Reuben Saltzman

Solar Tubes: Good or Evil?

For this episode, we will be learning different ways to add value to our homes with home improvement tips from the gang through some of the projects that they’ve been working on.

The show starts off with Bill sharing his experience on how he tried to fix his house on his own in the past and how he shifted from fixing it by himself to letting the experts do it. Tessa then talks about how important it is to do things right so that you don’t make your house worse.

Then, Reuben describes what a solar tube is and how he installed it in one of the darkest rooms in his house. Tessa then states the PROs of having solar tubes in one’s house and the CONs or potential problems if it is not installed properly. Reuben also shares his experience in replacing his old water heater with a power vent water heater. 

Tessa then shares different air sealing options for attic trusses and how to properly control the air layers and prevent leakage. Also, she shares her knowledge on how to prevent thermal bridging by putting a little sleeper in-between the foam layer and the roof deck. She mentions Pat Huelman’s research entitled “Project Overcoat: An Exploration of Exterior Insulation Strategies For One-and-a-half Story Roof Applications in Cold Climates” which she considers as a robust system. She discusses a little bit about this program which is called “Building America” which is funded by the US Department of Energy, researchers working towards improving the energy efficiency of our housing stock.



The following is a transcription from an audio recording. Although the transcription is largely accurate, in some cases it may be slightly incomplete or contain minor inaccuracies due to inaudible passages or transcription errors.

Reuben Saltzman: Tessa is here to criticize, condemn, and complain.

Tessa Murray: [laughter] Oh, man, that’s just depressing.

Bill Oelrich: Welcome, everybody, you’re listening to Structure Talk, a Structure Tech presenting. My name is Bill Oelrich, alongside Tessa Murray and Reuben Saltzman. As always, we are back to being a three-legged stool. I asked for and received permission to use my three-legged stool analogy. It’s not like I needed to, but I was… I had a nice LinkedIn conversation with a podcast host who uses a very similar analogy. He does it in terms of business, so… We’re here, a three-legged stool, and on today’s episode we’re gonna talk about some projects that we’ve all been working on, or at least Reuben and I are gonna talk about some projects we’ve been working on, and I’m sure Tessa’s gonna hyper-analyze whether or not we’re doing this right. That’s what’s on tap for today. So why don’t you all say hi, get this thing going.

TM: Thanks for that very nice intro you gave me, Bill. [chuckle]

BO: Was it not kind? 

TM: Just I’ll be picking apart all the things that you guys have worked on.

RS: Tessa is here to criticize, condemn, and complain.

TM: [laughter] Oh, man, that’s just depressing.

RS: No, no.

BO: Actually, Tessa, what it was is an underhanded compliment, is that what you call them? 

TM: I think it’s a back-handed compliment.

BO: Okay, yeah. Tessa, that was a back-handed compliment, because what I know is there isn’t a single house you’re willing to live into, like it won’t meet your standards, but it just happens that we have to live somewhere, so you go inside at some point and just accept the warts that are on that particular piece of property.

TM: Yeah, Bill, it’s a hard life, having a building science mind and knowing about houses, you’re programmed to see the negative. But yes, to that point, the place I’m living in now has some major flaws that I am not okay with, but somehow I’ve learned to live every day with it. So yes, life goes on.

BO: Blood keeps pumping and the air keeps getting exchanged through your lungs, it’s all good, it’s all good. I should tell you guys about one of the reasons I initially came into the home inspection orbit. So I had known Reuben’s dad Neil for a long time before that, but we did some work on our house, and I did a bunch of research and I thought I was doing the right thing, and then I did it and I was like, “Uh-oh, I’m not so sure this was the best decision. So then I had Neil come out, and at the time Neil came out, Barry was… He wasn’t doing anything, so he showed up with Neil, and they began to pick apart my house, which led me down this… I learned a bunch about houses and then I thought, “Well, I know a lot about houses already”, but this was all new and it was great, and then I really started to worry about my house. The more they talked the more I worried. And then I got to the point where I just gave up, I just threw my hands in the air and I said, “It’s old, it’s durable, I can’t ruin it, at least not in the next 25 years, and at that point, I won’t care.” So I just moved on mentally.

TM: I’m glad you feel comfortable about that, Bill, and I don’t wanna burst your bubble, but you actually can ruin your…

RS: Oh, here it goes.

TM: You actually can ruin your house in 25 years, if you do the wrong things to it. You can take a really durable old house and really mess it up these days with a lot of the things that we do to make houses more energy efficient, more airtight, which is I think is something that you’re probably… You’re insinuating when you said you did something and you’re really concerned about what you did. Didn’t you have a project where you did a lot of wholesale spray film in kind of like a slant ceiling area in your house? 

BO: Yeah, and I completely followed the experts’ recommendations. I for once said, “I’m going to get out of the way and not mess with the cooks in the kitchen,” and then I started freaking out afterwards.

TM: In theory, a lot of these energy improvements are really good things in reducing overall air leakage of the house and making it more airtight so it’s more energy efficient, more comfortable, less heat loss, but in reality, in the real world, executing that scope of work perfectly is really hard to do, and in some places, the way that the roof is framed, or say you’ve got a two-by-four framing this attic space and you can’t get adequate insulation in there, you’re still gonna have some snow melt and thermal bridging and then you won’t have any ventilation and… You change all these durability factors by reducing drying potential, by doing all this air sealing work, and you can actually create more problems that you started with. So as long as a house can dry out and you’ve got heat and air flow going through it, it will last hundreds and hundreds of years, but as soon as you start reducing that heat flow and that energy, you can start to rot things out and create big problems.

BO: Well, the whole reason we got onto this topic was because Reuben has been messing around with his house and making it much more vulnerable. Maybe we should let Reuben explain all of the things he’s…

RS: How dare you? How dare you, Bill? This is the follow-up on that podcast where we had Rob Vassallo on, I think we titled that podcast “There’s no such thing as a settlement crack.” We did that a little while ago, and during that episode we talked about solar tubes. Tessa, I challenged you and Rob to talk me out of installing a solar tube in my home. I had already purchased a solar tube the day before, so it was sitting in my garage ready to go in, and you guys did not talk me out of it. And I’ll tell you what, as soon as that podcast was over, as soon as we were done recording, I was on my roof within less than an hour of that podcast, cutting a hole in it to get that thing installed.

TM: Wow.

RS: So I did do it, I installed the solar tube. I’ve installed a handful of them, I’ve put them in every house I’ve owned ’cause I love those things, and I’ve always done the 10-inch, but this time, I went for the big boy, I went for the 14-inch. And four inch difference doesn’t seem like much, but man, that is a difference when you’re working with that thing on the roof and you gotta mess with the flashing kit and all that, it is a lot of work.

TM: You know what, Reuben? Do you wanna describe what a solar tube is to people that may not know? 

RS: Oh, yeah, good point, Tess. Basically, on your roof you’ve got this big dome, it’s a big plastic dome that sticks up above your roof. It connects to a big metal tube that runs down through your attic, and it’s gonna connect to what looks like a light fixture at your ceiling. It’s just this big round thing that mounts on your ceiling, typically they’re gonna be 10 inches or 14 inches in diameter, and it really can look like a light fixture. I’ll never forget the home inspection where there was this agent going all over the kitchen, she was so flustered, I was like, “What are you trying to do?” She was like, “I’m trying to shut that light off.”

TM: [chuckle] Yeah. They do, they do look like light fixtures. I know what you’re talking about. They’re kind of like a round, cylindrical skylight basically.

RS: Yeah. That’s about it. It’s just like a skylight, it lets in tons of natural light and it will brighten up in a big area.

BO: So what room did you put it in? 

RS: There is a second-floor bathroom with no windows in it, so we stuck it in there. It’s always dark. It’s very un-inviting, it’s the darkest room in the house, other than the basement rooms. And now it’s just, I mean, you can see light pouring out of there, it lights up the whole hallway. It’s awesome, I love it. And everybody should get one and you can order them from me at… No.


TM: Well, there’s a lot of pros to them. And I agree with you, they let in natural light, they can brighten up a space. And the only beef I have with them is that, yeah, it’s another potential… Well, you’re poking a hole in your roof and a hole through your ceiling, so it’s potential areas for water to leak in if it’s not flashed properly or you got some other issues. And also the hole from the ceiling to the attic could, if it’s not sealed properly, could allow heat and moisture into the attic in our cold climate and create issues with frost and heat loss and all that. But another thing that can happen too, which I’ve seen in other houses, is people install these solar tubes through a really tiny little attic space where there’s not a lot of volume. And then if you’re not insulating that tube, there’s gonna be some radiant heat coming off of it just from the sunlight, natural sunlight that radiates and heats up that small attic space, and that can actually melt the snow on your roof, which can lead to ice dams. So the recommendation is to air seal around that solar tube where it goes through the attic into the house so you’re not having heat loss and air leakage that way. But then also wrap it in insulation or spray foam it so that you don’t have the radiant heat getting into the attic space and warming up the attic and melting the snow. But you don’t have a tiny attic space, do you? You’ve got a pretty big attic.

RS: No. It’s huge. I had to buy a couple of extenders for this tube to get from the ceiling to the roof in that attic space. So it’s taller than I am, there’s a lot of space, so I really don’t have to worry about ice dams. I’ll send you a picture. My roof is covered with snow and you look on the roof and the snow doesn’t know that this thing exists. I’ll tell you that.

TM: Well good. That’s awesome. Yeah. Yeah. You should post a picture in the show notes, in the podcast notes.

RS: I will. But to your point, Tess, I mean, that is a really good point you bring up. When you have a really tight clearance between your ceiling and the roof, you got a big potential for melt. And I had that at a home that I used to own in Minneapolis, and I ended up… That was the house where I did the hot roof, and at the same time I had them spray the heck out of that whole tube. They insulated all around that whole thing, and despite all of that insulation I would still get snow melting around it.

TM: Really? Wow.

RS: So, just the volume of your attic space makes such a dramatic difference on your potential for ice dams. That’s a good point.

TM: Yep, definitely. Air sealing, insulation and ventilation, and you got all those three things, then you should be fine.

RS: You’d be proud of me, when I was done… In fact, I sent you a picture Tess, when I was all done with this, I used an entire can of Great Stuff, or that foam in the can that you buy at the store, just to foam the intersection between the ceiling and the solar tube, so that is buttoned up tightly. I looked into getting one of those froth packs like you and Rob were trying to talk me into, so I could really properly insulate that tube. But those things are like 200-300 bucks, it is a lot of money for one of those things. And I just said, “You know what, I’m not worried about this, I’m not spending the money on it. I’m calling it good enough.”

TM: And I think in this situation it sounds like it is. There are some attics and some spaces where you might need that or you want that, but in terms of a return on investment you probably won’t see that with your spending the $200-300 on a froth pack.

RS: Exactly. And you know what, let me share this little bit of advice. As I get older, I don’t feel old. I’ll tell you, I felt old when I was going on the roof putting this thing on, because I mean I tried to really follow the installation instructions, it said, “Pull all the shingles off around here”, then they want you to cover up that whole area with ice and water shield and put it over the vent and slide it up and put all the shingles back and caulk the heck out of it. And I mean, it took a while and I’ve got a fairly steep roof, I mean, I don’t know, I think it’s like somewhere between an 8-12 and a 10-12.

TM: Oh wow.

RS: So it’s not comfortable to walk on. But I had my Cougar Paws on so I felt comfortable. And as a home inspector, we can walk around on a roof for 5-10 minutes and we’re cool, but once you’re on there, just standing in the same spot for a couple of hours, it is exhausting. I mean, my legs just felt like jelly, I had to walk down from my roof so slowly when I was done, I was frozen to the core ’cause it was a windy day, my vent blew off the roof too. I lost my flashing kit, had to go find it on the ground, it was just… It was not fun. And I just thought, “You know what, I’m pretty sure this is the last solar tube I ever install.” I had been meaning to do this all year, but I was waiting till it was cool enough to where I wouldn’t die in the attic. And I waited just a little too long, it’s almost like there’s no great temperature. I’d say maybe 50 degrees is perfect. 30 degrees, too cold to be working on your roof, 70 degrees, way too hot to be in your attic.

BO: Where did you get the shingles and didn’t they break when you were trying to put this… Take these shingles off and put them back in? Weren’t they all sealed down? 

RS: I did have to break the seals on them to do this. I used a putty knife, I was very careful, and I used a bunch of the same caulk that I used to seal down the flashing. I used that to re-seal all the nailing strips on my shingles.

TM: Oh. So you just re-used the same shingles? 

RS: Exactly.

TM: Wow.

RS: And if you’re careful and tedious, you can do it. It’s just that’s what took me so long. That’s why I was up there for so long, I was…

TM: Yeah. I didn’t know you had to do the ice and water underneath that too, that…

RS: This was the first one I did that way. On the 10-inch ones I didn’t have to, either that or they changed their installation instructions. But for the Big Mama they required it.


RS: And I just happened to have a roll of ice and water in my garage and I was so thankful I hadn’t thrown it away from my last project, I was like, “Oh good.”

TM: So you were doing all this on a 10-12 pitch without anything but Cougar Paws? 

RS: It might have been a 9-12.

TM: Did your wife see you doing this? 

RS: She’s like, “I don’t want you up there.” I’m like, ‘Anna, you know what I do for a living.” She’s like, “Yeah, you sit in your office all day.”


RS: I’m like, “Yeah, touche. Good one.”

BO: Was it on the tall side where your walkout is? 

RS: No, it’s in between the walkout and the front, so it’s on a semi-tall side.

TM: It would have been a far fall.

RS: Yeah. It would not have been a good fall, it’s way up there.

TM: Wow.

BO: That’s why they have those cherry picker things. I can’t do that, I can’t do that at those roof heights anymore. I just freak out. There’s…

RS: I don’t think I can either. I think this is my last project like that. I mean, I’ll just go walk on the roof for something, but next project I have that’s gonna require more than about 15 minutes on the roof, that is a younger man’s game, or a younger woman’s game.

TM: 6-12 or less for me, if I was doing something like that. I don’t think I’d feel comfortable on anything steeper that high up.

BO: When you’re talking 6 and 10, and I always get those confused.

RS: Yeah, me too. I really don’t know, I’ll measure the slope and/or pitch, and I’ll tell you what it was, and I’ll take a picture, I’ll take a picture of snow around that area. It’s a wonderful project. It brings in a lot of light and it’s a good project to do when it’s not super cold. That’s my two cents on it.

BO: So you’re saying this is a DIY project, it’s not a problem…

RS: It’s an advanced DIY project. It’s not a simple DIY, but it can be done. There’s a couple of really good videos out there showing you step-by-step how to do it on YouTube, how to install a solar tube. There’s one where there’s this woman and she’s got her tool belt on and she’s like, “We’re gonna do this.” and she takes you through it, expertly, through every little step of the a way. And it’s just this petite little thing, and I’m like, “Alright, look at her. Look at her go, she is nailing this and making this look so easy. What am I doing? I’ve already done several of these, why am I considering even hiring this out? This is a piece of cake.”

RS: You know what though? But that’s a contractor who probably has some experience, and she’s also got a camera that can do some edits, so I’m just… Think about all the potential areas where, Here we go again, I’ll be the Debbie Downer. There’s so many people I would not trust to cut a hole in their roof. I’d be afraid that they would cut through a truss, or who knows what they could do, fall off the roof.

RS: I tell you, I must’ve spent probably about an hour laying everything out before getting to the point of cutting that hole. It was a matter of, “Where does it go in the bathroom? Where does it look good? Where are the trusses? Where does it go on the roof? Oh wait, no we got a vent here and it’s up through the attic, crawl onto the other side, back down.” I mean, there was a lot of layout involved before I ever got to the point of cutting a hole.

TM: You know, when Reuben says DIY, for Reuben it might be DIY, but for the rest of the population I feel like that is an expert-level thing. That’s something that you would probably wanna hire out.

RS: Possibly so. I did grow up doing construction.

TM: That helps.

RS: Yeah. Yeah. It does make it different. Well, Bill, what are you working on, man? 

BO: Our biggest project right now is we’re in the planning phases of the cabin. So we have a property way up north, up on the Canadian border, which has been a fun project. But when we bought it, the cabin it was termed “a tear down.” And we had thought, “No, we can save this. We’re gonna milk a few years out of this.” It’s torn down, it’s gone already, the amount of mice that shared the space with us humans got to be a little bit unnerving. In the summer time, they were… We’d go to bed and you’re like, “What?” They were right there. So yeah, so we had to go to the county, we had to start at the county, but the one thing I knew going into it was, “Yeah, we’re close to the water, and I knew there was gonna be some flood zone issues just because of proximity. We can fix those, but it might get a little weird around the cabin with having to bring in some fill or the cabin sticking out of the ground like four feet out of the ground and just looking a little bit goofy.”

BO: That’s not uncommon up there, but when I was told by a mortgage company that I needed flood insurance, I was like, “Oh boy, is this really, really, what I wanna do for the rest of my life is pay flood insurance?” So we’re repositioning the cabin a little bit farther up the hill, but our property out there, we’re locked in by a side yard setback, were locked in by… We can’t go any closer to the lake. And I actually have a municipal sewer easement that goes across my property because we don’t have a septic system on our property, we actually have city sewer. And up there it’s all bedrock, they had to side drill through bedrock and so wherever they did this drilling you can’t build on top of their pipe. Which gave us a really narrow, small footprint to get it in. And I was gonna have to do all kinds of weird things, but now that I’m going up the hill I’ve got a little more room to work with. So we’re in the process of laying out the cabin, I’m working with a contractor, I drew up the plans myself, I’m a draftsman.

TM: Wow. I didn’t know that, Bill.

BO: I’m not good [chuckle], but I kind of understand where everything’s gonna be. And now we’re just in the process of getting it priced out. We were hoping that it would be done kind of middle of the summer, but Rob has got me way… He says, “No way” ’cause I have to dry this thing out for 45 days or something, run a dehumidifier in it.

RS: What a wet rag he is, isn’t he? 


BO: Yeah. Yeah. I’m not sure we’re gonna do that. I mean, I get the logic behind it, maybe we’ll just go slow and get the shell up early and let it sit all summer and then start putting insulation in it later in the year. But right now that’s the biggest thing and…

TM: How many square feet is it, Bill? 

BO: A little under 1,000. It’s like 890-something square feet.

TM: Two bedroom? Or two bedroom and bath? 

BO: Yeah. It’d be two bedroom, two-bath.

TM: Two bath.

BO: But the bathrooms are tiny, they’re just… They’re like… I don’t know.

TM: Yeah. They’re just there for function not for leisure.

BO: That’s right.

RS: Cabin.

BO: Yeah. That’s right. And then there’s gonna be a little loft in it, ladder up to the loft, so no staircase. We don’t have any way to get water there either, unless I wanna drill a really, really deep well. So we need to put a cistern in the crawl space underneath the cabin.

TM: Really? So, I was surprised when you said you’re connected to the city sewer system up there. I thought you were on a septic system. So there’s no city water supply to it? 

BO: No, we’re a little ways away from town, but it was important that they be able to treat the waste around the lake, there’s no pollution going in the lake. And so it made sense to do the municipal sewer but I’m not sure it made sense to bring water out to all these houses. Yeah, that’s all I’m working on. I’m just in planning phases. We gotta wait for frost to get out of the ground, which is, I guess, mid-June in International Falls.

TM: [laughter] You have two months to build. Just kidding.

BO: That’s right.


BO: Tessa, I need to ask you about this building before we move on to something else, because it’s gonna be like a chalet-style roof and I’m not sure how we should insulate the ceiling. I was hoping that we would be able to just do it with cellulose insulation and have enough room, and I was gonna use what are called attic trusses in the area that was gonna be the loft and then we would just use whatever I-Joist or some other material to actually build a vault in our living room area, which would go floor to ceiling. If I’m looking at insulating that space, what’s the best way to approach it? I know we can use batt, I know we can use closed-cell spray foam, and I know we can use cellulose, but if this material is maybe 9 inches maximum thickness on these attic trusses, is that gonna be enough room to get enough insulation into that area to meet our current building standards? 

TM: Gosh, Bill, there’s so many parts to this question. I don’t even know where to start. In terms of building science and building performance, it’s really all about being able to control the air layers and the thermal boundary of the house, and preventing any sort of air leakage between the conditioned space and the unconditioned space, ’cause when you have that air leakage then you have moisture. And you don’t want moisture getting into these tiny little attic spaces ’cause that creates frost, it can rot out your roof deck, it can create all sorts of problems. So it’s really important to have a consistent, what we call, an air barrier, and that’s different from your thermal boundary, which is your insulation layer.

TM: And ideally, in a perfect world, your air barrier and your insulation would be aligned and they would be continuous. You don’t want any breaks in those two layers. So you’re talking about a complicated roof truss, it sounds like. One that, if you picture it, you’ve got this loft space but really the truss is one system that has this cutout in the center for living space. So really, when you think about, it you’ve got almost a story-and-a half-type roof style where you’ve got these almost like a side attic space, like with kind of a triangle-shape attic space, and then you’ve got this slant as you move up, the slant space, and then you’ve got this upper peak, kinda like another triangle attic space, with this truss. And so when you think about it, how do you get a continuous air barrier and thermal boundary when you’ve got one, two, three different attic spaces and lots of different framing angles? How do you get a consistent air-sealed layer and consistent insulation? And the tricky part is building in our frozen tundra, you need a lot of insulation too, ideally.

TM: Our current building code requires an R49. That’s a lot of insulation. So I don’t know how much space you’ll have in those slant areas but that’s the one, probably, challenging space to get enough insulation in those slants to prevent heat loss and air leakage. And even if you do fill those slants, Reuben, I know you had this problem in your story-and-a-half house in Minneapolis, you actually filled those cavities between the rafters with closed-cell spray foam. As much R-value as possible but you still had problems with snow melt. Why? 

RS: Because we didn’t have any type of thermal break for the rafters. Wood is a horrible insulator, and every 16 inches I had a 2 x 4. And we didn’t do anything to stop the cold coming through that or the heat from coming through it.

TM: From leaving, mm-hmm.

RS: So if we had covered the underside, the interior of the whole attic space with maybe one to two inches of rigid foam boards, we probably would have eliminated that, but I didn’t know it at the time.

TM: So Bill, one interesting thing is with these trusses, there’s lots of different air sealing options. The cheapest assembly is a fiberglass batt and poly vapor barrier. But I’d say it’s also probably the riskiest type of assembly, because to get that poly-plastic vapor barrier installed perfectly with no holes, no breaks, no inconsistencies is really difficult on that complicated roof truss design. And the fiberglass batts are kind of… They’re okay, but it doesn’t have the highest R-value per inch. Cellulose, you could use cellulose in the slant areas, and that’s a little bit better R-value per inch and they also kind of… Cellulose will reduce air leakage, it won’t prevent it but it will reduce it more than the fiberglass batt. So it’s a little bit more forgiving in terms of if you have some little breaks in that air barrier and you do have moisture getting up into the space, it’s a little bit more forgiving. But the one product that does the air sealing and the best insulation is the closed-cell spray foam, but it needs to be installed properly and you don’t wanna have any breaks or misses in that either. And once you install that closed-cell spray foam, you still may not be able to achieve that ideal R49 in some of those slant areas.

TM: And so how do you prevent thermal bridging from happening like what Reuben had in his house? Well, you could do rigid foam on the inside or what I’ve seen done on some story-and-a-half houses that had this issue was a layer of rigid foam was actually added to the roof deck on the exterior. So there was actually a double roof deck that was built. You picture your trusses, you spray in the closed-cell spray foam, you put the roof deck on, then you add a layer of rigid foam on top of that, and then you need to actually add another roof deck on top of that, something you can nail shingles to. But the ideal thing is to actually create some air space between the rigid foam and that upper layer of roof deck material so that you can have continuous ventilation underneath that roof-deck to prevent any sort of potential moisture issue or melt issue as well.

TM: So you add these little sleepers in between the foam and the roof-deck. That would be a very robust… As Pat Huelman would say, you’d be proud of me for using this word, robust system, having a consistent air barrier and air sealing through the closed-cell spray foam highest R-value per inch, and then doing some sort of rigid foam on top of that with the continuous ventilation. But probably the most expensive option as well [chuckle]

RS: And if somebody wanted to see what you’re talking about, Tessa, if you google up ThermaCal GAF. Actually, I don’t know if they bought ThermaCal or what, but when I google it up it takes me to GAF’s website, and they have a nice picture of what this looks like where you’ve got basically a roof sheathing sitting on top of little sleepers, and it’s a pre-manufactured product, not that you’d need to buy their product, but just shows you what you’re talking about.

TM: Yeah, and actually, to that point too, so Building America is a program funded by US Department of Energy, and there’s a lot of different researchers across the country that are working towards improving the energy efficiency of our existing housing stock. And actually Pat Huelman from the University of Minnesota, we had him on as a guest, he is working on this project as part of the Northern Star team here in Minnesota, and he’s got some other great people working with him, but there’s a research document about this very thing, Bill. You could look up this paper that he put together it’s called Project Overcoat: An Exploration of Exterior Insulation Strategies For One-and-a-half Story Roof Applications in Cold Climates. It doesn’t get any more scientific or specific than that, but that research paper has some good images and some good research on that system.

BO: I like the looks of this ThermaCal thing, this is very interesting, it looks like it would go on quickly, it’s got tons of venting in it, it’s got this continuous layer, it almost looks to a degree like a SIP. I like the look of it. I’m not gonna be there when all this stuff is going on, and I was thinking to myself that maybe the easiest product to use would just take your normal floor joist that has all that open webbing and just use those as your roof trusses and then blow in all kinds of cellulose insulation into that, and somehow make sure you have enough of an air gap at the top and just plug that up with cellulose and you’d probably get close. How many inches of cellulose do you need to get to an R49? 

TM: Well, what is cellulose? Is it like an R3.5 per inch? So, what is that? 

RS: Yeah, that’s right. I have to bust out the calculator…

TM: Yeah, me too.

RS: 49 divided by 3.4…

TM: Three and a half.

RS: 14 inches, 14…

BO: That’s a lot. That’s a big thick floor choice up in your roof. So I don’t like that idea.

TM: Some people might say, “Well, why wouldn’t you just use a SIP panel?” Those panels that are… You’ve got the rigid decking on the exterior, and rigid on the inside, the structure on both sides, and then the insulation in the middle sandwiched in between, and I’ve seen them used in our cold climate here, and I actually have seen more failures than I’ve seen successes with them. And the problem is with our extreme temperature swings here in Minnesota. It gets really cold in the winter and it’s warm inside, and so you get different expansion-contraction rates of the inside panel and the exterior panel, and what happens is those seams between the panels become weak points, and eventually what will happen is those seals will fail at the seams, and warm humid air will get in between the panels and basically rot out the wood structure on the interior and exterior of those panels at the seams. When I worked for that insulation company, the Home Performance company, years ago, we had a huge project on a SIP panel house that had all these failures on it, and it was a really expensive project to fix that, like hundreds and hundreds of thousands of dollars to redo those seams on those SIP panels. And it’s a fix, but I don’t even know if it’s a guaranteed fix and for how long it will last, so…

BO: How would you feel about using that I-Joist material with spray foam? Would you feel at all comfortable like that webbing is durable enough if it ends up getting wet, and/or would you want more of a solid wood surface that could be a little more durable if it ever did get wet for whatever reason? 

TM: Well, instead of prioritizing the durability of products, I would first try and prioritize reducing the potential for moisture and air getting into that space in the first place. So doing some sort of… If you did a layer of closed-cell spray foam against the lid to achieve that consistent air barrier and vapor barrier then I’d be less concerned about what material you have in the attic or for the framing, if you did that. ‘Cause then that’s gonna reduce the potential for moisture getting up there in the first place, and then having some sort of ventilation in that space will help too. But to answer your question, the composite wood materials that we use today are not as durable as a solid piece of wood from a tree that was cut down 100 years ago. Reuben, you’ve got a nickname for a lot of the composite wood products that we use today. What do you call that stuff? 

RS: I just stole that from Don Sivigny at the Minnesota Department of Labor and Industry. He calls it “was wood”

TM: Yeah.

RS: ‘Cause it used to be wood, at one time it was wood.

TM: It was wood.

RS: And now it’s something completely different.

TM: Yeah. The problem with that stuff is… You’re talking about the wood I-Joists and stuff, it’s made up of chunks of wood glued together and pressed, and when that stuff gets wet it turns to mush.

BO: Last question on this topic and we can move on, ’cause my head is spinning in this planning phase already. Have you seen where somebody will come in with just three quarters of an inch of rigid styrofoam and they’ll put that up as if it were drywall on all of the vaulted area, then go to the outside, spray in that spray foam to give you that continuous layer of protection that you’re talking about, then put the roof-deck down? Or is that like a backwards installation? 

TM: I’ve never seen that, but I think you could do it. And that’s what… Reuben, you were talking about doing that in your story-and-a-half house. You wish you would have put rigid foam on the interior to reduce the thermal bridging.

RS: That’s not what I was thinking of, I just had to think through what Bill was describing and it makes a lot of sense. But wait a minute, no, you can’t do it that way, Bill. I’m sorry, no. The reason being is the building code only allows you to do a hot roof if that insulation is applied directly to the roof decking. So it’s a solid no, it’s not an option.

BO: It wouldn’t be a hot roof, because the spray foam would be built up from the bottom chord of your truss up, leaving an air gap for ventilation.

RS: You wouldn’t fill that whole space, you’d still have it vented? Oh, well then I suppose you could.

TM: Yeah, in theory I guess, having the rigid foam in the inside, being your thermal break between the wood framing and the inside, and then having a spray foam applied directly to the back of that, consistently across all of that framing would create a consistent air seal. And then you could use a cheaper, less expensive insulation to kind of achieve the required R-value if you had enough space. That’s what a lot of people do. I can’t think of a single house, if you had a large attic where you’d would want to fill the whole floor of the attic with a closed-cell spray foam, just because of the cost of it. Yeah, and it doesn’t make sense. You spray two inches of it to get your vapor barrier and your air seal, and then you blow in a less expensive insulation on top of it to achieve your R-value. So if you’ve got a huge attic space, well, that’s the way to go.

RS: Not only the materials and all the expense, but the time. Because with that stuff you can’t install more than, what is it, two inches of insulation at one time? 

TM: One pass or whatever, yeah.

RS: Yeah, because you gotta let it cool off, and if you just try to build it all up, it’s gonna get too hot. It’s… What is it, it’s a exothermic reaction or something? 

TM: Yeah.

RS: And then you can actually start houses on fire by doing that. It gets crazy warm. And how long in between each pass do you need to let it cool down, Tess? 

TM: Well, if you’re spraying it just one pass at a time, it doesn’t take too long. I don’t have the exact number on that, we should have a spray-foam expert on. But I’ve seen contractors kind of do one pass on one wall, and then once they’re done, head back and start again and do it. So there’s strategy to it, and you have to be careful.

RS: I question if that’s okay or not [chuckle]

TM: I don’t know. Yeah I’ve never seen a house start on fire but I’ve heard it happens.

RS: We’ll get a spray-foam expert on here. Yeah.

TM: We should.

RS: Yeah, good idea.

BO: I’m currently thinking about eliminating the loft area and just have a normal roof, because this is turning into a pretty complicated project.

TM: [chuckle] You know what, here’s the thing about building science, the simpler the better. The simpler the roof design, it’s so much easier to get a perfect air seal and good insulation and good ventilation. The simpler, the better. The more complicated your roof lines, the more dormers you get, the more vaults you have, the more side attics, the more slants, the more complicated it gets to create a consistent thermal boundary, and air boundary, and pressure boundary.

RS: Yeah, you’re going balls-out complicated, Bill.

BO: Never met a project I didn’t want to complicate.


BO: What else you guys working on? 

RS: Well, I can tell you, Tessa, you’d be happy about this one. I told you about the solar tube, and I knew I’d get crap from you on that, but I just replaced my water heater and you’ll be happy to know I replaced it with a power vent water heater. I know you love them.

TM: Hey! I’m so proud of you, Reuben. What made you do that? 


RS: Isn’t that great? The fact that the last one was a power vent.

TM: [laughter] Oh okay, okay. I thought you would say something like, “Well, you know, my last one was backdrafting. I was worried about my kids and my wife’s health and the risk for backdrafting and carbon monoxide,” but…

RS: It wasn’t any of that. It was just the fact that I didn’t really have a choice, I had to go power vent. And I’ll tell you what though, you guys, with those power vent water heaters, I was trying to get one with a 12-year warranty, ’cause I was replacing one with a 6-year warranty, it doesn’t exist. They don’t make power vent water heaters with anything other than a 6-year warranty. And I was super annoyed by that, because here in Maple Grove all of our water heaters fail after six, seven, eight years. That’s all they last. I’ve helped several neighbors replace their own water heaters at the seven-year mark, ’cause our water is horrible. So I thought, “Well, I’m going 12 years this time.” Nope, no such luck. Can’t do it. I will say though, that I went to Home Depot to get my water heater and you can buy an extended warranty from Home Depot. It extends the manufacturer’s warranty by 5 years or something, and the cost was $70. And now if anything…

TM: That’s it? 

RS: That’s it.

TM: $70 for five years? 

RS: Yes, yes I couldn’t believe it. I felt like I was stealing from them purchasing this warranty.

TM: Yeah, wow.

RS: I would have paid a lot more for it. And so now if anything goes wrong with this… And get this, here’s the kicker, it covers the installation cost next time.

TM: Oh my gosh.

RS: They will do it themselves. And I mean, I read that fine print, ’cause I was like, “No, this cannot be.” Yep, that’s really what it is. So my advice is if you’re in an area with really bad water, get your water heater from Home Depot and buy that warranty. They are going to be paying through the nose when the time comes. This is a fairly new program that they have, ’cause I know the last time I got a water heater from them, they didn’t have this.

TM: That’s interesting. Well, as soon as the word gets out and people start doing this, that program might go away, so get it while you can.

RS: Exactly. I will say, this water heater replacement did not go smoothly. I’ve replaced a lot of water heaters for myself and friends and family, and usually it’s pretty quick and easy, throw in a couple of unions at the top to make it easier for the next person. But on this one somebody had already replaced the water heater, and they had made cuts in the copper tubing, and they had soldered new pieces in, so there was nowhere I could make a nice clean cut. I had to go way back to the beginning, and I had to put in all this new copper tubing, and it was just… It was a pain in the butt. And even today, Minnesota now allows those flexible connectors to connect to your water heater, and I thought, “You know what, I don’t wanna mess with all this sweating. I don’t wanna solder new pipes. I’m just gonna get a couple of these flex guys and call it a done deal.” The way it worked out was there was nowhere to put them where it was the right length, either it was too long or too short, and I had to kink them to get them to connect to the water heater. So I ended up having to return them and spend an extra hour and a half sweating pipe. I’m sure it would have taken a competent plumber like 10 minutes to do it, but a competent plumber I’m not. I can do enough to get by, and it’ll work and not leak, but it takes me a long time. And what a pain in the butt it is.

TM: So you’re saying this project took you probably like, what, three hours instead of an hour and a half? 


RS: Yeah, maybe even four hours. Yeah, it was a trip to the store to get the water heater, and then another trip to get more copper fittings that I didn’t originally anticipate needing. It’s like you gotta have a gofer, I can’t wait till my kids are old enough where I can send them to the store for this stuff. That’ll be a…

BO: I’d have a very low confident threshold if I sent my kid to the store to pick up anything related to hardware. I can’t even figure out what I need. I go buy multiple things, and then bring them all home, sort through it, and return everything that I didn’t use, just so I didn’t have to go back and forth four times.

RS: Man, I remember working at returns at Home Depot, and you would come in, Bill, and you would come in with about a year’s worth of leftover projects, and it’s like a huge cart just filled the bags and bags, and they’re all different trips and there’s a receipt in every one of the bags. And it’s like 20 trips over the last year and Bill returning everything that’s left over. And they’d just turn around and they’d apologize to the people in line like, “Yeah, sorry you might wanna read a book or something, this is gonna be a while.” It was always the worst.

TM: That sucks [chuckle]

BO: But you take them… HD takes everything back, so that’s one more reason to shop there. They never give you any grief, no matter how long you’ve had it.

RS: It’s so much easier now when you swipe your credit card. This was back in the day where you had to have all your receipts. Oh my goodness, what a pain in the butt that was. At least we’ve made some progress. You know, on another podcast we ought to talk about Home Depot’s old return policy. Did you guys ever know about their old return policy, where you could return anything and get cash back? 

TM: No.

BO: Yes.

RS: Yes, yes. Back when I started at Home Depot in ’99 that was the policy. You return stuff with a valid ID and they will give you cash back for your return. And you can only imagine the type of people that brought in, and the stuff that they were returning. It… Oh, man, I got so many stories.

TM: Oh my gosh.

RS: But that’ll be for another day.

TM: Yeah, that sounds good.

BO: Well, we should probably put a wrap on this one. We’ve been rambling on, especially about very technical stuff in the attic, in the trusses, and getting that right. So thank you, Tessa, for sharing your expertise again. I’m more frightened than I was before we started this conversation.

TM: You’re welcome. Reuben, what did you say I was good at, the three Cs? Criticism…

RS: Criticizing, condemn, and complain.

TM: There you go, check, check, and check.

RS: Yes, you did all of them, good job, Tess.

BO: Alright, the day we’re working on the roof I’ll make sure you’re on the job site, keeping track of the guys and the ladies, I’m not sure what the crew looks like. But you need to be there because surely it’ll get done, but I’m not sure it’ll be up to your standards.

TM: Gosh, I don’t mean to crush the hopes and dreams of you, Bill, or of this cabin, but building science is a real thing. When you’re talking about vaults in a cold climate, then it’s pretty risky.

BO: So I’m gonna let everybody just ponder that thought, how risky vaults are in a cold climate. Thanks, everybody, for listening. You’ve been listening to Structure Talk, a Structure Tech presentation. My name is Bill Oelrich. That person you just heard laughing is Tessa Murray, and Reuben Saltzman is there, still flexing his knees from the four hours he spent on his roof putting in the new solar vent.

RS: Amen.

BO: Thanks for listening, everybody. We’ll catch you next time.

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