Monthly Archives: July 2017

12:32 am - July 16, 2017 - Eric Whetzel

Insulation Baffles vs. Insulation Chutes

Our structure was designed with a “cold roof”, or ventilated roof assembly. By having continuous ventilation in our north and south soffits, with a ridge vent on the top of our roof, outdoor air can freely enter the soffits and exit out the roof’s ridge vent. The benefits of this set-up are explained in these comprehensive articles:

BSC – Roof Design

All About Attic Venting

FHB Roof Venting

Here is the product we’re going to use in the soffits:

Cor-A-Vent

In order to make this kind of roof assembly work, insulation baffles or insulation chutes are necessary, especially if the attic is going to have any kind of significant amount of insulation, in particular blown-in insulation that could potentially move around and block off the soffit ventilation from the attic, thereby short circuiting air flow from the soffits through the roof’s ridge vent.

When it was time to install the insulation baffles, I assumed I could just go to one of the big box stores and (thankfully for a change) just buy something off the shelf. It didn’t work out that way.

At Home Depot they had Durovent (a foam based insulation baffle) and an AccuVent baffle (black plastic). Both were a disappointment.

I didn’t buy the Durovent — even just seeing it on the shelf and handling it in the store, it looked cheap and unimpressive. It was hard to imagine it holding up under the pressure of any significant amount of blown-in insulation pressing against it.

The AccuVent product Home Depot carried only worked in a straight line (no curve to wrap over the back of the Zip sheathing at the top of the wall assembly), ideal for a cathedral ceiling application. After looking around online, I found this other AccuVent product:

Seeing the video made me think it would be an easy installation, but once I had the product on the job site and tried to install one, the realization hit that they would be a pain to properly air seal, and again, I had concerns about blown-in insulation pressing up against it for years.

AccuVent out of the box — *AccuVent on the job site. It’s hard not to look at these foam/plastic baffles, regardless of brand, and not think: “flimsy”.*

Here’s the specific product info:

And here are the installation instructions:

When I realized the AccuVent wasn’t right for our project, it was a moment of, “Uh-oh, now what the hell do I do?”

I assumed there must be a sturdier plastic baffle, but I never found one. Instead, I came across this article:

Site Built Baffles

As usual, GBA — had already addressed the issue.

It was nice to have a solution, but I also knew it would be time consuming and back breaking (also neck straining) — the only thing worse than working with sheet goods is working with sheet goods above your head on a ladder. Nevertheless, I would sleep better knowing it was panels of OSB rubbing up against 2 feet of blown-in cellulose insulation rather than sheets of flimsy plastic. Long term solutions do wonders for peace of mind.

first chute installed and sealed — *First insulation chute installed.*

I used small, cut pieces of 2×4 (six per OSB sheet) as a screwing base (visible in the photo below) to install each insulation chute — screwing the blocks first to the roof trusses, then, after putting the OSB into place, screwing through the OSB and into the bottom of each 2×4.

close up looking down chute before sealing — *The blocks were first screwed to the trusses, before each sheet of OSB was attached to the 2×4 blocks from below.*

Then, after installing each sheet of OSB, I went around the perimeter sealing all the gaps. Here’s the product I used for that:

close up Quad Max product label — *The OSI sealant I used to cover the gaps.*

Here’s what the chutes looked like once they were installed on the south side of the house:

And this is what the chutes looked like when completed at the top of the Zip sheathing:

sealed top of wall w: sealed insulation chute

There weren’t always sizable gaps where the OSB chute met the top of the Zip, but when there were, this was pretty typical:

unsealed warped chute before sealing w: small piece

Same area after adding a thin piece of OSB to help cover the gap, and then sealing the area with the OSI sealant:

Looking down a chute before sealing with the OSI:

Same view after sealing up the gaps:

I showed up on a rainy morning to continue installing the chutes, and this picture shows the dramatic before and after view of without chutes and with chutes installed and sealed:

blue glow before and after chutes — *On the left: no chutes and light visible through the soffit. On the right: chutes installed and completely sealed.*

Here’s a long view of the chutes:

epic long view of insulation chutes — *49 installed with one to go (far left corner).*

insulation chutes in corner — *Final chute installed and sealed.*

insulation chutes from outside — *View from outside showing the ends of some of the OSB chutes peeking over the edge of the soffit.*

close up of OSB insulation chutes from outside — *Closer view of the top of the Zip sheathing meeting the OSB chute.*

Intello from attic w: insulation chutes in bg — *In the attic with the insulation chutes in the background, after the Intello was installed on the ceiling below.*

Once the chutes were installed, I was finally ready to put the Intello on the ceiling, which thankfully I didn’t have to install by myself.

[December, 2020 Update: If you’re trying to avoid the time and materials associated with installing site-built plywood chutes, a newer (at least to me) product like Smart Baffles is probably worth considering:

https://dciproducts.com/smartbaffle/

Although, as with any new product, it’s worth the time and effort to do a mock up, in this case with a roof assembly (much like the one shown in their video), along with a partial wall assembly, in order to see how the product works (evaluate the durability of the product, ease of installation, final fit, etc.), especially where (and how) the baffle will meet up with the top of the outside walls. With a mock up, you can avoid (or work through) any issues with the product before you’re on the job site actually installing them (when time and money really matters).]

2:57 pm - July 4, 2017 - Eric Whetzel

Roof Details (Air Sealing #3)

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 illustration from Fine Homebuilding magazine showing a similar set-up:

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

Zach asked me to 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.

first-truss-swinging-into-place — *First truss swinging into place.*

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 silhouette of the house starts to come 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, top 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 our roofer 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.