3Q: Passive buildings rise in popularity and necessity

Katrin Klingenberg, the co-founder and executive director of Passive House Institute US, discusses her design philosophy and how passive buildings can support the low-carbon energy movement.

Francesca McCaffrey August 1, 2018 MITEI

Katrin Klingenberg is the co-founder and executive director of Passive House Institute US (PHIUS). She designed and built the first house in the United States that met the passive building energy standard, which led her to co-found the Ecological Construction Laboratory (e-co lab), in 2003 to serve as a non-profit affordable housing developer in the Urbana, Illinois area. That company expanded into PHIUS in 2007, where she now directs technical and research programs for the organization. She talked with MITEI following a recent seminar in which she discussed her passive house philosophy and how passive buildings can support the low-carbon energy movement.

Q. What is a passive house and how has its popularity evolved from its roots in single-family homes?

A. Passive house and building refers to a set of building science principles that, if employed in an integrated way, lead to very well-designed structures that are comfortable, healthy, energy-efficient, operate with a very low carbon footprint, and are resilient—able to withstand and keep people safe during severe climate events and/or power outages. Elements of passive building include employing continuous insulation and airtight construction; and installing excellent windows, a balanced ventilation system, and a tiny micro-load space conditioning system. Initially, Passive House Institute US (PHIUS)-certified projects were all single-family homes. The reason for that was simple: it was a new idea and the technology required some adjustment of “business-as-usual” practices. Single-family spec home prototypes were much easier and cheaper to build than larger structures.

Many builders and homeowners took it upon themselves to showcase the new idea and to create projects that they could invite friends or local lawmakers to tour. Those initial homes were very successful in promoting the idea and soon the affordable housing developers took notice. First Habitat for Humanity: in many places, chapters built single-family homes first. Then, the Washington, D.C., chapter embarked on the first duplex, and then a quadplex. Soon it became clear that ultra-low-energy and zero-energy-ready buildings (certified PHIUS+ passive homes) were very much in line with affordable housing goals: lower energy costs for inhabitants, increased indoor air quality and health, increased resilience in case of power outages, and reduced maintenance footprints for the developers themselves. It was a win-win for everybody.

Housing finance agencies around the country began to incentivize PHIUS+ certified projects and soon larger affordable projects were in planning. The first completed larger affordable project is located in Pittsburgh, Pennsylvania, with 24 units, and was certified in 2013. Then, multiple others followed across the country. Today, more than 80 projects are listed in the PHIUS+ database in various stages of completion. The largest completed, occupied and fully certified affordable project to date is located in New York City: it is an 8-story tall building with 101 apartments.

Q. How do the traits of a successful passive house change from climate to climate?

A. Passive building is impacted by climate as well as by building size and typology. In very cold climates that have little to no need for cooling, employing insulation in combination with capturing passive solar heat from south-facing windows is a really great strategy. This strategy reduces the need for active heating, but one has to be careful to not overly rely on heat from passive solar design because of potential overheating. Designing appropriately for any climate is a balancing act. In more mixed climates where heating, cooling, and in many cases, dehumidification, is needed, the design becomes more complex and is challenging. For example, a passive strategy for cooling in the summer is getting rid of heat by promoting heat loss, the opposite of the passive strategy of reducing heat losses in the winter. Lots of insulation is great in the winter, not so good in the summer. Since a building can’t change its “clothing” depending on the season, the designer has to properly strike a balance in mixed climates that suits both conditions similarly well, which typically leads to less insulation and a design for less solar heat from windows than in very cold climates. And in all cooling dominated climates, insulation only goes so far. Shading strategies, thermal mass, and if possible, night cooling become very important passive strategies to be applied first. After that, micro-sized mechanical systems will have to do the rest. Each climate requires its own characteristic combination of passive measures that will lead to the most cost-effective and comfortable solution.

Similarly, the size of a building matters. Larger apartment buildings have a higher density of people and appliances. Internal heat sources help to heat the building, like solar gain from windows, but they also increase the need for cooling. Even in moderately heating dominated climates, large buildings can be almost entirely cooling-load-dominated and behave as if they were built in one climate zone further south. The designer needs to be aware of that fact. Typically, they are also larger and have a better surface-to-volume ratio, which means there is also less heat loss compounding the problem. Both of those factors mean larger buildings need less insulation than smaller structures, relatively speaking, in the same climate. While a single-family home in climate zone 5 (Chicago) would need a wall of approximately R-50, or insulation about a foot thick, a 6-story apartment building in the same climate zone would only need about a 6-inch-thick insulated wall with an R-value of approximately 25. That is a big difference.

Q. What role do you see passive houses playing in the electric grid of the future?

A. Passive houses and buildings will enhance the capacity of the grid significantly because they are so efficient. That is especially important if the grid is redesigned for renewable energy production. Passive buildings can store excess or overproduced electric energy during the day. Energy can be stored passively by charging thermal mass wall components that then give off the energy slowly during the night and continue to heat homes and apartments. Energy could also be stored in smart hot water tanks or electric vehicles. Homes could produce energy themselves by adding a small photovoltaic system and store some of that production onsite for greater resilience. They can also sell their surplus energy once the new grid develops mechanisms for such transactions and contribute to distributed renewable energy generation. This makes more resilient microgrids (sub grids of the larger grid that can be islanded and still continue to function) possible.

Passive buildings are also crucial to help finance the shift to the new renewable energy economy. A lot of infrastructure improvements have to be made, with corresponding large and expensive investments. Passive strategies aim to tap into low-grade (free) energies first. They are affordable: the energy of the sun is free and insulation is one of the cheapest materials on a construction site. The result of total energy savings of up to 85% depending on building type and climate is remarkable. Energy savings from affordable passive design will then help to pay for the renewable upgrades and the redesign of the grid which is quite a bit more expensive requiring a much bigger investment. Furthermore, passive buildings can help modulate not only peak generation but also demand on a renewable grid. They don’t cause spikes in demand during extreme weather events because they only need little active energy to maintain comfortable temperatures. They act as a “capacitor,” increasing the capacity of the grid as a whole. With passive buildings at its core the idea of an all-renewable energy system becomes an economically and technically viable solution.

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Well, good afternoon, everyone. I’m Les Norford. I teach in the Building Technology program in the Department of Architecture. And it’s a great pleasure for me to welcome Katrin Klingenberg, who’s happy to be called Kat, to the MIT campus and to introduce her to you. There’s little bit of history I’d like to give before she gets started.

The idea of low energy houses in the US had its birth, if you will, in the early 1970s, in the aftermath of the first oil shocks. And in fact, it started partly in New England when the Harvard educated physicist, William Shurcliff, and a local builder, Gene Leger, built very low energy, super insulated, or so-called double envelope houses. But as the prices came down after the spikes, interest waned in that. And it took the Germans to rescue it some time later and codify what would be required for lower energy houses as the Passive House Concept and the Passive House Standard.

Kat, who was educated as an architect in her native Germany and then later in the US, was responsible in large part for its renaissance here by building a passive house in central Illinois. And that was 1,400 square feet. And it had two to three times as much insulation as codes at the time required; the best windows in North America she could get her hands on; a ventilation system imported from Germany, as I recall, that would carefully bring in air bypassing the very tightly sealed envelope, and then recover heat on the way out.

And put all that together, and the peak demand for energy in wintertime in a heating dominated climate is about a watt of square foot. And for 1,400 square feet, that’s about 2,000 watts. And for calibration, my little prop here– a home hairdryer– and if you come up afterwards, you peer in there, and you see about four coils of nichrome wire. That’s 1,875 watts. So there’s your heating system for her house.

So she not only built a house. But she built a movement. The year that house was finished, she founded the Passive House Institute US and is its executive director– co-director?– today. So for the last 15 years, she’s done that. And she coauthored the standards, the passive house– I’ve got the title right here– Climate Specific Passive House Building Standards. And the climate specific is important. Because this recognizes in North America there’s a wide range of climates. And what you require of a building varies with climate in order to meet performance targets on energy consumption, or say occupant comfort.

And she also recognized the need to get out of a one-off sort of thing and ally herself with entities that could help mainstream this technology. And so these standards have been developed with help of, or at least awareness of– well, in collaboration with the US Department of Energy and its Building America program. And as a warning, if you don’t do this, you end up with what we were talking about earlier, which is solar ovens in the middle of the Canadian prairie in wintertime.

She’ll talk more about the standards. But they’re a pretty remarkable combination of dealing with integrity of buildings, the economics of what makes sense– more in the building envelope, less on equipment– and some attention to global carbon budgets and our global responsibility to do something about that. So she in addition to her executive role in PHIUS she’s involved in building passive houses, consulting on them, leading an education effort to certify other consultants to carry forward this work, and directing the research programs of PHIUS. She remains a licensed architect in Germany. And she’s learned a huge amount in the last 15 years about what works and doesn’t work at what scale, at what cost. And so she’s happy to share a lot of those experiences and lessons with us today. So please join me in welcoming her to MIT.


Thank you. Can you hear me all right? All right, excellent. Well, thank you very much for such a kind introduction. And I do no longer have to go into the history. This was a great, great summary. And we can jump right into our presentation here. But before I do that, I’d like to say a few words about this slide right here. And some of you who have read the abstract that was on the flyer for this presentation tonight, you noticed that I was going to talk about low-rise and mid-rise. And this is clearly a high-rise.

So the good news here is that this is a little bit of a glimpse into the future. Where we are today with passive buildings, passive building standards? How far have we come to implement them in the United States? And we’re now seeing affordable high-rises on the drawing boards that are supposed to break ground next year some time. And this particular project is actually developed by a developer from Boston, Trinity Financial. And it will be built in the Bronx in New York City.

So very exciting stuff happening– and a lot of folks now have awareness again about passive buildings, passive building standards, and the benefits of them. And I like to go into the context here and the trends with you first, before we get into the principles and standards a little bit, and the lessons learned. And then I like to wrap up with new frontiers that we see as the next challenge on the path to further develop our tools and standards on the path to a carbon neutral built environment.

Maybe also before I talk a little bit more about this infrared shot here, really quick– in the Passive House Institute US that we was founded in 2003 as a nonprofit housing development organization. And that is actually how we started, with very small buildings initially. And then the Department of Energy took notice. And then it went from there. In 2007, we retooled our focus from community housing development towards certification of projects, quality assurance, to help the market transform, educate the professional sector, and also do research to again better our tools that we had at the time and to further develop the standards to better meet our goals.

The goals of the path of building standards– as Leslie mentioned, one big element here is to create a built environment that we basically can take off of the planetary carbon bill, trying to decarbonize the building environment. That is really the one main focus of the whole effort here, amongst quite a few others. But that is really the most pressing, for me at least personally.

So one quick comment to the infrared shot right here this is Jeanne Gang’s Aqua Tower in Chicago. And we had our office right across from the building for a couple of years. And so I walked past it every morning. And at some point, I had this vision of this infrared shot in my head. And I’m just like, this is a building that is driving past the speed limit, if you see what I’m saying. It’s like we have buildings that are not healthy for the planet. And we’re OK with it.

So in my opinion really, we need to come up with a solution to curb the carbon emissions in our built environment. And this infrared shot really shows the problem quite directly. We were joking about it. It looks like a radiator plugged into a comet in Illinois. And that’s not the only building. And it is a brand new building on top of everything else, right? So we have an issue here.

All right, let’s jump right in. I don’t think we have to talk about this very much. We know the climate is changing. You guys right here in Boston are right on the front edge of it. I just saw an article that sunny day flooding is increasing much sooner than scientists had expected. I didn’t know that term. I looked it up. It was basically tidal flooding. So we are advancing in this change process much faster than we had initially thought.

So I believe we need to really speed up our efforts here. Leslie already mentioned the whole energy efficiency discussion. This is not a new thing. Passive house is not a German concept originally. It was really a response to the energy crisis oil embargo in 1973 that the Department of Energy here in the US, as well as the counterpart in Canada, started to fund significant research into energy efficiency in buildings and how we could get away from using a lot of fossil fuels in our buildings.

And a lot of the principles that I’m going to discuss with you here and show you here in a second, they were already very much codified. If you read William Shurcliff and the fellow researchers of the time– Rob Dumont from Canada, Harold Orr– you will find those passive principles already outlined pretty much almost identical as we describe them today, which is quite amazing.

In the 1970s, also the first energy codes were authored, and then have developed over the years. You can see right here. For a long time, not that much happened. But then in 2005 right here, we see a significant effort, even here in the United States, to tighten the energy codes. So we are doing all right with our energy codes– International Energy Conservation Code 2012, 2015. But to get to the passive building standards where we would meet our global carbon reductions in the built environment, this is still a pretty significant jump. So we’re talking about something here that is really a significant paradigm shift in building design, not just tightening numbers or targets. It’s a different design process that we have to employ to get there.

So as Leslie mentioned we partnered very early on in our development of these standards with the Department of Energy. We had started out initially using the German standard. That’s what I used to design my house in Urbana in Illinois. And we learned quite a few lessons along the way. One of the most significant lessons was probably a project in New Orleans in Louisiana. And at that point, we were really obviously in a cooling dominated climate. And we started to realize that there’s more to it than just one target that can lead us to the ideal optimization of the envelope. We had to rethink the standards based on climate.

But the partnership with the Zero Energy Ready Home Program and the Department of Energy was aiming at a similar effort. We were also trying to harmonize with accepted industry practices and best building science practices that the Department of Energy already very well described and very well codified. So we partnered with RESNET, the residential energy network, and incorporated a very strict on-site quality assurance protocol as well into our certification. Because another lesson learned– if you don’t validate and verify on site what you specify in the drawings, it might not get built. And that is a big part of the equation.

So you can see right here the DOE staircase for energy efficiency, various programs, 2009 ISCC. That’s still the Building America baseline. I have this in here because the numbers on the next slide refer to that one. But then the next best Energy Star 3.1 program, then one level up, a zero energy ready home. And then after that, we have a co-promotion agreement with the Zero Energy Ready Home Program. Next level up that they recommend is PHIUS plus. And most recently, we also added a Source Zero certification. Because again, our goal must be to get to zero carbon.

So that is that. To give you an idea of what the energy savings are that we are looking at here under the PHIUS plus program, we use the 2009 ISCC baseline. Because that is the Building America baseline. The new standards were created in a Department of Energy grant. So you can see up here– actually in fact, I was supposed to use this green pointer. This is the average heating demand reduction nationwide throughout different climates that the standards are achieving compared to the 2009 ISCC, and then 46 for the cooling demand.

You can see there’s quite a bit of a discrepancy there, right? So lesson learned here is that reducing cooling via passive measures is quite a bit harder than reducing heating, which works very well in cold climates. So again, this is one of those lessons learned transferred from central Europe that is heating dominated and almost no cooling to climates that have both heating and cooling.

But in general, that’s what we’re looking for right here to meet our carbon reduction targets in the built environment. And again, that goes back to a calculation based on how much carbon we still can afford to burn on the planet and how much then that would mean we have to reduce per square foot in the built environment.

OK, ooh la la, now, I’m going too fast. It’s also worth mentioning that the passive building targets that we’re working with right now are actually quite well aligned with other zero energy efforts and programs. So here the 2030 challenge brought forth by [? Etmus ?] Rio. And if you apply passive building targets today, you’re already somewhat ahead of schedule. You’re already building a shell that then is at about 80% of the target. And that is mostly before PV. So this is really all happening because of the application of better improvement in the envelope.

And to give you an idea where we’re at today with passive building standards and certifications, this is the development right here. This is starting in 2009. This is when we officially started our certification program in the United States. We have some graphs that still go all the way over here to when I built my house. So it took quite a while. That was in 2003.

So you can see it took us it took us quite some time, and some persistence, and sticking with it. But then in 2013– a little drop in 2014– especially with the arrival of the new climate specific cost optimized passive building standards, we’re starting to see a nice trend developing here in terms of exponential growth in the certification sector.

There are still some European projects as well, some consultants who use the European standards. So those are both currently in the market. And there’s a little bit of a confusion out there. This is the level of certifications that the European Passive House Institute in Darmstadt is at right now. And you can see after 2015 it really started to flatten out. And there’s a reason. The new standards are more cost optimized. They are more climate appropriate. They are less prone to overheating. And they are really trying to get to the sweet spot between conservation and generation while taking the cost of PV into account. And I’ll show you in a second how we did this.

Now, only PHIUS certifications by themselves right now– there’s really good news. So always at the beginning of the year, we set our target. And we project. We’re generally very conservative. And this year, it looks like we’re already on target to very much exceed this projection. In April, we had already certified as many projects as we had in all of 2017. So we’re way ahead of schedule.

Now, you might be wondering– too fast again. Sorry about that. So in all of these projects, they are now really starting to be in all different climates zones. And we are also seeing all different kinds of building typologies here. Initially, it was only single family projects. And that was really because it was individual builders who saw an opportunity.

They built those spec houses. They brought in local policy folks and started to create interest and gain clients from it, and then built their business that way. And then eventually, it moved into multi-family construction, and then from there into commercial and larger construction as well. And now, we are even seeing government and school buildings as well.

OK, so most of these projects though, the heavy lift, most of the units and the square footage really comes from affordable housing developments right now. And that seems to be somewhat a sweet spot where these standards can very easily be attained at a fairly low additional cost. And there’s a reason for that. I’ll talk about this in a second.

These are various projects around the country right here. Again, this is not low-rise and mid-rise. But this is a project in Portland, Oregon, one of the first ones. This is New York City. This is a retrofit in Washington DC. So you can see they are happening pretty much everywhere. This is Maine, Portland.

This is Eugene, Oregon. This is Pittsburgh. This is another Hillsboro Portland, Oregon project, couple more New York projects right here. And this is really just the tip of the iceberg. We have now over 80 projects in certification. And I heard a number, which I still wanted to verify with the office– so don’t hold me to it. But I believe somebody said the other day 50 multi-family projects in New York City alone.

So that speaks to the next slide. But give me a second. I want to explain this down here real quick. So just to give you an idea of where these projects come in at, if you look at them from a point of view of EUI, Energy Use in Next Year, the site EUI varies from 10 to 25 KkBTU’s per square foot in year. And the reason why there is this big spread is because, first of all, climate.

Again, in a cooling dominated climate, it is not as easy to bring the EUI down by passive measures. But it also varies based on building type technology. It is much easier to get a better EUI for a smaller building than for a larger building. Because relatively speaking, multi-family projects are already somewhat efficient. The really inefficient ones are the single family buildings that we construct. So that there’s a little bit of a range there. But most of all– and this is really the high end. Most multi-family projects come in at about 20 I’d say.

And again, this speaks here to the point that I made earlier. The Zero Energy Ready Home Program, that is always the benchmark that we’re measuring ourselves against. The 50% better against the Zero Energy Ready Home Program, that happens in Alaska, a cold climate where we have high savings potential through passive measures. And then in Houston, Texas, it’s down to 20. Again, cooling is not as easily done.

So this wouldn’t be happening by itself, of course. We have seen significant will shown by municipalities and by housing finance agencies. And these are again just the tip of the iceberg. There are a whole bunch more of the housing finance agencies that have signed on across the country and that are now incentivizing passive buildings in one way or another. Some are very direct. They say you get 10 points if you build to passive building standards. And you move right up to the front of the line. And therefore, you are most competitive. Some just do it more as an encouragement. We encourage you to do it. But we don’t necessarily give you points for it.

But more significantly in regards to policy making, I’d say New York City really is on the front line. They passed an actual bill that has written source energy targets of passive into that bill for all capitol buildings. They’re still trying to figure out what exactly that means. But they are definitely on that path. They have started to use passive building standards as a means to meet their climate action plan.

And there will be more to follow. And also Massachusetts– where is it? Up here– Two years ago actually wrote passive building standards into the energy code as an alternative compliance path, which is a really great first step. So there’s a lot of motion in the policy and code area as well to incentivize these standards. And yes of course, city of Vancouver, also they are very far ahead. They are they have started to provide zoning incentives in addition to other incentives as well.

All right, so very quickly, a couple affordable projects that were successfully built and that have been occupied now for quite a while– the first one up here that you’re seeing, the Orchards at Orenco Phase 1, that still used the old targets from Europe. So this is a really great like proof of concept for us. Because we had the opportunity to see the standards play out right side by side.

And in Oregon actually, that climate is fairly similar compared to central Europe. So that was a great way to see. And then the second phase, the developer actually said, ah, this was too expensive. This was great. We believe in this stuff. We’re going to value engineer the next phase. And we just don’t have an additional grant to finance those additional upfront costs. And you can see right here that Phase 1 cost them 11% over their baseline. And that was quite high. So they could not really justify that.

And then that was when we came out with the new PHIUS plus 2015 cost optimized standard. And we offered them to calculate their value engineered project. And it turned out that it was an almost exact match. They had to do only very small upgrades. And they said, well, great, we’re doing it again. We’re going for certification.

And those cost optimizations led to basically 8% less– so above approximately a 5% additional premium. Now, that can be explained quite a bit also by significant cost increase. In the Northwest, you might have heard they have significant housing crisis in terms of not enough units. So construction is very expensive. While they are trying to get the cost down for passive, they also had to combat significant increases in the construction market itself. But in general, with all of the PHIUS plus projects now going forward, we’ve seen very consistent great performance. They are consistently built at about 1% to 2% additional cost now, which is of course what we were hoping for. So we’re very happy that these numbers are coming in at that level. This is the Hillcrest project here that was for the second, the largest one in the country, and then got surpassed by another mid-rise, also great performance, about 2% above their baseline here.

And then what good are performance standards if you don’t meet them when you measure the actual performance? So our modeling tool is an energy prediction. We are now finally getting actual measured results back from these first projects that have been occupied for one or two years now. And this is the first Oregon project right here, where you can see that the yellow line– this was actually our modeled prediction. And the green line is what we measured after one year.

There’s also a line right here, this red line. This is the European standard. And we can’t really go into the details of why the discrepancy is here. But just to explain that real quick, there are modeling protocol differences between the two standards. And mostly, the climate specific standards versus non-climate specific standards and those modeling protocols, they cost this discrepancy, which leads to a significant over prediction in the European model in regards to performance.

So again, we are very happy with this. In this bar chart right here, we over predicted this performance by about 2%. And that’s where we would like to be. But that’s not always the case on our projects. There’s a little bit of variation. But what we’ve seen so far, we’re within plus or minus 10%. We’re trying to calibrate. Given those numbers that we’re getting back, we’re recalibrating our model and trying to get better to get it into the plus or minus 5% bracket.

All right, that takes us to the paradigm shift in how we think about designing these buildings. We have partnered with the Fraunhofer Institute for Building Physics to build a new state of the art modeling tool designed specifically for passive buildings, very low-load buildings in different climates. And it’s a whole building energy balancing tool that can take all these different aspects into account– of course, weather data, climate, air exchange, inner loads, set-points, HVAC, all that that goes into the overall energy calculations.

And in addition to that, it can also calculate dynamically the conditions of a wall assembly, for example. So it can model basically using hourly data if there is going to be any potential of condensation in your walls simply depending on what kind of materials you are using in that wall assembly and which climate you’re in. So it is a very powerful tool that has a lot of opportunity for granularity. And that’s what we like.

So these are the principals here essentially that are being applied in passive building design. As I mentioned before, some of them were already codified during the first years in the US and Canada in the ’70s. So super insulation continues insulation around the entire envelope. Thermal bridge free design, airtight construction, heat recovery ventilation, and also very good window components. Those principles were already right there. And those are the ones that then were transported to Europe. And the Europeans picked up on those.

When we started re-implementing those passive building standards in 2003 and built our affordable homes, we found very quickly that, of course, shading and lighting is a big issue in more mixed climates, and also the more dynamic part of the circle of the design– how does the envelope interact with the HVAC system, hydrothermal storage and thermal storage? Those are all elements that are much better calculated in an hourly energy model.

These top level elements, they can be still fairly easily and quickly calculated in a static, simplified model. For design purposes, that’s a really great, fast feedback tool. But when it comes to more like hypothermal performance of the envelope, moisture performance, and comfort checks in your buildings, you really want the ability to be able to switch to a dynamic model. And that’s what this model is doing for us.

So once you employ these, let’s say, five strategies and 10 tactics correctly, your result is a building that is very comfortable and healthy, of course. The durability is very high. It will last a long time. It is cost effective, efficient. And best of all maybe, it is also resilient. Because it is a very low load building, it now can actually coast through power outages as well.

So that all said, so those are the principle strategies that we employ in designing passive buildings. They are different from the standards themselves. So now, we’re going to start to talk about the standards, which are essentially design parameters that guide us how to employ these principles to get to the optimal point between conservation, generation, and building design.

So a passive building standard is characterized by essentially a design process of three steps. First, you have design parameters that guide you to design your space conditioning, heating, and cooling. This is basically optimisation of the envelope itself. And then you have a source energy criterion, a budget design parameter for your overall energy usage in the building, not just space conditioning, heating, and cooling. And that overall total energy budget is essentially your equivalent carbon indicator, if you will.

And then we also have an air tightness criterion that is there to make sure that the building envelope is very well constructed and will last long and there will be no condensation. And then as I mentioned earlier, there is an additional certification. And that is the Source Zero, which is based on the baseline certification that I was just going through.

OK, so when it comes to climates, it’s getting really challenging. Because the standards actually they– as I said before, if you are in a solely heating dominated climate like in Germany, the conditions are fairly simple. You do not have to balance heating versus cooling. If you go to the United States where you have much greater temperature differentials, you very quickly get into zones where the climate is somewhat mixed. You have heating, and cooling, and you have even dehumidification on top of it.

All those conditions, they start to impact where the sweet spot is that you should design to. For example, if you are in a heating dominated climate, insulation is fantastic, right? It does a great job to reduce your heating demand. But in a cooling dominated climate, it starts to work against you. So those standards need to be set in conjunction with each other. They need to be calibrated.

And that’s exactly what we did in our studies with the Department of Energy with Building Science Corpporation when we created the climate specific person building standards. So some of you might have used the BEopt model from the National Renewable Energy Laboratory right here. It’s a very powerful building energy optimization tool that starts with again this 2009 ISCC Building America baseline. And then based on whatever the next lowest hanging fruit is, it picks the improvement into the envelope and systems until the measures become too expensive. And it starts to push back up into diminishing returns.

And of course, all this is being calibrated with an eye towards zero, so a cost of [INAUDIBLE] time is taken into account in this optimization process. This process led us to the conclusion that not just one number for heating or one number for cooling is sufficient. We need different numbers to guide the design to the best results in any climate.

So that means you need a different number for the heating demand, for the heating load, so not just demand but also load as required. And the same is true for cooling demand and cooling load. And everything varies. So all these values vary. We have our air tightness criterion. Again, this is our quality assurance. And then we have our final total energy limit here. And in our case, it was 6,200 kilowatt hours per person. This is now in the version I’m going to talk about here in a second being dropped significantly to 3,840. So we are clearly setting out to be on a glide path to zero, the latest by 2050. But I’m fairly certain that the tech committee will align with 2030 to get to zero by 2030.

So this is a shot here from an optimization case in the building energy optimization software from NREL for Chicago. You can see right here, this is the starting point for the 2009 benchmark. And then the optimizer starts picking these low hanging fruits. So this might be slab insulation, more insulation around the envelope. Maybe this is an ERV. So until it basically finds only improvements that are more expensive and that push back into diminishing returns that don’t pay back through the savings.

This is pretty cool. You can program it in a way that it actually blips up here. This rey little grip tells us when PV starts to get cheaper than envelope improvements. And this little yellow blip here, that was actually solar thermal, which in almost all climates was too expensive. That was interesting. We didn’t expect that. And again in comparison here, have the European standards that we started out with. And this explains why we found ourselves with very high additional costs in our initial project and also with over insulation in many cases. The European targets were not climate optimized. And they were pushing us up back too far into the diminishing returns, even to a point where the savings were no longer really justifying the improvement.

And this is how this looks like. So example of New York state– New York state is great. It has climate data for Climate Zone 7 through 4 I don’t show 7 here, only 6. There is, I think, only one place in New York state that isn’t climate zone 7. But here you can see how this plays out. So annual heating demand in zone 6 and 7. And your cooling event is 1.6. The peaks are clearly in the heating is dominant. Then as we go further south, in five, it starts to get closer. Peaks are getting closer. And then as you go into like Climate Zone 4, the two demands are almost– now, it’s switching to cooling dominated. And the cooling load is also higher. So it makes perfect sense, right?

And then here even more lessons. And they were really significant. And this is also a lesson learned that explains why this is taking off in the multi-family sector right now. So the bigger the building, the easier it gets. If we go to the next slide right here– so we had the opportunity to work on two very drastically different projects in New York City. One was a Staten Island rebuild, a very tiny single family home that was even lifted off of the ground. So was worst case scenario from a thermal perspective, ambient air around the whole thing, not very good surface to volume ratio. And we’re working on a very large 250 unit multi-family project.

Now, look at the difference in our values for the components right here. It is really significant. And that was just a feasibility study for the large multi-family project. We were not done with the final design. This was just a very rough first stroke. Once we were done with the optimization for that building, our values much closer to code. I think we ended up with an R20, 21 or so. Roof came– I think that’s code already. So it couldn’t come down. Slab might have gone away altogether, only perimeter insulation and R5 windows they are fine with.

So we also learned a lesson that actually components are obviously climate specific. But they are also specific to building apology. When you run the energy model for a very large internal load dominated building, it’s almost like as if that building lives in a warmer climate zone. It becomes cooling load dominated. And that meant that triple pane windows actually were keeping heat in. And the overall energy balance was better with a really, really good double paned window than it was with triple pane windows.

So again, back to the sensitivity of overheating, this is something the designer really has to develop a feel for and make sure that the building is not going to be in danger of overheating. Then also mechanical systems are building topology and climate specific– so either ERV versus HRB– internal humidity loading and very densely populated affordable housing developments, that’s a big deal. You might end up with very high interior humidity levels in a climate where you generally might like an energy recovery ventilator to reject the humidity in the summer. But if you’re producing a lot of humidity inside of the apartment, that can start to work against you. So that all needs to be calibrated. And then of course, also wall assemblies– depending on where your vapor control layer is in the wall, you need to make sure that those layers are designed correctly based on the location and the country.

All right, with all those lessons learned, we embarked on a new on the new version of PHIUS plus. We essentially committed to a dynamic standard that has to be updated because cost changes . And now, you might think like, yeah, climate will change, too. And we will have to find a solution to that as well, at least give people an option, maybe take a little bit of a futuristic view on climate data are you going to use for your design, right?

And all these lessons learned that not only climate is important for standards, but also occupancy, density of the building, and also the typology. So basically, big buildings better [INAUDIBLE] make big difference. So to all the architects in the room, I apologize. These buildings are– that’s the way how you draw in Biot. That’s not very pretty. But it’s really just to identify what window to wall ratio– and it’s just a diagram essentially.

So instead of basing our standard on one average 2,500 square foot home which we did in the past, assuming that anything that’s bigger gets easier and the standards would be easily met, now we are getting more granular. We’re running the standards. We’re creating standards for the very small home that was almost impossible to build because the standards were too tough.

We’re doing the average small home project in the country. And we have three different types of multi-family and occupancy. And we ran all of those now not for each and every spot that we had climate data for. But we ran those now initially only for the 17 ASHRAE climate zones. We can do this. These climate zones track pretty well with heating degree days and cooling degree days. That said when it comes to the peak, we have to do custom optimization still. So this is just for the pilot right now.

So we created a handy dandy little calculator that lives on our website. You can pick your climate zone out there. And then just as an example, you put in your floor area right here and then the occupancy right here , so 5B, let’s say. And then you can see for a small building in this climate zone you are heating dominate it. and you’re cooling this some. And here are your peaks. Now, if you go to a very big building in the same climate zone– 100,000 square feet, 200 people in it– you can see that the criteria flip. Make sense?

So based on the typology and the occupancy, it is really critical that you have the right targets. They will inform your design. And this is good news right here. The peak loads are very, very close to each other for the system’s design and very low.

All right, so that’s our pilot. And with that, I just very quickly want to– the heavy lifting is done and over, all the theory about standards and principles– quickly look at a couple details here with you. Again, the secret of the success, in my opinion, the community went out there and started building these projects. And what they found was we actually had all the technology that we needed. We don’t have a technology problem.

Most of these projects are being built with market available components, including windows. And people have been adopting the details that they were normally using quite well by taking into account continuous insulation, new thermal bridging, a continuous airtight layer, vapor control layer, all following the best building science practices, and they are successful in creating these projects.

So in this particular case right here, you can see this is an Oregon project, not totally thermally broken. But if you do a condensation calculation here, then you will find that there is no risk of condensation due to that small little perimeter thermal bridge. And that is OK. So you don’t have to go all the way around it. So people became very smart in figuring out what the right amount of insulation is, what the right amount of thermal bridge avoidance is for these particular projects. But generally, very typical construction techniques and materials.

So this is a project here in Pittsburgh in Pennsylvania. And that got a little fancier. And they had an interesting problem to solve. They had a cladding system which, of course, comes with a whole bunch of individual connections back to the structure. So they had a nice thermal bridge problem created for themselves there, which I show you the solution here in a second.

Air barrier design– at first, everybody was very concerned about air barriers for these large projects. But turns out that these liquid applied air barriers actually quite cost effective. They fit well into the regular flow of construction. This is the actual sheathing right here. This is the project in Pittsburgh. And the actual structural sheathing, this is where the air barrier is applied. And then there’s a layer of continuous outboard mineral wool insulation on top of that. And the spray applied of material is actually quite easy to check for mistakes, for where you might have missed a spot. And they have achieved very good air tightness results with this method.

That also is true for the design of the airtight layer. So all consultants now, they are very diligent drawing the airtight layer continuously into the drawings. There are even additional drawings sets added to the construction set just for air tightness detailing, exact specifications, large scale. How will the different materials connect to each other?

And this particular case is an example for how they changed their construction practices. Typically, they would run the wall up and have the parapet be connected. But to be able to assure that this is a continuous air tight layer right here, they interrupted the parapet, made sure that the airtight layer was continuous, and then attached the parapet on top of that, just an example of how they solved that here in this particular case.

Larger buildings, again liquid applied air barriers– this one is a project here in Queens, 100 unit mid-rise ICF, insulated concrete forms, built in airtight layer in the structure itself. And then of course, there are fancy approaches like prefabricated panels that have very intricate gasketing mechanisms that connect one panel to the next, quite a little bit more high tech here.

And again, this is the ICF project. And it doubles its purpose. It’s airtight and also is the continuous insulation layer. And the feasibility study that I showed you earlier for the 250 story project in New York City, they are building it out of the same construction material, also ICFs. So you can go quite high with that technology.

And even for basic standard practices, concrete frame, and even steel framing is possible. Just in that case, we would say don’t even waste your time and insulate the steel studs. There’s not enough insulation in the world to insulate steel, right? If you do the calculation, those steel studs, if you insulated this, this would not be worth the money. The IR is reduced by, what, like 40%.

So continuous, keep all the insulation on the outside, thermal bridge-free connectors right here. These are the Cascadia clips. And you get a nicely performing, continuously insulated wall assembly with pretty much fairly standard construction practices. And then this is the solution here they came up with. This is the Pittsburgh project where they had the cladding system. If you actually do a calculation to meet passive building standards and you do not take these thermal bridges into account– you have a clotting system. You do not thermally break them– that can kill your certification easily. Because all these individual connectors, they add up to a whole bunch of heat loss potentially.

So in this particular case, they put a little– it’s probably hard to see. But they put a little compressed plastic strip behind each and every connector that breaks the transfer sufficiently. And again, you can see here what this little connector here– for some reason, I don’t know why I don’t have the image that shows that. But this is how it looks like there is no thermal bridge interrupter behind it. So you have the cold being drawn into your wall quite significantly. And that could lead to condensation.

Structural thermal bridging– we’ve got those solutions as well. This is a product here that’s called [? Fabricka. ?] In multi-family construction, you might have the situation where you have the thermal envelope. And then you have a parking deck underneath. So your structure has to penetrate through ambient air. And you really can’t have steel go through from your insulated envelope all the way into the ambient. So that needs to be thermally broken. And that connector also has to be structural and capable to take the load. Those products exist.

And of course, this is what Jeanne Gang should have done in Chicago. And in all fairness to her, she actually did that. A thermally broken connector here was actually specced in the Aqua Tower. But it got value engineered out of the building. So that would have been a terrific solution right here and would have done the trick. It’s a significant piece of engineering. It’s not as trivial and easy as it looks. It’s a bit pricey. So you still have a cantilever and concrete balcony right here. And the trick to the engineering is this little piece down here to take the compression in that foam insulated space right here. And then this is a stainless steel rebar just for this portion. Because stainless has less connectivity.

And then mechanical systems, fairly simple, right? We have the continuous balanced ventilation with heat recovery or energy recovery. This is an example here again from one of the orchard projects. For low-rise centralized ventilation, it is OK. For three to four stories, we say you can do it. But if you get into bigger buildings, this is starting to create issues with the stack effect. So for low-rises, OK, this is a nice solution. In this particular case, it is affordable. So they wanted the ventilation run in the background. They don’t want to give people the option to turn it off.

So it’s a great solution. And they have the ventilator here. And they also have– I’m not sure where exactly that lives right now. But there’s an integrated heat pump in there. In that particular climate, the peak loads for heating and cooling are so low that an integrated heat pump can actually provide all the space conditioning to the spaces. So this is the ideal scenario in that particular climate with that particular building topology. It doesn’t always happen that way. But there, that works just like a charm. It’s great. And people are super happy. It’s Not getting too hot. And even Portland, Oregon now is getting 100 degree days.

So in New York City, what we see preferably is a ventilation system in each unit, especially if it’s a condo building and you want the controls. You as the homeowner, you want to make sure that you can actually adjust your ventilation yourself. And this is often then coupled with a with a centralized VRF, variable refrigerant flow, heating and cooling system, which works very well for the large multi-family projects. Because sometimes, you might need heating in one part of the building and sometimes cooling in the other at the same time.

This is the solution here. Initially, so the ventilator best lives right next to the wall assembly. Because any duct from the ventilator to the exterior envelope is essentially exterior envelope and is very prone to condensation and damage. And if there’s a cut in the vapor control layer around that duct, you will have water accumulate really quickly.

It’s a very touchy detail, so best to keep those ducts short. And then it’s also best to keep the ventilation supply separate from the VRF from the air handling for heating and cooling. Because they have different ventilation rates. And they start to fight each other. This was the first draft right here by the designer. And there, the ventilator was still feeding into the supply from the VRF. And we said, no, you better keep those separate. And in passive buildings often, you don’t need heating or cooling. So you might just need ventilation. You want the ability to couple those.

And this is just a single family, everything de-centralized essentially, like the heating and cooling system, the ventilation system. And this could be also seen as basically a multi-family unit that keeps it all heating, cooling, and ventilation systems with that one unit. And then OK, so this is for when we get into taller buildings.

This is really what we would like to see for ventilation. Have the per unit ventilator installed and also compartmentalize the apartments themselves. So you basically neutralize the stack effect and create a neutral pressure plane in each apartment. So stack effect is no longer an issue. You still have to deal with the elevator shaft and the staircases. But they get a separate ventilation system, pressurization, so on and so forth. But this is the ideal solution right here for larger projects.

Now, a secret to success that buildings actually perform the way you have designed them is actually very thorough quality assurance for design, during the design process as well as during the construction process. I think people underestimate how important that actually is. When we talk about passive buildings, it’s really just a very, very well-performing high performance building. And it is actually energy engineering that we as the designers are performing. And if that design is not verified and validated, it might not perform as such.

And we’re designing the systems to be much smaller now. And if you’re wrong, that could be a very costly proposition to fix. It may be OK for a single family home to experiment a little. But when it comes to a 20 unit multi-family project, you as the designer, you don’t want to get this call that the system is undersized and you’re liable for fixing it.

So quality assurance is really important. And then after the building has been taken into operation, also very useful is a monitoring system that allows feedback for the people who are managing the project. They’re running the project. And they keep commissioning the systems. Without these feedback loops, you can’t find where the system is not working properly.

Trained professionals– that’s a key to the success as well. And that’s not just designers, builders, and the verifiers on site. That’s also students. We actually have a training curriculum for universities as well. And just as a side note, I was just in Golden, Colorado for the Race to Zero as one of the grand jurors. The two first projects had used that curriculum, the grand winner and the second runner up. So we’re very happy that this is actually working in the academic environment as well.

Very quickly– I’m not sure how much time I have left.

A couple minutes.

A couple of minutes. Maybe we just skip this. This is a whole bunch of feasibility studies. Cool stuff, we calculated an all glass high-rise residential tower. And it turned out it was actually quite easy to meet our carbon targets and our energy targets. The big difference was the windows and the air tightness. And the hallway common lighting, that was the big hog in the whole thing.

But that could be easily done today with technology that we have. We just have to have the will to do it, yeah? And this is how we were able to crunch it down from basically what was the baseline was designed to meet code in Chicago. And after we were done, we were down here, so fairly easy really, as far as we could tell. And here is again a different way to show the reductions here.

And I’m done. This is just a summary for the sets, so skip this, a couple of cool details for one of the first cored shell projects that I can’t talk much more about. But hopefully, we’ll break ground in the fall in Chicago high-rise. Much better detail, right? So this is like the process that the design team went through, like, OK, we have really crappy details. How can we do this better? We came up with that one.

We share all of our lessons learned on our resource sites for commercial as well as for multi-family, if you want to look that up on our website. And I really just quickly want to get through the next frontier, just do the projects. Grid design is the next big question. How do we fit into the grid that’s being updated, the grid that starts to be interactive, transactive.

We need to figure out how to instruct our consultants to design direct current systems. We really want to go there. Maybe initially, it’s going to be a hybrid solution. But we should and will get there hopefully. Passive buildings can take care of the duct curve. They can passively store over production, in terms of the normal storage. You can park over production in hot water heaters. And of course, there’s the battery option, Tesla’s very cute little thing. Why do they make these sexy things?

So yeah, OK, this is one of the largest mid-rise right now in Queens in the Rockaways. It has a rooftop PV system produces 25% of its own consumption, also an affordable project. And this is really what I wanted to get to. So the next frontier– this is the first nanogrid project in the Mission District in San Francisco. If you ever are out there, it’s definitely worth it to visit.

The first floor has four Teslas in it, cars, and four Teslas, as in batteries. Each floor is one apartment. And each apartment owns a quarter of the canopy, which is PV. And the project overproduces the baseline is PHIUS plus certified. And this is one of the first PHIUS plus Source Zero projects, super cool. And same is true for the Rocky Mountains Headquarters in Basalt, also PHIUS plus Source Zero certified, and also over producing fantastically, feeding a couple electric cars in the garage. And I’d like to invite you all to join us for our 13th annual Passive Houce Conference here in Boston in September. And with that, I’m done. And thanks to all of our partners up here.


Questions for Kat?

Hi, great presentation. Do you have any good designs for insulating existing brick buildings?

Yes, on the outside.

Only from the outside?

No, not only. But it becomes more difficult to do it on the inside. Of course, it can be done, yeah.

The use of thermal mass, especially for cooling purposes and also the use of natural ventilation, because I see all the examples that you gave us, they all have artificial ventilation. But in the warmer climates, you can probably use just natural ventilation.

Yes, absolutely. So in all these projects, they are designed so that you can open windows and that you can use window ventilation. There are various reasons why projects can’t do that. For example, the affordable high-rise, they don’t want to rely on the occupants to do ventilation. So they don’t even factor that into the energy balance. If you have a single family home, always, always design for natural ventilation. Systems can always fail, right? So yes, you can open windows. And the other question, the first one was–

The thermal mass.

The thermal mass– so very important for cooling dominated climates and with that also for these big cooling internal load dominated multi-family projects. Thermal mass is very important for those, absolutely. It’s very effective.

Could you share why insulation works against you at a certain point in the cooling dominated climate?

Yes. So imagine yourself in Canada. Well, we don’t have to go to Canada. We can do it here. Imagine yourself in a– what’s the best skiing jacket that you can think of? Like best quality, company, whatever? I don’t know, Northface. Imagine climate zone eight. And you wear that thing on Times Square in July. And you cannot take that thing off. How do you think you feel?

Does that make sense? So the thing is you always have internal loads. And they are always there. In the winter, they work for you, great. They heat your house. But in the summer for the cooling purpose, you’re starting behind the starting line, right? This is always a liability. So you want to find that right spot between gains and losses. And you want to optimize that. It’s hard. Does that make sense?

Well, it doesn’t make sense to me. Because if your exterior temperature is higher than the temperature that you’re conditioning to in time, then–

If you were having a cooling system inside of your pocket? Yeah, that might work.

[INAUDIBLE] outside temperature maybe gets down to 100. The inside would be 70-75. You don’t insulate it. So you insulate your whole south wall with 15 inches of [INAUDIBLE].

You can do that, but then don’t put any heat inside of the building. But you live in the building, right?


And the heat exchanger again is not 100% efficient. So it will always warm your building. It’s complex.

Is the problem that you have a dishwasher and a blender and you’ve got stuff in your house that you’re using that generates heat?

Yeah, and people. And if you have daughters, you’re really in bad shape.

So this was very interesting in terms of what can be done. And it was fabulously presented. But I have a question on once you’re in the use phase. What is the expected lifetime of these buildings? How long are they being designed to last? And how do you think about that moving forward?

So they are essentially designed to last at least 70 years, if not 100. In our original cost optimization, we were very conservative. And we only calculated with 30 years for the cost optimization. But then for the second, for the 2018, now we’ve upped this to 70. Because there are studies out there that are pretty unbelievably making the case that buildings last on average for about 70 years.

I was just wondering about creative ways people are handling the dehumidification. What’s typical? And then is there anything on the forefront to do dehumidification?

So dehumidification is a really interesting one for many different reasons. But just imagine yourself in a single family home in whatever– let’s go to Austin or something. You crush the sensible cooling. But you’re latent cooling for the humidity demand is still the same. You can do a little bit with an ERV and rejecting it.

But the problem is that now latent cooling and dehumidification are very close together and that your cooling system, if you did it right, it shouldn’t really run much. So there’s not enough sensible cooling that can remove the humidity that you want to remove. So we really need to separate those two functions. And there’s really no off-the-shelf system there. And a lot of teams are struggling with this. And it’s very frustrating. It’s not that the technology is not there, that people are not thinking of it. They just haven’t really packaged it and put it on the shelf for passive building designers to readily use. Does that answer your question?


Have you used clay walls to absorb the humidity?

No, I personally have not. But yes. So the modeling tool that I showed you, the WUFI Plus tool, that can actually model the impact of a material that can hold moisture on the energy balance. It’s very cool. It’s so fine grained. So it’s a good idea. But now, we even have a tool that can actually put a number on it.

Well, if there are no other questions. One more.

I encourage you to finish. So you blurred through the one slide that said transactive on it. And I mean, in terms of how you see these buildings interacting with grids or power purchases or prosumer sorts of things, could you say just a little bit about that?

Yeah, so we are thinking about developing an aspect of the standard that rates buildings based on– we called it a flexibility factor, so, based on how it passively could start to take care of this overproduction to be able to assess that ability. It’s really just something that we’re just wrapping our head around. What are the elements that these passive buildings, these low energy buildings– how can they benefit the grid? How can we quantify it? And how can we then learn from it and design the new grid with that in mind? If we don’t know that, then we can’t design the new grid with that in mind. So it’s a little bit of a chicken and egg thing.

I had a continuation of the question for the natural ventilation. Because I was curious to know, how are you trying to address that especially in developing standards and codes? I imagine that you’ve shown some high rise buildings in which to make their standards work really well you have to control the neutral plane by floors and to deal with elevators and staircases. So if you can give the open windows option to people, that’s obviously going to throw the building out of balance, especially in certain climates, and especially if you’re pushing a very sensitive target, like very low. So how do you deal with that complexity when trying to regulate and when trying to tell people what they can or they cannot do to get their certification? Does that make sense?

Yeah, so the compartmentalization of the apartment should actually be a bulwark against that, right? So the apartment itself becomes airtight. And then you can open the window. And you’re not causing any problems for, if you open it on the bottom, somebody on top. So that’s essentially a measure to counteract that. That’s the best I can answer that, I think. We encourage natural ventilation. We do. Because that’s a good strategy to bring the energy down. We just don’t calculate it into the energy balance. Because we can’t trust the occupant to behave as we thought they would in the model.

Any other questions?

Let’s thank Kat again.


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