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Passive House + Net Zero Energy + Permaculture Yard

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Completing our Wall Assembly: Rockwool Batts, Intello, and Drywall

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Insulation for Exterior Walls

Once Wojtek and Mark were done installing our continuous insulation on the exterior side of our Zip sheathing (4″ of Rockwool Comfortboard 80), including the first layer of battens (no more errant fasteners through the Zip to worry about), I was able to move inside and begin installing Rockwool Batts (R-23) in our 2×6 wall framing.

Once we had moved on from our first builder, and after reading up on the available options for insulation, we decided to invest in Rockwool insulation, both the rigid Comfortboard 80 on the exterior of our sheathing and the Rockwool batts for inside our stud bays. Although more expensive, particularly the Comfortboard 80 for continuous insulation (used rigid foam would’ve been substantially less expensive), we felt that many of its properties made it worth the added cost.

In particular, by helping our wall assembly to be vapor-permeable (or vapor open), we felt the Rockwool could help mitigate any mistakes, should they be made, in the wall assembly details. This being our first build acting as a GC, we wanted to add some margin for error wherever we could find it.

More details on our wall assembly and how we finalized details, including our desire to maintain a high level of IAQ, can be found here: Wall Assembly

For environmental reasons, one of our goals was to try and be as “foam free” as possible throughout the build. In addition, beyond just this issue regarding the use of foam (in all its forms: rigid board and sprayed varieties alike), there’s increasing awareness about the carbon footprint of our structures, not to mention the total carbon footprint of our daily lives.

At any rate, if I had it to do over, I would at least seriously consider using reclaimed rigid foam for our continuous insulation over the sheathing (both for the potential cost savings and its status as a reclaimed material otherwise headed for a landfill), understanding that it does reduce a wall’s ability to dry to the exterior. As others have noted, using reclaimed rigid foam in this way may be the best, or “greenest”, use of foam insulation until the construction industry hopefully moves beyond its use altogether as better options become more viable (e.g., wood fiber insulation).

Here are some resources for reclaimed rigid foam:

http://insulationdepot.com/

https://www.reuseaction.com/sales/foam/

https://www.greeninsulationgroup.com/

https://www.repurposedmaterialsinc.com/polyiso-insulation/

I would also consider using dense pack cellulose in the 2×6 walls instead of the Rockwool batts if I could find an installer I was reasonably certain could do the work properly. During construction it felt safer to use my own labor to install the Rockwool batts, thus avoiding the possibility of any gaps in the wall insulation. I was hoping to offset the cost of the batts with my free labor, plus I just enjoyed doing the work. Had we gone with the dense pack cellulose, it would’ve been something I couldn’t do on my own (no equipment or training).

lights on in base 4 rockwool
Basement ready for Rockwool batt insulation.

Installing the Rockwool batts is fairly easy and satisfying work. They’re much easier to work with than fiberglass batts, which are horrible on your skin and tend to flop around as you try to get them into place. While the Rockwool also produces some irritating fibers when it’s cut (and requires a dust mask like fiberglass), I found that a shower easily washed them away. Wearing long sleeves during installation also easily mitigates this issue.

base knee wall w: rockwool going in
Insulating the exterior wall in what will be the basement stairwell.

Also, the fact that the Rockwool batts have a friction fit means they don’t require any additional staples or netting to get them to stay put once installed.

Because of the friction fit, it’s also easy to tear off small pieces to stuff into irregular shaped voids should the need arise.

rim joist w: and w:out rockwool
Basement rim joist without and with Rockwool batt insulation.

Like the Comfortboard 80, the batts can have some variation from one piece to another, with a change in the amount of density clearly visible. With the Comfortboard 80, this was significant enough that we avoided using the worst pieces, meaning those with the least amount of density (these pieces felt thinner and sometimes even crumbly). Although this inconsistency was still present in the batts, I managed to use almost every piece, saving the least dense pieces for use in some interior walls for sound attenuation (more on this topic below).

base kneel wall corner rockwool
Corner of basement with knee wall and rim joists insulated with Rockwool batts.

Overall, we were happy with the Rockwool batts, and would definitely use them again should dense pack cellulose not be a viable option. They’re also ideal for a self-build since anyone who’s reasonably handy can install them should they have the time available during construction.

rockwool around base beam
Rockwool batts packed into gaps around the basement steel beam.

In conjunction with the Intello that would eventually be installed over the 2×6 framing members and the Rockwool batts, we also used Flame Tech putty pads to air seal behind every outlet and light switch box. I had seen them used in a Matt Risinger video for sound attenuation:

The other option would’ve been to use airtight junction boxes. Here are a couple of examples: Small Planet Supply and 475HPBS.

In order to limit issues with all the air sealing I was doing, I tried to stick with products my subcontractors already used everyday. As a result, since my electrician wasn’t familiar with airtight junction boxes, I opted instead to come in after he had everything installed and apply the putty pads. I found installing them to be straightforward and pretty quick.

box label putty pads

The putty pads are attached to release paper. Once the paper was removed the pads were easy to mold around each outlet and light switch box.

label putty pad
Acoustical putty pads purchased on Amazon.

Here’s a completed outlet box:

putty pad on outlet
Putty pad molded around every outlet and light switch in exterior walls.

The trickiest area to detail for the walls was at the ceiling and wall junction. In our case, the roof trusses sit on 2-2×6’s turned on their sides, which sit on top of the wall’s double top plate. The 2-2×6’s create space for our service cavity under the bottom chord of the roof trusses.

extoseal-encors-as-gasket
2-2×6’s on edge, sitting on double top plates. Extoseal Encors acting as gasket once taped from the exterior face of the Zip sheathing over the top of the 2-2×6’s, thus completing an air sealed connection between the exterior (Zip sheathing) and the interior before roof trusses are set in place. More details here: Roof Details

Before cellulose could be blown into the attic, we installed Intello to the bottom chord of the roof trusses. At all outside edges the Intello was carried from the roof trusses down over the double top plates of the walls, anticipating the Intello eventually being installed on the walls, which required a connection point between the Intello on the ceiling and the Intello on the walls.

ceiling-wall b4 Intello - Rockwool
Ceiling and wall areas before installing Intello on the bottom chord of the roof trusses and Rockwool batts in the walls.

After the Intello was installed on the ceiling, a service cavity (or service core, or service chase) was created with 2×6’s screwed to the bottom chord of the trusses through the Intello.

string between junction boxes to make sure they're straight
Service cavity with 2×6’s attached to trusses through the Intello. More info on the service cavity here: Ceiling Details.

This gap was going to be a dedicated space for lighting and the 3″ Zehnder tubes of our ERV (as things turned out, we didn’t end up needing this space for the Zehnder tubes).

bare trusses - intello - intello w: single layer CB 80 - service chase
Intello coming down from the roof trusses to cover the double top plates on the wall.

Before installing the Rockwool batts in the walls, I was also able to fill this gap created by the two 2×6’s on their side that sit on top of the double top plates with leftover pieces of Comfortboard 80. The first piece of Rockwool fit snug inside the gap, while the second piece was attached to the first with some plastic cap nails and the friction supplied by the 2×6’s forming the service cavity. Some additional holding power was added at the gable ends by utilizing drywall clips (visible in the photo below):

intello onto top plates
Connecting Intello to top plates with a strip of Tescon Vana tape, creating a clean and solid surface for the eventual Intello on the walls.

The drywall clips were helpful in lending support to drywall anywhere that adding solid blocking would be time consuming or a physical challenge.

nailer for ceiling drywall
These drywall clips worked great in places where the sheetrock needed additional support.

Even though we utilized a 12″ raised heel roof truss, and we had 4″ of Rockwool on the exterior of our Zip sheathing, it was important to fill this gap created by the service cavity to make sure our thermal layer was unbroken around the perimeter of the house (4″ Rockwool on the exterior, 5 1/2″ Rockwool in the stud bays). The outside edge of the roof truss is also the most vulnerable to ice damming, so having the 4″ of Rockwool Comfortboard 80 directly below this area where blown-in cellulose would be installed offers some additional thermal performance to the attic insulation.

Another view of this area where roof truss meets the 2-2×6’s standing on their side, creating a gap between the bottom chord of the roof truss and the top plates on the wall below.

sealed top of wall from inside
Roof truss on 2-2×6’s turned on their sides, which have been sealed with Pro Clima tapes. HF sealant completes the airtight connection between the Zip sheathing and the 2-2×6’s.

If I had it to do over, I would go with a 24″ raised heel truss, as this would offer not only significantly more R-value in this area (for relatively little expense), it would also make any inspection or repairs in this area much easier to deal with.

mbr w: rockwool in walls
Installing Rockwool batts in the walls of the Master Bedroom.

As each piece of Rockwool batt was installed, it was important to keep any butt joints between cut pieces tight together. Also, once each piece was snug inside the stud bay I finished by gently fluffing the outside perimeter edges so the Rockwool sat as flush as possible to the 2×6 studs, thus maximizing their R-value.

mbr rockwool complete
Master Bedroom ready for Intello on the walls before drywall gets installed.
family rm w: rockwool
Family room ready for Intello and then drywall.

Intello

With 4″ of Rockwool Comfortboard 80 on the exterior of our sheathing, the code specifies that we could’ve just used latex paint as our interior vapor retarder (Class III).

Again, to improve our margin for error, I felt like it was worth the added expense and time to install a smart vapor retarder (CertainTeed’s Membrain product would’ve been another alternative) to avoid potential issues with diffusion in the winter.

When I asked a question on GBA about this issue, the consensus seemed to be that the Intello, although technically unnecessary, was a nice bit of insurance.

It also added a final layer to all of the previous air sealing details. With redundant layers of air sealing, even if small areas experience failure over time, there are still other areas to back it up, thus maintaining our overall air tightness for the long term.

intello at frt dr basement
Intello installed in the basement stairwell by the front door.
finishing intello mbr
Intello in Master Bedroom nearly complete.

Sealing the Intello to the subfloor was one of the final air sealing chores of the build. It was deeply gratifying to finally get to this point, especially since drywall and then flooring were up next.

tescon on intello at subfloor
Intello taped to the subfloor with Tescon Vana tape.
intello tvana complete mbr
Intello complete in the Master Bedroom.

Thoughts on Advanced Framing Techniques

If I had it to do over, I would use less framing around windows and doors, along with using pocket headers instead of the more traditional insulated headers we ended up with. Pushing the header to the exterior sheathing would mean being able to insulate the pocket on the interior side with Rockwool or dense pack cellulose, rather than the rigid foam we ended up with (unfortunately, XPS in our case).

family rm w: rockwool
Family room ready for Intello.

Before we had to fire them, the two GC’s we were still working with as framing began were unfamiliar with advanced framing techniques, and they were already struggling to comprehend the many Passive House details in the drawings (not to mention many of the conventional details) so, as I’ve noted elsewhere, I had to pick my battles carefully.

Another change I would make would be at points where interior walls meet up with exterior walls. Rather than using ladder blocking to make the connection, which is still better than more traditional methods (creating a boxed in void that’s virtually impossible to insulate), I would utilize a metal plate at the top of the walls to make a solid connection. In addition to making drywall installation easier since it would create space between the two intersecting walls for sheets of drywall to be passed through, it would also make installing insulation, especially batt insulation, much more straightforward with clear and easy access (no horizontal blocking to get in the way).

intello at ladder
Intello at partition wall that meets the exterior wall (using ladder blocking).

A ProTradeCraft article discusses what builder David Joyce believes is ‘worth doing’ in terms of advanced framing techniques. Perhaps just as important, he points out what he believes can be safely ignored, or is just ‘not worth doing’ when it comes to OVE.

In this Matt Risinger video, architect Steve Baczek delves into some of the key components he uses to optimize advanced framing techniques:

In addition to the pocket headers, the idea of using header hangers instead of additional jack studs, seems to make a lot of sense.

And here’s a ProTradeCraft video regarding their own take on Advanced Framing:

One final change to our framing would be opting for 2-stud corners instead of the California 3-stud corners that we have. Although a relatively small change, I think a 2-stud corner is cleaner and allows for slightly more insulation in this vulnerable area.

Clearly each designer, architect, GC, or framing crew will have their own particular views on advanced framing, so there’s room to make individual choices without undermining the goal of balancing structural integrity with reduced energy demand. Local codes, along with the opinion of your rough framing inspector, will also have to be accounted for.

My guess is these techniques will continue to evolve, especially if specific products come to market to aid the process (i.e. reduce the amount of framing lumber required while ideally also lowering labor costs, all without negatively affecting the overall strength of the structure).

intello kitchen
Intello in the kitchen complete.

One final attempt at some additional air sealing was around outlet and switch boxes as they met up with the Intello. With a bead of HF Sealant, it was easy to make an airtight connection between the Intello and the box.

cu intello at outlet
Completing connections around outlet and switch boxes with HF Sealant.

At doors and windows, I finished these areas off with a strip of Tescon Vana tape, just as I had at the top and bottom of the walls.

intello complete br2
Completing Intello around a bedroom window.

Because corners tend to be problematic in terms of air leakage, I also added a dab of HF Sealant to these areas for the sake of some added redundancy.

lwr lft corn wdw w: intello & tape
Lower left corner of window with some added HF Sealant in the corner.
upper rgt corner wdw w: intello
Upper right corner of a window just before final piece of Tescon Vana tape is run across the top of the window frame, tying together the Intello and the light blue Profil tape that is air sealing around the window.

Sound Attenuation

Since we designed our home with a smaller than average footprint, incorporating many Not So Big House principles (roughly 1500 square feet for the main floor, with another 1500 square feet in the full basement below), one way to make the floorplan feel larger than it actually is was to provide some sound attenuation in key areas (we incorporated several other techniques to “expand” the feel of the floorplan that will be discussed in upcoming posts regarding interior design).

For instance, we installed the Rockwool in the long partition wall that runs east-west down the center of the floorplan. This wall helps define the barrier between public areas (kitchen and family room) on the south side of the home and the private areas (bathrooms and bedrooms) on the north side of the home.

We could’ve used Rockwool Safe ‘n’ Sound, but at the time, during construction in the fall of 2017, it was a special order item in my area, whereas the batts were already in stock, both for my main 2×6 partition wall, a 2×6 plumbing wall, and the remaining 2×4 walls that we felt could benefit from the Rockwool.

In the photo below, the Rockwool in the main east-west partition wall is covering the refrigerant and drain line for one of our three Mitsubishi heat pump heads, along with the usual electrical conduit for outlets and light switches.

rockwool 2nd br entry hall
Rockwool added to some interior walls for sound absorption, thus reducing unwanted sound transmission between certain spaces.

Here’s another view of this partition wall, this time from the opposite side inside the second bedroom:

rockwool 2nd br interior side
Same section of east-west partition wall from inside the second bedroom.

We also added Rockwool to the wall that connects the master bath to the 2nd bedroom bath, and between the 2nd bath and 2nd bedroom. The Rockwool was even added to the wall between our kitchen and utility room, where we have our washer and dryer, in the hopes that it would limit the amount of noise coming from the machines (which it thankfully has).

rockwool bath walls
Rockwool in bathroom wall around main waste stack.

Although this doesn’t make for a totally sound proof connection between spaces (we weren’t prepared to take things that far — roughly equivalent to air sealing a Passive House in the amount of detail required), the ability of the Rockwool to significantly muffle sound between rooms is quite impressive and, for us at least, well worth the effort and added expense.

rockwool kitch - utility
Rockwool in the wall between the kitchen and utility room.

For instance, while standing in the master bathroom, should someone be running water or flushing the toilet in the 2nd bathroom directly on the other side of the wall, the majority of the sound that reaches your ear comes by way of the master bedroom doorway, not through the wall directly. Out of curiosity I tested this idea with music playing on a portable stereo in the 2nd bathroom with the same results — sound through the wall is dramatically muffled, while the same sound that easily travels out of the bathroom and makes it way via the bedroom doorway is crystal clear. With the door to the 2nd bathroom and our master bedroom door closed, this same sound is obviously further reduced.

It’s also nice to watch TV in the family room and know that as long as the volume is at a reasonable level you’re not disturbing anyone trying to sleep or read in the two bedrooms. This kind of sound attenuation also adds a level of privacy to the bathrooms while they’re in use.

And, again, it’s not that no sound is transmitted from one room to another, rather it’s almost entirely limited to doorways, thus significantly reducing the overall impact of the noise that is transmitted. In other words, our goal was rather modest, we were just after significant sound absorption, not sound proofing (e.g. the level of noise cancellation required in a professional recording studio or a high-end home theater room).

As a result, I would definitely use Rockwool for sound absorption again. In fact, I can’t imagine going without this kind of sound attenuation (or something akin to it using other products or techniques outlined in the videos above) now that we’ve been able to enjoy it in our new home. It effectively prevents the issues often associated with so-called “paper thin” walls.

Arguably, addressing this issue of unwanted sound transmission is even more important in Passive Houses or high-performance homes that are already much quieter than conventional homes because of the extensive air sealing and well above code levels of insulation. In our own case, outside noises either disappear entirely or are significantly muffled — this includes a commuter train a couple of blocks away.

As a result, any noises within the home itself become much more pronounced since they don’t have to compete with the typical noises coming from outside the home. For instance, when we first moved in the fridge in the kitchen was easily the most obvious, consistent sound in the house. After a couple of weeks it just became background noise we’ve grown to ignore, but it was surprising just how loud it was initially, especially our first few nights in the home when everything else was so quiet.

In addition to excessive air leakage and obvious temperature swings between rooms, along with poorly sized or placed window layouts, the lack of any sound attenuation between rooms is one of the issues we notice the most when we’re inside more conventionally built homes. Much like all of the conveniences associated with a modern kitchen, it’s easy to take something like effective sound attenuation for granted until you’re required to go without it (e.g. in the case of kitchens while on a camping trip or waiting for a kitchen to be remodeled).

With all of the Rockwool batts in place, and the Intello installed over the exterior walls, drywall could finally go up.

Drywall

We went with USG 5/8″ EcoSmart drywall (GBA article on EcoSmart). We chose the 5/8″ over 1/2″ mainly for added durability and some slight sound deadening between rooms.

I had read about Certainteed’s AirRenew drywall, but it sounded like the only VOC it absorbed was formaldehyde, which, if I understand the issue correctly, can be safely avoided with the use of appropriate cabinets and furniture. If memory serves, AirRenew works by utilizing a compound similar to triclosan, meaning a biocide, which some believe can have potentially serious health effects. It’s not clear to me, even now, whether the use of AirRenew drywall makes sense, or exactly what compound (or series of compounds) are utilized to absorb the formaldehyde since Certainteed has remained silent on this point, claiming the information is proprietary. Nevertheless, it has a Declare label, so ILFI must believe it’s reasonably safe to have on painted ceilings and walls.

At any rate, we wouldn’t be bringing in any new furniture that would have elevated levels of VOC’s (including flame retardants) once construction was complete. Since our last house was significantly larger, roughly 2,800 sq. ft., it was fairly easy to downsize, donating or giving away what we couldn’t use in our new house, while holding on to our favorite and most useful pieces. It also helped that we never really filled up our last house (e.g. we never got around to purchasing a formal dining room set), so we didn’t have as much “stuff” to discard as we might have.

Moreover, by being mindful of every finish we create or use (primers, paints, wood flooring, grout sealer, caulks and sealants, kitchen cabinets etc.), along with any other products we might bring into the new house (e.g. surface cleaners, new furniture, fabrics, even perfumes and colognes, etc.), we’re hoping to maintain a high level of IAQ.

The International Living Future Institutes’s Red List and their database of Declare products were a big help to us, even though we’re not pursuing any kind of certification with them. The Greenguard certified label was also helpful, in particular when it came time to choose tile and grout.

By consciously choosing every product and material that comes into the home, it’s possible to at least reduce our exposure to harmful VOC’s and chemicals. While still imperfect (Who can you trust?), these kinds of programs do allow designers and homeowners to take some control over the environments they’re creating and living in, which is empowering to a degree. Far better if the US regulatory bodies operated under a precautionary principle model when it came to industrial products.

Frankly, in a rational system, one that was truly looking out for the best interests of consumers, this kind of research — time consuming and frustrating busy work to put a finer point on it — would be considered laughable if not horrifying. In a rational system it would be safe to assume that any product for sale, apart from some careful instructions on their use and disposal, would be safe to have inside your home without having to worry about short or long term health implications.

Nevertheless, if unintended health consequences are to be avoided during a renovation or a new construction build, consumers have little choice but to do the necessary homework (or pay someone else to do it for them) and be as thoughtful as possible with their selection of materials.

drywall family rm
Kitchen and family room after drywall was installed. Ready for primer, paint, and flooring.

Now that all of the elements of our wall assembly were complete, it was time to have some fun with final finishes: flooring, wall colors, wood trim, doors, kitchen cabinets…

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 manage water safely and, unfortunately, largely go 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!

Gravel Border Around the Foundation

2

Before we purchased our empty lot we had been told that our subdivision has a fairly high water table, so managing underground moisture, especially with a full basement, was going to be a necessity.

In order to better control water below-grade we had our concrete subcontractor install drain tile on the exterior and interior sides of the foundation walls at the footings in order to maximize the amount of water that could be quickly and efficiently sent to our sump pump. Once our sump pump ejects the water outside it travels through an underground pipe to a culvert out by the street, moving with the aid of gravity, along with water collected from our neighbors’ homes, before ending up in the municipal system.

In addition to the spray-on damproofing applied to the exterior of our foundation walls, the 5″ of Rockwool on the outside of our foundation also encourages water to make its way down to the drain tile system before it has a chance to collect and sit, causing serious problems.

At grade, around the perimeter of the house, we also decided to install a gravel border, both for its decorative effect and its ability to encourage water to move away from the top of our foundation and down to the drain tile, particularly during periods of heavy rainfall.

We also considered various ways to protect and finish the top of the exposed Rockwool on the foundation. Here’s an older Green Building Advisor article discussing the issues involved along with possible solutions (as far as I can tell there’s still no single, obvious solution yet, although a parge coat or stucco finish is arguably the most attractive and durable, especially if combined with a gravel border as opposed to just top soil): GBA

After initially deciding to go with a combination of tile backerboard and Tuff II (giving the exposed insulation the look of finished stucco or exposed concrete), we ended up using metal flashing from coil stock instead (typically available in the widest number of options from a local roofing supply company).

It was only after construction began that I learned the tile backerboard manufacturers don’t honor warranties for this below-grade application (perhaps this will change in the future, or maybe they’ll develop a product for this specific application). Although I know the product is commonly used in this way (I couldn’t find an example of a bad experience, or a case of catsastrophic failure anywhere online), the lack of warranty protection doesn’t bolster confidence for its long-term durability.

In this regard, I imagine some kind of gravel border is probably essential, especially if the house would otherwise be surrounded by a lot of clay soil that likes to retain moisture. Also, just getting the backerboard attached to the foundation through the 5″ of Rockwool would have been time consuming (assuming you can find long enough flat-head concrete screws, which we unfortunately didn’t), so we opted instead for metal flashing mainly for its ease of installation and for some cost savings.

January, 2021 Update: Another option worth exploring is using sheets of PVC, as this project in Minnesota has done with Azek’s exterior grade PVC:

Starting on the green Zip sheathing as if it was a typical Z-flashing, we had the siding guys just continue the metal flashing down the face of the Rockwool on the foundation below where we knew the level of the gravel would end up (more on this in a future blog post regarding siding installation details). So far this has worked out well, with the metal flashing avoiding damage, and without much “oil canning”, even on the west side of the house, which has the largest amount of exposure. It probably helps that the metal flashing in this area around the house is the same color as our siding, helping it to ‘disappear’ visually to some extent.

When our excavator did backfill, knowing we were going to have to cover the Rockwool around the top of the foundation, we had him hold back on the top 16″ or so. With this ‘trench’ left exposed, we first applied landscape fabric in order to try and control weeds in the future, and to better contain the washed gravel that we would be putting down inside the trench.

gravel - west side w: just fabric
Setting up the landscape fabric.

As with many other areas of the house, we decided to opt for a more informal look, avoiding a perfectly consistent and squared-off border, preferring more of an undulating path as the outside edge makes its way around the house.

gravel nw corner
Section filled with gravel.

And instead of moving around endless loads of gravel with wheelbarrows, we rented a compact front loader, in our case a Ditch Witch (sometimes referred to generically as a ‘dingo’), which made the project go much faster while also saving everyone’s back.

We had watched Felipe move gravel and other materials around during the construction of our stone window wells, so we knew just how versatile and useful these machines can be — and they just look like a lot of fun to use, which they are.

changa on ditch witch

We rented the machine from a Rental Max location near us, which wasn’t cheap, but we definitely felt like we got our money’s worth, as it saved us from having to endure many hours of hard labor. My wife loved using it, in part because the controls mimic those used in video games, so it was fairly intuitive for her as she quickly learned to precisely and accurately move the machine around exactly where it needed to go, including some fairly tight spots around the house.

We think the machine is worth every penny of rental cost if you have a significant amount of landscape material that needs to be moved, especially if a wheelbarrow is your only other option, or if tight spaces preclude the use of larger machines.

guys helping me spread gravel on west side
Luke, Jesus, and Eduardo help me shovel and rake the gravel into position as my wife drops each bucketful in place.

The boys were profoundly disappointed that they were never given a chance to operate the dingo, especially when they saw how much fun my wife was having using it.

gravel n and w views
Northwest corner of the house as the gravel border takes shape.
setting up gravel on west side
View of west facade as gravel is installed and we prep for boulders.

On the west side of the house we decided to add some boulders where there’s a drop-off in grade. In addition to adding some visual interest, we thought the boulders could help with surface run-off during the heaviest rainstorms.

setting up for boulders
Adding these little gravel beds helped get the boulders set securely in the hard clay soil.

We purchased the boulders locally from Lurvey. They have a nice selection of boulders and flagstones in a wide variety of styles and sizes. We would’ve chosen even larger boulders, but we were somewhat limited in this regard, having to base our selection on what we thought the dingo could safely handle.

first boulders going in on west side
First boulders going in.

In addition to the boulders, once mulch and plants are added to this area we shouldn’t see any erosion in the future.

Setting the larger boulders in place, and selecting and arranging cobblestones around the edge of the gravel border, while it was a lot of work it was also a lot of fun. I can see why someone like Lew French, or Dan Snow, gets so much enjoyment from their work:

And apart from their decorative function, and their ability to help prevent erosion, kids can’t help but try out their balancing skills on the boulders.

ninja training
Ninja in training.
north side w: gravel and first cobblestones
Cobblestones going in around the edge of the gravel border for added decoration and to keep the eventual mulch in the yard separated from the washed gravel border.

There will be more photos showing how the gravel border turned out in a future blog post on the installation of the siding.

nature taking back

With the clay soil left exposed around the house for many weeks, mother nature didn’t hesitate to fill the void with a wide variety of ‘weeds’, some quite beautiful in their own right.

Attic Insulation

2

For high-performance structures relatively high R-values for insulation (at least when compared to current building code requirements) are required from the foundation all the way up to the attic (e.g. Passive House or The Pretty Good House).

After some initial research and product pricing, we knew we were going to predominantly use Roxul (with its recent name change, it’s now known as Rockwool) for our insulation needs. But after realizing blown-in rock wool wasn’t available (at least at the time anyway — presumably this will change in the future), and that batts didn’t make much sense for this application (too costly, and they’re considered more difficult to install properly), we knew we wanted some kind of blown-in insulation. The main options, currently, are fiberglass and cellulose.

Fiberglass vs. Cellulose
Best Attic Insulation

We wanted to avoid foam as much as possible throughout the build, both because of its  environmental impact and the fire risk associated with its use, so we didn’t consider spray foam as a real potential option.

After evaluating blown-in fiberglass and cellulose, we decided that cellulose made the most sense for us.

The next decision was to figure out how much, meaning how many inches did we want to blow into the attic. Our first builder was going to do R-49, which is the current code minimum standard here in Illinois. At the time, even before things went horribly wrong with this builder, this felt like too little. I had read stories about other Passive House projects using significantly more, but many of these were in even colder climates than ours (we’re in climate Zone 5 here in the suburbs of Chicago).

How much do I need?
How much insulation is enough?

We decided that rather than settle on a hard R-value as our goal, we would just do a solid two feet of cellulose since we would be doing the installation of the material ourselves (less out near the 12″ raised heel trusses on the north and south sides of the house). There wasn’t a significantly greater cost in materials to go from an R-49 (just under 15″) to the approximately 24″ we blew into the attic.

After doing a little research, and speaking with a Passive House consultant and a local general contractor who consulted with us on various issues as they arose, the consensus seemed to be that attic insulation was an easy, relatively inexpensive place to sneak in more R-value, which is particularly beneficial in our predominantly cold weather climate (the ceiling/attic is where a significant amount of conditioned air wants to escape in the winter anyway). The blown-in cellulose, like the Rockwool, also has some nice sound deadening qualities as an additional benefit.

How much insulation do you need for Passive House?

The cellulose brand in our local Home Depot is GreenFiber, so that was the product we ended up using. Their product is DIY friendly, even allowing homeowners to rent machines for the actual installation:

We started out with 200 bags delivered to the job site. We assumed we were going to need more (the GreenFiber insulation calculator suggested we would need 250 bags to reach 2′ throughout the attic), but thought it might be easier to estimate a final total once the first 200 bags were installed.

The boys, who helped us with various grunt work chores throughout the project, were nice enough to return and help us bring the bags of insulation indoors the night before we started the installation in the attic. We set up a bucket brigade between the driveway and the kitchen, so it went pretty quickly.

guys w: cellulose
The boys after helping us bring in the first 200 bags of cellulose insulation: Luke, Smitty, Eduardo, my wife Anita, and Ricky.

On the day of installation, getting everything set up and started was fairly straightforward. Apart from a loose hose connection at the machine, which a small strip of Tescon Vana tape rectified, we had no issues with the blower. While my wife fed the bags of cellulose into the blower, I was up in the attic directing it into place.

The first couple of hours were actually kind of fun, but getting a consistent two feet of insulation throughout the attic was time consuming and eventually mind-numbingly boring. The first 12″-18″ weren’t so bad, it was having to wait in each section of the attic for that last foot or so to be blown in place that it began to feel like real drudgery.

cellulose installed looking east
From the attic opening, looking east towards the front of the house.

It also didn’t help that I had a fever and a cold on the day of installation, so being up in the attic surrounded and covered in dust didn’t improve my mood. The process, although very DIY friendly, does require patience and a willingness to cover up — eyes, mouth, and nose — for adequate protection against all the dust floating around.

The day before blowing in the cellulose I went through the attic and marked my goal of 24″ of insulation on various roof trusses so I would have a good visual goal to shoot for. In fact, had I known just how dusty and challenging visibility was going to be during the blowing process, I would have marked every single roof truss at the 24″ level to make the job a little easier.

We didn’t have much in the way in terms of obstacles from various services, other than a few pipe vents for plumbing and radon, along with a small amount of electrical conduit for solar on the roof and a single light in the attic (we kept the majority of all services in our ceiling service core and our walls). This made for a fairly straightforward installation of the cellulose.

cellulose installed looking west
From the attic opening, looking west towards the back of the house.
south east corner w: cellulose
Another view, this time a little further to the right, showing the far northwest corner of the attic.
vents by bench w: cellulose
Cellulose at its full depth around the plumbing vents and radon stack.
cellulose at the attic hatch
Finishing up. The attic access hatch is visible at the bottom of the photo.
bench behind attic hatch opening
The bench next to the attic access opening as we finish up blowing in the cellulose.
building up cellulose around attic chutes
Cellulose hitting the underside of the insulation chutes as it gets blown into place at the edge of the roof by the raised heel trusses.

Thankfully I was able to keep the cellulose out of the insulation chutes, instead slowly piling it up just below each chute. The siding guys already had most of the soffits installed (this was the end of October, 2017 last year), including a channel for air flow for our “vented roof” assembly, so any cellulose that found its way into the chutes and down into the soffits would’ve been a real pain to remove (I’ll have a separate post later about the siding installation, including the many details of our rain screen and 4″ of Rockwool on the exterior side of the Zip sheathing).

The bench next to the attic access hatch ended up working out really well, and I was very thankful it was in place.

lid on bench w: cellulose
Lid of the attic access hatch sitting on its bench next to the attic opening after the installation of the cellulose is nearly complete.

By the end of the first day it was clear we didn’t have enough cellulose to finish the whole attic. We started with 200 bags, but we finished up the second day at just under 300 bags total (288 was the final number of bags installed, so a little more than the 250 recommended by the GreenFiber calculator). What we didn’t use we were able to return to Home Depot for a refund.

how much more cellulose
My wife wondering how many more bags until we’re done — unfortunately the answer was simply ‘more’ as she popped her head up into the attic several times towards the end of the installation.

Apart from the north and south sides of the attic around the raised heel trusses, we had a solid 24″ throughout the attic, in fact, a little more in the center of the attic where it was easiest to pile it up and let it accumulate (closer to 28-30″ in some areas). This probably explains, too, the additional 38 bags we used that exceeded the initial estimate by the GreenFiber calculator.

covered in cellulose
This is where a degree from Michigan gets you. #GoBlue. It was a long day.

On a side note, there was also some concern about the weight of the cellulose on the Intello (our ceiling air barrier), but in the end, even where the cellulose was at its deepest, there was thankfully very little sagging evident in the Intello. Even if it had been worse, the 1×4’s were in place to help support the Intello and the cellulose for the long term (the 1×4’s were spaced roughly 16″ apart between the 2×6’s of the service core).

sag1
Slight sag in the Intello evident after installing the cellulose in the attic.
sag2 closer view
Close-up of the slight sag in the Intello near the west gable end of the house.
sag3 Intello touching 1x4's
Another view of the slight sag in the Intello as it touches the 1×4’s directly below it.

It’s worth keeping in mind that the cellulose will settle a bit, especially during the first few months. This is obviously very important when it comes to establishing what depth you’re initially going to blow in and your expectations about long-term R-value after settling has occurred (something to consider before signing a contract if you’re going to be hiring someone to do the work — both parties should agree and understand what the final R-value will be before the work commences).

I was back up in the attic recently as I finished up painting the master bedroom and closet. Since I already had drop cloths down, I thought I should take what will hopefully be one last look at the attic.

ladder in wic
Ladder under the attic access hatch in the master bedroom closet.

On average, the cellulose looks like it has settled about 2-4 inches below its original depth, depending on where I looked.

settling1
Some of the red horizontal lines at 24″ now clearly visible in some parts of the attic.

Even with this settling, the attic probably still comes in close to R-70 on average —significantly less out at the north and south ends of the roof with the raised heel trusses, but a little more in spots towards the middle of the attic where some red lines are still hidden below the cellulose.

settling2
You can see my red arrow and horizontal line at the 24″ level off to the right.

Just under or over R-70 in the attic is in tune with both the Pretty Good House and Passive House metrics for attic insulation for my climate region (Zone 5 here in the suburbs of Chicago).

While I was up in the attic I also noted that there was no evidence of any water or moisture damage on the OSB roof sheathing, or any indication of wind washing of the cellulose, so the attic seems to be performing as designed, which is a great relief.

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.
foundation-garage-house-connection-inside-corner-of-garage-inside-corner-of-front-porch
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.
foundation-side-porch
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.
foundation-concrete-jewelry
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:

madrona-wall-assembly-914x1024-e1459377577722
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.

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