kimchi & kraut

Passive House + Zero Net Energy + Permaculture Yard

Tag Archives: air sealing

Roof Details (Air Sealing #3)

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Top of Wall and Roof Connection

Once the wall assembly details were figured out, and our ceiling set-up detailed, the transition between the two became the next challenge. In other words, how to carry the air barrier over the top of our exterior walls.

I found this helpful article by Chris Corson from The Journal of Light Construction:

An Affordable-Passive-House  (pdf)

Using a waterproof peel-and-stick membrane to wrap over the top of the wall (going from exterior sheathing — in our case 7/16″ Zip sheathing — to interior side of the top plates) seemed like the easiest way to maintain a continuous air barrier at the wall-to-roof junction. The membrane would also have a nice air sealing gasket effect after the trusses were set in place.

I also found this excellent Hammer and Hand video on YouTube (one of their many helpful videos):

Wall-to-Roof Air Barrier

Also, by being able to carry the Zip sheathing up above the top plate of the wall, hugging the bottom of the trusses, meant our 4″ of Roxul Comfortboard 80 over the Zip sheathing would rise above the top of our walls, so that thermally we would be protected going from the exterior walls to the attic, which will be filled with 24″ of blown-in cellulose — making our thermal envelope continuous for the whole house: under the basement slab – exterior of foundation – exterior walls – attic (except for one small gap at the footing-slab-foundation wall connection, which I talk about in a separate post: Foundation Details).

A high R-value wall meets up with a high R-value attic, with no thermal bridging, making our thermal layers continuous. When this is combined with an equally air-tight structure, conditioned air cannot easily escape — resulting in a significantly lower energy demand for heating and cooling (and therefore lower utility bills), and added comfort for the occupants.

Here’s a nice diagram from Fine Homebuilding magazine showing a similar set-up:

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Diagram from Fine Homebuilding magazine.

I tried using rolls of conventional peel-and-stick window flashing membrane, purchased from Home Depot and Mendards, but they performed poorly, even in unseasonably warm temperatures for February in Chicago.

I then switched to Grace Ice and Water Shield, normally used as a roofing underlayment along the first 3-6′ of roof edge.

grace-ice-water-shield

Purchased this box at Home Depot.

Since it came on a long roll about 4′ wide, my wife and I cut it down to a series of strips that could more easily be applied to the wall-top plate connection.

While the sun was out, the Grace membrane worked fairly well, especially when pressure was applied with a J-Roller.

grace-vycor-in-the-sun-ii

Grace Ice and Water Shield applied to the top of our wall — covering the Zip sheathing/top plate connection.

Unfortunately, the sun and warmer temperatures didn’t stick around long enough for me to finish.

sealing top of wall w: Grace Vycor in sun

Using a J-Roller to get the Grace Ice and Water Shield to stick better.

 

grace-vycor-in-the-sun

This Simpsons sky didn’t last long. In a matter of hours it was back to rainy, gray, and cold — typical Chicago winter weather for February.

When the weather went gray and cold again, we started to use a heat gun to warm up the Grace membrane, which had turned stiff and nearly useless in the cold.

wagner-heat-gun

Wagner heat gun for warming up the Grace membrane.

After wasting a lot of time and effort trying to pre-heat the Grace membrane before installing it, I finally relented and switched to the much more expensive (but also much more effective) Extoseal Encors tape from Pro Clima. Where the Grace membrane lost virtually all of its stickiness, the Extoseal Encors stuck easily and consistently, with the J-Roller just helping it to lay flatter and more securely.

extoseal-encors-as-gasket

Pro Clima’s Extoseal Encors available from 475 HPBS.

It was a case of trying to be penny wise but ending up pound foolish. Looking back, I would gladly pay an extra $300 in materials to have those hours of frustration back (including the time it took to run to the store and buy the heat gun, which turned out to be ineffective anyway).

installing Extoseal Encors on top of wall cloudy

Finishing up the top of the wall.

After finishing sealing the Zip sheathing-top plate connection on all the outside perimeter walls over the weekend, it was time for the trusses to be installed.

 

 

Trusses

first-truss-swinging-into-place

First truss swinging into place.

Zach let me stand by the front door rough opening and give the crane operator hand signals. It was a fun way to watch the roof take shape.

trusses-going-in-from-inside

Sammy, Zach, and Billy (out of view to the right), landing and setting the trusses.

Once the trusses neared the front door, Zach could signal the crane operator himself, so I was able to get some shots from just outside the construction fence.

 

starting-garage-trusses

Sammy, Zach, and Billy landing trusses on the garage.

 

long-view-of-crane-and-house-east-side

Setting the trusses on the garage — the basic profile of the house comes to life.

Once the trusses were on, and the guys had a chance to install the final top row of Zip sheathing (up to the bottom of the trusses on the exterior side of the wall), I could move inside to seal all the connections from the interior.

 

 

Top of Wall (Interior)

Because of the cold, the Grace membrane was beginning to lift at the edges in certain spots, so just to make sure it had a nice long-term seal, I went around the perimeter of the house and used a layer of Tescon Vana (3″ wide) tape to seal the edge of the Grace membrane.

sealed top plate from interior

Trusses sitting on Grace and Extoseal Encors (other sections of top plate), with the final row of Zip sheathing sealed to the trusses with HF Sealant.

The picture below shows all the connections involved: top of Zip sheathing meeting the roof trusses and the top plate of the outside wall:

sealed top of wall from inside

HF Sealant helps to air seal the Zip-truss and Zip-Grace/Extoseal Encors connections.

 

view of top row of Zip sheathing 1

Looking up at the top row of Zip sheathing attached to the outside edge of the raised heel trusses.

 

 

 

Shingles

We had to wait for shingles for quite some time. First we had to fire our GC’s, and then I had to find a roofer and a plumber (to make penetrations through the roof before the shingles went on). But before the plumber could even start, I had to get the Intello installed on the ceiling. And even before that, I had to figure out the insulation baffles, which I’ll talk about in a separate post.

It took awhile to find a roofer since they would have to make three separate trips for a relatively small job. The first trip was just to set down the Grace Ice and Water Shield at the edges of the roof, along with a synthetic roof underlayment (the consensus was that typical roofing felt wouldn’t hold up to long term exposure). As it turned out, it took weeks before the plumbers made their penetrations through the roof sheathing (literally the day the roofers showed up — a long, horrible story in and of itself that I’ll save for later).

synthetic underlayment at roof peak

Synthetic underlayment covering the ridge line until the shingles and a ridge vent can be installed.

The second trip out was to install the shingles on the roof of the house, while the third trip to install shingles on the garage roof could only happen after the Roxul on the exterior of our Zip sheathing was installed (in order to make a proper sealed connection between the wall of the house and the garage roof).

There weren’t many roofers willing to work with our unique Passive House sequencing, but Peterson Roofing was kind enough to take it on.

Grace ice and water shield rolling up after wind

Grace Ice and Water Shield rolling up on itself after the wind got ahold of it.

Unfortunately, the day after the guys installed the Grace membrane and the synthetic underlayment, we had a cold, blustery day. Once the wind grabbed the Grace membrane, the membrane rolled up on itself, turning it into a real mess.

Because of our recent past bad experiences with general contractors, I just assumed I was on my own, so I spent a couple of hours putting down new layers of the Grace membrane. When Peterson roofing found out, they were shocked I did it myself, and assured me I could’ve called them and they would’ve come back out. We were so used to people not following through, that low expectations meant it didn’t even occur to me to call them.

We initially were going to use Certainteed’s Landmark TL shingle, which mimics a cedar shake shingle profile, but Armando from Midwest Roofing Supply in Schaumburg, Illinois was kind enough to take the time to walk me through the options available, and explained that because our roofline isn’t steep, only the neighbors from their second story windows would get to appreciate the effect. He recommended we save some money, while not giving up on quality or durability, and go with the Landmark Pro product.

shingles being installed w: vents

Shingles going down on the roof of the house.

The shingles went on quickly since we have a relatively small and simple roof. In addition to the aesthetic leap the shingles made on the appearance of the structure, it also meant I didn’t have to go around cleaning up the subfloor every time it rained.

Although the synthetic underlayment worked pretty well at keeping the rain out, if there was significant wind combined with rain, the water easily found its way under the underlayment where it could then drip and fall on the subflooring below — pretty depressing showing up to the job site after a hard rain knowing I was going to spend the first hour just cleaning up and looking for leaks.

roofers shingling south side

Seeing this felt like a tremendous amount of progress was being made. It also meant an end to our roof leaks on the interior.

 

shingle installation progressing

Shingles going on quickly.

After they cut the opening for the ridge vent, but before it was installed, I managed to get this shot from inside:

attic just before ridge vent installed

Attic as cathedral.

 

 

Framing (Air Sealing #2)

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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 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.

 

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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…

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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

installing-floor-joists-w-bill-johnny

Billy and Johnny installing the floor joists.

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. 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:

More gymnastics required while applying the Contega HF 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 photos 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.

 

zip-on-framing-covering-tescon-vana-w-roxul-below

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

subfloor-done-blank-canvas

Our blank canvas.

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

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.

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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.

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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 north-east corner of house, and 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 (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 looking down 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.