kimchi & kraut

Passive House + Net Zero Energy + Permaculture Yard

Category Archives: Structure of House

Framing (Air Sealing #2)

2

Mudsills

In a conventionally built home, mudsills are typically an area of significant air leakage (if you’ve ever seen sill sealer — a thin layer of foam normally used to address this lumber-concrete connection — under an actual mudsill, you can visibly see just how poorly it performs).

In contrast, after reading about various strategies employed to reach the Passive House standard of 0.6 ACH@50 for air tightness, I decided to use the approach developed by architect Steve Baczek specifically for mudsills. There is an excellent article in Fine Homebuilding magazine that describes the details, and there is a companion series of videos available on Green Building Advisor (after the first video, membership is required, but it’s well worth it for this series of videos, as well as all the other information available on GBA).

We didn’t use the layer of poly, or the termite shield, but the remaining details we followed fairly closely. And we did make one product substitution — instead of using the Tremco acoustical sealant, we decided to go with the Contega HF sealant (less messy, lower VOC’s, and skins over and firms up enough to apply the Pro Clima tapes, all while remaining permanently flexible like the Tremco product —  these products are available at foursevenfive.com).

bill-and-phil-setting-up-chalk-lines-for-mudsill
Billy and Phil setting up chalk lines for the mudsills.
nils-running-bead-of-sealant-before-mudsill-goes-down
Nils applying a thick, continuous bead of Contega HF sealant, including around the bolts, before the 2×6 pressure treated sill plate gets installed with a BG65 gasket underneath.
ct-gasket-close-up-on-srap-board
BG65 gasket from Conservation Technology stapled to the bottom of a scrap piece of sill plate.
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BG65 gasket rolled up in the box it shipped in.
Sammy and Billy stapling the BG65 gasket to the sill plates before installation.
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Mudsill installed with some squeeze out of the sealant.

Installing the sealant on the mudsill (interior/exterior edges, seams, and bolts/nuts/washers) required some gymnastics:

selfie-by-window-buck
In theory, she’s helping me.
mudsill-with-gasket-and-sealant-garage-from-inside-basement
Mudsill after installation: sealant covering sill plate – BG65 gasket – concrete connection, with seams filled.

Once again, based on Steve Baczek’s design — going from exterior to interior — here is our Mudsill Air Sealing Approach:

  • Bead of sealant on the exterior side of the 2×6/foundation connection
  • BG65 gasket under the sill plate — along with a thick bead of sealant under the gasket and sill plate (including around bolts)
  • Bead of sealant on the interior side of the 2×6/foundation connection
  • And then, finally, a taped connection on the interior side of the 2×6/foundation connection as a last line of defense against air infiltration (which I’ll complete once all the trades go through the interior of the house).

The approach assumes I will make mistakes at certain points with each layer of air sealing, so I’m counting on these layers of redundancy to protect me from myself. Again, this is the first time I’ve ever done this, so the theory is that even if I make a mistake in one area, it’s unlikely that I will make a mistake in exactly the same spot with successive layers of air sealing.

Obviously I’m trying to do my best with each layer, but I like the idea of added layers of protection (a Passive House obsession), especially when accounting for the long-term life of the structure. Even if each layer could be installed perfectly, presumably each layer will fail eventually at different times and in different places (hopefully 50-100 years from now if the accelerated aging studies are accurate), so hopefully these layers of redundancy will help maintain significant air tightness far longer than if I chose to use fewer layers. Plus, I’m enjoying sealing everything up, so I don’t mind the process, which always helps.

For larger gaps (not just for mudsills, but anywhere in the building envelope), roughly 3/8″ inch or larger, I am utilizing backer rod to help fill the gap before applying sealant.

This is what it looks like:

The backer rod (readily available at any hardware store) makes life easier for caulks and sealants — less stress on the connection between materials as the inevitable expansion and contraction occurs in the gap.

Hammer and Hand’s Best Practices Manual has the best explanation for their use that I’ve come across:

“While the humble sealant joint may be uncelebrated, it is vital to building durability and longevity. Proper installation is key to sealant joint integrity and function throughout a life of expansion and compression, wetting and drying, exposure, and temperature fluctuation.

Note: Because sealants are just as good at keeping moisture in as they are in keeping it out, placing a bead of caulk in the wrong location can result in moisture accumulation, mold and rot, envelope failure, and hundreds of thousands of dollars in repair and remediation. If we know anything, we know that building envelopes will get wet – the question is, “where will the water go?” Make sure you know the answer throughout construction, especially as you seal joints…

2-1a-500x3892x
Diagram courtesy of Hammer and Hand’s Best Practices Manual.

… Joint Rule of Thumb: Sealant should be hourglass-shaped and width should be twice depth (shown in diagram).
Backer rod diameter should be 25% larger than the joint to be filled.
Joint size should be 4x the expected amount of movement (usually about 1/2” of space on all sides of the window casement).
Ideal joints are within a range of 1/4” at minimum and 1/2” at maximum. Joints outside this range require special design and installation.
Always use the right tool: sealant is not caulk and should never be tooled with a finger (saliva interferes with bond).
Substrates need to be clean, dry, and properly prepared (primer if necessary).
When dealing with thermally sensitive materials, apply sealant under average temperature conditions because joints expand and contract with changes in temperature…”

backer-rod-by-header
Example: Piece of backer rod being inserted into gap between header and 2×6.
garage-mudsill-w-gasket-and-sealant-corner
It’s not visible, but the wood-concrete connection at the side wall has a piece of backer rod embedded between the two materials, making it easier for the sealant to bridge the gap over the long term.

Air Sealing: Rim Joist – Floor Joist – Mudsill Connections

Since there was time between completion of the rim joist/floor joist installation and the installation of the sub flooring (a weekend), I took the opportunity to seal up all the visible connections.

installing-floor-joists-w-bill-johnny
Billy and Johnny installing the floor joists.

Once the subfloor goes in, these connections are still accessible from inside the basement, but the space to work in would be really cramped and uncomfortable (at least I thought so).

rim-joists-box-before-caulk
Rim joist – floor joist – mudsill connections prior to sealant being applied.

The same areas after applying the sealant:

I found the silver Newborn sausage gun (photo below) worked great for thick beads under the mudsills, but the blue gun worked even better for all other seams. Because the blue gun utilizes disposable tips, it was easy to cut the tip to exactly the size I needed, thus using (wasting?) less material (and hopefully saving a little bit of money).

An added benefit of the disposable tips is less time required for clean up at the end of the day (always a good thing). Both guns work great, and appear to be really well-made, although I would probably only buy the silver one again if I consistently needed a fat bead of sealant.

newborn-sausage-guns
Newborn sausage guns I found on Amazon. The blue one works great for thin beads, the silver for thicker beads (e.g., under mudsills).

In the photo below, I filled larger gaps with either backer rod, or in the case of the largest gap, bits of pulled apart Roxul Comfortboard 80, before applying the sealant. Since this is the first time I’ve done this, these are the kind of connections that I failed to anticipate beforehand. They are definitely worth planning for.

The temptation is to just fill these kinds of voids with sealant, but for the long-term durability of the connection backer rod or some kind of insulation stuffed into the gap is a better solution. Filling the voids before sealing doesn’t take much additional effort, so it’s definitely worth taking the time to do it right.

Knee Walls Installed

Because our lot is sloped, the plans called for a series of knee walls:

knee-wall-going-up
The guys installing the knee walls (left to right: Johnny, Nils, Sammy, and Billy).

When I saw the first piece of Zip about to be installed, I realized the bottom edge, which is exposed OSB, would be sitting directly on top of the Roxul on the foundation. While it’s unlikely that water will find its way to this edge (the flashing for the wall assembly will be installed over the exterior face of the Zip at the bottom of the wall), it seemed like a good idea to tape this edge with the Tescon Vana for added protection and peace of mind (even if it only protects this exposed edge until the rest of the wall assembly is installed).

zip-first-piece-attached
First piece of 7/16″ Zip wall sheathing installed.

Knee wall pictured below had all exposed seams in the framing lumber filled with the Contega HF sealant before also applying the Tescon Vana tape, all of which was done prior to the Zip sheathing being installed. The sealant takes about 48 hours to cure enough before you can effectively cover it with the Pro Clima tapes (something to consider when setting up scheduling goals).

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Knee wall being covered in Zip sheathing.
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Close-up of knee wall with Zip sheathing and sealed seams.

For the bottom, exposed edge of the Zip sheathing, I cut the Tescon Vana tape like I was wrapping a present…

Once the Zip sheathing was installed on the knee walls, I could move into the basement and seal up the connections between the Zip and the framing members, in addition to hitting any seams in the framing itself.

Once the house gets closed in, I will go back and tape the connection between the top of the foundation and the mudsill for one last layer of protection against air infiltration.

sealing-up-the-inside-of-the-knee-wall-stud-bays
Knee wall with Zip sheathing after sealing up all the connections.

Subflooring

We decided to use Huber’s Advantech Subflooring after years of reading about it in Fine Homebuilding magazine, and based on the online comments from installers who see the added benefits that come with what is an admittedly higher price point. For instance, it’s more resistant to moisture, so it should produce more stable, flatter flooring (e.g. hardwood or tile) when the house is complete, in addition to preventing annoying floor squeaks.

Billy Phil Nils first pieces of subflooring
First sheets of subflooring being installed by Billy, Phil, and Nils.

In order to maintain a high level of indoor air quality (IAQ), we’ve been seeking out low or no VOC products. So, in addition to the Advantech subflooring, which is formaldehyde-free, we chose the Liquid Nails brand of subfloor adhesive (LN-902/LNP-902) because it is Greenguard certified. Another great resource for anyone trying to build or maintain a “clean” structure is available at the International Living Future Institute website: The Red List

liquid-nails
The product takes much longer to dry when it’s cold and wet outside — at least 2-3 days in our experience (sometimes even longer). It’s nice to see more “green” products showing up in the big box stores, rather than having to always special order them.
view-of-water-tower-from-kitchen-doorway
Standing by what will be the kitchen door. The subflooring was installed with nails and Liquid Nails subfloor adhesive.
rim-joists-at-outside-corner-sealed-up
Corner of our slowly growing wall assembly. The connection between the subflooring and the top of the rim joists was eventually sealed with the Contega HF sealant. 

Basement slowly being covered by subflooring:

Walls Go Up

Our wall assembly is almost entirely based on Hammer and Hand’s Madrona House project, which I discuss here: Wall Assembly

subfloor-done-blank-canvas
Our blank canvas.

In preparation for construction, I built a mock wall assembly in order to easily explain to anyone on site how the various components should go together. It also gave me a chance to practice using the Contega HF sealant, along with the various Pro Clima tapes from 475 High Performance Building Supply.

It’s been exciting to see the walls go up, incorporating the many details in the mock wall assembly.

men-at-work
Men at work: Zach, Phil, and Sammy laying out the walls.
zip-going-on-the-walls-w-bead-of-adhesive
Zach and Phil installing the Zip sheathing over the framing.
zip-sheathing-w-phil-putting-on-continuous-bead-of-adhesive
Phil laying down a consistent and continuous bead of construction adhesive (trying to avoid a bead that runs back and forth between fat and thin), before the Zip sheathing is installed.
wall-being-prepped-w-tescon-vana-on-seams
We were fighting the rain, ice, and mud, but I was able to get the Tescon Vana tape over some of the seams in the Zip sheathing before the walls went up.
sealant-on-nail-holes-in-zip
Sammy and Billy help me apply the Contega HF sealant to each nail hole, and then make it lie flat with a swipe of the spatula, so the Tescon Vana tape that will be applied later will also lie flat.
zip-sheathing-prepped-w-tescon-vana-and-sealant-on-nail-holes
Section of wall nailed, taped, and nail holes caulked — ready to be raised up.

The final step before the walls were raised was to staple the B75 gasket to the bottom of each sill plate.

billy-zach-sammy-south-wall
First section of wall going up: Billy, Zach, and Sammy doing the heavy lifting.
phil-zach-plumb-sammy
Zach establishes plumb, while Phil readies to make the wall secure.
all-together-south-wall
The guys continue with the south walls.

View from south-east corner of the house with the guys framing in the shadow of the water tower:

The only section of wall where the B75 gasket rolled up on itself is shown below — no doubt because this was the most difficult section to get into place because of the stair opening. Otherwise, the guys had no issues with the gasket.

Even on this wall where the gasket did roll up on itself, I will cut off the excess that ended up on the interior side before sealing the connection with the subflooring, and then spend some time filling the void on the exterior side with backer rod and sealant as well.

east-wall-at-stairs-in-place-gasket-roll-up
Zach is the only dedicated, full-time framing carpenter on the crew (the other guys do a variety of carpentry-related work). He has a production background, and it shows with the energy and ease with which he works. He clearly enjoys what he does for a living (In photo: Zach, Sammy, and Billy). Sammy and Billy may not realize it yet, but they’re learning a lot from him (even if he does razz them all day long).

Below you can see some of the junctions where different materials meet, and the effort that’s going into air sealing these inevitable gaps: sealant at rim joist corners, rim joist – subfloor connection, and gasket under the wall sill plate:

wall-at-corner-w-b75-gasket-underneath
Wall is up.
wall-at-corner-w-b75-gasket-view-down-ext-side-of-wall
Same corner as above, but now looking down the exterior side of the wall.

We’ve tried very hard to keep foam out of the wall assembly and the overall structure itself (based on environmental concerns), however, one place where it did find its way in was the insulated headers for above our windows and doors:

billy-and-sammy-insulated-headers
Billy and Sammy putting the insulated headers together.
4th-wall-missing-from-backyard
End of the day. The fourth wall awaits.
east-facade-w-zip-sheathing
First look at what will become our front facade.

Once the perimeter walls were up, I went around with an impact driver and decking screws to tighten the connection between the Zip and the framing members, especially at the top of the walls. Although the Liquid Nails adhesive helps a lot, it still makes for an imperfect connection between the sheathing and the framing members:

top-of-wall-assembly-looking-down-gap-w-nail
Looking down at the top plate. The visible gap is between the side of the top plate and the Zip sheathing. I was able to close gaps like this one at the top of the walls using decking screws. The decking screws also closed similar gaps around window and door rough openings. This should make sealing these areas easier, and the connection more durable.
leaning-over-top-of-zip-sheathing
Leaning over the top of the wall to install the decking screws.

Having seen construction adhesive and nails in action, I would recommend a glue-and-screw approach if you’re trying to fully maximize the tightness of the connection between the sheathing and the framing.

sealant-with-water-tower
Nice view as I apply the sealant.
blue-chicken-pox
My wife giving our Zip sheathing blue chicken pox with the Tescon Vana tape in order to seal all the nail holes.
tescon-vana-embedded-in-ice-on-sill
It’s difficult to see, but this tape is embedded inside a sheet of ice. It rained overnight, before turning to ice. We’re asking a lot of these tapes and sealants. This piece of tape looks like fingertips holding on for dear life.
beast-looking-at-view-from-br-for-1st-time-close-up
The Beast gets a first glimpse of the view from her bedroom window.
pro-clima-pressfix
I was wondering why I would ever need more than one of these. Now I know — bent, scratched, and cracked, the Pressfix from 475 HPBS did its job well.

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