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Tag Archives: Comfortboard 80

Basement Slab (Air Sealing #5)

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The Bottom of our Thermal Envelope

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

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

 

airtightness_with_logo

Illustration courtesy of: passipedia.org

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

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

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

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

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

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

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

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

2-04_no-cap

Illustration courtesy of: foundation handbook.ornl.gov

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

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

 

 

Roxul Comfortboard 80 (2″ + 2″)

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

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

roxul long view two layers

The second layer of Roxul being installed.

 

roxul before stego

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

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

roxul stuffed in around basement pole

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

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

roxul around rough-in bath

Another view of the 2-layers, mostly installed.

roxul before stego - facing ladder

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

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

I’m glad we’ve been able to mostly avoid foam insulation in the build, but seeing the Roxul in a real world application does make me wonder if some kind of rigid foam might’ve given me a more consistent whole floor R-value.

 

 

Stego Wrap

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

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

 

Another product I came across while researching options was Perminator.

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

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

starting stego around roug-in pipes

Starting around the rough-in bathroom pipes.

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

stego going down

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

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

jesus helping me w: first row stego

Jesus helping me install the first row of Stego Wrap.

 

sealed basement pipe close up before pour

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

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

sealed basement pipes with overlapping Stego

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

stego w: foam close up

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

stego w: foam at slab edge

Roxul, Stego Wrap, and Foam installed.

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

stego w: foam at a corner

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

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

 

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

 

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

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

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

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

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

corner of basement pre-pour

 

 

Concrete

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

hole in floor for basement slab

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

 

concrete going thru floor

 

long view of brace for pour

The guys starting at the back of the basement.

 

leveling back corner of basement

 

back corner of basement pour #2

One corner complete.

 

pour heading towards basement stairwell

 

leveling towards stairwell

 

pour at stairwell

 

Tools at stairwell

 

finishing concrete at stairwell

 

troweling at stairwell

Enrique completing the trowel finish.

 

cement truck kissing corner of garage

Side of the garage kissed by the cement truck.

 

close sewer clean out

Close.

 

close long view sewer

Really close.

 

 

Slab Edge

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

How do I seal…

Stego Wrap and Foam cut away from slab edge

Cutting away the excess Stego Wrap and purple foam.

 

close up of slab edge

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

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

wall-slab connection after air dam.jpg

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

 

close up of wall - slab conection after air dam

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

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

Ceiling Details (Air Sealing #4)

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Installing Intello

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

 

 

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

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

2x6 on its side

2×6 on its side, circled in red.

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

another angle of 2x6 on side

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

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

long view w wdw to front door framing

Marking progress: Ceiling ready for the Intello.

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

unwrapping first box of Intello

Big day: opening the first box of Intello.

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

Intello instructions

Reading through the instructions one last time before starting.

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

Intello close up front side 2

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

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

close up Intello back side

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

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

experimenting w: Intello in corner w: chutes above

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

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

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

staple gun

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

Think you know how to load it?

side view of open staple gun

Staple gun ready for loading.

Guess again.

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

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

staple gun open w: staples

Loading the staple gun.

We started with these staples:

close up Arrow staples

But we ended up going with these instead:

close up heavy duty Arrow staples

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

stapling Intello to ceiling

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

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

taping Intello along dotted line

Follow the dotted line.

We checked our initial row from above in the attic:

first row of Intello from attic

View from the attic as the first row is installed.

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

Intello covering ceiling, chutes in bg

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

 

northwest corner of air sealed attic w: Intello

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

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

Eduardo and Jesus helping me put up Intello on ceiling

Eduardo and Jesus giving me a hand installing the Intello.

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

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

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

 

Intello from attic w: insulation chutes in bg

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

After learning about a project on the 475HPBS website…

Masonry Retrofit

 

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

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

OB applying tape

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

 

on plank

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

 

installing Intello on the ceiling around the basement opening

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

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

Intello on ceiling long view

Intello installed and taped.

 

 

2×6 Service Core

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

service chase w: first couple of 2x6's

First couple of 2×6’s going in.

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

Simpson L-Bracket w: fasteners

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

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

close up service chase w: bracket-screws

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

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

We installed the brackets first, before raising up each 2×6 to fit it against the brackets. Since the brackets were directly attached and under a roof truss, we were able to keep the 2×6’s fairly straight, even when the board itself was less than perfectly straight.

service chase w: just brackets

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

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

bird nest

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

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

trusses - Intello - Roxul

Adding Roxul at the top of our wall.

 

layer of Roxul at top of outside wall

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

 

Intello - Roxul - wall

Another view after the Roxul has been installed.

 

long view from west window w: service core complete

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

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

The plans called for the 1×4’s to be installed right after the Intello, but before the 2×6’s, which would have been a lot easier and quicker, but, unfortunately, the GC’s we fired installed the interior walls too high, making this impossible. Having no choice but to methodically cut each 1×4 to fit between each set of 2×6’s, OB was nice enough to help me get it done.

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

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

service core w: cross battens and L-brackets

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

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

ceiling w: 1x4 battens

Completing our service core.

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

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

Here’s some proof:

screw got me

A decking screw got me.

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

looking up at Intello and service core from basement

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

 

installing ceiling w: OB

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

 

 

Maintaining the Intello After Installation

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

small hole in Intello for rain before shingles

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

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

Tescon Vana covering hole in Intello

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

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

imperfection in the Intello marked for Tescon Vana

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

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

2 Cheshire Cats

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

 

Foundation Details (Air Sealing #1)

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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 too 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.