kimchi & kraut

Passive House + Zero Net Energy + Permaculture Yard

Tag Archives: Roxul

Siding Part 1: Continuous Insulation with a Rainscreen

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Continuous Insulation vs. Double-Stud Wall

Although builders can make either approach to high-performance walls work, we decided continuous insulation (or CI for short) made the most sense to us. And while continuous insulation has its own challenges, especially in terms of air and water sealing details around windows and doors, intuitively we felt insulation on the outside of our sheathing would give us our best chance at long-term durability for the structure.

In spite of the fact that these kind of wall assemblies are climate specific, for anyone interested in the performance of various wall assembly approaches this BSC paper is an excellent place to start:

 

High R-Walls

 

Or you can check out Hammer and Hand’s evolving wall assembly strategies here:

 

Passive House Lessons

 

And here’s a mock-up wall assembly by Hammer and Hand showing many of the details we incorporated into our own house:

 

 

While many believe a double stud wall simplifies much of the framing, we decided that a continuous insulation approach, which in theory should better manage seasonal moisture changes inside the walls while it also eliminates thermal bridges, was worth the extra effort.

 

 

2 Layers of Rockwool over Zip Sheathing

Based on the drawings from our original builder, Evolutionary Home Builders, who was going to use 3.75″ inches of rigid foam, and the recommendations of both PHIUS and Green Building Advisor for our climate zone 5 location (leaning heavily towards PH performance), we decided to go with 4″ of Rockwool Comfortboard 80 on top of our Zip Sheathing.

For more information regarding how we came up with the specifics of our wall assembly, go here:

Wall Assembly

 

 

Finding Subcontractors for a Passive House

In the Chicagoland area it’s still a struggle to find builders or subcontractors who are knowledgable about, or even interested in, “green building”. In fact, despite our well-documented experience with Evolutionary Home Builders, clients continue to hire Brandon Weiss (Dvele and Sonnen) and Eric Barton (apparently now on his own as Biltmore Homes, or Biltmore ICF) presumably because the options here in Chicago remain so limited. We assume this is the case because we still get the occasional email from current or former clients who have also had a negative experience working with Brandon or Eric. In addition, even though PHIUS has dozens of certified builders and consultants listed for Illinois and the larger Midwest region, it’s unclear just how many of them have worked directly on an actual Passive House project.

Until there’s more demand from consumers, or the building codes change significantly, it’s difficult to imagine the situation improving much in the near future. This is unfortunate since particularly here in the Chicago area, or the Midwest more broadly, homes could really benefit from the Passive House model, or something close to it, e.g. The Pretty Good House concept, because of our weather extremes (dry, cold winters and hot, humid summers). The combination of meticulous air sealing, high R-values, and continuous ventilation associated with any high-performance build is hard to beat in terms of day-to-day occupant comfort, not to mention the significant reduction in both overall energy demand and the cost of utilities.

In our own case, when I think of all the individual trades we had to hire, securing a siding contractor was far and away the most difficult. Our HVAC contractor for the ductless mini-splits was already somewhat familiar with “green” building and PH, so working with me on air sealing details and dealing with a thick wall assembly didn’t worry him. Also, if I had it to do over, I don’t think I’d bring up all the PH details with a plumbing or electrical contractor when getting bids since the air sealing details are pretty straightforward and can easily be planned for and executed on-site after they begin their work (assuming someone else, most likely a rough carpenter, GC, or homeowner is tasked with all the air sealing chores). And if the concrete sub is unfamiliar with insulation under a basement slab, or over the exterior walls of the foundation, then it’s easy enough for framers, or even homeowners if necessary, to do this work, along with installing a vapor barrier like Stego Wrap before the basement slab gets poured.

For siding, however, because of the level of detail involved before the siding itself could be installed, it was a real challenge to even get quotes. As things turned out, we had nearly twenty contractors (a mix of dedicated siding contractors and carpenters) visit the job site before we received an actual estimate. Many of those who visited the job site expressed genuine interest, most going so far as to acknowledge that this kind of wall assembly made sense and would probably be mandated by the residential code at some point in the future, but almost without exception they would disappear after leaving the job site — no bid forthcoming, and no response to my follow-up phone calls or emails.

Clearly they were terrified, not without justification, to tackle something so new, viewing our project through a lens of risk rather than as an opportunity to learn something new. From their point of view, why not stick with the type of jobs they’ve successfully completed hundreds of times in the past? It also didn’t help that I was a first time homeowner/GC, rather than a GC with a long track record of previously built homes in the area.

In addition, not only is continuous insulation over sheathing a novel concept in the Chicago area, especially in residential builds, even utilizing a ventilated rainscreen gap behind siding is almost unheard of — typically Hardieplank lap siding is installed directly over Tyvek or similar housewrap (this can be observed directly on hundreds of job sites across the city and suburbs). And this isn’t entirely the fault of contractors. For instance, how many homeowners when presented with the idea of continuous insulation, or a rain screen gap, balk at the extra costs associated with these techniques without carefully considering the potential energy savings or increased durability for the structure?

While there are any number of certified LEED projects in our area, and even some Passive House projects (both residential and commercial) in Chicago and the surrounding suburbs, for the most part consumers are still largely unaware of Passive House or other “green” building standards like Living Building Challenge. Clearly “green” building, let alone Passive House, has its work cut out for it here in the Midwest if it ever hopes to have a meaningful impact on the construction industry.

 

 

Installing Rockwool over the Zip sheathing

Mike Conners, from Kenwood Passivhaus, was nice enough to recommend Siding and Window Group, which definitely got us out of a jam. Thankfully, Greg, the owner, was up for the challenge and was nice enough to let us work with two of his best guys, Wojtek and Mark.

Initially Wojtek and Mark dropped off some of their equipment at the site the day before they were to start work on the house. This gave me a chance to go through many of the details with them directly for the first time. Although a little apprehensive, they were also curious, asking a lot of questions as they tried to picture how all the elements of the assembly would come together. In addition to the construction drawings, the series of videos from Hammer and Hand regarding their Madrona Passive House project were incredibly helpful (this project in particular was a big Building Science inspiration for us).

 

 

 

 

Also, this video from Pro Trade Craft helped to answer some of the “How do you…?” questions that came up during the design and build phases:

 

 

As sophisticated and intricate as some architectural drawings may be, in my experience nothing beats a good job site demonstration video that shows how some newfangled product or process should be properly installed or executed.

On the first day, while Wojtek and Mark installed the Z-flashing between the Zip sheathing and the foundation, along with head flashings above the windows and doors, I started putting up the first pieces of Rockwool over the Zip sheathing.

 

installing head flashing above wdw

We found it easier to embed the metal flashings in a bead of Prosoco’s Fast Flash. Once in position, an additional bead of Fast Flash went over the face of the flashing, ensuring a water tight connection between the metal and the Zip sheathing.

 

For the first layer of Rockwool we installed the pieces horizontally between studs as much as we could, knowing that the second layer of Rockwool would be oriented vertically. This alternating pattern helps to ensure seams are overlapped between layers so there aren’t any areas where the seams line up, an outcome that could undermine the thermal performance of the 2 layers of Rockwool.

 

z flashing nw corner

Z-flashing carried down over the exposed face of the Rockwool on the outside of the foundation walls — once installed, the gravel is pushed back so it covers the area where the flashing terminates on the face of the Rockwool. The other 3 sides of the house had much less exposure in this foundation-gravel border connection.

 

We didn’t worry too much about the orange plastic cap nails missing studs since they were sized to mostly end up in the Zip sheathing. In the end only a couple of them made it completely through the Zip without hitting a stud.

 

1st pcs rockwool going up n side

Putting up the first pieces of Rockwool on the north side.

 

Every so often Wojtek would come around the corner and watch what I was doing before asking questions about specific elements in the wall assembly.

 

orange cap nails for 1st layer rockwool

Plastic cap nails we used to attach the first layer of Rockwool. I purchased these from a local roofing supply house.

 

By the time I had about a quarter of the north side covered, Wojtek and Mark were ready to take over from me.

 

1st layer rockwool n side

First layer of Rockwool mostly complete on the north side. Before installing the bottom row of Rockwool we used shims to create a slight gap between the Rockwool and the metal Z-flashing on the foundation insulation to allow any water that ever reached the green Zip sheathing a clear pathway out.

 

In a pattern that would repeat itself with each layer of the remaining wall assembly, Wojtek and Mark would carefully think through the details as they progressed slowly at first, asking questions as issues arose, before getting the feel for what they were doing and eventually picking up speed as they progressed around each side of the house.

 

20171002_081038

Outside corner showing the Z-flashing covering the face of the Rockwool on the foundation with the first layer of Rockwool covering the Zip sheathing above.

 

Working through the many details with Wojtek and Mark — the majority of which occur at junctions like windows and doors, the top and bottom of the walls, along with mainly outside corners — was both collaborative and deeply gratifying. They demonstrated not only curiosity and an ability to problem solve on the fly, they also clearly wanted to do things right, both for me as a customer and for the house as a completed structure (it felt like both aesthetically and in building science terms).

 

1st layer rockwool at wdw buck

First layer of Rockwool meeting up with a plywood window buck. We tried to keep connections like these as tight as possible, especially since the window buck itself already represents a slight thermal bridge.

 

They never hurried over specific problem areas, arrogantly suggesting they knew better, instead they patiently considered unanticipated consequences, potential long-term issues, and actively questioned my assumptions in a positive way that tried to make the overall quality of the installation better. This mixture of curiosity, intelligence, and craftsmanship was a real pleasure to observe and work with.

 

starting 2nd layer rockwool n side

Mark and Wojtek beginning the second layer of Rockwool on the north side.

 

If a GC built this level of rapport with each subcontractor, I can certainly understand their refusal to work with anyone outside of their core team — it just makes life so much easier, and it makes being on the job site a lot more fun.

 

2nd layer rockwool at utilities

Second layer of Rockwool installed around mechanicals. Note the sill cock, or hose bibb: although it runs into the house, we left it loose so that it could be adjusted until the siding was complete — only then was it permanently soldered into place.

 

 

weaving outside corner w: 2nd layer

Weaving the seams at the outside corners to avoid undermining the thermal performance of the Rockwool.

 

 

2nd layer rockwool fastener at wdw

Close-up of the fasteners we used to attach the second layer of Rockwool.

 

For the second layer of Rockwool, Wojtek and Mark tried to hit only studs with the black Trufast screws. In fact, screwing into the studs with these fasteners, in effect, became a guide for accurately hitting studs with the first layer of strapping.

 

plates for 2nd layer rockwool

 

These Trufast screws and plates worked well and were easy for Wojtek and Mark to install.

 

trufast screw bucket

 

 

inside bucket trufast screws

The Trufast screws and plates were purchased from a local roofing supply house.

 

 

w side 2 layers rockwool

West side of the house with 2 layers of Rockwool complete.

 

 

1st layer rockwool into s side garage

First layer of Rockwool filling the gap between the house and garage framing.

 

If our lot had been larger, we would’ve gone with a completely detached garage, but unfortunately it just wasn’t an option.

 

2nd layer rockwool closing gap at garage

Second layer of Rockwool closing the gap between house and garage completely, ensuring our thermal layer is unbroken around the perimeter of the house.

 

 

nw corner 2 layers rockwool

Northwest corner of the house with the 2 layers of Rockwool installed.

 

It was exciting to see the house finally wrapped in its 4″ of Rockwool insulation.

 

 

Installing Battens and Creating our Rainscreen

Initially we were going to use 2 layers of 1×4 furring strips (also referred to as strapping or battens); the first layer installed vertically, attaching directly over the 2×6 framing members through the 2 layers of Rockwool and the Zip sheathing, with the second layer installed horizontally, anticipating the charred cedar that would be oriented vertically on the house.

Pro Trade Craft has many really informative videos, including this one on using a rainscreen behind siding:

 

 

Nevertheless, as the second layer of Rockwool went up, Wojtek and Mark pointed out that putting the siding in the same plane as the Rockwool/metal flashing on the basement foundation would be needlessly tricky. In other words, maintaining about a 1/8″ horizontal gap between the bottom edge of the vertical siding and the metal flashing on the foundation around the house would be nearly impossible, and any variation might prove unsightly.

As a solution, we decided to use 2×4’s for the first layer of strapping. By adding to the overall thickness of the remaining wall assembly it meant the eventual siding — now pushed slightly out and farther away from the Z-flashing covering the face of the Rockwool on the foundation — could be lowered so that visually it slightly covered what would’ve been a gap between the top of the metal flashing on the foundation insulation and the bottom edge of the siding. Wojtek and Mark also found that the 2×4’s were easier to install than the 1×4 furring strips directly over the Rockwool so that it didn’t overly compress the insulation (an easy thing to do).

Unfortunately, increasing the overall wall thickness with 2×4’s meant having to use longer Fastenmaster Headlok screws (it would also cost us later when it came to the siding on the north side of the house — more on this later). Apart from this change, the additional overall wall thickness mostly just increased the air gap in our rainscreen, which arguably just increased potential air flow while also expanding the drainage plane behind the eventual siding.

 

 

In one of the Hammer and Hand videos Sam Hagerman mentions that at least 1.5″ of screw should be embedded into the framing (excluding the thickness of the sheathing) for this type of wall assembly, but when I asked a Fastenmaster engineer about this directly he recommended a full 2″ of their screws should be embedded into the framing members in order to avoid any significant deflection over time.

As a result, we ended up using 8.5″ Headlok screws. The screws work incredibly well, requiring no pre-drilling, and they’re fun to use with an impact driver (keep your battery charger nearby). Along with the plastic cap nails and Trufast screws, I think we ended up with less than a dozen fasteners that missed the mark for the entire house — a testament to Wojtek and Mark’s skill. I was able to seal around these errant fasteners from the inside with a dab of HF Sealant.

 

headlok missed framing

Sealing around a Headlok screw that missed a 2×6 framing member.

 

During the design stage, using these longer screws prompted concerns regarding deflection, but based on this GBA article, data provided by Fastenmaster, along with some fun on-site testing, the lattice network of strapping (whether all 1×4’s or our mix of 2×4’s and 1×4’s) proved to be incredibly strong, especially when the siding material is going to be relatively light tongue and groove cedar.

For the garage, since insulation wasn’t going to cover three of the walls (only the common wall with the house was treated as part of the house wall assembly), we used significantly shorter Headlok screws for the first layer of furring strips.

 

monkey on furring strips

The Beast testing out the structural integrity of our strapping on the garage. Note the Cor-A-Vent strip below the bottom horizontal furring stip, helping to establish a ventilated rainscreen.

 

 

garage only 2x4s

Common wall inside the garage. Only a single layer of strapping was necessary in preparation for drywall.

 

Mark took the time to recess these screws to make sure they didn’t interfere with the eventual drywall.

 

recess 4 screws

Recessed Headlok screw on a 2×4 in the garage. Ready for drywall.

 

A small detail, but one of many examples showing Wojtek and Mark’s attention to detail, not to mention their ability to properly assess a situation and act appropriately without having to be told what to do.

Once the 2×4’s were all installed vertically through the structural 2×6’s as our first layer of strapping, Wojtek and Mark could install the components of the rainscreen, including the Cor-A-Vent strips at the top and bottom of the walls, as well as above and below windows and doors. In combination with the 2×4’s and the 1×4’s, this system creates a drainage plane for any water that makes its way behind the siding, while also providing a space for significant air flow, speeding up the drying time for the siding when it does get wet.

 

rainscreen2.jpg

Why use a rainscreen? Illustration courtesy of Hammer and Hand.

 

In addition to the Cor-A-Vent strips, we also added window screening at the bottom of the walls just as added insurance against insects. We noticed that on the garage, even without any insulation, the Cor-A-Vent didn’t sit perfectly flat in some areas on the Zip sheathing. Since the Rockwool on the foundation, now covered by the metal flashing, was unlikely to be perfectly level, or otherwise true, along any stretch of wall, it made sense to us to double up our protection in this way against insects getting into the bottom of our walls at this juncture.

 

starting 1x4s n side

1×4’s being installed horizontally on the north side in preparation for the charred cedar that will be installed vertically. Also note the Cor-A-Vent strips just above the foundation and below the window.

 

 

cor-a-vent-product-label

The main product we used to establish our ventilated rainscreen.

 

 

insect screen for rscreen

Window screen we cut to size for added insurance at the bottom of the walls around the Cor-A-Vent strips.

 

Wojtek and Mark also did a nice job of taking their time to shim the 1×4 layer of furring strips, thus ensuring a flat installation of the charred cedar.

 

shims behind 1x4s

Shims behind some of the 1×4 furring strips to ensure a flat plane for the vertical cedar siding.

 

This really paid off, not only making their lives easier when installing the tongue and groove cedar, but also providing aesthetic benefits in the overall look of the siding. This was especially true on the north side of the house, which has the largest area of charred siding with almost no interruptions, apart from a single window. It’s also the tallest part of the house, so without proper shimming the outcome could’ve been really ugly. Instead, once the cedar siding was installed it was impossible to tell there was 4″ of Rockwool and 2 layers of strapping between it and the Zip sheathing.

Really impressive work by Wojtek and Mark.

 

lking down furring behind rscreen at fdn

Looking down behind the ventilated rainscreen — 2×4, 1×4, with Cor-A-Vent and window screen at the bottom, just above the top of the foundation. This gap behind the siding provides ample air flow for the cedar siding, ensuring that the wood never remains wet for long.

 

 

rscreen furring at foundation

Strapping and rainscreen elements around a penetration near the top of the foundation.

 

Things got somewhat complicated around windows and doors, but once we worked through all the details for one window it made the remaining windows and doors relatively straightforward to complete.

Below you can see all the elements coming together: the window itself, the window buck covered with tapes for air and water sealing, the over-insulation for the window frame, the Cor-A-Vent strip to establish air flow below the window and behind the eventual cedar siding, along with the strapping that both establishes the air gap for the rainscreen while also providing a nailing surface for the siding.

Once most of the siding was complete around each window, but before the 1×6 charred cedar pieces used to return the siding to the window frames were installed, each window received a dedicated metal sill pan. The pan slid underneath the bottom edge of the aluminum clad window frame and then extended out just past the edge of the finished siding (I’ll include photos showing this detail in the next blog post about installing the charred cedar siding).

Here’s a JLC article discussing a couple of options for trim details in a thicker wall assembly with similar “innie” or “in-between” windows:

 

Window Trim

 

And here’s a detailed slide presentation by Bronwyn Barry regarding details like these for a Passive House wall assembly:

 

Sills and Thresholds – Installation Details

 

wdw rscreen and frame detail

The many details coming together around a window. In addition, each window eventually received a dedicated metal sill pan as a durable way to ward off water intrusion.

 

 

from int wdw rscreen and sill

Looking through an open window to the sill and the rainscreen gap at the outside edge. Note the Extoseal Encors protecting the sill of our window buck.

 

 

lking down wdw rainscreen

Outside edge of the window sill, looking down into the mesh of the Cor-A-Vent strip with daylight still visible from below.

 

 

rscreen at hd flash on wdw

Head flashing at the top of a window with doubled up Cor-A-Vent strips above it.

 

 

out corner hd flshng ready for sd

Same area, but with a 1×4 nailed across the Cor-A-Vent, creating a nailing surface for the cedar siding.

 

Many of the same details were repeated at the top and bottom of our two doorways. Below is a close up of the kitchen door threshold with Extoseal Encors and Cor-A-Vent again, along with additional metal flashing. Once a dedicated metal sill pan was installed (after most of the siding was installed), it felt like we did everything we could to keep water out.

 

kitch dr prepped 4 sd

Many of the same air and water sealing elements and rainscreen details present around the windows ended up at the top and bottom of doors as well.

 

In the photo below, you can see the many elements we utilized to try and prevent moisture damage around the front porch. For the door buck itself, I applied Prosoco’s Joint and Seam, both at joints in the plywood and the plywood/Zip sheathing connection, but also between the concrete and the door buck, as well as between the Rockwool and the concrete. We also kept the 2×4’s off the concrete, while also using the Cor-A-Vent strips to establish a ventilated rainscreen so that any moisture that does get behind the siding has ample opportunity to dry out in this area before it can cause any rot.

 

frt porch prep - rscreen water

Front porch: elements in place to try and prevent moisture damage.

 

 

west w: 2 layers battens

West facade prepped for siding.

 

 

flashing details on porch

Wojtek and Mark did a nice job with all the metal flashing details around the house — these kind of areas are the unsung heroes of a structure that manages water safely, and unfortunately go largely unnoticed by most homeowners.

 

In the next blog post I’ll go through the details for the top of the ventilated rainscreen when discussing how the charred cedar siding was installed.

 

Mark and Wojteck at front door

Mark and Wojtek installing Cor-A-Vent above the front door.

 

Even without the siding installed yet, it was especially rewarding to see all the underlying prep work involved in finishing our thermal layer and rainscreen come together so nicely.

 

Mark and Wojtek on the roof

Mark and Wojtek on the garage roof finishing up the battens for the front of the house.

 

Many thanks to Wojtek and Mark for executing all these details with such skill!

Basement Slab (Air Sealing #5)

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The Bottom of our Thermal Envelope

Following Passive House principles, we knew we were going to insulate and air seal our basement slab. As explained on the Passipedia website:

“The most important principle for energy efficient construction is a continuous insulating envelope all around the building… which minimises heat losses like a warm coat. In addition to the insulating envelope, there should also be an airtight layer… as most insulation materials are not airtight. Independently of the construction, materials or building technology, one rule is always applicable: both insulation and airtight layers need to be continuous.”

 

airtightness_with_logo

Illustration courtesy of: passipedia.org

 

The illustration above also shows the “red pen test”, which is supposed to occur in the design phase of a project, when it’s much easier to address weaknesses or errors in the details of a design — not necessarily just for air sealing, it’s also effective when looking for points of potential water intrusion (e.g., this GBA article), or even to test the thermal layer for areas of thermal bridging. The basic idea is that if your layers aren’t continuous you’ll find yourself lifting your red pen, meaning it’s an area that needs to be addressed.

An effective way of thinking about a structure, utilized by high-performance builders, is to think in terms of 6 sides rather than just 4 when contemplating the details for air sealing and insulating: 4 walls, the attic/roof, and the basement (or frost-protected slab).

A similar approach to Passive House for building high-performance structures is adopted by advocates of The Pretty Good House concept, even if it’s less stringent, more open to interpretation, and tends to be more “rule of thumb” rather than energy model driven (e.g. PHPP or WUFI).

Based on our climate region, which is Zone 5, we decided we wanted to shoot for 16/20/40/60 for insulation R-values — the series of numbers represent R-values for under the basement slab/ the exterior foundation walls/ framed exterior walls/ and the attic (our attic R-value proved to be significantly higher than 60, but more on that later) — which is in the ballpark for both PGH and Passive House (here’s an excellent overall summary of the PH concept I recently came across: EcoCor).

Arguably, the “sweet spot” for how much insulation makes sense for these areas, even when adjusted for climate region, is still a topic for heated debate. Nevertheless, it’s important to keep in mind that the more simple the form your structure takes — for example, 2-story cubes without basements —

 

 

the easier it is to achieve Passive House, or similar building standards, since it simplifies framing, air sealing, and limits the exterior surface area in ways that a single story ranch that is spread out and has all kinds of nooks and crannies does not (the difference also has serious ramifications for overall heating and cooling demand). Likewise, simple forms also make it easier to figure out how much insulation you need to reach a benchmark like Passive House or PGH. A simple form can also have durability implications.

Our R-values were based on a number of considerations: the construction drawings of our original builder, information made available by Hammer and Hand (in particular their Madrona House project), and articles on the Building Science Corporation (in particular: 1 and 2) and Green Building Advisor websites. These resources, all of which have proven to be indispensable at every stage of the build, have made our project possible.

In terms of the details around the slab and the foundation walls, this article from the DOE also proved to be especially helpful: Foundation Handbook

 

2-04_no-cap

Illustration courtesy of: foundation handbook.ornl.gov

 

After considering various insulation choices (Wall Assembly), we decided to go with Roxul for under our slab, the exterior of our foundation, and our wall assembly (blown-in cellulose in the attic was the only significant deviation from the use of Roxul).

Here’s how the basement slab portion of our project progressed:

 

 

Roxul Comfortboard 80 (2″ + 2″)

To get to an R-value of 16 we used two layers of 2″ thick Roxul Comfortboard 80 (R-4 per inch).

We installed each layer with staggered seams, although the Roxul representative I spoke with via email insisted that because the Roxul is so dimensionally stable this isn’t nearly as important as it would be with rigid foam insulation (the same holds true with a double layer of Comfortboard 80 on the exterior side of wall sheathing).

 

roxul in basement 2 layers

Putting down the 2 layers of Roxul Comfortboard 80 with help from the concrete guys.

 

 

roxul long view two layers

The second layer of Roxul being installed.

 

 

roxul before stego

Installing the Roxul around the rough-in bathroom pipes, sump, and ejector pits.

 

One of the many benefits of using Roxul is that the material wants to stick to itself, whether in batt or rigid board form. This makes for tighter joints between pieces, and even when cuts around obstructions are less than perfect it’s easy to fill in any gaps with torn apart pieces of Roxul (again, this holds true for both Comfortboard 80 and their version of batt insulation).

 

roxul stuffed in around basement pole

Stuffing bits of Roxul around the base of one of the steel columns.

 

Close up of the Roxul installed around the roughed-in bath PVC pipes.

 

roxul around rough-in bath

 

Another view of the 2-layers, mostly installed.

 

roxul before stego - facing ladder

 

A Roxul rep told me to take into account a loss of R-1 due to the compressive pressure of the poured concrete, thus our R-16 for two layers of Roxul is, according to Roxul, really an R-15. Having installed the two layers myself, walked on it during and after installing the vapor barrier (see below), my guess is in some areas this loss in R-value is even greater than R-1.

Based on the comments quoted in a GBA article (Sub-Slab Mineral Wool), I would have to say my experience was exactly the same: in some areas the Roxul seemed to lose most, if not all, of its rigidity. I’ve also noticed while working with both the Comfortboard 80 and their batts that there seems to be a variation in the material from one piece to another and even bag to bag. Some pieces are very easy to cut (these pieces are noticeably stiffer), while other pieces seem “mushier” or lacking in rigidity — either under or over-cooked perhaps — making them more difficult to cut and work with. This seems like less of an issue for vertical applications (i.e. walls), while potentially troublesome for horizontal applications under a slab — especially if you’re depending on that R-4 per inch to meet the demands of energy modeling for a certification program like Passive House.

I’m glad we’ve been able to mostly avoid foam insulation in the build, but seeing the Roxul in a real world application does make me wonder if some kind of rigid foam might’ve given me a more consistent whole floor R-value. Going with a denser version of Roxul would’ve been another, more expensive, option as well (Comfortboard 110).

 

 

Stego Wrap

Once the two layers of Roxul were down, it was time to install the vapor barrier over the insulation. While the Roxul acts like a blanket, helping to maintain a consistent temperature in the basement, the vapor barrier helps to keep moisture and soil gases (mainly Radon as I understand it), at bay.

The product I’ve seen used in most Passive House, Pretty Good House, or equivalent projects, is Stego Wrap. Here are two videos detailing its installation and its benefits:

 

 

 

 

Another product I came across while researching options was Perminator.

Here’s a video detailing the use of the product:

 

 

In my area — the suburbs of Chicago — the closest supplier of Stego Wrap was HD Supply.

 

starting stego around roug-in pipes

Starting around the rough-in bathroom pipes.

 

We used the 10 mil version of the Stego Wrap. The material is very durable and fairly hard to damage. Even when tears occurred, it was easy to patch with pieces of the Stego red tape, or a combination of a cut piece of Stego Wrap with pieces of the red tape.

 

stego going down

Stego Wrap carried up the wall and taped to keep it in place.

 

Installing the two layers of Roxul on the basement floor was pretty straightforward, while installing the Stego Wrap was generally a pain in the ass. Maybe I was just tired, but I really didn’t enjoy installing it at all. For example, it was difficult to keep it tight to the walls, although I learned to leave it hanging fairly loose at floor-wall junctions, which definitely helped. Getting the first row straight, flat, and smooth was time consuming, and annoying, but it did make getting successive rows installed straight much easier.

 

jesus helping me w: first row stego

Jesus helping me install the first row of Stego Wrap.

 

 

almost halfway w: stego wrap

Making progress with the Stego Wrap.

 

 

sealed basement pipe close up before pour

Stego Wrap wth red Stego tape and a Roflex gasket from 475 HPBS.

 

The pipes after air sealing with EPDM gaskets and red Stego tape:

 

sealed basement pipes with overlapping Stego

 

Once all the Stego was in place, we added a 1/2″ of rigid foam insulation at the floor-wall junction as a thermal break. I wanted to use Roxul Comfortboard 80 (their 1.25″ thick version) even for this, but time (Comfortboard 80 is still a special order item in my area, meaning it’s always about 2 weeks away from the time you place your order — hopefully this changes in the near future) and money made the foam an easier choice.

 

stego w: foam close up

 

We kept the foam in place by running a bead of OSI sealant on the back of each section before pushing it up against the Stego Wrap. For the most part this seemed to work well.

 

stego w: foam at slab edge

Roxul, Stego Wrap, and foam installed.

 

Here’s a close-up of everything installed in a corner:

 

stego w: foam at a corner

 

One of the real disappointments of installing the basement slab was seeing the concrete guys put down the welded wire mesh (typically noted as W.W.M. on construction drawings) — basically chicken wire with pointy ends (I exaggerate, but not by much).

 

 

If I could do it over again, I would look into using a concrete mix containing sufficient pieces of fiberglass, or some other alternative, so that using the welded wire mesh could be avoided altogether.

 

 

 

 

I was already familiar with the idea of fiberglass used in place of metal rebar in concrete forms, having experimented with decorative concrete last year and having seen videos like these:

 

 

 

 

I’m not sure why I didn’t think to ask for fiber reinforced concrete instead of the normal welded wire mesh — it was one detail that just got missed, unfortunately.

As the wire mesh went down, the guys could see how annoyed and concerned I was by the holes it was making in the Stego Wrap that one of them, Oscar, started helping me bend the pointy ends up. Once they were safely pointed up, I went around with the red tape to patch the many tiny holes in the Stego Wrap. Not a fun way to kill a couple of hours.

Why my architect or the concrete guys didn’t suggest a mix with fiberglass instead of the welded wire mesh is unclear. The reality with any green build, especially if you’re acting as GC, is you’re likely to be the only one who really cares about getting the many details right, especially if the architect and subcontractors have never built like this before — they were just doing what they always do.

A couple shots of the basement floor with the welded wire mesh in place:

 

 

A closer view with all the elements in place prior to the pour:

 

corner of basement pre-pour

 

 

Concrete

Here’s various shots of the slab itself being poured:

 

hole in floor for basement slab

It was necessary to cut a hole in the subfloor just inside the front door in order to get the concrete into the basement.

 

 

concrete going thru floor

 

 

long view of brace for pour

The guys starting at the back of the basement.

 

 

leveling back corner of basement

 

 

back corner of basement pour #2

One corner complete.

 

 

pour heading towards basement stairwell

 

 

leveling towards stairwell

 

 

pour at stairwell

 

 

Tools at stairwell

 

 

finishing concrete at stairwell

 

 

troweling at stairwell

Enrique completing the trowel finish.

 

 

cement truck kissing corner of garage

Side of the garage kissed by the cement truck.

 

 

close sewer clean out

Close.

 

 

close long view sewer

Really close.

 

 

Slab Edge

Once the slab was in place, I wasn’t quite sure how to deal with the edge along the perimeter. As usual when I get stuck on some detail, I asked a question on GBA:

 

How do I seal…

 

Stego Wrap and Foam cut away from slab edge

Cutting away the excess Stego Wrap and purple foam.

 

 

close up of slab edge

Close-up of the wall-slab junction after cutting everything down flush with the floor.

 

Using the Prosoco Air Dam seemed like the best, and most straightforward, option. In addition, after considering various ways to cover this gap after the Air Dam was down between the wall and floor, and after priming and painting the basement walls, I realized the gap visually disappears for the most part, and really wasn’t worth thinking about.

 

wall-slab connection after air dam.jpg

Junction between wall and slab after using Air Dam and priming and painting the wall.

 

 

close up of wall - slab conection after air dam

Close-up of Air Dam, after primer and paint, at the wall-slab connection.

 

 

another view slab:wall connection

Another view of the slab – wall connection.

 

By not putting anything down to cover this gap, if the basement ever does experience water damage, it’s one less thing to remove and replace.

Ceiling Details (Air Sealing #4)

0

Installing Intello

We thought about using the Zip sheathing as our air barrier on the ceiling, attaching it to the bottom of the roof trusses, something I had seen on other builds, but after learning about Intello we decided to use that instead:

 

 

Floris Keverling Buisman, from 475 High Performance Buidling Supply, did our WUFI analysis for us, and he suggested the Intello would be a better fit for our project. The Intello is a smart vapor retarder, so it can expand and contract when it’s needed, and it’s obviously less physically demanding to install than the Zip sheathing.

Once the air sealing was complete around the top of our outside perimeter walls, and the insulation chutes had been installed, we were almost ready for the Intello. At the gable ends of the house, one last detail needed to be put in place, circled in red in the picture below:

 

2x6 on its side

2×6 on its side, circled in red.

 

By adding this 2×6 on its side, which is in the same plane as the bottom of the roof trusses, it makes it possible to carry the Intello over the transition from the ceiling (under the roof trusses) to the walls (top plates). This is one of those details that is hard to ‘see’ when in the planning, more abstract, and two dimensional phase of designing a structure.

 

another angle of 2x6 on side

Another view of the 2×6 lying flat in the same plane as the bottom of the roof truss (far left).

 

Once the trusses were placed on the top of the walls and you start imagining how the Intello will be attached to the ceiling, it becomes much more obvious that something in this space at the gable ends of the house is needed in order to accomplish the transition from the ceiling to the walls.

 

long view w wdw to front door framing

Marking progress: Ceiling ready for the Intello.

 

After reading about so many other projects that utilized Intello, it was exciting to unwrap the first box.

 

unwrapping first box of Intello

Big day: opening the first box of Intello.

 

The directions are pretty straightforward, and the product is relatively easy to install as long as you don’t have to do it alone.

 

Intello instructions

Reading through the instructions one last time before starting.

 

I didn’t get a chance to touch and feel the product before ordering (always fun to do with any new product), so here are some close-ups of the Intello to give you some sense of what it’s like:

 

Intello close up front side 2

Front: shiny side of the Intello — this side will be facing the living space.

 

I was curious about its strength and tried to tear it with various objects, including the cut ends of 2×4’s and the brackets we eventually used to help establish our service core. The material is surprisingly tear resistant, but a utility knife, or a stray sharp edge will cut through it (as our first plumber proved to me with his careless actions — a story for another post).

 

close up Intello back side

Back: matte side of the Intello — this side will be facing the attic.

 

Having never used the Intello before, I decided to start small and began by experimenting with it in a corner. Getting the corners fully covered while getting the material to sit flat before applying the blue Tescon Vana tape proved to be the most challenging part of using the Intello.

 

experimenting w: Intello in corner w: chutes above

Starting in a corner to get a feel for how the material will work.

 

Here’s two more pictures of the flat 2×6 helping to make the transition from the ceiling to the wall on the gable ends of the house:

 

 

In order to attach the Intello to the bottom of the roof trusses, we used the staple gun shown below. Loading it is kind of counter-intuitive (online reviews complain about it not working out of the box, but my guess is — like me — they were trying to load it improperly), but once I figured it out, it ended up working really well, almost never jamming, and it’s very comfortable to hold because it’s so light weight. It should work with any standard air compressor. It was available on Amazon, and in Menards, a local big box store here in the Chicago suburbs.

 

staple gun

The staple gun we used to attach the Intello to the underside of the roof trusses.

 

Think you know how to load it?

 

side view of open staple gun

Staple gun ready for loading.

 

Guess again.

Instead of loading from the bottom, like all the finish nailers I’ve ever used, the staples load higher up, where the staples exit. And yes, there was quite a bit of swearing as I made the transition from “What the…” to “Ohhhh, now I get it…”.

It didn’t help that there were virtually no instructions on its use, apart from a tiny black sticker with an arrow pointing to where to load it (which, of course, I only noticed after figuring this out).

 

staple gun open w: staples

Loading the staple gun.

 

We started with these staples:

 

close up Arrow staples

 

But we ended up going with these instead:

 

close up heavy duty Arrow staples

 

They seemed to grab better (presumably the sharp ends make a difference), and they sit flatter on a more consistent basis (less time having to go back, or stop, to hammer home proud staples flat).

 

stapling Intello to ceiling

 

As we rolled out the Intello, it took some practice to get it to sit taught and flat before stapling.

The dotted lines near the edges of the Intello help you keep the rows straight as you overlap two sheets and progress from one row to the next. The lines also make it easier to maintain a straight line with the Tescon Vana tape (don’t ask me when I realized this latter detail — too embarrassing to admit).

 

taping Intello along dotted line

Follow the dotted line…

 

We checked our initial row from above in the attic:

 

first row of Intello from attic

View from the attic as the first row is installed.

 

Working our way through the interior walls, especially the bathrooms, was more time consuming and took more effort (I grew to hate those interior bathroom walls — first the Intello, then the service core details described below), but once we were out in the open the Intello was fairly easy to install.

 

Intello covering ceiling, chutes in bg

First three rows of Intello as they approach the basement stairwell. Note the insulation chutes in the b.g. in the attic — they took up so much time and effort, and now they slowly disappear (just like most important aspects of infrastructure).

 

 

northwest corner of air sealed attic w: Intello

View of the Intello from a corner of the attic — note the 2×6, far left, lying flat, that helps the Intello transition from the ceiling to the top of the walls.

 

 

Intello from attic at outside corner

Another view of the Intello from the attic after installation.

 

As Eduardo and Jesus rolled out sections of the Intello I followed, pulling on the Intello a little to help make it sit tight and flat before stapling it in place.

 

Eduardo and Jesus helping me put up Intello on ceiling

Eduardo and Jesus giving me a hand installing the Intello.

 

There were a couple of sections, some of the first ones we installed, that I managed to wrinkle (one, in particular, became problematic during our first blower door test — and, of course, it was in a tight spot around the bathroom shower area), but overall, the installation of the Intello went pretty well. Like most things you do for the first time, we got comfortable and good at it just as we were finishing up.

 

Eduardo Jesus and full moon night sky in b.g.

Eduardo and Jesus helping me finish up the main areas as a full moon makes the night sky glow outside in the background. It was a long day (longer still for Eduardo since Jesus was talkin’ trash and nonsense all day — they’re football teammates — needless to say, Eduardo has the patience of a saint).

 

 

Intello from attic w: insulation chutes in bg

View of the Intello from the attic — offering up its 2001: A Space Odyssey glow.

 

After learning about a project on the 475HPBS website…

 

Masonry Retrofit

 

… we decided to use the Tescon Vana tape to cover the staples, as well as all the seams, in the Intello. I have no idea what actual impact covering the staples has on air tightness, but visually as you tape over the staples you can see how, if nothing else, it will help the staples resist pulling out under pressure from the eventual blown-in cellulose in the attic.

Even as the build progresses, it’s interesting how details like this pop up, making building “green” a never-ending process of learning something new — someone’s always coming up with a new product or a new way to do things better, faster, or less complicated — which makes the process itself very exciting.

 

OB applying tape

OB — the Palatine High School legend — the man, the myth, helps me tape over the seams and staples in the Intello. One of the many jobs he’s been kind enough to help me get done. We’d be so far behind schedule without all of his help.

 

 

on plank

View from above what will be the basement stairwell while installing the Intello on the ceiling.

 

 

installing Intello on the ceiling around the basement opening

Almost finished installing the Intello — saved the hardest part for last.

 

This was a nice moment, being able to look back and see the Intello completely installed. It’s almost a shame that we have to cover it with drywall.

 

Intello on ceiling long view

Intello installed and taped.

 

 

2×6 Service Core

A design goal for the ceiling was to keep mechanicals, like HVAC and electric, on the conditioned side of the ceiling air barrier. By doing this, we avoid having to insulate any ductwork for HVAC, or air sealing and insulating around ceiling lights. In effect, we completely isolate the attic, making its sole purpose (apart from ventilating our “cold roof” assembly) holding our blown-in cellulose insulation (this set-up makes it much easier to air seal the ceiling and get the insulation right — at least based on the projects I’ve read about). In order to do this, we created a service chase, or service core, with 2×6’s:

 

service chase w: first couple of 2x6's

First couple of 2×6’s going in.

 

In addition to serving as a space to safely pass mechanicals through, the only other job for the 2×6’s is to hold up the ceiling drywall. The roof trusses, directly above each 2×6, are still carrying the load of the roof and stabilizing the perimeter walls.

 

Simpson L-Bracket w: fasteners

Simpson bracket and fasteners we used to attach the 2×6’s to the underside of the trusses.

 

Here’s what the 2×6’s looked like with their brackets once everything was installed.

 

close up service chase w: bracket-screws

Service core 2×6 with bracket and Simpson SDS bolts.

 

OB and my wife were invaluable as they helped me cut and install all the 2×6’s.

 

 

We installed the brackets first, before raising up each individual 2×6 to fit against the brackets.

 

jesus helping me install 2x6's

Jesus helping me install the 2×6’s.

 

Since the brackets were directly attached and under a roof truss, we were able to keep the 2×6’s fairly straight, even when the board itself was less than perfectly straight.

 

service chase w: just brackets

Brackets installed before the 2×6’s go up.

 

A feisty Robin kept trying to set up a nest on our partition wall (our windows and doors aren’t in yet). Apparently she believed we had created an elaborate bird house just for her. It took almost a week before she finally gave up — but not before starting multiple nests in multiple spots along the wall.

 

bird nest

Robin making one of her many attempts at a nest on our partition wall.

 

Along the outside walls, at the top of the wall assembly, there was a gap that we utilized for maintaining continuous insulation. This meant there will be no break in our thermal layer going from the blown-in cellulose insulation in the attic to the monolithic layer of Roxul Comfortboard 80 (2″ + 2″) that will be on the exterior side of the Zip sheathing.

 

trusses - Intello - Roxul

Adding Roxul at the top of our wall.

 

 

layer of Roxul at top of outside wall

Close up of the Roxul going in on top of the top plates.

 

 

Intello - Roxul - wall

Another view after the Roxul has been installed.

 

 

long view from west window w: service core complete

Marking further progress: Intello and 2×6’s installed.

 

Once the 2×6’s were up, we had to install our pieces of 1×4 in order to prevent the 24″ of blown-in cellulose that will be going into the attic from causing the Intello to sag.

The plans called for the 1×4’s to be installed right after the Intello, but before the 2×6’s, which would have been a lot easier and quicker, but, unfortunately, the GC’s we fired installed the interior walls too high, making this impossible.

Here’s what it should’ve looked like if we could’ve done Intello and then the 1×4’s (photos courtesy of 475 HPBS) before installing the 2×6 service core:

 

 

Having no choice but to methodically cut each 1×4 to fit between each set of 2×6’s, OB was nice enough to help me get it done.

 

close up of partition wall w: service core and 1x4 cross battens

 

Installing the 1×4’s between the 2×6’s began with some experimentation:

 

service core w: cross battens and L-brackets

Using L-brackets at first —  it proved too time consuming and expensive.

 

After experimenting with a finish nailer (too easy to miss and penetrate the Intello), we eventually settled on Deckmate screws. It was definitely a laborious process, but eventually we got into a rhythm and got it done, although we wouldn’t recommend doing it this way — way too time consuming.

 

ceiling w: 1x4 battens

Completing our service core.

 

We tried to keep the 1×4’s about 16″ apart, which should prevent any significant sagging in the blown-in cellulose from occurring (I’ll post photos once the cellulose has been put in the attic).

A lot of blood, sweat, and tears have gone into completing this house.

Here’s some proof:

 

screw got me

A decking screw got me.

 

In trying to avoid puncturing the Intello, I would hold a couple of fingers on the back side of the 2×6, feeling for any screws that would come through on a bad angle. A couple of times I drove a screw too quickly and paid the price.

 

looking up at Intello and service core from basement

View of the service core from the basement. Installing the 2×6’s and the 1×4’s also required walking the plank a few more times.

 

 

installing ceiling w: OB

OB making my life easier as I work on the plank installing the 1×4’s.

 

 

Maintaining the Intello After Installation

Unfortunately, there was a delay in getting shingles on our roof, due in large part to our first disorganized and incompetent plumber (again, more on this later). Consequently, we were in the awkward position of having our ceiling air barrier and service core all set up but every time it rained we still had a leaking roof. In most areas it wasn’t a big deal, but in about a dozen spots rain would collect and, in some cases, cause a bulge in the Intello as it held up the weight of the captured water. To relieve and ultimately to avoid this pressure, I cut small slits in the Intello where the rain would consistently collect.

 

small hole in Intello for rain before shingles

Slit in the Intello to allow rain water to fall through, marked with a red marker for easy identification later.

 

Once the shingles were finally on, I went back and found all of these slits and taped over them with the Tescon Vana.

 

Tescon Vana covering hole in Intello

Hole in the Intello covered and air sealed with the Tescon Vana tape.

 

We also found a couple of weak spots in the Intello as we installed it, and even later, during the installation of the service core. These spots were marked as well, and they, too, got covered with the Tescon Vana tape just for added insurance against air leakage.

 

imperfection in the Intello marked for Tescon Vana

Weak spot, or imperfection, in the Intello. This got covered with Tescon Vana as well.

 

After having to fire our GC’s, we couldn’t have kept the project going without the help of family and friends. As awful as some aspects of the build have been, it’s been heartwarming to find people willing to help us see the project through to the end (much more on this later).

 

2 Cheshire Cats

Couple of Cheshire cats — clearly up to no good — helping us to keep the job site clean.

 

Foundation Details (Air Sealing #1)

14

Footings

For the top of the footings we used a product from Cosella Dörken called Delta Footing Barrier. Acting as a capillary break, the membrane is supposed to help prevent moisture from wicking up from below the footing, where it could then migrate into the foundation wall and into the basement, or even the wall assembly above (worst case scenario), causing mold or other moisture related damage. It should contribute to making the basement a very livable space (especially when combined with significant amounts of insulation on the exterior walls and under the slab).

Here’s a detail from the construction drawings:

 

footing-thermal-bridge-up-from-soil

Red arrow shows thermal bridge and gap in the vapor barrier up through the footing from surrounding soil if Delta membrane were not present.

 

In other words, this junction represents a weak point in our thermal envelope and vapor barrier. Passive House proponents often talk about using a red pen on a construction drawing to follow the air barrier and thermal envelope (the goal: no gaps in air sealing or the layers of insulation) . In theory, you should be able to do this all the way around the structure without once lifting your pen. If you can lift your pen (meaning there’s a gap in your air barrier or thermal envelope — which would be the case without the Delta membrane on top of our footing), then it’s a weak point that should be addressed (if at all possible).

Even with significant insulation on the exterior wall of the foundation (Roxul Comfortboard 80: 2″ + 3″), along with a sprayed-on waterproofing membrane, as well as a vapor barrier (Stego Wrap) and insulation (Roxul Comfortboard 80: 2″ + 2″) under the basement slab, this junction where the three elements meet — slab, footing, wall — is a weak point. Although it doesn’t address the weakness in R-value, at least it should keep the moisture at bay (probably the biggest complaint associated with basements).

With a 9′ basement, we’re hoping the temperatures at this depth are consistently mild enough to avoid any kind of significant energy penalty. I’m confident this will be the case because in our last home, a typical suburban tract house without much insulation, the basement always stayed cool in the summer and warm in the winter, even though the ducts to the basement had been closed off so the space never saw any direct benefit from the HVAC system.

For minimal cost in materials, the Delta membrane seems well worth it for the added peace of mind.

 

foundation-delta-membrane-in-box

Rolls of Delta Footing Barrier on site and ready to go.

 

 

 

Here is a video and some photos from our job site:

 

 

The guys from Tynis Concrete didn’t seem to mind trying something new, and the membrane went on without any issues.

 

foundation-delta-fabric-close-up-in-corner

A corner of the footing with the Delta membrane “keyed” into the footing.

 

I couldn’t find any local suppliers who carried the Delta membrane, so I ordered online from: spycorbuilding.com

 

foundation-mud-shot

Detail of the bottom of our hole, being prepped for the footings.

 

 

Foundation Walls with Roxul Comfortboard 80

For the walls, first we used a spray-on waterproofing membrane from Tremco:

 

 

After the waterproofing was complete, we began installing the two layers of Roxul Comfortboard 80 (a dense, rigid form of insulation that can be used below grade, to the exterior side of wall sheathing, and even under a basement slab), which will give the basement foundation walls an R-20 of insulation value.

 

roxul-delivered-to-the-site

Roxul delivery shows up on site (Comfortboard 80: 2″ and 3″ thick). Roxul is showing up in the Big Box stores here in the Chicago area, so it’s becoming easier to order.

 

When questions came up about how to install Roxul, or which product to use where, their technical help via email was great — in our case, Fiona Schofield, who gave us a lot of useful information — including the document below, a study on the long-term condition of Roxul (aka stone, rock, or mineral wool) in a below grade application (i.e. up against an exterior foundation wall):

 

external-thermal-and-moisture-insulation-of-outer-basement-wall (pdf)

 

In addition, after finding the video below online, in which what looks to be a European version of Roxul is attached to a cinder block wall with an adhesive, or a thinset mortar,

 

 

I contacted Fiona and heard back that it was ok to use an adhesive for our first layer (PL Premium, or similar polyurethane adhesive caulk), so long as we used a mechanical fastener for the second layer. In effect, the first layer just needs to stay on long enough for us to get the second layer up and attached with a mechanical fastener. This really saved us some time since the guys didn’t have to drill two full sets of holes.

 

sammy-butters-the-back-of-the-roxul

Sammy hitting the back of the Roxul with Liquid Nails before setting it into position. The adhesive worked really well at keeping the Roxul in place, even when the foundation was damp in certain areas.

 

The guys also didn’t seem to mind cutting or otherwise working with the Roxul. We used serrated knives we purchased from Home Depot, made especially for cutting rock wool…

 

serrated-knife-for-roxul

This knife, purchased from Home Depot, works really well cutting the Roxul.

 

… which worked fine, but then after some experimenting, the guys also began using a small, handheld sawzall (reciprocating saw), and even a table saw, to get the exact sized pieces we needed to ensure staggered seams. I had my doubts about the table saw, but Phil said the Roxul cut easily, and it really didn’t seem to kick up a lot of dust (although he did wear a dust mask for protection).

 

nils-and-bill-getting-1st-layer-of-roxul-up

Billy and Nils (in the hole in the background) gluing up the first layer of Roxul.

 

Once the first layer of Roxul (2″ thick) was in place, we could then install our second layer of Roxul (3″ thick) over the top of it.

After a lot of research, and even posting a question on Green Building Advisor…

 

Attaching Roxul Comfortboard 80 to Exterior of Foundation Walls

 

… we decided to go with the Rodenhouse fastener (Plasti-Grip PMF):

 

 

These really are as easy to install as depicted in the video. Using a hammer drill with a 5/16″ bit, the guys drilled a hole to the depth of the fastener, before tapping the PMF fastener home with a hammer. It’s a genuinely straightforward process. Sometimes a fastener wouldn’t sit perfectly, but as long as a majority of the fasteners on each board did, it didn’t seem to be a problem. Based on what I read online, they were much easier to work with than if we had to use Tapcon or similar concrete screws.

 

rodenhouse-fastener-close-up

Close up of the Rodenhouse PMF fastener.

 

They weren’t cheap, but they were well worth the cost in materials for the savings in labor (and frustration). And Mitch Mahler, from Rodenhouse, was easy to work with via email in terms of ordering or getting answers to technical questions.

 

rodenhouse-fastener-box-w-label

The box the fasteners came in.

 

 

in-the-trenches-w-roxul

In the trenches, as the second layer of Roxul gets attached with the Rodenhouse fasteners.

 

 

long-narrow-piece-of-roxul-w-3-fasteners

Long, narrow piece of Roxul with 3 Rodenhouse fasteners.

 

Normally, Roxul recommends 5 fasteners per piece (4 in the corners, 1 in the middle), but we found that 4 on a normal piece, and 3 for a long, narrow piece worked fine — at least for the foundation, where the backfill will help to keep the Roxul in place over the long haul.

 

 

Thermal Bridging in the Foundation

Following Passive House science principles, we tried to remove as many points of thermal bridging in the structure as we could. One area where this was addressed in the construction drawings was a 7″ thermal break between the basement foundation and the attached garage foundation. In other words, there would be no physical connection between the garage and house foundations at all. The only connection would occur above, at the level of framing, where they would be tied structurally together. The idea was that we could place our two layers of Roxul (2″ + 3″) in that gap, thus maintaining our 5″ of Roxul on the exterior of the foundation, uninterrupted (the key point here) around the perimeter of the basement foundation.

On the day the footings were installed, however, our concrete subcontractor expressed serious reservations about the long-term structural stability of the framed house and garage above this gap — in effect, he was worried that over time the two foundations might settle and move apart, wreaking havoc with the framed structures above.

So I was back to post another question on Green Building Advisor (a fantastic resource for any green build or self-build) on the topic:

 

How important is a thermal break between a house foundation and an attached garage foundation?

 

Here are some photos showing these connections:

 

foundation-north-corner-garagehouse-connection

Garage foundation meeting up with corner of house foundation (north side of house).

 

 

foundation-garage-house-connection-north-corner

Close up of this garage-house foundation connection, from inside the garage.

 

 

foundation-front-porch-garage-to-house-porch-to-house-connections

Front porch. Thermal bridge from garage to house is off to the far right.

 

 

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Inside corner of garage where garage-front porch-house connect.

 

 

foundation-front-porch-to-house-connection-outside-corner-of-porch

Outside corner of front porch. Technically, another thermal bridge from porch to house foundation.

 

 

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Wing wall for side porch stoop. Yet another thermal bridge to the house foundation.

 

Unfortunately, there just doesn’t seem to be a lot of information available as to how to proceed. In the end, we decided to ignore these connections, hoping that the thermal bridging at these two points (garage-house, garage-front porch-house), in particular, won’t be all that significant (to our heating and AC costs, or, for example, cold getting into the foundation and then rising up and getting into the wall assembly above these two points where it could become interstitial condensation — unwanted, and potentially dangerous, moisture in the wall).

I assumed Passive House builders would incorporate rigid foam insulation into the concrete forms at these points, but I couldn’t find any pictures or descriptions showing or talking about this in books, magazines, or anywhere online. Either Passive House builders ignore these kind of connections, or I just missed the information somehow. 

 

*** If anyone knows of good sources on this, let me know, and I will post links here to help others in the design stage of their own build ***

 

 

Update: David Goodyear is building a Passive House in Newfoundland, and he has successfully used rigid foam between the house and garage foundations. You can read about it on his blog here:

Flat Rock Passive House: A Tale of Two Foundations

 

 

foundation-side-porch

BEFORE: Monument to Italian Brutalism.

 

 

side-porch-getting-wrapped-in-roxul

AFTER: Wrapped in snuggly blanket of Roxul. The wing wall was eventually entirely covered except for the tops.

 

Below are the other points of thermal bridging in the foundations, now covered in Roxul:

 

south-inside-corner-of-garage-w-roxul

Corner of garage foundation meeting up with house foundation (standing inside garage).

 

 

south-view-of-garage-house-foundation-connection-w-roxul

Same corner, from outside, looking at house foundation to the right.

 

 

inside-garage-garagehouse-connection-w-roxul

Garage-front porch-house connection (from inside garage).

 

 

front-porch-w-roxul

Outside corner of front porch meeting up with house foundation.

 

We did our best to cover these thermal bridges, but clearly it’s imperfect, so all we can do is hope there won’t be a significant energy penalty associated with these connections.

 

 

Basement Windows and Roxul

As the Roxul was going on the foundation, Phil and Nils installed window bucks for the two basement windows. The bucks were sized so they meet up flush with the two layers of Roxul. Eventually a layer of HardieBacker board and two coats of Tuff II (the product we’ll be using for the parge coat) will cover the window bucks, and also the transition between the top of the foundation walls and grade around the perimeter of the house.

 

nils-installing-basement-window-bucks

Nils installing the basement window bucks as the Roxul is being installed on the exterior side of the foundation.

 

I initially intended to use the R-Guard line of liquid membranes by Prosoco for air sealing and waterproofing all seams and window/door openings, but cold temperatures made this impossible (they require 40° F and rising, which would be the exception rather than the rule here in Chicago for December and January). Maybe because of years house painting (caulking and drywall patching) the liquid membranes seem easier to use and less fussy to get right (the big issue with the tapes is avoiding wrinkles and properly shingle flashing to get water moving in the right direction).

Our Plan B was the series of Pro Clima products sold by 475 High Performance Building Supply. Most of them, including the sealant, can be used down to 14° F without issues.

Another option would’ve been the line of Siga tapes, another popular choice used in Europe, available from Small Planet Supply.

So as the window bucks went in, I followed, applying Contega HF sealant to all the seams and gaps. The sealant is acting as our first layer of air blockage. It’s super sticky, so I don’t doubt that it’s permanently flexible. I did a mock-up of our wall assembly months ago, and the HF on the seams is still tacky to the touch. It goes on light green, then slightly darkens as it dries.

 

contega-hf-sealant-in-20-oz-sausage

Contega HF sealant in a 20 oz. sausage. It’s also available in the more familiar 10 oz. caulk tubes.

 

A few suggestions for using the HF Sealant:

  • I’ve found that completely snipping off the metal clip on the end of the sausage (as opposed to just cutting a couple of small slits around it) prevents it from getting jammed in the front end of the gun.
  • If I have a half-finished sausage of HF at the end of the day, I put it in a tightly wrapped plastic bag overnight (see photo below), which allows me to use it within a day or two without any problems.
  • Use a tiny spatula (see photo below) to tool the HF into place rather than your finger, as you normally would with a caulk — it’s just too sticky.
  • Because the HF is so sticky, I wear Nitrile gloves, so when it starts to get everywhere — and it will get everywhere if you let it — I just simply change to a new pair.
  • For clean up, the Citrus Solvent we’ve been using with the tung oil works great.

 

newborn-sausage-gun

The Newborn brand of sausage gun we’re using for the HF sealant. Found it on Amazon. A really well-made tool.

 

 

ateco-spatula

Found this on Amazon. I thought it was construction grade, but it’s made for kitchen use. It’s durable, and I like the thin blade since it offers more “feel” than a thicker blade, making it easier to tool the HF into place without displacing too much of it in the process.

 

It’s easy to forget the realities of a construction site when planning details, like the use of the Pro Clima tapes. I pictured it being a pretty straightforward process, not a winter day in the 20’s, fingers numb, propped up on an unbalanced ladder in the hole, while the other guys are cutting wood and Roxul around me — a case of adapt or die, I guess, and a reminder not to be overconfident about the products you’ll be using, or the installation process that inevitably goes with them.

 

installing-pro-clima-tapes-on-ext-side-of-base-wdw-bucks

Applying the Pro Clima tapes to the exterior side of the window bucks.

 

It was important that the connection between the window bucks and the concrete of the foundation be air sealed and made water tight before it gets completely covered by the two layers of Roxul.

It’s been in the 20’s and 30’s, so the HF sealant took a couple of days to firm up before I could then apply the series of Pro Clima tapes. I’m using a combination of tapes, including the Tescon Vana (the bright blue), Profil (light blue — great for making inside and outside corners), Contega Solido Exo (black, 6″ wide), and the Extoseal Encors for our sills (475 HPBS has a great series of videos showing how to use each tape).

 

installing-pro-clima-tapes-on-basement-window

Finishing off the buck from inside the basement.

 

We knew the bucks would be sitting for some time, exposed to the elements, before the windows actually show up, so we decided to completely cover the openings just to be safe. This gave me extra practice using the tapes, which definitely helped, and it meant not stressing out every time the forecast called for rain or snow.

 

basement-window-buck-covered-in-tape

Basement window buck covered in Contega HF sealant and Pro Clima tapes.

 

The only tape that’s giving me fits is the black Contega Solido Exo. It’s thinner than the other tapes, so it has a propensity to want to stick to itself (wrinkles are more difficult to avoid), and I find it much harder to pull it away from its peel-and-stick backing than the other tapes. I worried that the Extoseal Encors might be difficult to get right, but it — along with the Tescon Vana and Profil tapes — has been surprisingly easy to work with.

This video was my Bible for installing the Extoseal Encors:

 

 

In lieu of on-site training from someone who’s used a specific product consistently, videos like this one are invaluable when using new products and you want to get the details right. Without videos like this, you’d be in for a frustrating process of trial and error.

For instance, even with this excellent video, I noticed when I did our mock wall assembly that because the Extoseal Encors can stretch around corners it’s easy to stretch it too much, thereby inadvertently thinning it out. I’ve found that when I get to a corner it’s better to just fold it around the edge rather quickly, without overthinking it too much, which helps to maintain the thickness of the material at and around the corners (arguably the product’s strongest attribute in helping to avoid water damage).

I can’t recommend enough doing a mock wall assembly, or practicing on scraps, to get a feel for using these products, before you find yourself on-site doing it for real.

 

basement-window-buck-before-roxul

Basement window buck sealed and taped on the exterior side before being covered in Roxul.

 

 

close-up-basement-wdw-buck-covered-by-roxul

Basement window buck surrounded by two layers of Roxul.

 

 

basement-window-buck-and-roxul-meet-up

Close up of outside edge of basement window buck and Roxul connection.

 

We’re almost ready to climb out of the hole. It will be exciting to watch the guys start framing so we can see the basic form of the house begin to take shape.

 

foundation-tools-ready-to-leave-site

Tools ready to head to the next job site. Concrete guys (they’re mostly guys) are the unsung heroes of construction (excavators should be included as well) — like offensive linemen in football, no one pays much attention to them until a mistake is made.

 

 

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Concrete jewelry.

 

 

queen-of-dirt-mountain

Queen of Dirt Mountain.

 

Wall Assembly

0

Or: Dude, what’s in your walls?

When choosing what to put in our walls, we knew we wanted to try and balance high R-values (well above the current building code) with a limited environmental impact.

Here are three articles that address the issue:

 

Best Wall Choices

 

Without Foam

 

Twinkies

 

After evaluating various materials, including sheep wool,

goodshepherdwool.com

blackmountaininsulationusa.com

we decided to use many of the following elements employed by Hammer & Hand:

 

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Hammer & Hand wall assembly for their Madrona House.

 

In terms of materials, there are any number of options for putting a wall assembly together. For instance, we really wanted to use the sheep wool, but cost and worries (unfounded or not) about availability, led us eventually to Roxul (the Hammer & Hand videos below proved especially helpful in this regard).

After seeing the wall assemblies Hammer & Hand has been using, and how they’ve evolved over time, we felt the Madrona House set-up represented a good balance between cost-environmental impact-availability-ease of installation. We will also be following their lead by using the Prosoco R-Guard series of products to help with air-sealing our building envelope.

Nevertheless, we did make a couple of changes to the Madrona House set-up. For example, we’re using 4″ of Roxul Comfortboard 80 on the exterior side of the Zip sheathing (based on our colder climate zone), and we will be using Roxul R23 batts in the stud bays, along with the Intello vapor retarder, stapled and taped to cover the stud bays. Otherwise, we will be sticking pretty close to the Hammer & Hand Madrona House wall assembly.

So from drywall to exterior siding (interior – exterior), this will be our wall assembly:

  • 5/8″ Drywall
  • Intello Plus vapor retarder (475 High Performance Building Supply)
  • Roxul R23 Batts in 2×6 stud bays (24″ o.c.) (roxul.com)
  • Zip board (for structural sheathing and WRB; seams covered w/ Joint and Seam Filler)
  • 4″ of Roxul Comfortboard 80 (two layers: 2″ + 2″)
  • 2-Layers of 1×4 furring strips (aka battens or strapping) as a nailing base for the cedar siding
  • 1×6 T&G Cedar (charred and oiled with a few boards left natural as an accent — most of it oriented vertically, hence the need for a second layer of furring strips).

 

wall-assembly-color-coded

A crude rendering of our wall assembly using my daughter’s colored pencils.

 

A collection of helpful videos explaining the various elements we’re going to use, and why they’re effective:

 

 

 

 

 

 

 

 

 

 

Without the information available from sources like Building Science Corporation (they have a lot of interesting research documents) and design-builders like Hammer & Hand (not to mention Green Building Advisor and similar sites and forums that allow consumers to Q&A with expert builders and designers in “green” architecture), trying to build structures to such exacting standards (e.g. Passive House – Pretty Good House – Net Zero) would be exceedingly difficult, if not impossible, for those without previous, direct experience in this type of building program. I can’t express how thankful I am that so many individuals and businesses like these are willing to share their years of experience and knowledge with newbies like myself.

Here are the Hammer & Hand videos that initially sparked my interest in using Roxul rather than foam:

 

 

 

 

 

 

Instead of using tape for exterior seams, we are going to use the R-Guard series of products from Prosoco:

 

 

 

 

For various interior seams and connections we anticipate using the Tescon Vana tape, or an appropriate gunned sealant.

 

Helpful Links

GBA (Green Building Advisor): Building Green (Starter Q&A)

GBA: Article on minimum thickness of exterior foam by climate zone

GBA Question: Foam vs. Roxul

GBA: 10 Rules of Roof Design

GBA: “Greenest”

GBA: Passive House Design (5-part video series) Requires membership after Part I, but well worth it.

BSC (Building Science Corporation): Perfect Wall (pdf)

 

 

BSC: Hygrothermal Analysis of Exterior Rockwool Insulation (pdf)

BSC: Moisture Management for High R-Value Walls (pdf)

BSC: Cladding Attachment Over Thick Exterior Insulating Sheathing (pdf)

GBA: Mineral Wool Over Exterior Sheathing

Passivhaus Trust (UK): how-to-build-a-passivhaus-rules-of-thumb (pdf)

 

 

 

 

 

 

 

 

 

 

Also worth considering:

GBA: The Pretty Good House

GBA: Passive House Certification: Looking Under the Hood