Here is the text version of the webinar Getting Enclosures Right in Zero Energy Ready Homes, presented in February 2016. Watch the presentation.

Alex Krowka:
Welcome to DOE Zero Energy Ready Home's technical training webinar series. We're really excited that you can join us today for this session on getting enclosures right in Zero Energy Ready Homes. Our presenter today is Joe Lstiburek. Today's session is one in a continuing series of technical training webinars to support our partners in designing and building DOE Zero Energy Ready Homes. My name is Alex Krowka. I'm providing webinar support for the program and would just like to cover some general notes on webinar housekeeping. All attendees will be in listen-only mode, however, we do invite you to ask questions throughout the session in the questions section of the GoToWebinar program. We'll monitor the questions throughout the webinar, and after the presentation, we'll have about 15 minutes or so to go over your questions. And we may also answer some questions in the middle of the webinar, as well. This session is being recorded and will be placed on the resources page of the Zero Energy Ready Home website, and a copy of the presentation will also be on Joe Lstiburek's website. If you could allow some time for this, since it does take a couple of days to go through a process to be added online, that'd be great. The presentation should be up within the next week or so. Also after the webinar, we'll send out an email with a link to the PDF of the presentation and information on our upcoming webinars. And now I'm going to hand it over to Sam Rashkin to give an introduction to the program and introduce our presenter.

Sam Rashkin:
Thank-you, Alex, and thank-you, everyone, for attending this webinar. This is part of a series of technical webinars and sales webinars we do for the Zero Energy Ready Home program. As many of you hopefully know, Zero Energy Ready Home is a new label for builders, and what we've strived to do is to present this program as a vital way for builders to reduce their risk and achieve critical market differentiation.

First presentation slide:
Particularly as builders are building, even for code-minimum homes, insulated and airtight buildings, many of the requirements of this program help them manage their challenges moving forward. And so this webinar series is a way for us to showcase what are proven innovations and solutions, best practices builders who are working with this program or interested in working with this program and pretty much off-the-shelf solutions for achieving these outcomes. And today to help us with showing how to do high-R assemblies in Zero Energy Ready Homes, we have a person who probably needs no introduction, Dr. Joseph Lstiburek. He's a principle of Building Science Corp. and an adjunct professor of building science at the University of Toronto. He's also an ASHRAE fellow, and that's as much as I'm going to say about Dr. Joe from the script. What you really need to know about Joseph Lstiburek is he's one of a kind. He can take the most complicated building science subject matter and together make it incredibly interesting and understandable. He's an expert that's not afraid to give practical guidance, specific guidance that's actionable, and he's just the best I've seen. So I'm so glad that we have Dr. Joseph Lstiburek today. I'm going to hand it off to him.

Joe Lstiburek:
Well, good day, everybody. And Sam, thank-you for those very, very kind words. You've been a friend to the industry for the past 25 years, and you're good at everything except skiing, and we still have some hope for you in that regard.

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This sounds like a really stupid question, but what is a building? A building is a different thing to different people, and I'm going to approach this from the perspective of the engineering approach to a building. From an engineering perspective, the type of engineer that I happen to be, a building is an environmental separator.

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It keeps the outside out and the inside in. Sometimes the outside sucks and you don't want it inside your building. Sometimes the inside, if it gets into the thing that separates the inside from the outside, it can lead to a problem. So the overall strategy is fundamentally simple: Keep the inside in, and the outside out. But every now and then, the thing that separates the inside from the outside gets whacked from the inside, and you have to decide whether whatever gets into it from the inside you want to let and go through completely to the outside, or to kick it back. And sometimes the outside gets into the thing that separates the inside from the outside, and you have to decide whether to kick it back to the outside or let it through. That's it. That's the physics, the overview of what a building needs to be as an environmental separator.

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There's a very specific list that was done in the 1950s on what the metrics need to be to do that. Most of the stuff that we're going to focus on today in this session is from the top of the list. It's not that they're the most important. It's that they're the most important that we haven't gotten around to dealing with. You know, structure and fire, historically they're pretty good. They're much more important than air flow and heat flow. Dying is much more of a serious issue than being irritated. So it's important not to kill yourself and not to kill your clients. That's where the structure and the fire comes through. The heat flow, the air flow, the vapor flow, the rain, you don't die from that. I mean, you could if you do silly stuff with combustion appliances. But we're mostly focused on durability and comfort and operating costs. The thing to remember, the perspective to put in this, is that none of the things at the top of the list should interfere with health and life safety issues.

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What we have to understand are the laws of thermodynamics. There are four of them, and we number them up to three. Don't ask. It's insane; it involved Germans -- that's all I can tell you here. The one that's most interesting to us is the second law.

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And this is how it's taught to engineers. Who writes like that? I mean, nobody understands that. When it was first written, it was written in German. It's insane. Let me translate the second law into something that is useful.

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Heat flow is from warm to cold. Why? Because. Moisture flow is from warm to cold. Why? Because. Moisture flow is from more to less. Why? Because. Air flow is from a higher pressure to a lower pressure. Why? Because. And gravity acts down. And as simple and logical as this is, it gets complicated for us because ...

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... this is where we build. This is North America. We have cold climates, we have hot climates, we have humid climates, we have dry climates. We have to apply the second law of thermodynamics to North America. If you think about it, if you're building a building in Miami, in your air conditioning, the moisture flow is from the outside to the inside. If you're building a building in Montreal that's heated, the moisture flow is from the inside to the outside in the opposite direction. Then in the middle of the country, you've got flows in both directions. So when you design your building enclosure, you have to understand where you are on this map, because that's going to have a big impact on the enclosure systems, and on the mechanical systems that you employ. This is just a map of temperature and humidity. We call it hydrothermal. There's something even more significant that we have to deal with.

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This is another map. This is a map of rainfall. And where it rains more, we need more rain control. The reason that we have all kinds of building problems in Seattle and Vancouver, Canada is not only is it a miserable place from the hydrothermal perspective, but it rains a great deal. Any place where it rains a lot and you have temperature differences and moisture differences between the inside and the outside, it's a challenge. It's pretty easy to build in hot-dry climates where it doesn't rain. Doesn't mean that there aren't issues in hot-dry climates. There are, of course. but they're nowhere near as significant as in hot-humid climates, cold-humid climates, wet climates. We spent the last 30 years, 40 years, significantly adding thermal resistance to the building enclosure. That's a good thing. But the second law put to music means you can't get your money for nothing and your chicks for free. The second law has consequences. That insulation reduces energy flow, which means there isn't energy available to evaporate moisture if a building enclosure gets wet. So if things get wet and a building is highly insulated, that thing will stay wet longer, and that's an issue. So high-performance, highly insulated buildings need to have much greater emphasis on rain control, air control, and vapor control, because there isn't energy available to dry things out, should things get into difficulty. Another way of saying this is that there's no such thing as a free thermodynamic lunch.

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We can simplify all of the physics, all of the geography, into four steps. A building enclosure needs first and foremost a water control layer. It also needs an air control layer, but the water control layer is way more important than the air control layer. We also need a vapor control layer, but it's not in the same league of importance as the air control and the water control. And we also need a thermal control layer. Of the four control layers, the thermal control layer is the least important to durability, but it is one of the most important in terms of efficiency and ultimate performance. So again, water control, air control, vapor control, thermal control, in that order. We want all four, but boy, do we want to get the water control one done right. In all of the years I've been doing this, I've never gotten a call at 2 in the morning saying, "My building is leaking air!" But I've got that call about water. Alright. So if we need these, what would be the outcome of configuration?

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Well, in the 1950s, this is what was figured out, and it's valid today. We put the control layers on the outside of your structure. So that heavy black line is first and foremost a water control layer. You can also have it act as the air control layer. And also act as the vapor control layer. And then the blue layer on the outside is the thermal control layer. And then outboard of that is the cladding. And the significance of the cladding is that there's an air gap behind the cladding. And the function of that air gap is to provide drainage of penetrating rain, and to provide back ventilation to enhance the drying of the cladding system. The reason that that's so important today is that we don't have very much energy coming from the inside of the building escaping to evaporate and dry cladding systems. It was amazing in retrospect to think that this was figured out in the 1950s, and here we are, 2016, more than a half a century later, with, in essence, the perfect wall.

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Well, if you take the perfect wall and you flip it one way, you get the perfect foundation. You flip it the other way, you get the perfect roof. This is what I refer to as an ah-ha moment. The physics of walls, roofs, and foundations are the same.

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The optimal roof would have the control layer directly on the deck with the insulation and in essence the cladding or what we would refer to ballasts on the top of this. We want that control layer hidden down in the assembly, because we want to protect it from the damage functions, such as water, heat, and ultraviolet light. This is called an inverted roof. This is the best of the best roofs that you can specify for a building. Now, if you replace the dirt, grass, you'd get a vegetative roof, you'd basically call this a green roof. I am not particularly impressed with the dirt and the grass; I view that as a feel-good thing. What you really have is expensive ballast. The physics, however, rocks. Control air right on the deck.

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You flip it, and you've got the perfect foundation. You have dirt, stones, insulation, your control layer, your concrete slab. It doesn't get better than this.

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You take the perfect section and you put in the perfect, wall, the perfect roof, the perfect foundation. Now comes what again I refer to as another ah-ha moment. All we need to do is connect the roof to the wall to the slab. And how we connect it is the magic. We connect the water control of the roof to the water control of the wall to the water control of the foundation. The air control of the roof to the air control of the wall to the air control of the foundation. The vapor to the vapor to the vapor and the thermal to the thermal to the thermal. When I teach the youngsters in my firm, or I get to abuse graduate students when they get a chance to teach at the university, I say it's real simple. All you do is take a colored pen and trace it around the details, to trace the continuity of the control areas, and wherever the pen leaves the paper, you've identified a discontinuity that needs to be addressed. Of course, the youngsters -- no respect for elders -- say, we don't use pens anymore; we use electrons. You're going to have to update your terminology. OK, OK. Well, the biggest problem are at penetrations, and the biggest penetration of all happens to be a window. We have fabulous windows today. We have fabulous walls. But we have more window problems. It's not the window, it's not the wall -- it's the connection between the window and the wall. Fundamentally, it's pretty simple. You want to connect the water control of the wall to the water control of the window, the air control of the wall to the air control of the window, the vapor control of the wall to the vapor control of the window, and the thermal to the thermal. As simple as that is, that's one of the most complicated details because aesthetics and constructability issues interfere. Sometimes the window is an outie, sometimes it's an inny, sometimes it's a tweenie, and how you frame and suspend that window in a heavy insulation layer is not an easy thing to do in a high-performance building. If there's one thing that we want to get right after we decide where the control layers happen to be in a particular wall or roof or foundation is, how to connect those control layers to the window and allow the aesthetics to be whatever the aesthetics need to be. So there are three classic versions of the perfect wall.

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One is the institution wall, this is if you're building a library or a post office building or a laboratory building or something that you want to -- church -- something that you want to pass on for hundreds of years, you'd build out of rocks. You'd build out of concrete. And then you'd put the control layer on the outside covered with insulation and air gap and the cladding. And that control layer could be a fully adhered membrane, it could be a spray-applied product. The main characteristic is that it needs to be continuous. I like fully adhered stuff. I don't care whether it's vapor open or vapor closed, candidly. They all work in all of the climate zones because of the place the insulation is located outboard of all of that. You can't use a non-adhered membrane because it's hard to staple tar paper into block or concrete. Now, let's say we wanted to get almost as good -- that we wanted to economize on the budget, we would get the second of the classic perfect wall systems.

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This would be a commercial wall, where we would replace the concrete and the masonry with steel studs, and gypsum sheathing on the exterior. Outboard of the gypsum sheathing, you have all of exactly the same control layer characteristics. It could be a membrane or a trowel or applied layer. It could be virtually anything. They all, all work. Notice that there's no insulation in the steel stud cavity. And the reason for that is that it's in my view a thermodynamic obscenity to insulate a steel stud. If you take a six-inch steel stud and insulate it with an R-20 fiberglass batt, the effect of thermal resistance is about R-4. That's because of the conductivity of the steel. Steel is almost 400 times more conductive than wood. I know this because I've never seen wood wiring or a wood frying pan. The only way that you can deal with steel structures is to insulate them on the outside. I learned this growing up as a child in Canada. As all Canadian children do, when it gets cold, we pull the sweaters over the outside of us. We don't eat them, shove them into our ribs. So you have to decide you want to be a sweater wearer rather than a sweater eater. Now is there any reason to air-insulate a steel stud? And the answer, yes, not thermally, but acoustically. A soft insulation system like fiberglass or cellulose provides a phenomenal acoustic control. So you wear your sweater for thermal reasons, then you insulate with a sound-absorbing material, at your steel studs for acoustical reasons. So the acoustics are necessary, important, but they're different from the thermal control.

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And then you have the third of the classic perfect walls, a wood frame structure. What's nice about the wood frame structure is that when you insulate the cavity, you not only get acoustic benefits, but you also get the thermal benefits. So you wear the sweater and you eat the sweater; residentially, wood allows you to do that. You can use whatever sheathing that you want on the exterior. It could be plywood; it could be OSB. You can put any kind of a membrane system on the outside of that. It could be tar paper, building paper. It could be a whole bunch of things. And I happen to like systems that are easier to apply, to provide water control and air control continuity. We'll talk about them later. So I'm a particular proponent of the fluid applied or the systems that involve tapes on the sheathings themselves. Outboard of that is rigid insulation. And it could be any of the rigid insulations. isocyanurates, expanded polystyrenes, extruded polystyrenes, mineral wool, rock wool. They all work. The cavity insulations could be anything. Fiberglass, cellulose, low-density foam, high-density foam. Ground-up blue jeans, it doesn't matter. In this configuration, they all work. The magic thing about this is in this configuration, this configuration works in all of the climate zones. You don't even have to know geography. This works everywhere.

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This is a net-zero energy home we've done on the NIST campus in Gaithersburg, Maryland. It has advanced framing, 2-by-6 and 24-inch center single plates, and outboard of this we're going to put our water, air, and vapor-control layers.

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The details of the material that we selected was a fully adhered, peel-and-stick stick membrane. Notice that there are really no overhangs here. We're basically wrapping the entire thing in an ultra-tight, water-and-air-control and vapor-control enclosure. The windows are going to be outies, and we have a window frame, a rough buck that's made out of half-inch plywood that's pushed outboard of the face of the water-control layers. It's pushed outboard four inches because for this wall system we're going to have four inches of continuous rigid insulation on the outside of this.

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There you see the entire box. The water control of the roof connected to the water control of the wall, the air control of the roof connected to the air control of the wall, the vapor to the vapor. Over this is going to go the thermal control layer.

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This particular building, the thermal control layer is two 2-inch layers of foil-faced isocyanurate. And again, it could have been anything. Notice that we're building outriggers to handle the overhang. And you'll see how this is integrated momentarily.

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Over the outriggers that are filled with rigid insulation on the top, we have another layer of OSB or plywood, and the membrane and shingles. In this image, the windows are already installed.

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The way that this worked is that a fluid applied control layer was wrapped around or coated around the cantilevered bucks in essence to provide air barrier and water control continuity to the actual window itself.

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Furring strips going over the four inches of rigid continuous insulation. These are installed with epoxy-coated steel screws. And then onto the furring strips will be the cladding or the trim system.

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There is an image showing the application of the cladding and the trim. The cladding is back-ventilated and drained. 1950s technology applied to a 2016 structure.

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And there it is. The -- from the outside looking at it, you can't tell that this is an R-60 wall, a R-60 roof, R-5 glazing systems. The airtightness of this building is incredibly tight. It's 0.5 air changes per hour at 50 pascals. This is insanely tight.

Jamie Lyons:
Joe, let me interject quickly with a question from one of the attendees, asking about the rafters in the shot showing the framing -- it looked like those were LVLs? Is that the case, and if so, why?

Joe Lstiburek:
They were LVLs because they were cheaper from the structural perspective. You could have used 2-by-12 rafters if the structure permitted it. We have longer spans. We didn't want to go to parallel trusses. We didn't need I-joists. We could have looked at I-joists, but the LVLs were what the contractor liked and the structural engineer liked, and I liked. But it wasn't significant. You could have done it with all of the other alternatives.

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The cavity insulation was netted cellulose. This image shows the mounting brackets for the windows. The windows are attached to the rough frame. The way that you'd install a window in a high-performance wall like this is that you're in essence using -- you're thinking that this is a masonry opening, where you're basically using the masonry mounting clips to attach to a wood rough buck.

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Here's another image of the end shot. It's real important that you connect the flashing system of the roof to the flashing system of the wall or the water control of the roof to the water control of the wall. I'm a coward here, and I have two layers of protection. We had the roofing membrane tie in directly to the peel-and-stick membrane behind the insulation, and then we had a second flashing system connecting to the face of the isocyanurate. You don't ever want to deal with roof-wall leaks. They're a big deal. So belt, suspenders, clean underwear, good judgment -- all system redundancy where you have roofs meet walls.

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This is a graphic illustrating in essence the water and air control. The orange is the fluid applied, and it shows how the peel-and-stick membrane water control is bumped out to the outside face of that penetrating buck, where it will connect to the water control layer of the windows.

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This is how the windows are installed. They're standard phalanged windows, but we have attached the masonry mounting brackets to make the connection to the frame. Notice the sequencing and the layering of all the water control elements.

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This is a section showing the connection between the roof and the wall. This is with a fairly large overhang. This is about a two-foot overhang, hence we used the -- in other words, the lookout framing.

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When we have a less of an overhang, you can use this standard block theme assembly here, and you don't need the lookouts. And this is probably the most common way of doing it, and why did we choose this on the NIST house? The architect wanted a bigger overhang. So if you want a bigger overhang, you're going to have to have bigger stuff.

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Most of the stuff that I do -- apparently I'm not into bigger overhangs -- is with the blocks theme arrangement.

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Where we have the lanais or we have the decks or the hoods or the porches -- covered porches -- we're having to attach in essence the structure through the rigid insulation. Notice here that we've got a 2-by-12 ledger board with long epoxy-coated steel screws, screwed through the rigid insulation into the backup structure. Now we used isocyanurate, but we've done the same thing with rock wool or mineral wool. So you're not -- if you have a particular dislike for isocyanurate and extruded polystyrenes, you can do exactly the same thing with mineral wool from a structural perspective, and as well as from the building science or the physics perspective.

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This is the connection between the foundation and the wall. And this is where things get complicated. I'm apparently not mainstream because I'm now old. I do not like external foundation insulation. When I first started in this business in the late '70s, I was dealing with insulating foundation systems on the exterior, and candidly, they're insect interstates, they're a nightmare to protect during the construction process. They don't provide anywhere near the thermal benefits that are claimed. And it's insanely difficult to do. And so since I crossed the dark side, I do all of the insulation in our high-performance buildings and foundations on the interior of the assembly. Now that leads to an issue, which is the only insulation systems that work on the inside are air impermeable and low-vapor perm transmission insulations. That means you're looking at extruded polystyrene, foil-faced isocyanurate, and two-pound density closed-cell polyurethane foam. The open-cell foam won't work on the inside of the foundation wall, nor will rock wool or mineral wool. If you are part of the club of people who do not like those products, then you have to insulate on the outside with mineral wool, and now you're going to have to deal with the inside protection and the physical protection. And that's going to have to be done with physical -- the insect protection will have to be done with physical barriers. I keep hearing, well, mineral wool is not an insect thing. Liar, liar, pants on fire. We've done it -- we've been doing this since, well, a long time. But it's so easy to put in a membrane physical barrier on the top of rigid insulation like fiberglass or mineral wool to provide that insect screen to prevent an insect interstate from having the bugs and critters enter at grade and up into the structure. Notice that the air seal between the rigid insulation on the inside of the foundation wall and the rim joist happens to be open-cell foam insulation, which is vapor open. How come we can get away with it there? Well, because I have all of that rigid insulation on the outside of the rim joist. And I want the open-cell because if any water happens to get into the assembly, into the wood framing, it's able to dry to the interior through the open-cell insulation. If there's vapor inside the building, which of course there's going to be, that passes through in a form of diffusion through the open-cell, it's not going to accumulate or condense at the rim joist, because the rim joist is warm by virtue of all of the rigid insulation on the exterior. So this is the rationale and the reason for this particular geometry. It's real important.

Sam Rashkin:
Hey, Joe, can I inject one question?

Joe Lstiburek:
Yes, sir.

Sam Rashkin:
This one's from me. Do you have any experience with the precast foundations that have the R-10 insulation built into a web configuration, and then on each rib face you have your nailing, I think, steel and wood phase to that? Do you have -- because that's 5,000 psi concrete, plus it's the rigid insulation built in. Do you like that solution or not?

Joe Lstiburek:
Well, I do. Two thumbs up. I think it's great. It's just, it's not -- it's very expensive. If it was more economical, it would dominate the industry. Let's digress here. I wasn't planning on talking about this, but ... With a foundation wall, you can insulate it on the inside, or on the outside, or in the middle. The best place in the world is in the middle. You're protecting it from the nasties from the outside and the nasties from the inside. And if you put it in the middle, it could be rock wool, it could be extruded polystyrene, isocyanurates. So these precast systems with the insulation inside of the (inaudible) are as close to the ideal as you can get. But they're a specialty product, Sam. They're not available all over the place. And so I -- they usually aren't available in a timely enough way, where I can use them when we specify things. So I go to the conservative approach by insulating it on the inside. If I had time and if I had a custom home and a great deal of money, I would basically build two foundation walls. I'd build a thin, four-inch wall on the inside put my rigid insulation in the middle, and then cast another wall on the exterior. And on high-end projects -- well, I'm doing this webinar from Aspen, and the people in Aspen can afford this, but the people where I live in Boston can't. But long-winded way. Love that product. It's not the most economical, and it's not always available all over the country.

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At the bottom of the foundation wall, you want to completely thermally isolate the concrete slab from your footing and from your perimeter foundation. And this is how it's done. Notice that there's a capillary break on the top of the footing that separates the footing moisture from the concrete -- cast concrete wall. A little subtlety here, which is a big deal is, notice the two red dots. I do not run a complete sheet of rigid insulation up the wall. I have a strip of insulation at the perimeter, and those red dots are air seals. Because, as amazing as it seems, water, vapor, soil, gas, radon, pesticides, herbicides, formidicides, whatever, are able to get between the rigid insulation and the concrete, and lead to issues. If this is a spray-foam product, of course, this wouldn't be an issue. You could, of course, run the polyethylene vapor barrier and mechanically seal it to the wall prior to that strip. So there are other options here, but this is the one that seems to work easiest for us. The point here is that you want an air control seal between that heavy blue line -- the 6 mil poly -- and your perimeter concrete wall. And that foam layer complicates things. So don't screw this one up, guys and girls. This is a big deal.

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Guess what? Rigid insulation is not particularly very structural. And when you put it on the outside of your wall, you're going to need racking resistance and sheer.

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And we traditionally do it with plywood or OSB at the corners and sometimes along many of the high-wind zone areas you're going to have to basically sheath the entire building. Over this structural control layer needs to go the water, air, and vapor and thermal control layers. You can try to integrate them, maybe have the sheathing act as the water and air control layer. Or integrate all three. But you're going to need to do something. And when in doubt, go back to first principles: water control, air control, vapor control, thermal control.

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In a number of the production homes that are high-performance production homes that we're dealing with, we typically use half-inch OSB at the corners, covered with an inch of rigid insulation, so that leads to an inch and a half thickness in the corners. And then we have inch and a half rigid insulation in the field of the wall, so that the rigid insulation runs continuously on the outside, one inch at the corners, an inch and a half in the field, one inch at the corners over half an inch of the OSB for the sheer of the racking resistance.

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This is how that corner detail works. Notice that with the one-inch rigid insulation over the corner, we have a three-eighths-inch strip of rigid insulation to create an air gap to provide an air space to provide back venting and drainage over our cladding system. We use a lot of cellular PVC trim and fiber cement siding, and we always have a three-eighths of an inch gap between those cladding systems and our continuous insulation. There's nothing magic about the three-eighths of an inch. The reason that I've been using three-eighths of an inch is because that's the thinnest strip of rigid insulation I can find. I often use sill gasket material, which is three-eighths of an inch. If I had -- a quarter-inch would work, but I don't have anything cheap enough that gives me that space for your quarter-inch. Anything over a quarter-inch works. Three-eighths happens to be easy for us because we can use off-the-shelf materials.

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So let's summarize a lot of this and say, look, if you start with a basic assembly, which would be an advanced frame building 2-by-6 and 24-inch centers -- that's to the far left side of the screen -- you can insulate that with anything you want: fiberglass, cellulose, spray polyurethane foam, low-density, high-density. That gives you, candidly or conservatively, an R-20-ish kind of a wall. And that would work for say, Florida and the Gulf Coast up to Atlanta. Climate zones 1, 2, and 3. That's a pretty awesome wall for those climate zones. And if you run your numbers, R-20 is what you're going to need to as a minimum in those climate zones to get you to your net-zero energy-ready structure. You get into the climate zones 4 and higher, you're going to have to put a layer of rigid insulation to the outside, and that's the second wall assembly from the left. And that rigid insulation could be expanded polystyrene, extruded polystyrene, foil-faced isocyanurates, stone wool. They all work. The key here is that you have that water, air, vapor, thermal control layer on the outside of the structure, and any cavity insulation works. Any continuous insulation works on the outside. You get to climate zones, in the northern part of climate zones 4 and certainly 5 and 6, you're not going to be able to do it with just one layer of rigid insulation. You're going to end up having to go to two layers of two-inch or more. And you just simply double it up. And the issue here is that you're going to now need wood furring strips to make the structure work. And you're going to have interesting issues with your windows, whether they're innies, outies, or tweenies. The detailing at the window-to-door and window-to-wall and the door-to-wall interfaces is a real big deal when we make multiple layers of rigid insulation and the furring strips. It's all doable. DOE and their libraries have got all the details posted. We've got stuff on our website. If you know where to look, the information is there. Now, if you now look at the next image, the second next one from the right, you can go to an R-80 wall if you want. And if you want to do this with cellulose insulation, you want to do this with blown fiberglass, you can do this with a truss. A truss wall. And all we've done is applied the same physics that we have to the other walls. It's just that we now have another structure that's hung off of the main body of the structure, and that cavity that's formed we can fill with fiberglass or cellulose. Now the key to this assembly is that the vapor control and air control layer is on the outside of the inner wall. It's the same water-air control layer with all the other assemblies. If you try to wrap this and do this on the inside, it does not work. People claim that it works. I first did this work in the '80s, and I've got news for you: We had to fix a lot of them. And finally, you get to the double wall. And the double wall is a -- think of the truss wall on steroids. And you've got that second wall outboard of that. And again, that cavity is filled with fiberglass or cellulose. But the key point to understand is that the water control, the air control, and the vapor control is on the outside of the inside wall. In other words, that base assembly to the far left takes you through all of the high-performance configurations that you can think of. And that base assembly allows you to use virtually any cavity insulation and any continuous rigid insulation you want on the outside, and it's constructible.

Next several slides:
The next series of images are, in essence, just three-dimensional versions of what we've just talked about. I'm not going to spend time on them, except pointing out a few interesting ones. EIFS, extra insulation finished systems, can be used in high-performance walls. The key point to make is that they have to water-managed and drained. And so there has to be a drainage gap (inaudible) channels between the expanded polystyrene and on the exterior of that water control layer. And you're good to go.

Next slide:
If you want to use a flashing batt system such as two-pound spray polyurethane foam -- high-performance wall, we can see a lot of this in the Midwest -- you can spray that to the inside of the sheathing. Again, the water control and air control are on the face of the exterior sheathing, and the thickness of the high-density spray foam is based on the climate zone that you're in. The colder the climate, the thicker the R value of that spray-applied insulation system. The building code has a very nice table that delineates precisely what R value you need in what climate zone to control condensation. And like all of the other assemblies that we've talked about, the cladding is always over an air gap and always back-ventilated and drained.

Next slide:
You could fill the entire wall with high-density foam. This is your hybrid. You can do the entire wall with high-density foam. You can change the high-density foam to low-density foam in climate zones 2, 3, and 4. When you get into climate zones 5 or higher, the low-density foam doesn't have the vapor resistance that high-performance wall needs.

Next slide:
There is our classic double-stud wall. And again, the key is the air control layer and vapor control layer on the exterior of the inside wall. And again, notice how we've got cladding system on furring strips so that the cladding is back-ventilated and drained. That back ventilation and draining of the cladding system in a double-stud wall is absolutely critical, because there's no energy available to evaporate water when you have an R-50 to an R-60 wall. That air space is necessary. You can get away with dumb things in low thermal resistance wall assemblies. You can't get away with anything in a high-performance wall.

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This is the truss offset. Same -- exactly the same comments apply to this one as to the double-stud wall.

Next slide:
Could you use spray foam in the exterior of the double-stud wall? This seems to be fairly popular in New England. I don't understand why. But it works. So the short answer is, yea, OK, you can do it and it works, but why? These two work really, really well and are less expensive, but knock yourself out.

Next slide:
I love the high-density spray foam applied from the outside of an assembly on a retrofit, with basically these 2-by-3 framing members offset with in essence long screws and tubes. I've done lots of these. I'm a real proponent of spray foam on the outside of old structures with these offsets. It works very, very, very well.

Next slide:
What about structural insulated panels? Love 'em. They work as well, but notice the key element here. There is an air gap behind the cladding. The cladding is back-ventilated and drained. Folks, back-ventilate and drain your cladding at all high-performance assemblies.

Next slide:
And finally, what about ICFs? Love ICFs. But look what we're doing with the cladding: back-ventilating and draining the cladding.

Next slide:
Here are some photographs of some of the stuff over the years. This is a 2-by-6 wall with two inches of extruded polystyrene with the joints taped. What goes over this are furring strips and the cladding system.

Next slide:
This is a system where OSB is turned into an air control layer with the fluid applied system on the joints.

Next slide:
This is a liquid applied flashing at the window-to-wall interface. I think this is a technology that is going to dominate our type of construction because it eliminates the origami that takes place at the window-to-wall interfaces. This is where we're going with the window-to-wall interfaces with innies and outies and tweenies. This is a tweenie window. Of course it would be.

Next slide:
This is using a roller and mesh reinforcement with another fluid applied system at the window-to-wall interface. This is where we have gypsum sheathing on the exterior and the air control and water control is a fluid applied system. Over this goes to the continuous rigid insulation.

Next slide:
Some of the systems are spray applied; some of them are paint applied.

Next slide:
This is a really neat system, where the sheathing itself comes with the water control element already on its surface, and then the joints are taped to provide water and air control continuity. These types of approaches are tending to dominate commercial construction and are migrating residentially, the logic being that it takes time to put the liquid applied and spray applied on the sheet goods, whereas if the sheet good comes with the product already on, all you're dealing with are the joints. The marketplace will figure out where this is going to -- which is going to land, but if you're asking me, I'm kind of leaning to this approach because that's the approach that has won over the commercial side of the industry.

Next slide:
Having said that, this is my office. This is my house. And I went old-school and went fully adhered peel-and-stick with outie windows.

Next several slides:
Of course, being my house and being insane, I have eight inches of rigid insulation on the outside and 10 inches on the roof, and we floated the roof. This is with the blocks beam on the outside. And there you go, folks. I advise this, the perfect wall and the perfect roof and the perfect foundation. You need a water control layer, an air control layer, a vapor control layer, and a thermal control layer. I like to wear the sweater, and the big concerns are the window-to-wall interfaces and the roof-to-wall connections. With that, I'm happy to turn it over for questions.

Jamie Lyons:
OK, Joe. Thank-you. This is Jamie Lyons. I support the DOE Zero Ready program, as well, so I'm joined here with Sam to kind of queue up some of the questions for Joe. There were quite a few questions going back to the net-zero home constructed at the NIST campus in Maryland. I'll queue up a few of them, but right out of the gate there were questions about how the two separate two-inch layers of exterior foam were attached to the framing. How were the furring strips attached outboard of the foam, etcetera. So attachment details on that wall assembly.

Joe Lstiburek:
Well, all we used was, the two layers of insulation, the joints were offset horizontally and vertically. We used basically long screws with plastic washers to tack the rigid insulation into place, to hold it in place. And then over that would go the 1-by-4 wood furring, where we were using epoxy-coated steel screws to screw into the studs. And so it's the 1-by-4 furring that held everything together, or locked everything together. Maybe I can illustrate that with an image -- is this image showing up?

Next slide:
You guys see this? Alright. This is in essence what we were doing with the NIST house. The 1-by-4 furring has not been installed yet, but every now and then you see a white circle with a screw in it. If you look where the yellow ladder is, just to the left, in the middle of the thing that says "DOW Super-Tough R," there are these little white circles. Those are sort of the plastic washers on screws that are holding the foam in place temporarily until we put the 1-by-4 wood furring over to lock it in place. So that's how it was done. And notice how then you can see the multiple layers. And again, this being my house, I was insane with the number of layers. But you get the idea. I've built another outbuilding that I don't have pictures of at my place that I did the same thing with rock wool. I did two 2-inch layers with rock wool with the joints offset. We used exactly the same approach: plastic washers on wood screws to hold the rock sill in place, and then the 1-by-4s tied everything together.

Jamie Lyons:
OK. Let me sort of roll together several questions all sort of around the theme of marginal costs. Just general inquiries about what are the marginal costs to build to the various levels that you've shown here in some of these projects, compared to lower levels of performance.

Joe Lstiburek:
Oh, man, that's an incredibly politically charged answer that I'm going to skate on. I'm going to simply say that a 2-by-6 advanced frame wall with no continuous insulation on the outside is probably the most economical high- performance wall you can build. It's actually less expensive than a standard 2-by-4 frame wall with 16-inch centers with double studs and jacks and triples. And that wall system will probably take you all the way through to climate zone 3 for high performance. The water and air control, I happen to choose Huber ZIP, because it's insanely easy to sheath the building with that product and get ultra-high performance levels of airtightness. And so to me, that approach is no cost difference. You're there. Now when you get to climate zone 4, then you get your marginal cost increases, because you're going to have to now put continuous insulation on the outside. And to me, what continuous insulation you choose no longer matters. They're all roughly R-5 (inaudible), and the ones that say they're R-6 and a half, that's not true. They're all roughly around R-5. And they cost more to put up. Now are we talking -- we're talking probably 3 to 5 percent. But none of this changes the airtightness and the fundamental water and air control. When you get to double wall construction, I can't see that ever being economical, unless you believe that the price of energy is going to be high, and that we really have a significant issue with respect to climate change. Now I'm the guy that has the R-50 wall and the R-70 roof. And so it's hard to do this on a straight payback basis. My argument is that I believe in resiliency. In my neck of the woods, we run out of power all the time. We have ice storms. It's hard to run a business without electricity. I think our infrastructure -- we're so inconfident in our infrastructure that I believe these high-performance buildings make sense not from a payback perspective but you need to do them right away in order to basically survive the vagaries and the unreliability of our power and communication grid.

Jamie Lyons:
Yea. Very good. And just from the DOE Zero Energy Ready Home perspective, we've looked at the marginal costs between a '09 code home or 2012 IECC code baseline house compared to a Zero Energy Ready spec. We've looked at the energy savings as well as the marginal costs. And taking that jump up in performance and cost, the added amortized costs that's added to the mortgage for the marginal costs of the upgrades is more than offset by the monthly utility bill savings, based on our analysis of homes in different climate zones. And we have that type of analysis to go on our website, for people to take a look at. Let's see ... Just going down a little bit into the attic space, there's a question about preference or recommendations for either vented or unvented attic spaces.

Joe Lstiburek:
I'm always a proponent of vented attic spaces. They're the first, best destiny for an attic. But practical considerations end up interfering with the perfect physics. To me, it's hard to be at a flat ceiling that's airtight with a whole bunch of blown insulation on top of that, with continuous soffit vents and continuous ridge vents. I put that in Orlando, I put that in Minneapolis, I put that in Toronto, I put that everywhere. The trouble is, most of the United States, people put their mechanical systems in the attics. And the moment you put your mechanical system in the attic, it makes no sense to have a vented attic. You need to make a conditioned attic. Making that -- in the vented attic, making that attic ceiling airtight is not easy when you get into complex roof geometries, and you have all kinds of tray ceilings and kooky ups and kooky ins. And I deal with insanely talented and crazy architects, and it's impossible to have reliable air control at the ceiling interface. And so we take a more robust approach and put the air control at the roof deck, and that way we get the high level of airtightness. I forgot to mention that a net-zero energy home needs to be between 1 and 1.5 air changes per hour at 50 pascals. That's double the airtightness of 3 air changes at 50, which is the code minimum. So you want to be between 1 and 1.5 at 50 pascals. And you're not going to get there with a complex roof geometry with a vented attic with 100 or 200 penetrations through it. But if you're talking about a very small production home with a reasonable flat ceiling, a vented attic rocks. Now let me tell you insane. Here I am in a high snow load area with very complex roof geometries. I build an unvented roof for that reason. But to deal with the ice dam issues, I have to put a vented overroof over the top of the unvented underroof. Venting is always better than unventing. Unventing is a compromise necessitated by architectural complexity and the location of the mechanical systems. And I'm the guy that has been the big proponent of the code changes for unvented roofs. They're not the first choice. So how come I have an unvented roof in my office? Well, because the attic is working space. I moved into the attic, that's what.

Jamie Lyons:
Alright. I think a few minutes ago, Joe, you had shown some pictures with foil-faced polyiso on the exterior of the wall. So we have a question as to whether that places a vapor control layer at the wrong location, whereas we want that vapor control layer at the face of the framing and structure instead. Can you comment on that?

Joe Lstiburek:
Sure. I'll put up an image. And ... you guys got this?

Jamie Lyons:
Yea.

Joe Lstiburek:
At that blue layer is a foil-faced isocyanurate. The vapor control layer needs to be on the face of the sheathing, the face of the structural sheathing. And so whether it's a vapor open continuous insulation or vapor closed doesn't matter if the vapor control layer is on the outside of the sheathing that's directly applied to the wood studs. So in other words, I don't care whether it's foil-faced or non-foil-faced as long as my primary air and water and vapor control layer is behind that. Now the R-value necessary in some climates to control condensation with basically that vapor barrier is important. But whether it's done with vapor open insulation or vapor closed insulation doesn't matter. The vapor profile doesn't change. So the short answer is, it doesn't matter whether it's foil-faced or not, because the vapor control is behind all of that, correctly on the sheathing on the outside of the studs.

Jamie Lyons:
Thank-you. Let's take a few more here before we wrap up, and this one seems like a real launchpad --

Sam Rashkin:
Jamie, could I still follow up to that last question? Assuming that the foil-faced insulation with the vapor control layer is more expensive than unfaced insulation -- and that may be a wrong assumption -- why did you personally go with the foil-faced layer?

Joe Lstiburek:
Oh. It was easier for me to get the foil-faced than the un-foil-faced. I was in Westford, Massachusetts, and I couldn't get anything except foil-faced iso board. So the short answer is, I don't care which one you use, Sam. I used one because I could get it.

Sam Rashkin:
OK, good answer.

Joe Lstiburek:
Well, thank-you. It was nice to finally get an answer right with you! ... That's tongue-in-cheek, Sam. You're smiling.

Sam Rashkin:
I am, I am. You can see me over the screen.

Jamie Lyons:
Alright. Joe, do all claddings really leak, and can we really make a building too airtight?

Joe Lstiburek:
All claddings really leak, every single one of them, even stuccos. That's number one. Number two, you can't make a building too airtight but you can make it underventilated. Whoa. You guys ought to invite me back and talk about ventilation in tight houses. But it might end up being a death match, if we have some of the other people on at the same time.

Sam Rashkin:
Joe, would you come back and talk to us about ventilation in tight houses?

Joe Lstiburek:
All you have to do is ask. Let me give you a preview of the biggest issue. The issue in a tight house isn't the actual rate. The issue is makeup air for a clothes dryer, makeup air for a kitchen range hood. The problem is how do you deal with air-consuming appliances that have traditionally relied on enclosure leakage to function? It's not easy to put in a 200 CFM exhaust dryer in a house that's 1 air change per hour at 50 pascals. I'm a real proponent of balanced ventilation with deliberately interlocked makeup air. The actual rate is less important than getting the balance right.

Sam Rashkin:
Yea, eventually we won't see vented clothes dryers in high-performance homes. But the cooktop exhaust remains the issue.

Joe Lstiburek:
Yea, and Sam, it's been driving me crazy, and the only solution seems to be restaurant technology. And that's why ASHRAE applications, that first chapter on restaurants, we just need smaller stuff. I don't need 1,500 CFM of makeup air. I need 100 CFM of makeup air. And how I get that in a 2,000 -- 1,500 to 2,000 square foot house with 1 air change per hour at 50 pascals is difficult. And we sure as heck don't want to put in those recirculating range top things. That's like a toilet that never flushes and just throws the stuff 'round and 'round and 'round. We don't want to go there. I think I got another smile out of somebody.

Sam Rashkin:
Yea, that was very vivid. Thank-you.

Jamie Lyons:
Switching gears back to the enclosure. Quick question on vinyl siding, which seems to have its own air gap behind it, so when we're using vinyl do we still need furring strips?

Joe Lstiburek:
When you're using vinyl, you do not need furring strips if you're installing the vinyl over less than two inches of rigid insulation. The problem is how do you attach the vinyl through four inches of rigid insulation? So the furring strips in essence are giving you the structural support in order to attach the cladding through that much continuous rigid insulation. So the short answer is, vinyl comes with its own air gap, doesn't need an air space, when you're up to an inch and a half, two inches. When you get more than that, the structural attachment issues end up giving you the furring strip that -- so the furring strip is there for structural reasons as opposed to the drainage. Fiber cement cladding requires an air gap. And I've been using the sill gaskets. So in other words, let's say that I'm building in Atlanta and I'm going to do a 2-by-6 advanced frame wall with a zip sheathing on the outside, and I'm taping the joints. I staple sill gasket over the studs, and then I put my fiber cement board over that. So I've got my fiber cement three-eighths inch in space, and my OSB water / air control layer. And I typically use cellulose and then gypsum board with latex paint. That's my go-to wall for climate zones 3, like Atlanta, Dallas, Houston, hey, central Florida -- why not? That's a fabulous wall.

Sam Rashkin:
So when you do that, Joe, are you screwing all the way through that insulation to the sheathing? Because you can't screw to the foam strip like you could with the furring strip.

Joe Lstiburek:
Well, that's correct. That foam strip is -- you can actually use a nail gun; you just fire it through the fiber cement into the OSB, right? It's right there, Sam.

Sam Rashkin:
OK. But even with that extra thickness. OK.

Joe Lstiburek:
Yes, it's trivial. You know, if the darn people that make fiber cement siding gave me fiber cement siding with bumps on the back side, I wouldn't need the darn furring strip! Geez. Guys, get me stuff.

Jamie Lyons:
On the topic of attachments, there were a couple questions: When we are going through thicker layers of exterior insulation, can you offer any guidance on the availability of these longer fasteners? Are they readily available? Is it the cost premium?

Joe Lstiburek:
They're readily available. But here's a little trick. Don't go to the stainless steel screws; go to the epoxy steel-coated screws. One is $3.50 a screw; the other is 35 cents a screw. And on the furring strips, you need them every 12 inches. Building America and the DOE paid for an awful lot of work to get the cladding attachments stuff figured out. It's on the DOE website. It's on our website. So you've got furring strips every (inaudible) these long screws that are 12 inches apart. The arithmetic -- it's not a big expense if they're epoxy-coated steel. And the furring strips do not need to be and should not be pressure-treated. If you pressure-treat the furring strips, then you have to go to the stainless steel. But you don't need pressure-treated furring strips, because the furring strips are in a vented air gap. So you go with 1-by-4s, epoxy-coated steel screws, you're good to go. That's affordable. And that's why God invented Federal Express and UPS and the Internet. You can buy them all over the United States and have them shipped to your job site within a day or two. It's insanely easy. Don't try to do this with 1-by-3s, because they split. 1-by-3s will work; it's just that they split during the construction process. I'm using -- the 1-by-4 is selected for constructability and robustness, not because for some reason I needed that 1-by-4 for its actual nominal dimensions.

Jamie Lyons:
Very good. OK, we're just about up against our time limit here, at 15 after the hour. So I'll pass one more along to Joe, and then Sam and Alex, you could sort of wrap us up with the closing slides here. Joe, do we have a durability concern if we have continuous insulation on the inside of the structural sheathing?

Joe Lstiburek:
No. I don't believe that you do. I think that there are some racking issues that you have to deal with, but there are a number of manufacturers -- I think two -- that have an OSB that's adhered to a continuous insulation that's designed to be put on the outside of structural framing. Whether that control layer -- whether that foam layer is on the inside of the OSB or on the outside both work, I prefer to put it on the outside, because I get a significant enhancement in my structure, because the OSB is directly attached to the frame. But from a durability perspective, both work.

Jamie Lyons:
Very good. Thank-you, Joe, so much. And I know there were quite a few other questions that came in. With Joe covering so much material, I think he hit on quite a few of those as he went through his slides. And again, as Alex mentioned at the outset, this webinar will be made available on our website, and many of these materials are also available through the building science website, as well. Alex, you want to take the reins back and wrap up the session here?

Alex Krowka:
Sure. So as ...

Jamie Lyons:
Next slide:

I can cover this slide, actually, I guess. I just want you to queue it up.

Alex Krowka:
Yup, OK. Take it away.

Jamie Lyons:
So we can't thank Joe Lstiburek enough for all his insights and guidance he's offered here today on the webinar in support of DOE Zero Energy Ready Home. Here you can see the website for Zero Ready program. buildings.energy.gov/zero, or you can use the long form there. We will continue to have these technical trainings online in webinar format. Sam Rashkin and some of our other program staff like myself do in-person training at different industry events, with allied organizations. So look for us at those conferences. And then if you want to look at the website, we have a partner locator tool that will help you identify builder partners, energy rater partners, and we have a new partnership launching for innovation partners. Those are manufacturers, nonprofits, utilities, and other groups that are helping us really to promote the DOE Tour of Zero, which is an online showcase of some of our very best Zero Energy Ready Homes and the builders that have built them. So innovation partners are our latest partnership category with the program. And then last but not least, you see there at the bottom of the slide the Building America Solution Center. I'd like to sort of describe that as DOE taking 15-plus years of really good building science research and packaging it up in an online, very easily navigated format, so you can get answers to design questions and the right way, the wrong way to do things. Look at CAD details, pictures, specifications, all throughout the building, whether it's the envelope, the HVAC, ventilation systems. You can search by building system and several other search formats. So that's the Building America Solution Center. Sam describes it as your new best friend, so we encourage you to take a look at that, as well.

Last slide:
So with that, and Sam, unless you have any closing words, again, I'd like to thank Joe Lstiburek from Building Science Corp. joining us today and making this webinar possible. And thank-you all for spending part of your day with us, as well. Bye-bye, everybody. Thank-you.