It’s very cliché of us.

Phil: [Laughing]

Chris: Fine. Fine. Happy to be back.

Phil: Let’s talk today about Passive House, in general — and essentially, that there’s sort of a split in the Passive House community.

Chris: Right.

Phil: And we’re here to kind of poke at it a little bit, dig a little deeper, and ask some questions and try to understand the difference between PHIUS+ and Passive House.

Chris: Right. Yeah, the new 2015 standards and PHI, the European thing. Basically, here’s my take on it (and maybe this is the theme for the podcast): it’s like they’re our Passive House parents, and they got a divorce… right? And we are their children and they want us to come to their house for Christmas. And we have to decide which flavor of Passive House we’re going to certify. And like any good divorce, we need alcohol to go with it.

Phil: That’s right. It’s the only way we’re going to make it through Christmas.

Chris: I know! Christmas with the divorced parents. Oh my God, what we really need is a Manhattan.

Phil: That’s right.

[The guys talk about this episode’s cocktail.]

Phil: Hey, do you want to talk about what we’re doing the podcast on?

Chris: Oh, we’re doing a podcast?


Phil: Oh, I almost forgot!

Chris: All right, okay! Yeah, right. PHIUS, Passive House, ya-da, ya-da, ya-da. Right. So, by now if you’ve made it to this podcast (if you’ve not been living under a rock, and you’re an architect of some kind, or builder, or green building enthusiast), you’ve heard of Passive House. You may even know their standards. What you may not know, or what you are probably coming to know is that there are flavors of Passive House.

Phil: Just like there are flavors of vermouth and bitters.

Chris: Exactly. And you can have an excellent Manhattan with a certain combination, or you can have an excellent Manhattan with another combination.

Phil: Right. And one’s not necessarily better, but they’re different.

Chris: They’re different. And you’ve got to know what you’re getting into. So first, let’s start with a real quick history of Passive House. Real quick, because we’re assuming, at this point, that you already know about Passive House. You already know the standards. We don’t need to go through that completely, but it helps with a little bit of history to know that Passive House… Basically, everyone thinks of it as European but all the principles really started in the United States (in Illinois, and even Canada a little bit) during the energy crisis in the ’70s. We started having these uber-efficient, double-envelope and tight-envelope houses. Basically, once that energy crisis is over, Reagan comes in and rips off Jimmy Carter’s solar panels. “Everyone relax! Everything’s good now.”

Except the Europeans, they don’t have the same relaxation and they keep working at it and then, you’ve got — who do you have? — you have Dr. Feist, of course, and Bo Adamson and Robert Hastings. Those are the guys who are championing Passive House. They write some papers and they’re doing some research and they’re talking about this idea of having a house that is heating itself with internal gains and solar, and needs very little other heat. That’s this “Passivhaus,” and of course they eventually, in Darmstadt, Germany, build the first Passivhaus (that everyone has seen pictures of and they know about). And then Dr. Feist invites Amory Lovins, who (of course) is an American from the Rocky Mountain Institute, who was instrumental in saying — in fact, you can look at our old podcast. We don’t have the audio for it, but we’ve got the transcript of it where Dr. Feist is talking to Amory, who says to him, “This is not just a scientific experiment that you guys have done. This can be applied. This can be a real thing.” And that helps transform that into the standards that we have today: Passive House standards.

And then, of course, enter Katrin Klingenberg and E-co Lab and Mike Kernagis and those guys. You know, this American wing that sort of goes to Darmstadt, learns all the stuff, brings it back. Sort of gives a little American spirit to it or whatever. Then Katrin does her first Passive House. I think it was 2002? Is that right.

Phil: It was only that long ago. I guess so.

Chris: Oh yeah. I think in 1996 — what are we talking about? — was the first Passive House. I don’t know. Someone’s going to have to fact-check because we’re just drinking and chatting like we do and that’s how we roll here.

Then, of course, Katrin Klingenberg (who is now very close with Dr. Feist and they have a lot of synergy) founds PHIUS (Passive House Institute U. S.). Of course, Dr. Feist has already founded the Passivhaus Institut in Europe (and that’s international) and PHIUS is just, sort of, the American wing of it.

And then, we’re not really going to — I think in this podcast, Phil — dwell on what happened, on what caused the divorce. Because that’s history. We don’t care. I mean, we could get into it. And I’d rather not.

Phil: Right. I mean, we’re not taking sides here. We’re really trying to do our best to objectively look at this. And I think, Chris, you and I both have that same attitude. Neither one of us falls on one side or the other.

Chris: Right. We like to think of our office as being Passive-dextrous. You know? We’ve got one PHI project, we’ve got a PHIUS project in certification. That’s all we’ve done, but we’ve been living this thing for a long time. It’s amazing — you think, “Well, we’re doing Passive Houses!” Oh — we’ve done two.

Phil: You’ve done one of each. Are you “bi”? Would you consider yourself bi?

Chris: Yeah, I’m bi. Of course I am, Phil. You know me.


God, this Manhattan is awesome! In this office, we have the attitude where we want to be very flexible. We’re ready to do either one.

Up until 2015, the standards were exactly the same. The Passivhaus standard. Do you want to do those standards? We’ll talk about them real quick.

Phil: 4.75 kBTUs per square foot per year.

Chris: Right. That’s the big one for us in the northern climate, in Climate Zone 6. That’s the one that we have to hit. And then you have primary energy. We need the equivalent of 11.1 kilowatts per square foot.

Phil: And then we have our airtightness: 0.6 ach50.

Chris: Which is at 50 pascals. We’ve talked about that.

Phil: Mm-hmm.

Chris: And there’s also peak load that you have to hit, that we never hit here in Climate Zone 6. You have to — and we’ll get into this — you have to either hit the annual load or the peak load right now in the European standard. And for us, we just ignore the peak load because we never hit it. Peak load has to be 3.14 BTUs per square foot per year for heating and for cooling. I think it’s 2.54 but we don’t worry about cooling up here. That’s nonsense. Well, you do in other zones.

Phil: Right. So, we’ve got these standards that were essentially developed in Germany and brought to fruition in Germany. And Katrin and her crew has brought them to the U.S. and realized, “It’s a really different climate here.”

Chris: That’s right. Several climates.

Phil: That’s right. We’re all over the place here. And suddenly, some of those things are much harder to hit in some parts of the U.S. and really much easier to hit in other parts of the U.S.

Chris: Exactly.

Phil: So, what are we doing here? Are we trying to save the world? Are we trying to save the earth? Or are we trying to just meet a standard?

Chris: I’d like to think, Phil — and we’ve talked about this before — that we’re saving the planet, one building at a time. As much as we can. And we’re half-joking, but we’re also serious, dude. Right?

Phil: Absolutely. We’re serious. No, I mean that. That’s why we get up in the morning and…

Chris: Beat this drum!

Phil: … pump our fists as we drive into work.

Chris: My God, yeah.

Phil: Yeah, because it excites us and we want to make a difference.

Chris: And, these standards, we should say, were not developed completely in a vacuum. I mean, the annual heating requirement and cooling requirement was actually derived… They came up with 0.6 ach50 first, because that was the healthiest, most energy-efficient, air-sealing standard that they could come up with that actually protects the assembly as much as possible. And then, once you figure out that 0.6 ach50, and you’re shooting for 0.3 air changes per hour for the entire building, there’s only so much heat you can put into that amount of air volume that you’re changing. And that air volume plus the highest amount of heat at whatever temperature is, 122 degrees Fahrenheit (no one uses Fahrenheit except for us in the States, but), that’s the maximum amount of heat that you can possibly put just using the filtered air, the balanced ventilationMechanical ventilation system in which separate, balanced fans exhaust stale indoor air and bring in fresh outdoor air in equal amounts; often includes heat recovery or heat and moisture recovery (see heat-recovery ventilator and energy-recovery ventilator). . So that’s where they came up with those numbers.

And to us in the United States, that seems arbitrary. I mean, when you hear about how that comes about, you’re like, “Oh, that makes sense.” That is based on one climate in central Europe. That’s that climate. And if you look at the United States, you go from Miami to us in Maine to Alaska — you know, heck. Or even Minnesota (I suppose they rival us).

Phil: Yeah, they do. But what happens when you present a system to our tribe, our people (our group that get excited about this and want to save the planet)? The harder, the better.

Chris: Well, exactly.

Phil: Let’s go for it.

Chris: Well, all right.

Phil: And that group of people starts to push. They push and say, “We’re going to go for it.” And we start looking at the numbers and we start looking at what we have to do in certain climates and we say, “Oh, you need 14 inches of rigid insulation underneath your slab in this region.” And we’re playing, and playing, and playing with our PHPP spreadsheets to get these numbers and kind of scratching our heads. It’s really good — we are saving the planet — but is this right for our climate?

Chris: Right. Yes?

Phil: Yes. Well, maybe. Maybe, because we’re still saving the world. I don’t mean that judgmentally at all.

Chris: Right.

Phil: But that’s why some people started to ask the question.

Chris: Well. And I’ll go on a tangent with you if you want to climb on board.

Phil: Please.

Chris: Having done a Passive House before — when you get to the point where you just need a little bit more insulation to hit your numbers, boy! — the slab is the easiest place to add more insulation. It’s like, you have so many dials to turn, you know, in terms of increasing your glazingWhen referring to windows or doors, the transparent or translucent layer that transmits light. High-performance glazing may include multiple layers of glass or plastic, low-e coatings, and low-conductivity gas fill. efficiency, your solar heat gain coefficient(SHGC) The fraction of solar gain admitted through a window, expressed as a number between 0 and 1., your ERV efficiency, your volume…

Phil: Right.

Chris: …all that jazz. It’s so easy to say…

Phil: Good. Are we saving the slab, or are we saving the planet, Chris? Because that’s a lot of rigid insulation that, we could put one inch on how many houses?

Chris: Right.

Phil: …versus fourteen inches underneath one.

Chris: True. True. I don’t think we’re going to go down that road.

Phil: No, no. But it’s…

Chris: It’s there.

Phil: We’re saving the planet, here.

Chris: But that takes you to where we are when we have this great schism.

Phil: Say schism again.

Chris: Schism.

Phil: I really like that.

Chris: Sounds dirty!


Phil: Only when you say it.

Chris: So, I invited Dr. Feist and Katrin Klingenberg — back when they were together (before the divorce) — I invited them to a nice dinner out and, I have to say, Dr. Feist was the most pleasant, nicest guy in the world. Because he was on European time (after coming to Boston — it’s now dinnertime) for him it must have been like, 3:00 a.m.? And we’re going out to dinner, and I’m like, “Hey, can I record a thing? You know, put the little mike on the table while we have dinner and chat some more about Passive House?”

Phil: Right. That was spectacular!

Chris: And it was really amazing, but I was struck by the fact that — if you look through the transcript of that — they alluded (both Katrin and Dr. Feist together) to the fact that they had already divided the world up into different climate zones and they were working on standards for all the different climate zones and this was back when they were together. And then, when this divorce happens, it’s PHIUS that is really driving the different standards for different climate zones. And now I think maybe we’d better talk about that.

Phil: That’s great though, Chris. I’m going to go back and listen to that podcast now. That’s a little piece of history.

Chris: Well see, I wish you could listen to it. I’ve listened to it, but it just turned into transcript. It’s just the best bits. I wanted to go to a quiet bar, a quiet little restaurant. There’s no such thing on Newbury Street, in downtown Boston. My God. And we ordered the loudest fajita I’ve ever heard in the world.


It was excruciating for me to just get through that thing, to listen to it, and I can’t subject listeners to that. But it was really great. And they were together and they were smiling. So I kind of have this perspective of things just didn’t work out. You know? Honestly, it’s like a divorce. It’s like, I’m a kid; I love them both. I think they’ve both done fantastic work and they’re both dedicated to it and really serious about moving things along and they just had this bump in the road that they can’t get past — whatever that was. And we don’t need to dig it up — what caused the separation.

But, where we are now is… well, let’s get into it. With PHI (Passive House Institute, that’s European), to work on that project, to decide “I’m going to do a PHI project,” you’ve made the decision, “I’m going to work with the PHPP (Passive House Planning Package)” as your energy model. That’s Number One. And there are some new versions of the PHPP that have a SketchUp plug-in — I have not seen this or worked with it — and I think that is in reaction to what PHIUS (the American version) is doing, where they have been using WUFI. They have decided, “Okay, PHPP is awesome; it’s rigorous.” You’ve done that, right… or you’ve worked with that in your office?

Phil: Yeah. That’s right. Absolutely.

Chris: The PHPP — for those of you who don’t know by now — is a spreadsheet. That’s all it is. But it’s open-source.

Phil: It’s just a 26-tab spreadsheet. That’s it. That’s all.

Chris: Aw, dude. And those aren’t namby-pamby tabs, either. Just start inputting windows. Oh my God. But it’s also open-source, so if you have these issues where you have these anomalous little pieces of your building that are quirky — you know, like, “This is not inside the envelope, but we’re insulating it anyway. It’s a buffered space” — you can add a tab and figure out some things and some clever guys can tweak it and go, “There you go, kid. That’s a more accurate thing.” It’s actually one of the more accurate energy models you could possibly have. But it’s enormously rigorous. It’s the type of thing that, you and I, when we sit down, we go, “God. I don’t want to do that all day.” It’s cells and a spreadsheet.

Phil: But, you’re still using the spreadsheet with WUFI Passive.

Chris: Right. Right. So PHIUS said, “Okay, we’re also accepting WUFI Passive.” They’ve had this partnership with Fraunhofer, who’s their testing company. Sounds German; I want to say they’re German. I don’t know that they’re German, but I’m assuming they’re German, because...

Phil: I’ll go with that.

Chris: …Fraunhofer. Sure.

Phil: It doesn’t sounds Italian.

Chris: It doesn’t sound Italian or American or Spanish. Anyway, they’ve teamed up with WUFI to develop WUFI Passive, which is energy-modeling software, which you and I are a lot more keen to work with, because basically you just import your SketchUp model — everything’s geometric, you know? — and then you just go through the little folder tree, you fill in the data and it tells you where you’re wrong. It tells you, “Oh, I can’t… this is missing. This cell is missing. These things are missing. This is probably too high. This is probably too low. Check it.”

And then you’re done, and “Boop!” — it gives you your data.

So, I’d say to the graphic person, it’s much more user-friendly than to the spreadsheet-type person. But we know these spreadsheet-type people and they might gravitate towards that. So, in a way, there’s, like, how you energy-model your house — from the get-go, right there, that’s different. You’re using WUFI Passive.

I think — actually, I don’t know this, but I think — PHIUS was happy to accept PHPP or WUFI Passive, whereas PHI is like, “Well, you use the PHPP. That is how it is done. There is one way to do this.” It’s very German.

Phil: So, what else is different, Chris?

Chris: Oh, Mamacita: buckle up! All right. The biggest thing is — like we talked about before — the climate-specific standard. So your annual heating and cooling, from the PHIUS standpoint, is not this single number. It’s not 4.75 BTUs per square foot per year. It is, “Click on this web site and click on your local weather place — your climate data set that’s closest to you — and then you have your new benchmark that you’re trying to hit.”

And there’s a lot of snobbery out there for the European version — because it’s tougher, right? It was first, “Why are you deviating from it?” It was this thing: “Oh, you need help hitting these standards for your climate? Here’s an easier set of standards, you pansy.”

But, I’ll tell you, that’s not exactly right. Because, of both my Passive Houses that I’ve done, if I did the PHIUS version, they would fail; but on the European, they pass. Here’s where they fail: the Viridescent House (which maybe I’ll put a picture of on this page)…

Phil: Yeah.

Chris: Yeah, yeah. I’ll do that. [See Image #1 at the top of the page.] The Viridescent House, which is going for PHIUS certification right now — all on the old standard, not on the new standard — so we’re hitting all of the same European standards for both of these houses. But for the 2015 standard, the peak load threshold is higher, but we actually have to hit it before we could choose whether or not we want to hit peak load or annual load. And the peak load, you always miss. You always miss it. There’s no way we, at a peak load, can get down to that low number. You’re just not going to hit it.

And so, the number’s higher. And so you think, “Oh, it must be easier to hit.” Yeah, but you have to hit them both. You have to hit annual and peak and we just missed the peak on the Viridescent House for the 2015 standard — which means we would go back and we’d tweak something and we’d do it. So, that’s one thing: you have to hit both of those.

And for the other house, it’s a much larger house, and we would have probably just missed the air sealing.

Phil: You have to get much tighter.

Chris: You have to get tighter on the larger house.

Phil: Because it’s tested for a cfm per square foot of shell

Chris: Correct.

Phil: …versus ach50 now.

Chris: Right. Now, this is big if you talk to PHIUS people. This is a big adjustment (a big correction), because there is sort of this bias to the larger building if you’re basing it on volume, because your larger building has much more…

Phil: The ratio of skin to volume.

Chris: Exactly.

Phil: So with PHI, the big buildings are much easier to hit.

Chris: Exactly. So, with the Viridescent House – it’s tiny! And, my God, that was the most aggressive air-sealing thing we’ve ever done (that I’ve ever been involved in), and we’re still sweating it at the end when these numbers are coming in! I’m watching the blower door dance — the cfm numbers dance — and my heart flutters.

Phil: We had the same thing with BrightBuilt Barn. We were just starting to pass and we had the goal of 0.6 in mind, and that thing was tight, tight, tight.

Chris: Because it’s so damned small.

Phil: But we just barely got there by the skin of our teeth.

Chris: And see, with the PHIUS, you’d probably coast through it. Not coast through it — I mean, let’s not sugar-coat it: both of these standards are very respectable. You are still doing a very energy-efficient, super-tight house. Here’s the other trick to that for PHIUS: you know the TFA, right?

Phil: Right, right.

Chris: Treated floor area.

Phil: Right. It’s like a net versus gross, now. Right?

Chris: Exactly.

Phil: They measure it differently. So how do you get apples to apples?

Chris: Right.

Phil: Why do you need to get apples to apples is where we are going to end up, okay?

Chris: All right. So then the question is, “Why did PHIUS go and rock the boat and change TFA?” Confession: I’ve had a couple of drinks and I’m doing this from memory, but I’m pretty sure that TFA is basically your floor area times 8.2 feet. So your volume could be much more voluminous, but you’re capping it. You’re just saying that’s what you’re really ventilating. And then you have all these other rules for mechanical spaces, spaces under stairs, and things like that. Well, the ICFA is basically — they say it’s like the golf ball — you fill your building with golf balls until you subtract the interior partitions like you do with the CFA.

Phil: Right. You fill it with fluid and then you dump it out and that’s what’s left over.

Chris: Yeah, that’s what it is. And you get the little window niches. I feel like I’ve been talking for a while.

Phil: You also know this better than I do.

Chris: No, that’s not true. I mean, you guys are doing Passive Houses out the wazoo as well.

Phil: Yeah, we are. And we were just up against this in a big project, trying to look at both of the systems, really trying to hit some Passive House standard. And the truth is that one is not easier than the other.

Chris: Right.

Phil: They are just different. Absolutely different.

Chris: So, you have to know what you’re going into for it.

Phil: Yeah. The truth is that PHIUS+ should be called something else. We should think of it as a really wonderful American low-energy goal.

Chris: And to that point: a lot of these new, climate-specific data points were all not developed in a vacuum. They were all based on different metrics to generate safe, economical, comfortable structures and that was interpolated across these different things.

Phil: And, as I understand it, PHIUS attempts to monitor the amount of energy per person.

Chris: Correct.

Phil: …versus PHI, which talks about the energy per square foot.

Chris: And the way they do that (per person) is they do it by bedroom (which is very much like RESNET). And so, they knew what they were doing in partnering with other organizations to develop these standards so that they’re sort of consistent in the United States.

So basically, you take the number of bedrooms plus one, times 6,200 kilowatt hours, times 3.412 (which is the loss).

Phil: [Starts moaning.]

Chris: Buckle up! I know, hang on. So, that’s the energy loss. That’s the line loss to get that 6,200 kilowatt hours to your house. (You have to multiply it times 3.412 to get the actual amount of power that you did). [Editor’s note: You multiply watts by 3.412 to get BTU/h.] And then you divide that by the ICFA, which is different than TFA.

So, you see how complicated… It gets a little fuzzy, but it’s really not that big a deal.

Phil: And the source energy piece is different, right?

Chris: Well that is — yeah, that’s the different part.

Phil: It’s because we have dirty power here in the U.S.

Chris: Right. Yeah, power is different in different places.

Phil: But then again, in the U.S., we’re using hydro or coal.

Chris: Right. Exactly. And it does not get that nuanced, thank God. Right? Does it?

Phil: Well, here is one of my concerns (and it’s really strictly from marketing): Passive House has been on a roll. And there had been a unified tribe who said, “This is a great thing and we’re going to change the world. This has been the most stringent energy goal that we have out there.”

There’s Living Building Challenge, but Passive House has had a full head of steam. And PHIUS+ has really made it more accessible in a lot of ways to the U.S. market. At the same time, there’s a marketing problem.

Chris: Yeah?

Phil: Because we had three metrics that we all started to get into our heads.

Chris: Right.

Phil: And now, it’s… Well, it could be anything.

Chris: Right.

Phil: You know, it’s the same issue you have sometimes when somebody’s asking you, “Chris, how much are you going to charge me to design a house?”

Chris: Oh God, Phil. I don’t know. There are so many variables involved. How big is your house?

Phil: Blah, blah, blah, blah. Not listening anymore.

Chris: [Laughs] Right.

Phil: Tell me, “60 grand.”

Chris: 60 grand?!

Phil: That’s too much. Tell me, “40 grand.”

Chris: 40 grand?

Phil: I’ll take it.

Chris: Good!

Phil: Thank you.

Chris: Let’s sign you up.

Phil: Just get a number down.

Chris: I’ll work up a proposal and have it on your desk in the morning.

Phil: And the right amount of people are just going to say “yes” right away. They get it and they want to move on.

Chris: I like those people.

Phil: But if you start trying to talk about it in detail in too many units, I think you have a marketing problem.

Chris: Interesting. So, do you think PHIUS has a marketing problem — out of curiosity?

Phil: Well, I’m concerned. I’m concerned. I think, in some ways, it’s smart because more people can attain PHIUS+, but I think it’s going to be over certain people’s heads. Again, we’re not making judgments here, but that’s what comes to mind.

Chris: I agree. I agree with that. But here’s their power play: WUFI Passive (which I mentioned) is free! It’s now free. You can go get WUFI Passive for free! Your own energy-modeling software that’s pretty sophisticated and pretty nice. It only does thermal stuff. WUFI’s famous.

Phil: But how much does it cost to learn it?


Chris: A [bleep!]-load of time.

Phil: That’s right!

Chris: A [bleep!]-load of time.

Phil: That’s okay. Time is free.

Chris: I got bleeped twice! And it’s one thing for you and I to learn it. I should say this too: I just came off of getting my CHPC (certified Passive House consultant training).

Phil: Hooray! Cheers!

Chris: Thanks, dude! Through PHIUS. So that’s the route I went, just because it was most convenient. Again, I really wouldn’t have cared. No, that’s not true, because I was pretty enchanted with WUFI Passive. I could see myself sitting at my desk, doing WUFI Passive. Whereas, I could see myself sitting at my desk, doing PHPP and being less happy.

Phil: Hmmm.

Chris: But that’s just because I know myself. WUFI Passive — WUFI is famous for doing hygrothermalA term used to characterize the temperature (thermal) and moisture (hygro) conditions particularly with respect to climate, both indoors and out. analysis of assemblies where you can tell where your dew point is (and “is this assembly wet at this point, or not?”). That is its call to fame. But WUFI Passive doesn’t do the moisture part. It just does thermal. The free part. But you can get WUFI+ and then do everything else. That’s going to cost you. That’s how they get you.

Phil: That’s how they get you.

Chris: They get you all excited.

Phil: They get you one way or another.

Chris: And you get all geeked-out, and you’re like, “This is awesome!”

Right. What else do we want to talk about? So primary energy is calculated differently.

Phil: Mm-hmm.

Chris: So that’s different. And then your infiltration, your 0.6 ach50. Now we’re not 0.6 ach50 — we’re concerned with 0.05 cfm per gross square foot of shell area. And it’s very easy to convert your ach50 number that you’re used to calculating and convert it to your shell, but you need to know your shell envelope [area] and you need to know everything you needed to know to get your ach50 —your volume and such.

Phil: It’s different.

Chris: It’s different. It’s just different. Everyone, just relax. It’s just different. You can go to Mom’s house for Christmas or Dad’s house for Christmas. You’re going to have a good time. Everything’s going to be great and fine. And they’re going to be happy for you, for your choice, and hope that you’ll come to theirs next Christmas.

Phil: That’s right. They are going to both make very different meals, but either way, you’re going to come out fed.

Chris: I like schnitzel. I don’t know, that’s a very German thing to say. I don’t know. That’s probably racist. I’m being racist again!

Phil: I don’t think so.

Chris: I actually do very much like schnitzel. It’s very good.

Phil: And I like burgers and fries.

Chris: Who doesn’t? Who doesn’t?

Phil: That’s the U.S. version.

Chris: You American. All right, so. Last thing. I think we’re ready to wrap this up.

Phil: Yeah, I think so.

Chris: Because, I think, more than just you and me blabbing on about it, there’s plenty of links that we’re going to provide you. Katrin just posted her own little blog on GBA. And we’re going to invite Dr. Feist to also chime in.

Phil: Are we going to read…

Chris: Read her letter? Yeah, absolutely. The other thing I did prior to this: I like to give these important people a couple of days’ notice before we go online. We did three questions. We sent an email out to each one of them. Right?

Phil: Mm-hmm.

Chris: And Katrin replied back.

Phil: Dr. Feist, not yet. Hopefully we’ll hear from him.

Chris: Maybe he’ll chime in, and that would be great. He had someone over there… Benjamin chimed back and he sent me a couple of links to some really great things — new things that are happening with the Passivhaus Institut. And they basically revolve around the fact that… We’ve talked a lot about PHIUS and the change — probably rightfully so — but PHI is also evolving. You know, they are getting a SketchUp plug-in for PHPP to help people like you and me. They’ve also developed the Passive House Classic, and they’ve got Passive House Plus and Passive House Premium (which has to do with being net-zero.). Are you integrating PVPhotovoltaics. Generation of electricity directly from sunlight. A photovoltaic (PV) cell has no moving parts; electrons are energized by sunlight and result in current flow. into your building if you are Passive House? Then you are Passive House Plus. Are you net-zero? Then you are Passive House Premium.

Phil: So, I’m a little confused. Is this like the New Coke?

Chris: It’s like a New Coke. It tastes better.

Phil: Okay, I got it. All right.

Chris: It tastes better. Just try it. Give it a chance. No, no, no. It’s really the exact same thing, only they are recognizing renewables. That’s really what they’re doing.

Phil: Oh, okay. Interesting.

Chris: Because before, Passive House was...

Phil: Right — it didn’t matter.

Chris: It didn’t matter. It was all about energy demand. Its beauty was its absolute simplicity. You know? It was just energy demand. You may hit this standard and be a Passive House or you may not. It is up to you. That’s it. And in a way, that’s gorgeous. You know?

Phil: Yeah, I really appreciate the elegance. And again, marketing: nice job!

Chris: Nice job! Done. And now they’re saying, “And, if you add renewables, good for you. We’ll put a Plus on it.” So, I don’t know. They are throwing the Americans a bone there, the Germans.

Phil: That’s right. Americans, we like those little extra stars.

Chris: We need pluses and we need…

Phil: “Daddy, can I get a blue sticker? Can I get a little extra blue star?”

Chris: Yah, yah. Yes, you can. Yeah, we love golds and silvers and platinums.

Phil: Gold is the best. Gold is worth more.

Chris: Aw, I don’t know. Platinum. I made up a platinum and it’s better.

Phil: They all look sparkly and silver to me.

Chris: So, we emailed Katrin and Dr. Feist. Katrin got back to us. Dr. Feist did not get back in time. So, I’ll tell you what we’ll do. Let’s take a break, refresh the drinks, come back, read Katrin’s answers, and plow on. Sound good?

Phil: Sounds great, Chris.

[Music intermission]

Chris: And we’re back. How about that?

Phil: How about that? Welcome back.

Chris: Yeah. You look different.


Phil: I got a haircut while we were gone.

Chris: Yeah? It looks good!

Phil: Thanks.

Chris: Handsome man.

Phil: Yeah. So, you’re going to tell us what Katrin Klingenberg has to say, based on the three questions that we asked.

Chris: Right. And I don’t want to — You know, I feel like this has been PHIUS-heavy in our conversations, but PHIUS is the one that is changing. They are the one doing the new standard right now, so maybe it’s fine that we’re doing that. But, this went out to both Katrin and Dr. Feist and (like I said before) Dr. Feist is a fantastic dude, a very kind dude, and I’m sure he’d reply. But, I didn’t give him a lot of notice, and he’s a busy guy. But Katrin did, which was nice of her.

So here are our questions I asked both of them. And so, only Katrin got back to me in time for this airing.

I asked, “Do you believe the division of PHI and PHIUS is a good thing or a bad thing for the building industry and why?”

She responded, “It is a good thing. There are options and different takes on the Passive House approach and related standards in the marketplace. Diversity in viewpoints and open scientific discourse facilitates the evolution of concepts and leads to better results.”

Very well said, actually.

Phil: Yeah. Mm-hmm.

Chris: The counterpoint to that (I’ll just throw in) was that, when the division happened, I was mid-project when it happened and it was very tough, man. Because I was like, “Who is going to certify this thing?” Everyone I was talking to was PHIUS certified. You know? So then we switched wagons. We didn’t know what to do.

Phil: Yeah, it’s a tricky position that we’ve been put in, people who are mid-process.

Chris: Oh, exactly. The kids in the divorce. We have to navigate our own path in this whole thing. Not that we don’t love them, because we do. It’s going to be fascinating to see how this all plays out on the American side. And by the way, screw the metric system.


Chris: I don’t know why we’re not on the metric system. Don’t you remember being in grade school?

Phil: Oh, yes. I absolutely do.

Chris: When you were a kid in grade school…

Phil: Yeah, we started to learn it.

Chris: Yeah, it was like, “Kids, you’re going to have to learn this because we’re switching to the metric system pretty soon. In your lifetime. In your generation.”

Phil: And what happened?

Chris: Nothing.

Phil: Was it the same time the solar panels got ripped off the White House and Reagan said, “I’m too old to learn this crap. Forget it. Never mind.”

Chris: [Voice impersonation of Ronald Reagan] “I’m too old to learn this crap.”

Phil: That was frighteningly good.

Chris: Oh, thank you. I could imitate anybody…

Phil: After a Manhattan.

Chris: …with a couple of drinks. Yeah, Sean Connery.

Phil: Let’s hear it.

Chris: [Voice-impersonation of Sean Connery] “Lovely party, but I wasn’t invited. You boys and your, your green architecture.”

Phil: [Laughter] Outstanding!

Chris: All right. Thank you.

Phil: How about Number Two?

Chris: What do you mean, Number Two?


Phil: You know, we’re doing a podcast.

Chris: You mean, Number Two, from the Mike Myers movie? Oh, come on… the International Man of… Austin Powers, International Man… Number Two? Oh, I’ve lost it.

I asked, “There are a lot of architects and builders who are just beginning their understanding of Passive House concepts and are just learning that there is a European original certification system and set of standards, and that there is also an American new certification system and set of standards. There is a lot that I’m sure that you’d want them to know, but what do you think is the single, most important thing that they should know about this difference?” Phil, I’ll let you read her response.

Phil: Thanks. Should I do it in her voice?

Chris: No. No. No! I think that she would be offended. No.

Phil: Okay, let’s not do that.


Chris: How good is your German accent?

Phil: I don’t know. I’m just trying to…

Chris: Go with it?

Phil: You started with your Sean Connery and I’m not sure what else I have to…

And so Katrin said, “First, I think it’s really important to accurately relay the history to newcomers. A wise friend of mine once said, ‘If you don’t know your history, you have no future.’”

Chris: Very wise.

Phil: “The original Passive House research and concept was developed in Canada and the U.S. in the ‘70s and ’80s. Passivhaus standard (the guiding energy metric) was established in Europe based on those North American building science principles in the mid-90s. It would behoove the discussion…”


Chris: Behoove.

Phil: Good word.

Chris: Great word.

Phil: “It would behoove the discussion and the community to clearly distinguish the two: a set of principles about which there is complete agreement versus metrics.”

Chris: Right.

Phil: “This, to fairly attribute the contributions of the early North American pioneers and to those who did important work in Europe, including the idea of a pass-fail performance threshold.”

Chris: Right. Great. You can see why Katrin’s where she is. I mean, she is very deliberate about what she’s doing. It’s not out of thin air. And I like what she says there about making sure that we all understand that we’re all after the same goals. The principles are exactly the same; the metrics are different. You know?

Phil: Right.

Chris: So, very good.

Question number three: “What is the latest development in your respective organizations that you would want architects and builders to know about?” And I site examples: “Development and software for energy models, new standards, new methods for certification, new methods of training.”

Do you want to do her voice again?

Phil: Sure. That was good last time?

Chris: Yeah. Yeah.

Phil: “We made the transition to WUFI Passive, a dynamic passive modeling software program for more accurate modeling results in varying climates. Regarding certification, PHIUS+ 2015 certified projects are also qualified by our partnership with the U.S. DOE and are zero-energy ready.”

I had heard that.

Chris: Mm-hmm.

Phil: “The most important and most recent development is the PHIUS+ 2015 Passive Building Standard. It’s the product of three years of work under a Department of Energy study in which the applicability of the European standard to North American climate zones was investigated and adjustments were proposed as a result of the research. It was officially launched in March 2015. PHIUS+ 2015 makes important adjustments to the metrics while maintaining the same principles as its base assumptions. Most importantly, design-guiding energy metrics are now climate-specific and cost-optimized using North American construction and energy cost data, which will remedy costly overinvestment in the envelope and overheating issues that had occurred under the European standard. As part of the effort to take the next logical step in getting off carbon, we launched a source net-zero energyProducing as much energy on an annual basis as one consumes on site, usually with renewable energy sources such as photovoltaics or small-scale wind turbines. certification, the PHUIS+ 2015, as an envelope baseline essentially certifying a building as producing sufficiently positive energy amounts to offset all carbon emitted operating the building during the year.”

Chris: Right. Very good.

Phil: Mm-hmm.

Chris: Boom!

Phil: That was concise, and that was a lot of the stuff that you and I had introduced the last time we talked about this.

Chris: Indeed. Yeah, I feel pretty good that we kind of covered that too. PHIUS (like PHI) — they have their PHIUS+. You know, they recognize that if you’re a net-zero building. And they are teamed up with the Department of Energy and the net-zero-ready standards.

So, great. Done. Feel good?

Phil: I feel good. And hopefully, this will spur a little more talk, as it has continued to do over the last couple of months.

Chris: Yeah, I’m sure we did not cover everything, but we’re going to provide some links on the side. The new PHIUS 2015 standards, I think, are going to be — they are going to go through the ringer and, you know, we’ll see how it comes out the other side. I know that cooling, for example, is a bigger thing… You know, the mid-European climate? There’s really not a cooling component to it. And when you start applying that to Miami, you know, all of a sudden cooling standards are really hard to meet on the new PHIUS standards. Whereas, they are almost nonexistent on the PHI.

Phil: Yeah, that’s interesting. Katrin’s pretty clear about that in her GBA article.

Chris: Right. Yeah, I urge you all to go actually hear this from the horse’s mouth. Phil and I are just kind of alerting you to the fact that there are two new different systems. Just relax. No big deal.

Phil: They are different things. You just have to think of them as different certification systems. We’ve got a bunch of them now, and they’re all good because they all drive us as an industry in the right direction.

Chris: Right. Yep. You love them. They’re your parents. You like them.

Phil: No fisticuffs.

Chris: No fisticuffs.

Phil: Back to hugs.

Chris: Back to hugs. Have a cocktail and just get on with it, dude.

Phil: Cheers!

Chris: Cheers, buddy.

[The episode closes with a song by Mountain Goats: “Foreign Object.”]

Image Credits:


Nov 30, 2015 12:06 PM ET

No Audio?
by Nick Gray

Is it just me or is there no audio player for this episode?

Nov 30, 2015 12:25 PM ET

by Christopher Briley

Audio added. Sorry about that.

Nov 30, 2015 9:31 PM ET

by Malcolm Taylor

"but all the principles really started in the United States (in Illinois, and even Canada a little bit)"

A little bit? Let's get things straight. We taught you and the Germans everything you know :)

Entertaining as always. Keep them coming.

Dec 1, 2015 11:33 AM ET

Hey, you said no Fisticuffs!
by Greg Labbe

Great podcast as always. However, the cheery, yet seemingly violent song seems to belie your "no fisticuffs" request and I couldn't help imagining Fiest vs Klingenberg with foreign objects a flyin'. Sorry the divorce has been hard to take.

Dec 1, 2015 2:58 PM ET

Not polite
by Andrew Michler

I know it's not polite to say but my experience with trying to get a project certified through PHIUS (pre-PHIUS+) was a debacle on a few accounts. The most glaring was their climate data was notably inaccurate (my experience was just confirmed by another project with the same issue that eventually became PHI certified). QA was haphazard or redundant, and communication channels were blurred if non existent. I was certainly to blame for some communication issues but the process was opaque as a newbie.

I know others had both good and poor experiences with them (more bad than good from my conversations with other very experienced passive house folk, btu everyone is bias to a degree). Because PH is a very sensitive metric it's worth looking at the fine grain before claiming parity.

PHIUS in general and Klingenberg in particular has put a lot of effort into discrediting PHI and "classic" PH. If that is their prerogative so be it but we are talking about a very small corner of a small pond next to a lake which feeds into the ocean. Not wise to swim the wrong direction.

Dec 1, 2015 3:46 PM ET

Canada, Wrestling, and PHIUS
by Christopher Briley

Chris, you're right in that I did not give the Canadians the credit they deserve. We'll try to feature some Canadian whisky in our next cocktail as penance. Sound good, eh?

Greg, there was no intentional connection between the song and the subject matter, though I wonder now if there was a subconscious one. I'll have to chat with Phil about that.

Andrew. I hear you. I have feelings, criticisms, and interactions good and bad with both PHIUS and PHI. I've come to the conclusion that it often is a factor of timing, and communication. I've learned that patience and an understanding that these groups are often operating with incredibly minimal resources helps. (as well as knowing that their intentions are truly genuine) What also really helps is having a passive house consultant that really knows the ins and outs of the certification process.

Thanks for listening, guys.

Dec 1, 2015 9:50 PM ET

by Malcolm Taylor

Fortuitous timing - a friend of mine just opened a micro-distillery a few houses down the road. If you are ever out on Vancouver Island you can raise a glass.

Dec 3, 2015 10:00 AM ET

Song choice
by Phil Kaplan

Wow, I'm absolutely cracking up at the irony of the song we used. I guess a song with the quote "I literally will stab you in the eye with a foreign object" was not the best choice here. It was certainly NOT intentional in any way.

Catchy tune though, eh?

Dec 4, 2015 7:31 PM ET

by Greg Labbe

OK, I had to listen to the song again it's pretty catchy. Oh, and not to be outdone by those crafty Vancouver Islanders with their awesome Green MP, but this Cdn distillery is but 1km from my house :

This one might be more available:

I know, navel gazing canuck.... Do love the Woodford Reserve and need your recipe for bitters...

So much good booze, so little time...

Dec 5, 2015 10:13 PM ET

by Dan Kolbert

I know from the lyrics what song it is - my favorite album of the past year.

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