LEEP NZE Wall Videos
These construction training videos correspond directly to the LEEP NZE Wall Guide Series. LEEP worked with RDH Building Science and BCIT’s Zero Energy Buildings Learning Centre to produce this video series. This online video series examines each of the documents in the wall guide series and expands the learning options for students in construction and trade programs. It also offers reliable content and flexible scheduling options for continuing education programs and can be used by homebuilders’ associations across Canada, municipalities and building officials, energy advisors, professional designers, builders and renovators.
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LEEP NZE Wall #1
This is a construction training video produced by BCIT-LEEP. It explains the LEEP NZE Wall Assembly #1: Split Insulated Wall using vapour permeable exterior insulation and an airtight sheathing membrane.
Transcript
0:08 (James) So these guides, along with good processes, all of a sudden high performance is easy.
0:22 (Graham) You know, this rethink towards net zero is rethinking a lot of the traditional building enclosure assemblies and building them better.
0:28 (James) I get excited, but I also get depressed. I'm depressed because I'm old and if I were younger, I would embrace this
0:33 (James) opportunity for this change. I see the young builders and to me, I get excited for them.
0:41 (James) Hey, Graham, how are you doing?
0:43 (Graham) Good.
0:46 (Graham) All right. We're here at Wall number one, which is our vapor, permeable exterior insulated wall with airtight sheathing membrane.
0:55 (Graham) This represents wall number one in the guide here, which is all the details that we put together. And we're going to walk through this wall system here and talk
1:03 (Graham) about the design considerations. We'll talk about constructability, and we'll generally walk you through this and explain how this works.
1:17 (Graham) So we've got a mock-up here that was built by the BCIT High-Performance Lab. And we're going to walk through this wall here and talk about the details in the
1:27 (Graham) Leap guides on how this was built. So when we look at it, we got on this case, we've got exterior vapor, permeable
1:35 (Graham) mineral insulation as vapor open. And then we got our house wrap here.
1:41 (james) We have another insulation too right on the inside.
1:42 (Graham) Yeah, we'll get into that. So we got host wrap on the outside and if we go in the inside of this wall, we've got bad insulation and polyethylene for vapor
1:50 (Graham) control. So when we look at this wall and code minimum in most areas right now is
1:55 (Graham) just the two-by-six wall, Right? So, it's a two-by-six wall with bad insulation and poly, you know, R-16 to
2:01 (Graham) R-18 depending on the type of insulation you're putting in there. And so this wall here in the mock-up is being built on R-27.
2:09 (Graham) So if we're going to say R-35 or R-40, we'd have two layers of insulation up to six, maybe seven or eight inches in some of the higher cases. So we've on the mock-up here, wall number one, it's vapor, permeable insulation.
2:26 (Graham) So we've shown a mineral, a rigid mineral wall and we'll talk about the cladding attachment later on this in this same assembly, you could substitute this for a rigid fiberglass if you found it, wood fiber insulation, you might have different considerations for water control but essentially this is other.
2:43 (James) - Permeable.
2:44 (Graham) - Permeable insulation.
2:47 (Graham) Yes, we want vapor, permeable insulation in this assembly here. And because that dictates what we do for the vapor control on the inside.
2:54 (Graham) So with this wall assembly, we've got vapor, permeable exterior insulation, and in this case here, about three inches to get an R-27.
3:02 (Graham) And so traditionally the vapor control in this wall or a traditional wood frame wall assembly would have been your polyethylene typically on the inside.
3:09 (James) - That's typical. Yeah.
3:12 (Graham) And as we add vapor, permeable insulation to that wall assembly, it starts to shift and shift the dew point out essentially in simple terms, but also increases the temperature of the sheathing gets warmer and warmer.
And as the sheeting gets warmer and warmer, the need for that poly on the inside starts to decrease, right?
So as you shift more and more exterior insulation, you can change the vapor control on the inside.
3:38 (James) At some point, you can probably put it right to the outside then or eliminate it completely, or how does that work?
3:42 (Graham) Yeah. So, once you get enough exterior insulation in this assembly here, your plywood or your OSB sheathing actually will function enough to be your vapor control there. So for the mock-up here, we've got three inches on the outside and we've kept the polyethylene vapor control layer on the inside that poly, and this assembly could be changed to a smart vapor retarder or vapor retarder paint.
And that's covered a bit more in the guide.
4:05 (James) The poly are kept here because this mock-up doesn't have enough exterior insulation on it to consider taking it out of the equation
4:12 (Graham) It's close yeah. - And if you want to be a bit conservative, you can leave it in.
4:15 (Graham) And so with permeable insulation, you can leave that vapor barrier on the inside fairly safely. When we get into other assemblies with impermeable insulation, that's really where we start getting into changing that.
4:26 (James) So having a permeable insulation, let's say I want to leave the poly, I want to put the poly, no problem, right?
4:29 (Graham) Yeah.
4:30 (James) Okay. So I can just leave it no matter how much I put. - That's right. - I can leave the poly without detriment.
4:35 (Graham) That's right. And one of the benefits of this wall assembly one here is that you can keep your traditional practices and you just add the insulation without rethinking potentially your vapor control. And then if you're already using an exterior air barrier approach, just keep building off of that.
4:53 (James) Yeah. So I kind of look at it as the plywood is like my skin. So if I go outside in the fall, I wear a thin sweater and if I go outside in the winter, I wear a thicker sweater just to be comfortable. -So yeah. - That's kind of a neat concept. -
5:04 (Graham) Yeah. And the neat thing about this too, is when we look at near net zero, if you're building to a near net zero level or passive house level, you know you're going to have thicker amounts of insulation if you're building to code minimum or if
you're building on your way to net zero. It's just a matter of changing three inches to six inches or one and one-half
inches, whatever it is, it's just adjusting that insulation, but everything else stays the same.
5:26 (James) Yeah, So you can master your process.
5:27 (Graham) Yeah.
5:28 (James) Without risks with the permeable insulation.
5:32 (Graham)That's the idea, with the guide and the mock-up of those prepared here is that this represents any sort of thickness and details that come with that.
5:39 (James) Yeah. Starting point.
5:41 (Graham) Yeah. - So when we look at mineral vapor, permeable mineral as an exterior insulation, the insulation itself is water repellent, but you notice you have
gaps and other things, flashing and other components tie back into the house wrap
here. So from a water control standpoint, we're not going to rely on the face of the
mineral well to keep the water from getting into the wall. We're still going to have a water-resistive barrier at the backup at
the sheathing. So just like we would build a typical two-by-six framed wall where we have house wrap on the outside of that wall, as our water-resistive a
barrier we're going to keep. That water-resistive barrier behind the insulation in the [inaudible].
6:22 (James) Then tape it and make it the air barrier also.
6:24 (Graham) Yeah, we'll get it, yeah, we'll get into the air barrier details in a minute here. But from a water-resistant barrier standpoint, we're going to have this and
all are flashing and details are going to come back in there. And so when you look at the guide, all the details take all the flashing and the water controller back to the wall system.
So you do all your water is just a barrier and air barrier details first, then you put the insulation on and so you're managing and flashing and everything's detailed back here.
6:55 (James) So same process as we're building now.
6:57 (Graham) Yeah. And so the unique thing about mineral oil is you spray water at this, it doesn't tend to go through it's hydrophobic for water to get behind it.
It sort of has to find a detail that can sort of run back through. And then by diffusion, it can dry out.
7:11 (James) And if there's enough moisture for whatever reason, there is a free-draining ability.
7:15 (Graham) That's right.
7:16 (James) This type of insulation.
7:17 (Graham) You can drain it out or it can also dry out by diffusion. And that's what vapor permeable insulation means, is you can dry through it. And that's one of the, you know, in a wetter region, people would look at this approach. So we got our water-resistive barrier at the backside here, and that's where it makes sense to put it.
When we look at air barrier options for this wall, the insulation itself isn't aired impermeable, so we can't use the insulation as an air barrier, but we already have the house wrap, which we know we can make an air barrier, we can make the sheathing an air barrier.
We could also use traditional approaches like polyethylene or drywall on the inside to use that as an air barrier approach. So you have lots of choices.
8:00 (James) And we can have both, two air barriers, right?
8:02 (graham) Yeah, that's right. And generally, as you add more exterior insulation, it's safer to shift the air barrier further out, and as talked about in the guide and
the insulation flowchart there, as we add more exterior insulation, the air barrier shifts from the inside and traditional approaches to the outside and we'll get into some of the nuances of that detail later on.
But for the purposes of the mock-up, it looks like we've got an air barrier this isn't sealed up here because this is tying in here and we'll walk through some of these details in here in a minute. But the air barrier approach is our host route.
8:38 (Graham) So let's walk through the air barrier strategy for an exterior air barrier on this wall. Simply, we're going to start down here at our foundation.
We got here in the case of the mock-up here, we got an ICF Foundation, we got concrete here, we got the insulation on the ICF, we've got the waterproofing, the peel and stick that's been applied to the ICF, and then the air barrier, transferring the air barrier all the way through this assembly from below grade all the way into the in the mock-up here into the attic.
So we've got [INAUDIBLE] flashing, we've got peel-stick here and then we've taped the house wrap, Right? We tape the house wrap to the peel and stick and then every Lap In the house wrap gets taped to the vertical and horizontal seams.
The air barrier comes into our window here and our flashing, we tie in the air barrier into the back rod and in the sealant that's applied over the back road, through our window, along the jambs with the sealant into the head.
9:36 (Graham) And then we've got the air barrier transitioning up here behind the detail here. So we've lopped and taped this and then we're transitioning in this case here on the inside, we've got polyethylene as our air barrier right on the ceiling.
And so we need to transfer the air barrier through this interface. All right. So we've got our house rap made as our air tight element here.The challenge is we have now the barrier ceiling, which is still polyethylene, a traditional approach with more insulation in there.
10:04 (Graham) So we need to transfer the air barrier through the top plates. And this is one of the trickiest details when you go from an exterior to an interior barrier approach, if you don't do this right, the air just comes up through here and into your attic and so it's a big point of leakage.
And so there are a lot of different ways to achieve the air barrier transfer through this top plate.
So we got, you know, essentially we've got to go from what's been shown here is we've got the house wrap and then we've seal that against some caulking along the top of the walls that's compatible with the house route.
10:37 (Graham) And then it gets gasket by the insulation. But the challenge with that is we need to transfer through this plate.
So there would have to be some forethought put into putting sealant in between here and then to the inside to transfer through the top plate.
10:52 (James) So yeah, so the framers would have to put this in for you, and any time you had a joint you'd have to seal between that joint.
So there's some sequencing and Care that need to be taken in order for that to be as successful as one would like.
11:09 (Graham) A traditional approach is where people put, you know, they've put a layer of house wrap between as a pre-strip. The problem with that is it gets ripped and torn and corners.
11:17 (James) What about the corners where you're locking your plates and all that and trying to...
11:21 (Graham) It's very difficult to get to the air tightness levels you need for net zero and this is where it needs that rethought to the approach and that's why you got this approach here with sealants which is you know, you can.
11:31 (James) It shows the intent. - Shows the intent
11:32 (Graham) and the idea, there are other ways too, you can use tape, especially tape the sticks to wet wood. If this happens to be wet or peel and stick along the top here.
So something that allows you to make that transfer from the inside to the outside.
11:48 (James) Through that top plate. And I think when you do this top plate thing, you also got joints in that plate that also need to be sealed. And I think it's a three dimensional world.
And the two dimensional approach I think is sometimes mistakenly employed to not a great result.
12:01 (Graham) And this is one of those details where, you know, inspecting it and reviewing it as you're putting it together, and you can see if you can see a hole, then you need to seal it up.
12:08 (James) Yes. And that's having that person on site who is your air boss or your envelope reviewer.
12:16 (Graham) So, James, how do we transfer the air barrier from our house wrap to the poly on the inside of the top of this wall assembly?
12:22 (James) With this assembly, we had the plywood sheeting with the [inaudible] sealant at the top plate to make that connection. And then the air barrier was set [inaudible] in the plywood.
So the air barrier connects to the sealant, connects the plywood, connects the sealants, and connects to the plate. So we then have to run the sealant on each of the joints of the plate.
12:40 (James) Alternatively, yeah, you can use high-performance tape, bring a tape from the plywood onto the plate, tape the Tyvek air barrier or similar to that tape, tape all the joints and run your acoustic seal, and run the polyethylene air barriervapor bearing the sealing into that acoustic seal.
It's a very clean way to go. It's a good alternative. You don't have to involve the framers. You're not weather-dependent because the tape works on wet wood. And if it's raining, the framers putting sealant in there is not going to be your
best bet.
13:10 (James) And so that's another way of handling.
13:12 (Graham) A little more weather friendly if you use the right tape. How do builders what's the saying they can do to remember that?
13:16 (James) The saying they can do the tape to the tape.
13:18 (Graham) Yeah. How do you do it.
13:21 (James) What do you mean how do I do it. Tape to the tape.
13:25 (Graham)Tape to the tape to the tape.
13:26 (James) Tape to the tape. You put an initial tape before the [inaudibel] has come. When the barrier comes up, you tape that air barrier to that tape.
13:33 (James) The best part about that, that I'm going to go off on a little bit here because I can't help myself. So the best part about that is when you use that series and that system.
In various parts of the building, you'll see this magical tape, and people want what's their little pieces and rings of tape here and there. Those are your transitional points. What happens when you do that, by osmosis, people understand the air tightness and the planes of air tightness because they'll just [inaudible] the tape not knowing why once explained, light bulb, perfect.
14:01 (Graham) You know what so James, tape and air barrier transitions you can see instead of sealant have other benefits.
14:08 (James) You walk up to the building and you see this white ring around the top and you go, they got a plan? Yeah, I got a plan. Tape to the tape.
14:15 (Graham) This is hard to inspect and hard to see.
14:17 (James) I've done this. I'm trying to review if there's a ceiling there. It's a blind seal, avoid blind application for high performance.
14:25 (Graham) Great. So this. This mock-up demonstrates the sealed house wrap air barrier approach because it's seen as cost-effective. It's something that most builders are already pretty familiar with doing.
And so this mock-up here takes us through the details from below to above grade, through the window, through details. The guide shows penetration details and our tricky transition detail here at the roof to all interfaces.
14:53 (James) And I find sometimes that the guide shows it and everything shows it. But when you get to the site and you're looking at this, this big wooden box here
that you're making and you go, okay,
I'm doing an air barrier, just connect the dots and make sure that one connects to the next and you can be successful, but
15:09 (James) when you're first trying to establish this, it can be a little bit confusing, we have garages and stuff which semi-conditioned space and how you
transfer it across a back wall of a garage or air barrier.
And there's a whole bunch of stuff that needs to be considered but if you connect the dots, as they say, you can do what's necessary through standard materials and process and work that into your program and have an airtight building.
15:32 (Graham) Yeah. And this approach, you know, as you talk about garages and things like porches and balconies.
15:39 (James) Rejections overhead, stuff like that.
15:41 (Graham) You need to pre-strip with this, right? And so there's definitely that sequencing of the air barrier that comes into place there. And of course, there are other ways to do this as well.
In this approach, we could use plywood as the air barrier. We could seal that from the outside with tape. We could use self-assured membranes, which are, you know, basically sticky
15:57 (Graham) We've got liquid-applied membranes and joint treatments. All these approaches can be done on this outside face here depending on what your budget is, and your ease of construction, some of these products like selfies or membranes, make all this taping and [inaudible] a whole lot easier than.
16:16 (James) It truly is a system. What I find interesting is through your talk here that you can use wood as part of your air barrier system.
16:21 (Graham) That's right.
16:23 (James) You can't blow air through that.
16:24 (Graham) That's right. So and you're losing wood where it makes sense to make that air barrier transfer. So you don't need a piece of plastic going through there like people in the past may have stripped into pieces of polyethylene or something on the top here.
16:38 (James) The trust has come in and it can be a little bit of a problem
16:40 (Graham) if you fall off your roof right. So we've got to keep safety in mind, too.
16:43 (James) interesting.
16:44 (Graham) So as we look at this wall assembly and, you know, starting with our sort of code sort of level here in R-27, you know, R-40 out a bit more, just all we're doing is adjusting this.
We're keeping this as a two-by-six in this case here, you can actually go back to a two-by-four and actually have more exterior insulation.
17:03 (Graham) So if you don't need to buy six framing for the bat and structure, you can get away with two-by-four. Two-by-four actually makes a lot more.
17:10 (James) Most homes are two-by-four construction is structurally adequate. -
17:14 (Graham) One and two storey homes are even taller.
You know, you essentially go back to a two-by-four, and then you have more exterior insulation because you're going to end up with a thinner wall, a higher R-value wall with that two-by-four to the two-by-six, just because of the less thermal bridging that you have all the way through the wood frame assembly.
17:33 (James) To me and I've talked with building staff is just thinking of it as a new plywood because everything you're doing on this insulation is what previously you would have done on your plywood.
You might put your flashing on it, and mount you strapping on it. It's just like you would do before putting insulation outside. It's a neat way to look at it.
17:51 (Graham) So when you look at exterior insulation, the first question you often get is how do I attach my cladding through my exterior insulation to the backup wall, rigid insulation, no matter how rigid it is, it's not something you're going to be screwing into and attaching our cladding through.
So we need to attach the cladding back into our framing, potentially even back into the studs, depending on loads of our building.
And so when you look at approaches that are available for this, you know, one of the simplest and what we found works really well for residential wood frame construction is you just use long screws through the vertical strapping we've got here to back into your studs or if you want to design for you into your sheathing to then attach, then your cladding to this, this strapping.
18:35 (James) And That's right. And one of the things that I'm always hit with is what's too soft.
So when I put my screw in and I put a screw into here, you can see the screw has a bugle hat.
So that means that the force necessary to sink that bugle has to get
transferred through the insulation, which doesn't make any sense because you never install things stressed, right?
So if you just simply take a counter sink bit. You make a bugle shape. Put the screw in, you can sink the screw and cinch it right to the strapping without removing it.
There's actually a benefit, is you can adjust the wall if the framing is a little out of plain. I use it typically a five-foot rod when I'm doing this, so I can do just random checks.
And when I find framings, not plumb, which happens occasionally, that you can actually square up a straighten up walls using this approach. So it's entirely doable and I think misunderstood.
But many that you can't do this, and I guess you and the research world have done all kinds of studies that you can hang what you like on that.
19:46 (Graham) Yeah, that's right. [inaudible] We've done you pretty much hang your pickup truck off the side of your installation now.
So the way this works and you've got, this is cut for the mock-up here, but your vertical straps, you know, eight-ten foots straps up the wall and you just put screws in every 8 to 16 inches on center, depending on on the load of your cladding, your wind load where you are.
But typically every foot you're putting in a number ten or number 12 screw and into the strapping and then your cladding, we get then nailed or screwed or however, you attach your cladding traditionally onto this strapping.
20:22 (James) These screws have to hit a stud right? Is there anything else we can do with that?
20:26 (Graham) Generally designed to hit the stud and the guy talks about how you would do that.
You know, there are many different cases here, and the backup framing might be different, you might need straps at different positions for different types of cladding for example, generally, you try to line these up every 16 inches on the center line up your stud pattern.
But there are times when that's not going to be possible. You know, in many cases you're going to get reduced capacity of that, but in most cases for lightweight cladding, is not that big of an issue.
But as we get into heavier claddings or a higher loads, what you can actually do is you can change your sheathing at the design stage or construction stage instead of using half an inch, go to three-quarters, and with three-quarter-inch sheathings, the testing that's being done shown that with three quarter inch sheathing you actually don't need to hit your studs three quarter and sheathing, we found the same pullout resistance for this as you would through half-inch sheathing, and you're ending into your stud by one inch.
21:25 (James) Right? So by putting the three-quarter sheathing on, I can now set my straps where I need to without having to perhaps by backing to the back side or being concerned that I have reduced areas of stopping.
So my actual installation process could be accelerated by the freedom of installation if that makes sense where I can freely put them as long as I keep under part nine my 80% net free area.
I see we have three-inch straps here which add 16 inches on centers providing 13 over 16, 81.25% net free area.
So then you're okay to do that. So can when you have details now, you put more straps in to suit it, but the average overall is still at 80. I really like the three-quarter-inch plywood that you mentioned.
22:13 (Graham) Yeah. So you notice here that we are using three-inch straps, which is intentional so we have that the maximum sort of surface area here for lining up cladding and trims, you know, conventional rain screen strapping would have been, you know, an inch and a half or so.
That's not quite enough area here to attach into sometimes. So that's why three inches is preferred, there are things with three inches on this approach is you get more bearing area when the strapping compresses into the insulation and so you actually get more load capacity. And the way this approach works structurally is the long screws through the insulation and you actually create a truss, right.
And you're creating a trust with those screws that are installed horizontally is you've got your vertical strapping here and you've got your long screws that are going through every 12 inches or so those are horizontally, and that screw becomes your tension member and you got compression into your insulation and you got some friction here that's all also holding in more or more stiff.
23:11 (graham) And so essentially what happens is you got this truss which now you're hanging your load off of this vertical strapping in the outside.
And so a lot of testing has been done to prove out that load carrying capacity. And you can hang a whole lot of weight off of that more than you need for any sort of conventional cladding systems. And it's compressed enough in there and then it's held into place and it provides rigid substrate for your cladding.
And so your cladding fasteners are only going into the supply [INAUDIBLE. Plywood tends to be preferred over dimensional lumber just because it doesn't split as much. You can use one by three as well, but it's not necessary.
And the guy goes into more detail about pressure treatment and where you might need that or choices for the lumber that you have.
24:02 (james) I looked up the fun on the 11-pound density mineral wall. It's 586 pounds per square foot compressive resistance, and it was like I was surprised and I take that over a uniformly loaded wall on a 12-pound, three-square foot cladding Kind of a no-brainer.
24:26 (graham) And so, you know, one thing to note with this insulation, this is a rigid mineral. And, you know, we're familiar with a semi-rigid mineral wall that you use your batts.
And even softer insulation you use in commercial applications and cavity rolls, this is definitely, you know, a more rigid product. And that rigidity is what allows us to be done, you're not going to be putting bats or you're squishing in.
24:49 (James) No, no.
24:50 (Graham) And when you install these, you know, you're getting minimal compression in there. It's just seeding into place, into the face. And that's what you're looking for with that installation.
24:58 (James) And it's interesting you say that because when you do install them, they kind of seed a little bit right? And even the data sheet that I looked up said, you know, 586 pounds, that 10% compression so once you seat that, you're utilizing its full ability to resist loads. And so it works very, very well.
25:14 (Graham) That's another thing too is you don't need to screw it in super tight, you don't need to compress it, it just needs to be [inaudible].
25:21 (James) So boom. And then if you need to, you can bring it in a little bit or you can bring it out a little bit as needed it works really well, so.
25:28 (Graham) So with this wall, with wall number one, we've highlighted some of the unique detail and considerations you have, and most of them come in with the roof-to-wall air barrier detail.
You've got to get the exterior air barrier to the interior, but also our window details. Unique detailing with exterior insulation typically comes up when you start looking at your window details.
The biggest question is, okay, where can I put that window into the wall? How do I install the window? What do I do for window flashing penetrations?
This becomes the hardest point and once you figure this out, then everything else, all the other details, you have become a lot easier.
So with the window installation details, you know, first off, there's a whole bunch of different windows you can buy there are hundreds of companies of windows you can buy across Canada.
And so, you know, it's looking at fundamentally when you look at the offerings of Windows, we have windows that are installed with clips or on the inside or with flanges.
26:27 (James) Flanges. Yeah, right.
26:29 (Graham) And so we've got flange and nonflange windows. And so what we've shown in the mock-up here and the reason we've shown, because it's easier to install and it gives you more flexibility as a nonflange window if you want a non if you wanted to put a flanged window in here, however, the guy walks through a few more details, it becomes a bit more complicated.
But a nonflange window with exterior insulation becomes a whole lot, a whole lot more flexible with how you get to where you get to put it in that wall and how you flash in details.
26:58 (James) As long as the glazing is structurally supported you have that flexibility.
27:03 (Graham) That's right. And so with this wall system here, we've got our nonflange window and its bearing is still in the wood.
And so what we've done with this exterior insulation detail here is we have the window sitting on the structural framing.
You know, you can't sit the window out on the insulation without putting some sort of structural connection out there, support.
And so the easiest way to make that transition from current practice to exterior insulation is you keep the details very similar to [inaudible] had in the past reusing a nonflange window here which it's bearing on shims at the base and then we're on the inside we're actually using clips.
And, this particular detail, there's a number of different iterations of this, we've shown a back a rod and sealant here and that sealant is creating that air and watertight layer.
A common practice in many parts of Canada is to use a back down whether it be a wood back dam or aluminum or metal angle, shiny 90 type thing where you have that [inaudible] and stick coming up on that angle and then sealing that and that provides,
28:10 (James) Some windows actually require that as part of their installation method and so you have to put that angle for attachment.
28:18 Graham So when we look at our options for window sealing, we've got option A here which is backer Rod and Sealant, and option B, which is a sill angle, and option A as well we can also slope the sill so we can improve the water shedding of the sill by providing a bit of slope for drainage to take that water away.
But if you look at option A, we got back a rod and sealant at the inner perimeter of the window frame going from the sill all the way around it's a nice continuous seal providing our air and water control.
Option B we have a sill angle and the idea with the sill angle is we got aluminum or a steel angle on the inside, the waterproof membrane, the flash membrane runs up the sill angle and then we have sealant between the flashing membrane and our window frame.
And then the window frame is typically screwed structurally attached.So we don't have to put fasteners down through the sill there, it is also a variance of this where you could have a wood sill angle or the membrane comes up and you can seal in between depending on your structural attachments.
So these work really well and a lot of the, when you look at the leap wall systems with exterior insulation, they all show a nonflange window and that's because it simplifies a lot of the detailing that we run into with exterior insulation it allows that membrane to transition right out at the height of the sill.
When you get into a flange window option so a flat window flange would be where you attach your window on the exterior side of your wall with a flange that runs around the perimeter.
The challenge with the flanged window is we need to provide drainage from that, that space between behind the flange and the frame out. And by putting that flange there, it actually interferes with our exterior insulation.
We either have to pull the insulation down a bit add another membrane below, or we look at draining through or chiming off that flange to provide drainage in behind.
Likewise, with the nonflange window, wether you seal it with a perimeter seal like on the inside it could have a sloped sill here as well just a bit more complicated when you have a sloped sill on the flange, but still can be done. And then a perimeter angle just like before as well.
30:29 (James) I got a question. So the window is in his placement. Is there any advantage to putting it in the inboard side of the thermal plane, The middle of the thermal plane, or the outside of the thermal plane, or are you just worried about getting it structurally supported?
30:42 (Graham) Yeah. So great question. So, you know, traditional approaches on thinner wall assemblies, you know, the windows typically with flanges would be more towards the outside and rebate would be sort of, you know, sort of sitting around where it is right now, as we add exterior insulation, you know, you've got the sort of the effect now that you start getting these deeper spaces in the outside that you have to flash and trim right?
And so if you want to create that sort of traditional look where you have the window flush with the cladding, you need to push that window out, which means then you need to build a buck.
31:13 (James) So thermally, it's not is not the difference. It's aesthetically.
31:16 (Graham) Well, aesthetically to start. So usually driven by aesthetics, you know, in or out. And you can get that look either way by pushing it in or out.
Just with exterior insulation, you're going to have to add some support for that. But thermally, the best place for this window is somewhere near the middle.
So you want to line the window up with the thermal continuity. And in this wall, we've got insulation or cavity insulation out here so that's roughly in the middle.
31:39 (James) - Fair enough.
31:41 (Graham) And thermal standpoint, that's optimal. - Yep. - And so the details in the guide are showing simple details where the insulation stops around the window perimeter
31:50 (James) Around the rough opening.
31:52 (Graham) And if you look at the passive host and actually some net zero projects, what you'll start to see in some of their window details is they're going to encroach the insulation over the head, maybe an inch or two, and maybe at the sill on the gem.
And so that's not shown in this guide, but that's where we're going.
32:05 (James) Where we're going down the road.
32:07 (Graham) Down the road, yeah. So if you start seeing details where installations like pulling over the frames, that's what they're doing. And what they're trying to do there is reduce this flanking thermal bridging that's occurring through here. You've got, you know, R-27 here and you got a window with much less thermal performance, but then you've got all this wood framing, so you're trying to reduce that thermal bridging at these interfaces, right?
32:27 (James) - Yeah, that makes sense.
32:30 (Graham) So window details really highlight a lot of those considerations with exterior insulation where you put the window, how you seal the penetration, this is our plane of air and water tightness back here you go in the window, back out.
And so really when you start getting into all the details, it's about sealing and getting back to this location here. And in the case here, they've got the insulation on the outside providing that thermal.
32:52 (James) Nothing, nothing much is really changed you still frame your two-by-six wall -
32:56 (Graham) Yep.
32:57 (James) You put on your barrier system, be it air and water on the outside, taped and shingles and all that kind of stuff.
33:02 (Graham) Inside.
33:03 (James) You put on the new sheathing, which is now your insulation and you strap it and clad it. So the process is pretty simple. There are a couple of things that I see from a construction perspective that could be challenging; I see a membrane coming out over my window or out of my window here there's going to be on long before this comes on and I'm just wondering if there are alternate ways to address this I suppose. I think the guy touches on that a little bit.
33:31 (Graham) Yeah. So with window sill details here, I mean, you know, usual sequencing is, you know, the house wraps on the windows in and the insulation is going to come in later on. You know, you're not going to put the insulation.
33:42 (James) or even the starter around the window you go to lock up that kind of thing.
33:45 (Graham) And so the way the detail is shown in the mock-up here, we've got an extra piece of [inaudible] going over this insulation. And the reason we're showing that is we don't want to dump water in behind here if we can avoid it.
33:57 (James) No, it's a planned drainage path and yeah, I think you're supposed to send the water to the exterior somewhere in the code it mentioned something about it.
34:03 (Graham) Yeah, you really don't want to dump water in any type of external insulation behind it if you can avoid it. So what this is, is a supplemental flashing membrane that's below the window. Now, you know, this here in this particular case here, you know, it's going straight across the top here. You could also drop this insulation down and do a detail here where you actually.
34:23 (James) And then just put a little insulation plug back in. That makes sense to me, and I have done that detail based on some of the alternatives shown in the guide and found that it works out quite well.
34:34 (Graham) And if you have flange windows, if you really want to use a flange window with this, that's going to create the flange and that attachment point. And you can't think of sequencing-wise, you don't really want to pull that insulation up to that flange for drainage. And so you actually it's preferential to actually drop the insulation down here and...
34:50 (James) Probably required because there's a flange in the way so you're not really going to have this membrane sticking out. So I just thought I'd point that out, you know, it's about the intent this is the mock-up.
35:02 (Graham) Yeah, that's right. Okay. So when we get into window sill flashing with exterior insulation, we have a few different options.
So if we look at the baseline preparation, we have a two-by-six wall with our self-adhered membrane at the sill, our flashing membrane.
When we add the exterior insulation, we don't want to dump the water behind the insulation so we actually want to flash from that rough opening and the prep and the [inaudible] membrane there over the insulation and the easiest way, and if we don't have we have a nonflange window is we just have an extra piece of membrane that goes over the top of the insulation down you can cut the insulation on the slope and [inaudible], if you have a flanged window, however, that flange gets in the way from that direct transfer out.
And so you have to go down and out. And this adds a course complication and then there's a large space where you don't have exterior insulation unless you take a small piece and cut it and put it in place, which is good practice, of course considering the drainage that you're going to get in there.
There are scenarios, however, where you know, the amount of water that you're going to expect behind that window might be pretty low or you might have a cross cavity flashing, you know, a foot or so below your window, say like a floor-to-ceiling window.
You might have a cross cavity flashing anyways at a floor line, and therefore you could just drain the window down behind that insulation if it's drainable and then out, especially in the wall assembly where we provided drainage.
That's only really recommended if you have intended for that, but essentially allows you to go down and out at that location. So with windows and window sill options, we have lots of options and the important part is getting the water that does get in out and draining it where you want it to go.
36:51 (James) Good. This would member here that's around it. That's installed for what reason? So when you look at your trim details around your windows, you need to attach this to something. So in this particular mock-up, they've put in a piece of wood blocking, intermittent wood blocking here to provide a nailer for this wood trim.
If you had metal trim, you could tie it into the frame or you could, you wouldn't necessarily need that but this wood intermittent blocking here is put in there
intermittently it's not continuous to pick up your trim pieces.
37:25 (Graham) I can see here that also using the side of the strapping. So you actually have two attachment points that you can attach. Do you have drainage at the head here?
37:36 (James) Yeah, that's right.
37:39 (Graham) Yeah. If you look at this detail here, this is just in the mock-up. You've got bug screen here, you got this piece of strapping here is just put in there and you got drainage in behind there.
37:46 (James) The little gap right here so that you have a backup underneath.
37:49 (Graham) Yeah. And this window had detail. You know this when you look at this you know when you look at our window head detail, this mock-up is being put together for a trimmed detail.
There are about four or five different ways you can do this in terms of sequencing. And it's going to depend on how you sequence, If you do pre-strip or full house wrap and cut it out.
And so the idea and the whole fundamental for designing is from a water-shedding standpoint, any water is getting here is draining drained out. If we didn't have the flashing here and say we didn't have a wood trim, we could do it down here, right?
And so the reason we have the flashing here on the wood trim is to protect the top of the wood, make that transition from our fiber cement to our wood here we have a ledge that flashing flashes out the wall.
So this is flashing out the back as well as the face here. But you could also move all of the flashings down to here and drain out that as well.
38:46 (James) So from a constructability standpoint, get the membrane, your air barrier and water is just a barrier on, do your review, and make sure that everything is installed as should be and one of the things that I like is and should be thought about is, when you place your straps, I guess you need to kind of have a plan because you're not going to want to pull that out again and put a new one in because you're going to leave holes in your air and water-resistive barrier. So if you're going to do that, then you should repair it if you're going to move it over.
39:18 (Graham) Other testing that we've been doing is actually looking at if I screw through this insulation into my house wrap, which is an air barrier, am I putting a big enough hole in that air barrier to cause a problem?
39:30 (James) Are you?
39:31 (Graham) Well, when I screw right through and if I leave the screw in that hole is [inaudible] and it's compressed by the insulation in the house wrap in there.
And so that actually is not a problem, however, if you pull those screws out, you end up with these little holes, and enough little holes there will cause an issue.
So if you put the strap here and then needed to move it, say over here because you put it in the wrong spot, you'd have to pull this out then you have to pull the insulation out, tape the house wrap, which is not hard to do, but you have to do it.
And so the worst thing you can do is just move these without, or the easiest thing, the simpler approach just leave it in place and add another piece of strap
40:09 (James) Yeah, and there are a couple of ways to do that.
So if you have the three-quarter strapping or plywood, sorry, maybe just leave it and move it over to a new one and just leave it no harm done.
The other thing that I have done is I have a little cordless [inaudible] hole and I just cut the heads off the screws and I just take the strap I leave the screws in. Yeah, they seal it off, you cut it so there's no issue, I move it over and I'm done.
So I always have the little cordless [inaudible] all with me for the oops I made a booboo moment. Okay, so that's not really a problem.
The other thing that is really, really cool, and as I understand is you can actually improve your air tightness using a sandwich approach that many of the leap walls actually utilize to the advantage right, where the air tightness increases by sandwiching this membrane and applying basically a pressure gasket over the surface.
40:56 (Graham) Well it's really neat is we've been testing a lot of buildings with say House [inaudible] as an air bearer in both exposed cases where it's just behind strapping or cladding and in cases with exterior insulation, we're seeing large buildings now with exterior insulation sandwich, and house wrap they're coming in consistently tighter than passive host 0.6 ACH and lower very consistently with good details and sandwich membrane. And when it's not sandwich, we see results all over the map but if you do a really good job, you can also get to similar levels. The sandwiching makes your life easier and it keeps things in place.
41:34 (James) So as far as any challenges with this wall, I'm not seeing a lot of challenges even from the basic sequencing and skills that are currently on site. We're doing this now. The code says you need [inaudible] air tightness, so make a plan of air tightness as you do. This Insulation is very easy to install because you already put the plywood on, so it's kind of like just putting another layer on and then using this for attachment. So I don't see too many challenges, I think the skill set out there can easily manage this wall number one.
42:08 (Graham)Yeah, this is you know, when you look at wall number one, it is a simple step forward to using exterior insulation with traditional backup details. You do have complications and new details, I should say, around windows and penetrations, but it's not overly difficult. It requires retraining and rethinking the way you do these things, but it puts you on that path, right? And so whether we're doing two inches or six inches, it's the same. So you learn on the simpler jobs and then extrapolate.
42:36 (James) Start with what you know and just add a little bit to get a little bit better.
LEEP NZE Wall #2
LEEP NZE Wall #3
This is a construction training video produced by BCIT-LEEP. It explains the LEEP NZE Wall Assembly #3: Split Insulated Wall using low vapour permeable exterior insulation and an airtight sheathing membrane.
Transcript
0:08 (James) So these guides, along with the good processes, all of a sudden high performance is easy.
0:22 (Graham) You know, this rethink towards net zero is rethinking a lot of the traditional building enclosure assemblies and building them better.
0:28 (James) I get excited, but I also get depressed. I'm depressed because I'm old and if I was younger, I would embrace this opportunity for this change. I see the young builders and to me, I get excited for them.
0:40 (James) Morning, Graham.
0:41 (Graham) Morning.
- Oh, yeah.
0:47 (Graham) Hey, James. How are you doing today?
0:48 (James) I'm all right, Graham. You?
0:49 (Graham) Good. Good. I see you built us here a little mock-up here.
0:52 (James) I did.
0:53 (Graham) You tell us about it.
0:54 (James) Yeah. It's a split insulated wall assembly. Pretty, pretty traditional.
It starts with ICF Foundation, bad insulation on the inside with drywall and vapor barrier paint.
So, you know, pretty traditional stuff, two-by-six framing on the outboard side. I have five inches of foam, that's the split insulated assembly.
The foam is grooved and we'll get into that. But as far as the assembly goes, standard headers, and then I have a vented outer space. So again, nothing unusual.
Same old wall assemblies, but a little more performance here on the outside I have to spin that so you can have a little better look at what's going on. You can see it's just a rain screen cladding, strapping, and cladding system pretty traditional.
And that's what I built for you to talk about.
1:48 (Graham) Great. Let's dive right in.
1:51 (James) Dive away.
1:52 (Graham) So we've got our leap wall System three here represented in this mock-up. And as you mentioned, we've got five inches of IPS
2:00 (James) That's correct.
2:01 (Graham) And insulation over a two-by-six wall with house wrap. Air and water-resistive barrier.
So we're about R mid R-30 right about R-35 or so for this assembly. So from a water control standpoint, we've got our cladding and we got our water-shedding surface and how we control water with this insulation here.
2:21 (James) So a couple of things have been considered here due to the nature of the insulation and the wall types and there's a whole thing that we can get into a bit deeper, but it's a traditional approach where I used to use a sheathing membrane, which that's what we do, and that's the air and water control layer.
And the same thing applies obviously in the bottom half. The interesting thing is the insulation itself is actually grooved on the backside to allow for considerations of moisture within the wall assembly.
Very simple.
2:52 (Graham) You want to show us some of that inside?
2:53 (James) I got a piece here.
2:52 (Graham) Yeah.
2:54 (James) I got a piece here and many types, but that's in its basic form.
3:02 (Graham) So we've got standard IPS, but we've got grooves that are being cut in here.
3:06 (James) And there are lots of different types of groups [inaudible] where the point is just a place that can handle moisture.
3:11 (Graham) Yeah. So what's unique about this assembly is we've got a rain screen, but we've got our foam insulation and our cavity over our house wrap, but we've got drainage behind the insulation.
So if any water gets in during construction or in service, it can drain out.
3:24 (James) And you know what? There are other ways you can do that. Let me show you something else about it.
If you don't have grooved insulation, you can use a very fine drain mat that would be attached to the wall.
Any insulation installed over you can attach that with maybe stainless steel staples pack it on, and install the insulation.
So the point is considered to control moisture that could potentially end up behind that.
3:50 (Graham) And that's great because there are a number of builders that are concerned about putting foam plastic on the outside of wood framing.
And this provides that buffer to allow impermeable insulation to be drained in the water to get back out.
4:01 (James) Yeah, very much so. And there's just a lot to that. And I guess we're going to get into a little deeper discussion on that.
But how much are you putting on. All these things, where are you building it, all this comes into play.
This allows you the flexibility to build a traditional split insulated wall with foam plastic. That's why I built this.
4:17 (Graham) Yeah, this is great. Yeah. So and when we look at this assembly here, we've got quite a bit of insulation on the outside
4:23 (James) Yeah five inches.
4:24 (Graham) You know, tradition, maybe a more conventional approach, maybe only a couple of inches or so.
So we've got enough insulation on the outside here so the ratio is quite high. So we've got about R-20 and about R-20 here so we got 50-50 or so split.
4:36 (James) Yeah, exactly.
4:37 (Graham) Which in most places is going to essentially push your dew point into the outside of your wood frame assembly, but also keep the temperature here warm enough that you don't have a risk of condensation, but also warm enough that it can dry out.
4:51 (James) That's correct.
4:51 (Graham) I also notice that you don't have a vapor barrier on the inside. So what have you done here?
4:55 (James) On the back side of the wall assembly? You can see here there's a vapor barrier paint on the gypsum as a measure of managing the interior to outside vapor drive.
It also can allow some back drive and drying because it's a retarder you didn't want to put poly in this assembly with foam on the outside it's just not necessary and it elevates unnecessary risk.
5:20 (Graham) That's great. So if we look here so we got a vapor retardant paint that controls the vapor diffusion through that assembly but also [INAUDIBLE] the dry back out.
And what's really neat about this, too, is this ratio of insulation, is actually in a situation we might not even need a vapor retardant.
5:36 (James) Maybe.
5:37 (Graham) And so if we actually put in maybe a bit more or in a drier climate, we don't even need to worry about special paint.
5:42 (James) This then becomes the controller.
5:44 (Graham) Yeah, and the sheathing and the foam itself. Now instead of vapor retarder paint, I've heard some concerns from building inspectors that they can't see it, so they want to see something.
5:53 (James) Is it there?
5:54 (Graham) Right. So and Poly is so traditional, but poly is the wrong thing here. You don't want to put poly om the inside of this wall with the foam on the side, because if water ever gets in, then it can't dry out or it's built-in, right?
6:04 (James) That's right.
6:05 (Graham) So you know, there are other products like smart vapor chargers would that work here?
6:08(James) That would absolutely work here. And it's an excellent point that you make that if you can't see it, is it there right?
And one of the things about a vapor retarder paint is it's a function of area coverage. And when people get paint, the traditional approaches stretch it as far as possible.
Yeah, that does not work for vapor paint it's set area coverage per volume that makes its performance characteristic.
So having a sheet [inaudible] a pre-manufactured approach to a smart vapor barrier that allows that a little bit of drying and resistance in the directions necessary is a good way to go and a simple approach.
6:41 (Graham) Great. So we've got our vapor control, we've got our insulation, the air barrier in this assembly. I like how you've chosen a traditional approach.
You got house wrap which is taped and sealed. You can't really see it in this mock-up but we got our house wrap is the air barrier and the guy goes through all the details.
6:57 (James) All the joints are taped the traditional approach for an exterior synthetic sheathing membrane.
7:01 (Graham) Yeah. So house wrap is a good choice and we'll get into some of the details in a minute. But what else could you use here? Could you tape the plywood in this case here?
7:08 (James) If you wanted that air barrier approach, of course, you could.
That's a really tremendously excellent air barrier but when you put a synthetic sheeting membrane on, not only is it simple but also requires less tape and you have a compressive element against it, you really get a tremendous air barrier so if you want to keep it simple, just use a synthetic membrane in my opinion that's why I built it this way.
You could tape all the plywood joints but what's interesting is when you get down to doing that, you realize, holy cow, there's a lot of joints. It's not the same with the tieback.
It comes in nine-foot rolls. You can cut it to whatever size you want and you can install it in a manner that minimizes the joints because what leaks is the joints.
The plywood is airtight, the tapes are airtight, the synthetic membranes are airtight, and the tapes are airtight. But you still get air leakage, what's leaking the joints?
7:57 (Graham) That's right. Yeah. So we got house wrap, a pretty traditional approach. We could use self-adhered versions, we could tape.
We need some water control back here, though. We've got to remember that because we're potentially [inaudible] on water. We've got that drainage, we have water control and air control.
And as we're detailing everything back here, we have flashings, we got flashing here above the window head, which we need by code.
8:18 (James) But not metal. And so the code indicates and I have this discussion with builders, lots of times where you've got to put flashing and that's metal, no it's not metal, the code makes it clear that it is a membrane even understanding roofing practice, [inaudible] roofer flashing it's a membrane, not a metal. And you don't want to stick the metal through here for that thermal bridge.
8:36 (Graham)That's right.
8:37 (James) It wouldn't be necessary. It's also inherently difficult. The flashing is a water-shedding element. It's intended to bring out any moisture that may come and bring it out.
It's not intended to be stitched into your air barrier. Yeah, because it's not part of the air barrier.
8:49 (Graham) It makes it way easier to detail this to you.
8:52 (James) Put your air control layer on. Run the membrane back over from the air barrier so you're marrying membrane to membrane is a much simpler approach.
Put the metal on the outside for deflection, the back leg stops right here, and so that's why I built it this way. It was not only simple.
I'll show you something, it actually functions as intended.
9:23 (Graham) It's a lot of water. Wow. Look at it come out there.
9:25 (James) And the water drains out. And so that's what was intended.
9:29 (Graham) That's amazing. That works really well, James. So we've got our air barrier.
We have other choices other than the house wrap. We've an air barrier, and we've got to think about the continuity, right. So let's start down the grade here, got our ICF Foundation. And ICF, what do you think is the most airtight?
9:44 (James) Well, you've got a couple of things to consider. When you do an ICF, you can have, make waterproof membranes intended to go outside that foam and that can be integrated into whatever your floor slab air barrier system is we're not going to get into that but you need continuity everybody knows that, right?
So, if I had a membrane run up the ICF, I could integrate that membrane with my air barrier here by way of flashing them.
10:08 (Graham) Flashing up. So we've got peel and sticks, we've got our air barrier, whether it's the membrane on the outside or touching into the concrete here as well.
So we got air continuity from the below grade to the above grade on the outside tracing it up.
10:18 (James) But there's one other consideration for ICF that must not be overlooked.
If you don't have an appropriate waterproof membrane on the outside of that, you need to lock it to the core. The concrete core would be the airtight element then, ok?
10:29 (Graham) You need to actually have, you would have a lap in there or you'd have to potentially even pull the framing back in to get the seal right to.
10:36 (James) Run the membrane through whatever you need to do to make that connection from the foam back out to the outside so you can run a membrane, whatever you need to do.
But when you build these types of walls or you know, this, this here assembly or any assembly, you need to be able to track those barriers.
10:49 (Graham) So we're tracking the barrier up. We'll get back to the window here in a minute with the window details, but the window, the air barrier from the wall goes into the window it goes into our back down goes through the window itself through.
10:59 (James) And it's connected here with sealant at the backdown.
11:01 (Graham) It's very important you seal that up and we'll get into some of the alternates here in a bit because a lot of questions about window details and what's the best way to do the seal with exterior insulation. We'll come back to that in a second here.
11:11 (James) And the sequence of construction, that plays.
11:13 (Graham) That, definitely. So we've got our house wrap through at the head, the sealant up to the head up here and what's going on up here. I notice we've got some we got some tape, we've got some.
11:22 (James) So you want me to get into this? I'll get into this, then let's get into it. So when you need to transfer an air barrier from the outside.
11:32 (Graham) To this on the inside.
11:32 (James) To the poly by default, PVD, as I like to call it, poly by default, the PVD here because you have a vented roof, this is your air and vapor control which must connect, so these two must connect this piece of wood.
Do you think you could blow through that if I held up a two-by-six? Could you make my hair move? I think you could make my hair move with a hairdryer anyway. But you can't blow through this plate.
So if I can connect this Tyvek air barrier in this case to this plate, I have a connection, how did I do that? I take a high-performance tape. This high-performance tape would, well, that's interesting, would come across from the plate across here and down like this.
12:16 (Graham) So you definitely have to do that before the foam is on, right?
12:18 (James) Well, yes. And the key that I can tell you is how many times I get a call to give a hand and I come to the site, and the trusses are on it's like, oh my goodness, you need to install this while you're waiting for your trusses.
And you know what's really interesting about sequence construction is when you're [inaudible] the trusses what do you have? Well, this built-in scaffolding around the inside, they're all ready to go because we don't walk the plates anymore.
At least I hope we don't because safety's first. And so you have the scaffolding, it's right here, your top plates. You can walk around with a high-performance tape in a matter of a couple of hours and ring that building.
12:52 (Graham) Just tape the top and see [inaudible]
12:53 (James) Right here from the plywood.
12:54 (Graham) And then what do you do with joints between the plates here?
12:57 (James) And then you run a piece of tape across each joint. So at the end of it, you have this monolithic top plate all connected to the plywood on the outside. So when you bring the tie back up, I can simply tape the tieback to the receiver tape, and I'm now connected to the [inaudible].
I had nothing in my way, no choice, no nothing. The problem is when people are trying to build this, they always think about this after the trusses, the key to the success of building this and even others that I build sometimes, while I guess it's just a simple plan and that's all we need to do to build a leep wall is have a simple plan because everything you see here, it's already on site.
13:36 (Graham) So and you know, we've got the tape. So obviously we need a tape that might stick to damp wood. So we pick the right tape we're not probably the red tape. It's probably a.
13:43 (James) Red tape is a sheathing tape. It is made for plastic membranes, not plastic, not appropriate.
13:50 (Graham) What if you could also put a piece of peel and stick across top here? If I.
13:53 (James) I wouldn't because I prefer to have as much drying ability.
13:57 (Graham) There you go.
13:57 (James) During the course of construction, you can't just know how much wetness you get. But the tape I choose for this here happens to have a 1.72 Perm rating.
14:06 (Graham) And it's Covering a small area
14:07 (James) And it binds to wet wood.
14:07 (Graham) Yeah, and so and so we've got the tape method that could do peel and stick but we don't necessarily need it. You could also transfer through with sealant here, but you have to get sealant, your framer to put sealant between your sheathing and your [iaudible]
14:18 (James) Let's talk about the sequence of construction, ok?
14:20 (Graham) It's hard to do, right?
14:21 (James) They frame in the rain and they frame, I don't know too many framers are going to say, yeah, I'm all over putting sealant in there for you, big shooter.
It's not going to happen.
It can happen.
It's a viable approach.
I found from my experience, the key to having success is minimizing the amount of work that interferes with the framing process.
Get the building framed before the trusses have come make your air connections visible.
14:45 (Graham) Just think about it ahead of time, it's all sequencing right?
14:47 (James) Even the framers. Here's a quick example.
If you have a garage, it's not part of your air barrier system, but you come down a side wall, how do you transfer through the garage to the other side wall? Well, that back wall needs to be part of your air barrier, here's an idea put three-quarter plywood and tape the joints.
The homeowner gets a pegboard for all his tools and you transfer for the air barrier cross. Just food for thought, right?
This is what we need to do; is feed the brain and think about it. And there are a few places on any build that you need to consider for that transition once that's learned, which is easy, it just needs to be done.
This will all be successful.
15:18 (Graham) Great. So air barrier transfer I noticed a steel truss here or a special trust that we're actually raising it up to get insulation continuity here.
15:26 (James) That's correct.
15:27 (Graham) Which is different than past practices.
15:29 (James) It's a planned approach. How much you put in here, you raise your heel appropriately.
15:32 (Graham) This is great, but it means you also have this the air barrier transfer isn't coming up here, right?
15:36 (James) No, I do not need an air barrier in my vented attic, right? And so this here Tyvek that I put on here is a synthetic sheeting membrane that is simply a function of a water-resistive barrier, and it laps over the air barrier, which is also the water-resistive barrier.
So the WRB is continuous and the air barrier takes what I call a left turn at Albuquerque and heads this way. Okay?
15:56 (Graham) That's great. Well, it makes a lot of sense, I mean, you got a rain screen, primary control. The face of that insulation sheds any water that is going to get passed is very little.
16:05 (James) It's a little bonus layer that comes into that, ok?
16:07 (Graham) Separating your rain screen from your water-resistive barrier llike this huge benefit for water control, very little water.
And if any does know, like you showed, it just drains back out.
16:15 (James) Yeah, it's an excellent wall.
16:17 (Graham) And then this assembly because we don't have a vapor barrier in the inside if moisture somehow does get in during construction let's say, or a leak gets in somewhere, then it can dry back to the inside.
So we've provided that [inaudible].
16:28 (James)There is a space behind the insulation also.
16:30 (Graham) Cool. Let's talk about the window detail here. So I notice you have a pretty traditional installation, you know you're resting the window on the framing itself you're not building a buck like we have seen for some assemblies.
16:41 (James) And the idea is I wanted to bring the insulation and the window is intimate as possible for continuity. But one of the things that's neat to consider is this here window sill is intended with a waterproof membrane by code because there's a potential for water
16:57 (Graham) That's right.
16:58 (James) And if I have this water now, would it be okay to send my water down a groove? I don't want to do that.
17:03 (Graham) Don't really want to do that.
17:04 (James) It's a backup system, not a primary system.
17:07 (Graham) Unless you like, showing of.
17:08 (James) That's a key difference. Yeah, it's like, Hey, check me out, you want to bring the membrane out here, so any moisture that does accumulate here will trickle out the board as the same function as the wall assembly, the same function as here. Everything comes outboard. I didn't drain it down behind here and out the head.
17:24 (Graham) Yeah, and I noticed nicely slope of the insulation because it's easy to do that. We didn't slope the sill here, but you could if you wanted to slope the sill you could.
17:32 (James) Yeah you could. And one of the things that are really, really interesting and, and I think changes are coming where I think the 440 stuff is going to change a little bit, where the back angle is a requirement of many manufacturers now with these box type windows and it's fastened in through here, right?
But these being typically about an inch and a quarter high, they're high enough to resist the design pressures for residential assemblies where you know you need 250 Pascals to raise water an inch.
So even if your seal was poor, you won't get water ingress from the air so there are a lot of benefits.
18:03 (Graham) Yeah. So we've got our rebate or nonflange window here, you know, it'd be kind of a lot more difficult to detail if we had a flange sticking in here, right.
So rebate window really makes this a lot easier to keep the insulation up [inaudible]
18:15 (James) It also allows the flexibility of coming in and out on the assembly, it avoids the need that you have to route out for the flange assembly and all the rest of it and your sub-seal drainage and the rest that comes in with that.
Also, it's much easier using a rebate-type window, but if we still do with the flange, no problem, you can do that, I chose for this that I built for you I chose this approach I find it a nice way of moving forward because of my flexibility of where I can place this in the thermal plane.
18:41(Graham) So I notice we've got a sill angle in this detail. You know, that's a lot of window manufacturers are wanting this now for attachment so you don't put a fastener down through the sill. We've got clips on the jam on the head for that attachment. You could also do a backer on sealant there.
18:57 (James) Absolutely.
18:58 (Graham) Yeah.
18:59 (James) You can do that.
18:59 (Graham) It's just really a risk and how wet it's going to get and.
19:01 (James) The function of the installation when you don't have the back angle you're relying on the integrity of that install period. With the back angle, I'm relying on physics and physics always wins, so but I want to go back to the clip.
There's an important point with the clip ok.
19:16 (Graham) We should get the clips.
19:17 (James) Omitted or missed on many applications as the clips are a lovely thing. It's simple for the installation you plumb it up, this is really great.
However, you then install the rotten cotton here, if I don't get sealant behind these clips, then I'll have a blow-by pass for air leakage. So when you install these windows, what I like to do is I'll install the window with all the clips.
Then I'll go back and only put one screw on each clip, Then I'll go back I'll undo the one screw load it with sealant put it back. Undo the one, and load it with sealant put it back.
Then I'll load my back in rod and cock it and I'm assured to have that, so installing a simple process is an extreme benefit because that can really be an unfortunate thing that could happen.
20:05 (Graham) And one thing here too, I noticed we don't need a vapor control layer on the inside of this insulation here because we've got enough insulation on the outside, Right? And really we've got all the sealing finishes and everything else.
So and then our built-up wood framing there, so this makes it a lot easier than trying to cut out poly or spray foam into your room joists you just put bat in there just to match the same insulation level here.
20:26 (James) I got a question. You talked about the bat and all this down here and we don't need vapor control, but we have vapor control here.
And can you explain a little bit about the need for vapor control? And then on top of that, I have one other question, I chose to use five inch, because I have to have five inch, but let's say I want to put an inch and a half on the outside for this wall that I want to build.
So between those two things, the vapor control and a reduced insulation out here. What's the deal?
21:03 (Graham) Yeah. Great question.
21:05 (James) Well, I just saw that it mattered, but didn't matter. And I want you to clarify that.
So everybody kind of gets a sense of that because well, I want to know.
21:13 (Graham) Yeah. Yeah. So the need for vapor control on the inside of this assembly with exterior insulation depends on the ratio of the exterior insulation to the cavity insulation, right?
21:25 (James) And what climate zone you build in?
21:27 (Graham) So and it's not only the ratio but also its exterior conditions but also interior conditions. So how humid it is in particular in the wintertime at the design conditions.
So say it's -20 outside and it's 40% humidity on the inside, then you need a certain amount of insulation if it's higher humidity, then you're going to need even more insulation, so, tends to be the colder it is and the more or the more humid it is indoors in the wintertime and those cold temperatures, the more insulation you need.
What we've generally found in the past, we talked about two-thirds on the outside so if we had R-20, we'd have R-30 on the outside, that'd be a safe ratio, that's a two-third one-third rule, generally, 50-50 for most construction or most, most climates, but also most occupancies, 50-50 will work, and once you sort of exceeds that threshold, then you actually really don't even need much of a vapor control of any on the inside.
So it's great that you showed the vapor barrier paint. But the interesting part is you really don't need that vapor barrier paint even with the ratio here, you'd only really need it if you had, say, an inch or an inch and a half of insulation.
So it's nice you showed it because we can talk about this, but with this ratio here, you're actually set up that you have enough exterior insulation that the interior vapor control needs drops and this is talked about in the guides and a lot of detail looking at the type of insulation you have, the R-value ratios and then all these things we talked about like where is your air and water control layer in this assembly?
So because we've got enough insulation on the outside, we don't really need a vapor control on the inside for most occupancies, if we had a high humidity, indoor environment or we didn't have quite the ratio then we would potentially look at doing that.
Now below down here, we've got a bit more insulation. So the ratio is a bit skewed, although so if you look at this.
23:17 (James) A smart barrier just down here.
23:18 (Graham) Yeah. You could spend the time cutting it out and putting it in with.
23:22 (James) Tape it to the foam.
23:23 (Graham) And what if it's just a small piece of foam? You know, foam is a good vapor retarder so you could put, you know, an inch of foam in here to some scraps you had leftover from outside shove it in there. The reason we use the bat in here, is because it's cheaper than foam, right?
23:35 (James) Yes. Now, my question was on the vapor control and that understanding of the ratios.
23:42 (Graham) Yeah. I'll talk a little bit about the IPS on this wall. So we've used IPS, which is expanded polystyrene and it's not completely vapor closed like a faced poly so and it's not as vapor and permeable as extruded polystyrene XPS.
And so when it's thin, it can inch IPS around three Perms, so it's not completely closed off and so there are assemblies where you could actually put a vapor barrier with, say, IPS and you'd still be okay with the code, although what we find is, you know, you're getting pretty low and as the thickness increase, especially five inches here, this is impermeable.
And so once this is impermeable or pretty close to impermeable, that's really where you want to be much more careful with the vapor control in the inside. Now, the good thing is, as we increase the thickness of insulation, that sheathing really never gets that cold anymore.
And therefore the risk of condensation or high humidity in there is really, you know, stopped.
24:35 (James) Yeah, it just stays above due point, I'm a bit concerned I mean, if you put a single layer on.
24:41 (Graham) Single layer?
24:42 (James) Gaps and the potential and that's why I was leaning toward the smart barrier on the inside. I, you know, I don't think it's detrimental. I'm not sure if I'm incorrect there, but you maybe enlighten me, but if you wanted to like we have a lot of outside conditions that are redundant, would it make sense to consider a smart barrier on the outside until you got to extreme exterior insulation?
25:07 (Graham) I mean, the vapor retarded, the smart vapor retarders in particular on the inside are going to keep any of that vapor from going through.
But if it needs to dry out through, you can get some drying inwards with the ratios you have here, the likelihood of air leakage, condensation is quite minimal actually. Once you add any exterior insulation, the risk of air leakage, and condensation drops, right?
And so in B.C., we're really fixated on rainwater. And that's why, you know, if water does get in there, having that high ratio keeps it warmer and then it speeds up the drying actually, and having that vapor openness on the inside that allows that drying to occur.
You know, it's kind of like the scenario if you had plastic on one side and it was closed off on this side and water did get in, the humidity is builds up in there and you know, it can't go anywhere, and that's the fear that I think some builders have, so this assembly here has that buffer on both sides and allows you to use a lightweight, low cost, rigid insulation.
26:04 (Graham) The other thing I want to talk about with Wall three here is this assembly allows you to use really any type of foam plastic on the outside foam plastic EPS, XPS and faced [inaudible] so it can all be used in this scenario here.
And it doesn't have to the material itself doesn't have to be tested as an air barrier or water-resistive barrier, so when we talked about wall two with the XPS, the surface of that insulation was taped and sealed and those manufacturers had gone through the testing to prove in Canada that that will be a long term air and water-resistive barrier.
This approach allows you to use any type of insulation that's suitable for exterior application over a traditional house route.
And a unique thing here, you either drainage with a drain mat or drainage with drainage groups.
26:53 (James) So it functions well. And my takeaway here is it's a good wall and be cognizant of the ratios that you use on this type of wall and plan accordingly.
27:06 (Graham) That's great. That's a great summary. Yeah. This wall can work quite well and, you know, it's well thought out.
I think the key thing here is you're thinking about the insulation ratio, the water control, and the air control behind the insulation. The vapor control is sort of thought of when you have the buildup of the insulation and the guides walk you through all the details, walks you through all these details from the roof to below grade and through a window and really hits on the points of what we're looking for here.
And I think for builders, you know, more insulation in this assembly is always going to be safer, especially as you're starting to use double layers and staggers for even keeping more of the water out. But it's the thinner mounts of insulation that you really have to think about.
So for shooting R-30 or R-35 to R-40, getting a lot safer. Now, one thing you could do to improve their ratio is you go back to a two-by-four instead of two-by-six.
28:00 (James) Well, should we use two-by-six now just to satisfy well, in British Columbia, our building code requirement, it's not a structural requirement in most cases.
28:08 (Graham) Yeah. So as a builder, if you had a client that wanted this window to be flush with the outside to match that older or the aesthetic that they're used to, what would you do in this assembly?
28:20 (James) I'd have to integrate a structural block around the window.
28:25 (Graham) They you can put the window on the staff?
28:27 (James) No, no, you can't do that, ever picks up a triple-glazed window? It's a serious load and it needs to be structurally supported and those loads to be transferred through your structure it's a requirement.
28:40 (Graham) So we're going to build a buck there?
28:42 (James) And so I'm going to build a buck structure that can take and transfer those loads to the building itself and carry the load down. And there are lots of ways to do that.
28:48 (Graham) And if I had a buck, what would I do if my water controller airs run into that buck? I probably want to sloped, right?
28:54 (James) Yeah, on the slope buck itself.
So I want to carry my barriers through my structure because from the sequence of construction makes it simple.
You can put all your barriers on and then add to it. I'll still integrate drainage above it, but I'm going to carry it through my buck.
And the idea is to keep it simple, don't have so many transitions, cover the building with the control layers, and then build on top of that.
29:22 (Graham) This has been a great overview of Wall three. Thank you very much, James.
29:27 (James) You're welcome. Came from the guide, I read the guides and that's why I asked the questions about the bottom because I wanted to talk about those ratios and stuff. Because you've got to read the guides. You got to understand it and it can be very, very successful.
English (Canada)
LEEP NZE Wall #4
This is a construction training video produced by BCIT-LEEP. It explains the LEEP NZE Wall Assembly #4: Interior Insulated Double Stud Wall using an interior and exterior air barrier, with an optional service wall.
Transcript
0:08 (James) So these guides, along with the good processes, all of a sudden high performance is easy.
0:22 (Graham)You know, this rethink towards net zero is rethinking a lot of the traditional building enclosure assemblies and building them better.
0:28 (James) I get excited, but I also get depressed. I'm depressed because I'm old, and if I was younger, I would embrace this opportunity for this change. I see the young builders and to me, I get excited for them.
0:41 (Graham) Good Morning.
0:41 (James) How are you doing, Graham?
0:48 (Graham) All right, James, what we got here is leaf wall number four, and leaf wall number four is a deep or double stud wall with cavity- fill insulation, with no exterior insulation in this application.
And the way we're getting our R- value towards our net zero targets is we're making this wall fatter and fatter and potentially adding in a service wall, an additional wall on the inside.
So the traditional approach to this double wall is a 2x2x4 framed walls. The cavity is filled with insulation, we'll get into the insulation and you leave a gap between the two stud walls to get your R- value so you need more R-value. You just increase.
1:27 (James) Increase the gap, sure.
1:29 (Graham) And so when you're getting in and you imagine this during construction, you've got double wall framing, it's going to be very difficult to cut and fit in batts just from an installation standpoint.
So typically this cavity is filled with dense- packed cellulose. You could also, you can use dense pack fiberglass, you can use open cell spray foam are all sorts of variants of this.
But with dense pack cellulose, you're packing this into this wall assembly here, usually three and one half or pound density to get enough density so that it doesn't settle in this cavity.
You can see here we've got a cutaway showing the cellulose packed in for this mock- up.
2:08 (James) That's friction on the side, just [inaudible] the density.
2:10 (Graham) Yes, you need to re- tighten it and it should be as tight as your mattress. I mean, this is not quite tight enough here, and if this mock- up were to sit for a long period of time, that insulation would probably settle down.
2:21 (James) I'd need a new mattress.
2:22 [laugh]
2:24 (Graham) You'd be sleeping on the floor yep.
James, we are at wall four and just wanted to clarify some of the questions about air and vapor barriers with a double stud [inaudible].
2:33 (James) Good idea.
2:34 (Graham) Yeah. So traditionally with a framed wall, we put the air barrier and vapor barrier on the inside, and it's no different with a double or a fat wall. Right?
2:40 (James) That's been our past program.
2:42 (Graham) Yeah. And although in modern years or recent years, we've started to use more modern approaches with exterior air barriers and house wrap.
2:49 (James) Agreed.
2:49 (Graham) Now the risk with putting making the house trap the only air barrier and a double wall is that if air gets into this deep space, it's really cold in here, then we can get condensation.
And so a lot of these double walls too, we have cellulose, typically cellulose, we try to get in at 4 pounds per cubic foot.
What's your experience getting that cellulose tightly packed into everywhere, though?
3:11 (James) I find it and it goes to a basic principle. My experience is the densities are inconsistent. The principle that I try to work in a bias is everything I do is in front of me, this is a blind install, you can't see what you're doing, so you're relying on a density test after you don't know if it gets hung up or what's happening inside that wall assembly.
It can and has been done successfully for me also. So don't get me wrong. But I've also had success with The Last Job came in at 2.9, and I asked for four and I was like, okay guys, it didn't really quite work out.
It's very important that we get a good dense pack for a convective looping person. You can talk about convective looping, that's something I read in the guide.
3:48 (Graham) So when with these deep walls with fibrous insulation, there's a risk that with cold air falling in the sheathing and warm air rising on the inside, we get this looping, looping inside these wall assemblies where it can bring with it moisture.
And so it's important to have interior air tightness. The other thing, the interior air barrier in this case is also doing this is plastic we are using polyethylene or potentially a reinforced polyethylene or another product here on the inside.
This is also performing the function of our vapor barrier. So it's the same as before. It's an air vapor barrier and it's only an air bear because we're doing a really good job of detailing.
We're going all the way from our foundation. We got Styrofoam on the inside of our concrete wall. We've taped all the joints.
We've taped the joints in our rim joist, We've got the transfer through the acoustic seal to the poly into our windows and tied into our window frame here.
4:35 (James) That's fine. But my experience is that's also difficult with all the amount of penetration on the inside.
What else can you do, if you want to make it simple?
4:42 (Graham) And what we're really seeing with a lot of the higher performance double walls we're seeing with passive hosts and net zero projects is we're seeing in almost every single case builders build a third wall or a second wall on the inside or a service wall in the service wall.
The idea with the service wall is your air vapor barrier is left here at a two-by- four, two- by- three, or even two by two.
It can be vertical, it could be cross- dropping, could be whatever is essentially built on the inside here you've got, to put a bit more insulation for our value, why not? But you run all your services in here and the air barrier doesn't even get touched.
5:14 (James) Well, that's a good idea. I suppose you could put an OSB or something here also and keep it on a hard board. Or is that necessary?
5:20 (Graham) Yeah. You know, a lot of builders are also looking at alternatives to plastic, right? There is polyester
5:24 (James) That's the question. That's what I'm hearing.
5:26 (Graham) Hasn't served them well. So they look at OSB as a rigid air barrier for higher performance and it can seal up in detail really well.
OSB is really unique in that it is when it's dry on the inside, it's a vapor controller, it's a vapor retarder, it's about a Perm when it's dry, and it's also most of it most zero speed is actually airtight or airtight enough to be.
5:46 (James) Well, that's good. So tape the joints in, and we would serve what we need. Thanks. I appreciate that.
5:49 (Graham) The only concern that law builders have with this wall is sheathing on the inside water and it's sheathing on the outside.
The way this wall works to get your R- values is you increase the thickness. You look at the type of insulation and in the leap guides, we've covered different types of insulation and gaps.
If you want to even use two by tens or two by twelves or if you really want to go crazy, then you can use that as well. We'll get into some of the details later on.
One of the other ways to improve, and increase R- values: you build a service wall on the inside of this wall.
So if we look at this, the detail here, we get our double wall, it's good there, double wall. And so we got like say R- 30 here and we need another R- 10 we just build another wall on the inside here and we get R- 10 on the inside.
6:35 (James) And all the services run here so we don't affect any of the air barriers. Yeah, minimally affect the air barrier?
6:40 (Graham) Yeah. Let's talk about the air barrier. Let's talk about the air barrier.
6:43 (James) There's an interesting air barrier approach here.
6:45 (Graham) Yeah. So with our deep walls in Canada and the cold climate, we need some degree of air tightness on the inside so we can put the air barrier for the building anywhere within we can put on the inside, the outside, we can put it somewhere in the middle.
We could put it, you know, a whole bunch of different locations, right? A common approach with the deep wall. If you want to get a primary air barrier on the inside.
What you do with a deep wall is you don't want warm, moist air getting in and convecting. And what will happen is you get the air will flow through this, a hot air rises, cold air falls and you get happens, you get convective looping inside these deeper walls, especially if there are gaps in the insulation.
And so what you want to do is you want to have an air barrier on the inside of these wall systems. So you're managing that air flowing in there.
7:30 (James) Wouldn't a dense pack itself prevent that convective looping?
7:33 (Graham) Definitely
7:34 (James) If you managed to get the density everywhere?
7:36 (Graham) Yeah. And one of the reasons people use dense-pack cellulose is it does fill the gaps. If you're using bats and you're shoving it in there, you're going to end up with some gaps. And those gaps are bad for the performance thermally, but also from a moisture standpoint.
So with the air barrier on the inside, one of the challenges, as you know, from traditional construction is, you know, you've got plugs and other penetrations and outlets through this wall.
8:01 (James) Lots of them.
8:01 (Graham) Lots of spotlights in the ceiling. Right. And so one of the strategies we've seen quite successful is you keep the air barrier there, whether it be polyethylene, reinforced polyethylene if you're blowing in behind cellulose or smart vapor retarder, in some cases, there's a whole bunch of different products you could use here.
8:18 (James) But you're going to use a blow-in system that's conducive to the mesh or poly or whatever you're using.
8:26 (Graham) That's right.
8:27 (James) Because they are different ones, right?
8:28 (Graham) That's right. Yeah. If you're blowing in cellulose, traditionally you need a mesh here.
It's air permeable, you blow it in and then you have to put another poly vapor barrier afterward.
There are systems now that allow you to blow in. They basically neutralize the pressure.
8:45 (James) On air release at the same time blowing in. So you can use something like this or maybe what we'll talk about down there.
8:51 (Graham) That's right. Yeah. And so polyethylene is a good air and vapor control strategy for this wall. We also see a lot of builders using OSB or plywood sheathing.
And so OSB or plywood sheathing when they're on the warm, dry side of this wall assembly actually functions as a vapor retarder they're actually smart vapor retarders because the premiens increase.
9:11 (James) Varies with humidity.
9:13 (Graham) That's right. And actually, on the outside, it's quite vapored open. But if you use it on the inside, it closes in, Right?
And so we see a lot of walls where you use OSB or plywood instead of polyethylene as your vapor control and your air barrier.
So one of the ideas with the service wall is you got all your insulation in here and then for all your services, plumbing, you don't even need to run your plumbing through the interior walls.
You can run it through the exterior walls if you wanted to, all your electrical outlets, everything. And you plug it into this wall here and the air barrier is now protected by this service wall.
9:44 (James) Yeah, except for the occasional penetration which you can in detail.
9:47 (Graham) That's right.
9:47 (James) And services.
9:48 (Graham) Yeah. So that's the idea here. So when you're looking at this wall assembly overall the R per inch of this, the cavity insulation is lower than the rigid installations we covered with the [inaudible] walls on the outside. You know this is 3 to 4 per inch.
10:05 (James) I noticed something on the inside here that, on this mock-up I think shows a couple of different approaches where we clearly see the interior barrier coming through and connecting to the window to the plate here.
But down in the service wall, we also see a compartmentalized approach.
10:23 (Graham) Yep.
10:24 (James) For this area here, any reason can you explain what the concept does to reduce the potential for convective looping in this kind of stuff?
10:32 (Graham) So for this wall assembly to get the R-value you need, whether you're building in Winnipeg, BC, or wherever you are, you're going to be adjusting the depth of this wall and typically the R-value per inch of fibrous insulation like cellulose and fiberglass 3 to 4 per inch, maybe a bit more than four for some of the high-density [inaudible].
And so you can do quick math to figure out or if you need 40, what that thickness is going to be with all the thermal bridging and everything in there. So these walls tend to be pretty fat, and so when you for higher R-values and so when you think about service wall and other cavities, you end up with a fairly thick wall.
And so what you're trying to do is you're trying to minimize the amount of thermal bridging for all the wood. And then also and that's why you tend to have a gap between your double walls there. And in the service cavity wall here will be pretty lightly framed. You know, not you don't need all the extra framing that you would use that supporting the rest of the wall.
11:26 (James) And the inner wall can be like 24-inch centers as long as the openings line up and everything like that. And this would be your structural wall on the outside.
11:33 (Graham) Yeah, that's a good point. Yeah. So typically the exterior wall, exterior framing, I should say, is your structural wall in the interior is tilted in after.
11:42 (James) Right. And using the plywood as your plate connections- That's right- between the two walls.
11:48 (Graham) Yeah. So on this, on the mock-up here and then the guide, we talk about two air barriers. And the reason we've shown to our bears is we want interior tightness, but we also appreciate that a lot of builders are getting really good at building exterior air barriers really tight.
So using the house wrap or the sheathing as the primary building air barrier and this is really in the inside for your walls for keeping that convection from happening, but also could form part of the overall all strategy.
So what you'll see in the details is you've actually got exterior air barrier details here and interior details. So we're going to go spend this around.
So on the outside of this wall assembly to a builder, it looks exactly the same. You wouldn't know looking just at this.
12:32 (James) No.
12:33 (Graham) What the R-value is in behind here. And so one of the one of the benefits of this deeper wall system is on the outside. And what we've got shown here is a rain screen wall system. On the outside, it's pretty traditional.
We're showing a rain screen wall in the leak guides for moisture reasons. The main reason is we want to provide a bit of extra drying capacity here, when we add more and more insulation on the inside, that sheathing is colder and colder.
And so it's at risk of condensation or it's at risk of getting condensation on it from air leakage or vapor diffusion. So we want to have that outward drying capacity.
But also if we get rainwater leaks, say, around a window, flashing detail, that rain screen space in a cavity and the airflow and the drainage that's provided, which is common in wetter parts of Canada, provide that benefit.
So when we switch to these deeper insulated walls, we're going to see a lot of the time rain screen cladding attachment systems.
13:33 (James) Which makes sense, I mean, if you increase the risk of something, then you should provide something that can manage that risk. And so if you can have potential moisture or issues of condensation, you've put the rain screen on, it's really quite simple to do.
13:47 (Graham) Yeah. And so when you look at your details here, so if you're familiar with house wrap as an air barrier, you can see that starting here at the foundation.
So we've got in this particular wall, we've got a concrete foundation wall with potentially a damp proofing on it or just moreover just bare concrete.
We've got peel and stick transition to go from the concrete to the wood. We've got a flashing in here that we've taped, or we could seal it to the flashing, but essentially transfer the air barrier from the concrete to the peel and stick through the flashing into the house wrap.
And then we've got air tightness into our flashing around our windows, window flashing details all the way to the top of the wall
14:23 (James) back through.
14:24 (Graham) Yeah. And so with the double wall here, we've got there are many different ways to frame a double wall, you may end up if you're doing two two-by-fours and you wanted to tilt them both up at the same time, you would use essentially plywood plates. So you do it all at once.
You could also tip out the outside one like traditional and infill on the inside. But we've shown it here for mock-up with plywood.
And so we need to transfer the air barrier from the outside to the inside of this detail, so we've got polyethylene air barrier and sealing, air barrier out here.
We do have the polyethylene air barrier on the inside here as well, and that transfer is super easy, right?
You've got the air barrier, acoustic sealant, and then we've got poly, and then the drywall, when it gets installed, squishes it all together.
15:09 (James) Similar to the plate concept, just using the plywood.
15:12 (Graham) Yeah. So the plywood here is transferring. So, this is our primary air barrier, then we've got that transfer through the top and it's still wet. Thank you.
15:21 (James) Oh, did you get it?
15:22 (Graham) Yeah, I got it.
15:23 (James) It's an amazing product. Acoustic seal, because if it's wet, somebody will find it Okay.
15:27 (Graham) That's right. It's usually in my hair.
15:30 (James) So some interesting air barrier transfers here using the wood framing, etc. at the inside corner. Just show some of the flexibility.
15:42 (James) Yeah, great observation.
15:43 (Graham) So, working with polyethylene as the barrier here. Most drywall and stars are going to shred this when they cut out the drywall around your windows.
15:57 (James) Rotor zips in town.
15:58 (Graham) Yeah, exactly right. So the acoustics caucus here on the face transfer through the polyethylene should actually run down here to the floor.
But there's a couple of different you know, you can transfer it through as we've
done here for the plate, the bottom plate, so everything sealed up,
16:08 (James) through the wood. It's a mock-up to look at options.
16:12 (Graham) So yeah, there are different ways to do that. But you can see here, we've tied in the polyethylene to the wood here.
And the idea is that the wood buck here becomes part of the air barrier and then you can see the transfer through to the tape here.
And then we've got the sealant on the inside of that window frame that's forming the air barrier on the inside.
16:30 (James) You just cut the poly, that's how you ended up with the V, so it was actually made simple by just cutting the flap in.
16:37 (Graham) Yeah. So you're getting some redundancy in there and really improving your polyethylene air barrier detailing. So you're actually getting transferred into the wood and then into the window.
So, James, you'll notice this window is installed right in the middle of this wall. So one of the nice things about a deep wall like this and we've used a three-quarter inch plywood buck around the liner, liner basically span across between the outside framing, the inside framing, and, you know, the deeper the wall is a deeper buck.
And if you had a service wall, you just your buck would come out even.
17:09 (James) Sure.
17:10 (Graham) So with our nonflange window here, we can install it anywhere within that rough opening.
If you have flanged a window and potentially on the outside, if we wanted a flanged window, you could buck out this with framing and install the window on that.
However, that creates a whole bunch of other complexes.
17:27 (James) That's a very complex way to go about something that could be simple.
17:29 (Graham) That's right. So a non-flange window allows you that flexibility to install it wherever you want in that rough opening. One thing you'll notice down here is this is flat. And, you know, in areas where potentially a lot of water is sitting here, we'd potentially want to add a bit of slopeness.
And so we can actually slope the bottom quite easily by putting this on shims, or tape or cutting this or building up on top of the peel.
17:55 (James) For the back dam angles is kind of advantageous that it would even by volume.
18:00 (Graham) That's right.
18:01 (James) Drain forward, not instead of backward, and on a waterproof membrane, the amount of water is usually minimal and would dry.
18:08 (Graham) Yeah. So this window here, we've installed it with back dam angled peel and sticks coming up and over down the face traditionally wood and that's got clips on the inside and back and on the sealing.
And there are lots of different ways you can install this but generally, you want to get that window in the middle of this wall assembly.
That's the best place for your R-value and actually for minimizing the thermal bridging.
18:31 (James) And attachment is quite simple if you simply have a plywood liner for your returns, cladding, etc.
18:38 (Graham) That's right. So this wall really, you know, it takes a lot of traditional approaches, you know, from, you know, exterior water and air barrier detailing.
18:48 (James) It's the same, yeah.
18:50 (Graham) It's just fatter. It's just, you know, it's stretched out to increase the R-value you're using typically insulations that are lower cost per R-value just because they're fibrous and blowing in versus a rigid product.
You know, when you look at this wall assembly is something that, you know, some homeowners could even build themselves. You look at the detailing here that doesn't require a lot of special tools and it's something that you can take on as a do-it-yourself or even.
19:21 (James) Yeah, no, I understand this wall is built in quite a few places across the country. I believe it's quite prevalent in Alberta.
It's kind of I find it just amazingly interesting that across the country we have different wall types and technology and understandings for each of the various reasons. You know, it's this one wall type across the country that doesn't exist.
And so I think Leap is really helping to unify high performance for whatever you want to build as a starting point.
20:01 (Graham) One of the good things I've heard from builders about this wall is how cost-effective they can make this.
A lot of builders see a deeper double wall is a lot cheaper than one with exterior insulation. You know, they look they do look at the material cost and, you know, this type of insulation is a lot cheaper than rigid insulation.
20:21 (James) There are still nuances and considerations when you build an interior deep stud wall which could come back on you. So you really need to understand that.
20:32 (Graham) Yeah
20:33 (James) It may be costly on day one, but if it doesn't work well because you avoided some considerations, Then it's not Cost-effective.
20:41 (Graham) That's right. Yeah. So this may be cost-effective, but this wall requires very good air tightness for the details.
20:47 (James) On the Inside.
20:48 (Graham) That's right. It's critically important to get air-tightness. Right. If you don't get air tightness right with this wall, it is a higher risk than exterior insulation.
20:56 (James) Yeah, and that was my point.
20:58 (Graham) So, James, you'll notice this wall assembly, we've shown a rain screen.
21:01 (James) It's a capillary bag from the watershed surface to the water-resistive barrier, provides drainage and drying potential for whatever moisture may from whatever source accumulate.
21:11 (Graham) That's right. And so the idea with a rain screen wall, a rain screen cladding on this wall assembly is to provide that extra durability to allow drying of that sheathing. The sheathing is going to be colder and therefore damper, and with all that insulation on the inside and so in our wetter and damper climates, it's very important to allow that outward drying.
When we see even double stud walls and deep walls built all across Canada, you know, they're building above code anyways and we're seeing most of them actually use some sort of rain screen approach because the builders will actually appreciate that they need some drying there, and some bit of redundancy when they're building a higher performance wall system.
So in our deep and double walls, from a building science perspective, we've got our sheathing on the outside, got our vapor control and air control on the inside, you know, outdoors, cold, warm, indoors.
And so this sheathing with all this insulation on the inside is actually quite a bit colder than we used to have with our 20-22 BATTS Right? We've got our 40-50 on the inside of this now, sheathing becomes appreciably colder and closer to the outdoor conditions.
As that sheathing becomes colder, the humidity actually goes up around on the inside and on the outside.
And so the moisture content of that sheathing tends to be higher in these double walls or deep walls than maybe traditional assembly.
So because that sheathing is colder and the higher humidity and higher moisture content any small leak now can push it over the edge.
So this assembly, if you're not careful with air and vapor control, can be riskier than a traditional approach.
And so that's why we have taken all these steps to put, you know, improved air barrier detailing. That's why we'd look at using the service cavity here.
And the idea of the service cavity is it protects the air barrier.
23:04 (James) And rain screen.
23:06 (Graham) And the rain screen. And so the leap approach to this wall has been, you know, good air barrier details. You can protect your air barrier details with that service cavity on the inside, especially as you start getting into needing R-30 to R-40.
It's going to make sense to do this anyways. You know, R-35, depending on what you're putting in here, is going to be a gap anywhere between two and four inches, somewhere in that range.
And so if you're looking at mid R-40, it's that plus this assembly on the inside. You can even look at two-by-sixes and you know there are all sorts of different ways you can construct this.
23:41 (James) Quite a bit of real estate to get at either [inaudible] Might want to consider that too I guess.
23:46 (Graham) Or are you looking at higher, you know the reason you use a high-density dense pack of cellulose is you get a higher R per inch out of that dense pack than you would with say fiberglass or something else that's blown-in.
English (Canada)
LEEP NZE Wall APPENDIX A Selecting Materials
This is a construction training video produced by BCIT-LEEP. It explains the LEEP NZE Wall Assembly #1: Split Insulated Wall using vapour permeable exterior insulation and an airtight sheathing membrane.
Transcript
0:08 (James) So these guides, along with good process, all of a sudden high performance is easy.
0:21 (Graham) You know, this rethink towards net zero is rethinking a lot of the traditional building enclosures, and some ways of building them better.
0:27 (James) I get excited, but I also get depressed. I'm depressed because I'm old. And if I was younger, I would embrace this opportunity for this change. I see the young builders and to me, I get excited for them.
0:40 (Graham) Howdy.
0:41 (James) Howdy, partner. Are you ready to chit-chat?
0:45 (Graham) Yep. I'm going to walk you through Appendix A, which is the material selection Appendix of the Leap Guides.
The purpose of Appendix A is to put together a list of materials as a starting point for what to look for. When you're detailing out your sheathing membranes, your flashing membranes, the sealants and insulation, and tapes.
So when you look at materials under the building code, we are governed by a number of standards. When we're selecting appropriate materials for air barriers or insulation or sealants or tapes, it's important they do their function.
Air-bearing materials need to stick to each other, and they may be from different suppliers or different manufacturers.
And so it's critical to pick sealants and tapes and membranes and things that are all compatible and things that are going to stick in during the life of the building. So when you're looking at where it is start, you get a lot of suppliers and manufacturers in Canada that can help you out.
But often you're going to be combining above-grade to below-grade components, and they may not all be from one supplier and you may not be able to even locally get all these different materials.
So the idea with this appendix is we wanted to put together a starting point for sheathing membranes, flashing membranes, sealant, and insulation, which are widely available in Canada as you can go to and know they work.
And then with your own experience and mock-ups can go even further. So in terms of when you're choosing materials, the first thing is durability, the air barrier, and the materials you're using need to be durable.
And so they need to withstand in case of an air barrier, the air pressures, and the air pressures that are on the air barrier.
If they're exposed to UV, they need to be resistant to UV or have some sort of protection, or be covered up. The other aspect to look for is compatibility. A lot of building material components aren't compatible.
A good example is bituminous membranes and PVC balcony membranes or roof membranes, for example. Those two membranes don't get along and so you get chemical incompatibility.
And so a lot of these are understood in the industry, you can do some searching or you can look in the guide here and understand there are certain products that you shouldn't be mixing together. So the guide here touches on things and materials that are compatible and that aren't. Adhesion If you're applying all these sealants or tapes as part of your air barrier, it needs to stick and it needs to stick really well and needs to stick for the life of that component.
So adhesion and the best way to look at adhesion is actually doing mock-ups. And so people will often do like a builder will take some sealant they're planning to use and apply it to the house wrap and all that are materials and make sure that it's going to stick.
And what you're looking for with adhesion is you're looking for the material to be very difficult to remove but also cohesively fail, so where you're actually pulling apart the material rather than having it peel off.
Constructability, of course, if you're using tapes and sealants and sequencing, implying cold weather and rain to damp materials, all these things come into play.
So the first thing we're gonna look at is the sheathing membrane, so sheathing membranes have a number of code requirements that are covered here, both views as air and water-resistive barrier, so if you're using that sheathing membrane as the air barrier and the water-resistive barrier, it needs to be tested and evaluated as such.
And in Canada, there are many materials that are available. And so when we look at sheathing membranes, we have non-adhered so mechanically attached membranes and then we also have adhered membranes. And so we've given a number of different example products, things like Tyvek, house wrap, vapor shield, wrap shield [inaudible] and delta vent, Sigma HVS, SRP, air Shield, type R, host wrap, and Nova wrap here.
These eight products are a good starting point. There's a lot more that can be used as well. And we collected these materials based on feedback from builders across B.C. and other parts of Canada where people were looking at already building net zero-ready walls, so these assemblies have been already being sort of used in those applications.
There are lots of other materials you could use. And then these are a good sort of starting point. Also, we have adhered sheet membranes, so adhered sheet membranes are self-adhered membranes that are often used as air and water-resistive barriers.
Again, seven materials here that are available pretty widely in Canada that can also satisfy that component. Liquid-applied membranes, liquid-applied air, and water-resistive barrier membranes. Again, there are a number of different chemistries here Silicones STP, which is silio terminated polyether, acrylic based, a whole bunch of different liquids there.
This is sort of your starting point for a number of different products that are available and work quite well in that application. Moving on now to flashing membranes and tapes when you look at flashing membranes.
So when you look at flashing membranes and tapes, the key thing you're relying on here is air and water tightness again, and so what you're looking at is that membrane to stick of course to the substrate and what you're applying it to, and then often in air barriers is part of your continuous, in an air barrier application as part of your continuous air barrier from below grade to above grade walls and to your roof.
And so you're often transitioning flashing membranes from below-grade waterproofing, for example, use a lot of flashing membranes around penetrations and windows. And so what you're looking at there is adhesion, the workability, how tough that material is, and how it's going to stand up to the details, you know, the big thing is, you know, with a lot of these self adhere membranes and flashing membranes, do they need primers or do they not?
And so following the manufacturer's recommendations for that is critical. You know, for example, products blue skin suprema so pre-seal stick protector wraps, protective seal, and there are dozens of other peel and stick products that can be used in this application.
Tapes and tapes are used as part of the air and water system barrier, a number of tapes. And the key thing with tapes is to understand there's a wide range of different types of tapes. So sheathing tapes, things like duct tape, and Tyvek tape are examples of materials that are more rigid tapes but they're really good for sealing up sealing membranes.
As we get into something like a weather mate, a Sega tape, three M all-weather tape, or Owens Corning tape, these are more flexible tapes with slightly better adhesion properties, and you say with some of their products and they're often used for air bearer details where you need a bit more workability, flexibility and even just a bit of robustness and adhesion.
So lots of different tapes and again, mock-ups and trying different components out there. The next one is sealants. So with sealants, if you where you're using sealants and around window perimeters to seal different transitions, you've got to find a sealant that's going to stick to the substrate.
House wraps or we have a lot of sealants are notoriously hard to seal to. And therefore special sealants that have been tailored for house wraps are critical to use. And so what we're looking here is for cohesive adhesion to that substrate.
And you can often find this from the manufacturer, but often this is just easy to get some of these sealants So you could be using and recommend starting point here and then try the mode on your substrate, build that mock-up, test them out, and do the pull testing yourself.
So with sealants, it's critical to properly apply them for the manufacturer's recommendations for Surface Prep, then tool the sealant, proper application of the sealant, and direction that you're applying the sealant is also critical there as well and of course the compatibility.
There are a number of different types of sealants, we've got silicone sealants, polyurethane sealants, and acoustical sealants. And so some starting point here and there's a whole number of different products.
Silicone sealants tend to have the longest service life, they tend to last the longest out of any sealants just because of the chemistry. And so a silicone cylinder typically used in exterior applications, polyurethane sealants are good, really good at sticking, adhesion and cohesion to surfaces, but they don't necessarily last as long and are exposed to UV and heat, and so you tend to use those in more protected environments or places that you can replace them.
Acoustical sealant, the block sealant you see around polyethylene is used for a flexible long-term air barrier seal to transition in polyethylene and other interior details, sometimes also use an exterior as well. But these are sealants that remain essentially uncared for there for their life.
Insulation, in the other videos, we talked about the different types of insulation. So we've got batts, we've got rigid boards, we've got in the rigid boards, we've got XPS EPS, we got a rigid mineral wall, we've got semi-rigid mineral, which is softer density than the rigid, we've got fibrous loose blown so things like cellulose and blown-in fiberglass and then we have spray foam, and spray foam is typically involved installed by professionals, these are usually two components spray foams, closed cell or open cell spray foams.
And so again, some starting points there for suppliers in Canada that can help you out. So Appendix A really provides a starting point for a builder to look at. Okay, here are my details, here are the materials, here's a material that builders of other builders have tested and we know likely works in this assembly here.
There are lots of other products available in Canada and North America that you can also use to say that these are better than the other ones.
These are just a starting point for you to work off of.
English (Canada)
LEEP NZE Wall APPENDIX B Selecting Exterior Insulation for Split Insulated Walls
This is a construction training video produced by BCIT-LEEP. It introduces Appendix B of the NRCan Net Zero Wall Guide Series. Appendix B presents a process to help select insulation materials and determine the vapour control options for split-insulated wood-frame walls.
Transcript
0:08 (James) So these guides, along with good process, all of a sudden high performance is easy.
0:21 (Graham) You know, this rethink towards net zero is rethinking a lot of the traditional building enclosures, and some ways of building them better.
0:27 (James) I get excited, but I also get depressed. I'm depressed because I'm old. And if I was younger, I would embrace this opportunity for this change. I see the young builders and to me, I get excited for them.
0:52 (Graham) Okay. I'm going to walk you through Appendix B, which is selecting exterior insulation for split into wood frame walls.
This is an appendix to leap net zero ready wall design guides, and it covers the rationale and design decisions made for selecting vapor control with different types of exterior insulation.
So if you have questions about "Do I need a vapor barrier? What should my vapor barrier be with different types of exterior insulation? Or how much exterior insulation do I need?" This is the appendix for you.
So the way this works is you're going to have an R-value target you need. Depending on your energy model. It could be based on net zero ready, it could be depending on what you're building to today, you're going to calculate your effective R-value you get your target, you calculate the R-value to match that.
And so that's based on, in this case, using a certain thickness and type of exterior insulation to meet that target. You're then going to select some exterior insulation based on vapor permeability so you're going to choose permeable or impermeable insulation, either works, and either we'll follow you through here.
Then you're going to calculate the insulation ratio and this talks about that calculation there. It actually provides a number of tables for that. And then you're going to check other design criteria and run through the critical barriers of vapor, air, water, and cladding attachment.
And then some examples here. So it's a five-step process, and I'm going to walk you through this as a high-level summary for further information there are longer webinars available on the topic.
So the first thing is where you are, and this is specifically put together for BC, but it also applies across the rest of Canada using 936, depending on where you are in the climate zone, you have a minimum code requirement and then if you're looking at step code or net zero ready, you're going to have a different target.
But typically your target R-value is going to come from an energy model when you're doing performance-based buildings. So net zero, ready, the designer, the team, the energy modeler is going to say, I need an R-35 or R-40 wall So that's your target effective.
So then you're going to go in and you're going to look and say, okay, with that R-5 wall, I've got a number of different ways of doing this. I want to use our four per inch or our five per inch exterior insulation with bat framing.
I'm going to need roughly, you know, let's say five inches to get to R-36 or five inches of mineral oil or EPS or four inches of XPS. So you can sort of see in the table there that would be your target.
So you use this table to figure out the target figure out the thickness of exterior insulation. Once you've sort of figured out the thickness of exterior insulation you need and type of insulation, you're going to calculate the effective R-value.
You're going to use parallel path calculation and 936, if you do the calculation here, but this is how it's done where you've calculated the R-value for all the pieces of the R-value, including the framing factor added in with the exterior insulation to figure out your overall array.
The next step is to choose your insulation or select the insulation based on the vapor Permians. Then the way this category looked at is we've got low vapor Permians, insulation and high vapor Permians insulation, and the divider here is less than 1 US Perm or 60 nanograms per second meter squared or more than 1 Us Perm or more than 60 nanograms.
So you've got a low perm and then a high perm insulation. And so in here you can see you've got a table if you don't know and depends on thickness and the type of insulation. For example, here EPS, EPS at one inch thick is five Perms so we're going to put that on the high Permian side.
If we have five inches or six inches like we're going to see with a net zero ready wall, that becomes impermeable. Then we're going to follow the red side of the chart and the flowchart here.
So we look at the table here, foam plastic insulation of the top five here, and they're all at thickness the thickness is what we're usually talking about for net zero levels, in that R-35 to R-40 range to a six wall.
You know, that's somewhere in the generally impermeable. So simplistically foam plastic insulation can be looked at as low. Permians from a simple standpoint and things like fibrous insulation like mineral wall, wood fiberboard, cellulose, and rigid fiberglass, tend to be vapor permeable.
So you're going to follow the green or the right-hand side here. So we've got our target R-value We know we need, let's say five inches of exterior insulation and now we make the decision whether we use vapor, open insulation or vapor closed.
And so in the leak guides, we've covered both and wall number one covers that high Permians vapor, permeable insulation, and walls two and three, in two different methods of air and water control covered that low Permians insulation.
So we've selected our insulation based on Permians. We're then going to look at the insulation ratio. And the reason we're looking at the insulation ratio is we want to look at the outward to cavity insulation ratio and what this does, and if you run through the calculation here, what you're looking for here is, you want to get enough exterior insulation, or you want to look at how much exterior insulation you have, and if you can get enough exterior insulation that you potentially don't need a vapor barrier on the inside.
Or moreover, there are a couple of different ways to look at this. The question is "how much foam or impermeable insulation do I need to put on so I don't need a vapor barrier?" Or with a say Likewise with vapor, permeable insulation "if I've got six inches of vapor permeable insulation, do I need a vapor barrier?".
So there's two ways of sort of looking at this, and generally the higher the insulation ratio, the less vapor control you need on the inside.
So the whole point of doing this calculation is to figure out where you're at. There's a minimum requirement, but there's also a quality building science requirement.
And the building sciences walked through here talking about walls with and without vapor control, how they work and how exterior insulation moves, increases the sheathing temperature, moves that dew point, so to speak out of the assembly and different types of insulation.
So if you have impermeable insulation, you don't have outward drying, if you have permeable insulation, you do have that outward drying. And if you have that outward drying, then you can stop the vapor flow on the inside with little risk of that having that wall without the ability to dry out versus if you have impermeable exterior insulation, you tend to want to drop the vapor control in the inside or reduce it so you can allow some inward drying.
And so it's all about allowing that wall assembly to dry out as much as possible. And so when you look and follow through, the building science discussion there and then gets into some guidance, okay, "what ratio should I have or what ratio would be safe for this wall assembly?"
So if we look here, we have this table here of ratio of outward total thermal resistance. And depending on where you are in Canada, you look at your average wintertime low temperature here. So if say zero degrees and then you got an indoor wintertime humidity, there's been discussion there.
But generally, we're in the 30 to 50% realm and depending on what you're designing for here, But let's just say if you're designing zero degrees, so in the coastal B.C., you know, zero degrees average at 50% humidity says I should have around 47% or 4.47 ratio on the outside to inside or outside to the total.
And that means that I should have 50-50, sorry R-20-R-20, and that's, you know, sort of that's what a 50% ratio means. Likewise, if I'm in a colder region and I also have the humidity is going to be a bit less in drier parts of the country, and especially when it's -20 or -30 outside, the humidity is just not going to be at 50%, it's going to be 30%, maybe below 20%, if you're humidifying the spaces generally between 20 and 30%.
And so you can see here, the colder it gets, generally the more exterior insulation you need.
And so with exterior insulation, you may find that you might need up to two thirds or 70 or 80% of the insulation on the outside before, when you look at the vapor control on the inside.
So depending on what this table tells you, that's the ideal ratio. If you don't have it, that's not a problem. If you do have it, it does, it sets a different criteria. So you've got your wall, you got your insulation, you figured out what Permians you have, you figured out your ratio here and you sort of following this through and you're writing things down.
There are a few examples here and generally around 50%, 50-60% is going to be safe for most of Canada. The two third, one third rule that many people have heard about in the past generally is a bit conservative, but it's a good sort of rule of thumb as well to be safe.
So you now have your choice, you have your assembly, you either have a low ratio or a high ratio and then you go through the charts here to assess what to do for vapor control on the inside as well as air control.
So you have either low ratio or high ratio. Both will work. And that's important to realize is both these assemblies can work. It just there are slight differences to what the best strategies are to do for vapor control and also air replacement.
So we get into the charts here. You got Section five, we got to look at vapor control. So the first thing with vapor control is we have low Permians insulation and then we have high Permians insulation.
On the left hand side, we have low Permians insulation with high ratios and low Permians insulation with low ratios.
And the vapor flow control guidance is different. If you have a lot of exterior insulation, the exterior insulation is entirely controlling the vapor flow if you have a little bit of insulation, you might not have enough insulation to warm that sheathing up enough. And that's what the ratio is looking at, and therefore you may need some vapor control in the inside.
And that's entirely what this table is walking through, so I encourage you to sort of walk through some of your own examples here to look at high and low ratio. Both can work and so there's likewise vapor, permeable insulation guidance for high and low. And there's a number of specifics that come through this.
So vapor control is covered, air barrier, an ideal air barrier placement is also covered in here. And then we also talk about different air barrier types. And if you're placing air barrier on the inside of the outside, you have a lot of choice. And this talks about where the air barrier ideally would be in those assemblies as well.
The third thing that gets looked at is water management. So water management, you've got your assembly, you've got the exterior insulation, you've got some thickness of exterior insulation.
So then what do I do for water control? What's the best thing I could do and what, what's going to drive This, is where you are. Are you in a wet region of the country? Are you in something with an area with a high moisture index?
And if you're an area of the high moisture index, you can take a bit more conservative approach with your water management, in code currently that would be things like rain screen designs and other details for water management and flushing's, versus in low regions where the risk of water penetration is much lower in drier parts of the country.
And so there's two approaches, and this is where wall three and wall two get differentiated. So wall two generally recommended for low moisture index regions, wall three with the details that we cover in the guide generally recommended for the wetter regions. So you've got the two choices and you can use them.
Then on the right hand side, we've got vapor, permeable insulation and so you got moisture tolerant insulation versus moisture sensitive. The key rule of thumb there, is if it's moisture tolerant, things like mineral wall, then the water resists a barrier can be inside of it.
If it's not moisture tolerant and sensitive like things like wood fiber, then you need water control in the outside. And so that follows through into the flow chart there. And then what's talked about in the last part here. So we've got our insulation, we got the air barrier place, the vapor barrier, and then how do we attach cladding?
And so with thinner or thicker amounts of insulation, there's guidance here around that and it talks about long screws through insulation and how you attach cladding to strapping that is screwed through your insulation for thicker amounts of insulation.
A number of alternate configurations are also talked about, if you have say vertical board and batten or shingles, things like that, where you need horizontal strapping, how to how to do that [inaudible] talked about. And heavier cladding are also mentioned in here as well.
So figured all the building science got the cladding attachment worked out and then it finishes off with a few examples for a few different cities and different assemblies to basically help you understand how to make any type of exterior insulation work with really any type of cladding, and then getting the right air and vapor control in behind that.
And so it becomes almost seamless. And so this flowchart will help keep you out of trouble by looking at those ratios and looking at placement of water control, for example, with the impermeable exterior insulation.
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