kimchi & kraut

Passive House + Zero Net Energy + Permaculture Yard

Tag Archives: blown-in cellulose

Attic Insulation

2

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

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

Fiberglass vs. Cellulose
Best Attic Insulation

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

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

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

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

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

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

How much insulation do you need for Passive House?

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

 

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

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

guys w: cellulose

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

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

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

cellulose installed looking east

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

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

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

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

cellulose installed looking west

From the attic opening, looking west towards the back of the house.

 

south east corner w: cellulose

Another view, this time a little further to the right, showing the far northwest corner of the attic.

 

vents by bench w: cellulose

Cellulose at its full depth around the plumbing vents and radon stack.

 

cellulose at the attic hatch

Finishing up. The attic access hatch is visible at the bottom of the photo.

 

bench behind attic hatch opening

The bench next to the attic access opening as we finish up blowing in the cellulose.

 

building up cellulose around attic chutes

Cellulose hitting the underside of the insulation chutes as it gets blown into place at the edge of the roof by the raised heel trusses.

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

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

lid on bench w: cellulose

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

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

how much more cellulose

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

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

covered in cellulose

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

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

sag1

Slight sag in the Intello evident after installing the cellulose in the attic.

 

sag2 closer view

Close up of the slight sag in the Intello near the west gable end of the house.

 

sag3 Intello touching 1x4's

Another view of the slight sag in the Intello as it touches the 1×4’s directly below it.

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

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

ladder in wic

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

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

settling1

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

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

settling2

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

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

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

 

 

 

Attic Access Hatch (Air Sealing #7 )

0

Our attic is designed mainly to hold our blown-in insulation (a future post will go over the details), as opposed to a place for running HVAC equipment, conduit for electric, or as a potential area for carving out additional storage space.

Nevertheless, in order to have access to our attic for future maintenance or repairs, I installed a well-insulated attic hatch in our master bedroom closet ceiling.

Following Passive House and Pretty Good House principles required trying to protect the thermal envelope, even in this relatively small area, in order to avoid what can be a notorious point of air leakage and heat loss (i.e., the stack effect).

There were two main products I considered using for this:

Battic Door (R-50 / without ladder)

They also have a product that allows for a built-in ladder for easier access to the attic (you won’t need to drag your ladder in from the garage) while also maintaining a high R-value:

Battic Stair Cover

The other product I considered using was from ESS Energy Products:

Energy Guardian Push Up Hatch Cover

We ended up going with the Battic product, which I purchased through the Home Depot website (this saved me a trip to the store since it was delivered to site).

 

 

Some other products that I’m aware of include:

475 High Performance Building Supply used to sell a Passive House certified version with a fold-down ladder included, but I don’t currently see it listed on their website:

WIPPRO Klimatec 160

Or this product that also incorporates a ladder is available from Conservation Technology:

Attic Ladder

Because the Energy Guardian hatch is made out of rigid foam, I thought the Battic door was the better choice since it seemed like it would be a little sturdier and more durable. To be honest, once the product arrived and I unpacked it, I realized it was something I, or anyone with basic carpentry skills, could put together themselves (assuming you have the time).

Following the directions, I cut an X in the Intello on the ceiling between two roof trusses (and our 2×6 service core below each truss) in order to establish the opening for the Battic frame.

I folded the cut edges of Intello up into the attic for the two long sides of the Battic frame. For the two shorter sides of the Battic frame it was easier for air sealing to push the Intello down into the living area.

At this point I was able to screw the Battic frame into place.

looking up into battic attic hatch

Battic frame initially installed between roof trusses and 2×6 service core.

Once in place, I used a mix of Contega HF Sealant and Tescon Vana tape to air seal the Intello to the Battic frame.

battic - taped sealed to intello

Air sealing the Intello to the Battic frame (short side between trusses).

 

tescon vana air sealed battic w: HF behind Intello

Another view of the Intello sealed to the Battic frame.

 

looking down at air sealed battic from attic

View of the installed Battic frame from the attic.

 

attic access air sealed - attic side

Air sealing the connections between the Intello, the Battic frame, and the roof trusses in the attic.

 

air sealed corner of battic

Using HF Sealant to make the connections as air tight as possible.

Once the outside perimeter of the Battic frame had been air sealed to the Intello, the only place left for air infiltration was where the lid would meet the frame of the Battic hatch once it was installed (more on this later when I discuss my first blower door test).

There was some additional framing required, but it was just a couple of “headers” between the roof trusses to add structural integrity to the two shorter sides of the Battic frame.

attic access from below

Battic frame with additional 2×6’s on one of the short sides.

Since we were using a significant amount of blown-in insulation in the attic, it made it necessary to build up the sides of the Battic frame in the attic with some plywood to get the top of the opening above where the insulation would eventually stop.

 

 

 

 

Here’s another view of the 3 sides of plywood installed:

attic access looking down - directly

The fourth and final side of plywood was installed just prior to blowing in the insulation — in the interim this made getting in and out of the attic much easier.

After a couple of practice attempts, it quickly became apparent that raising and removing the lid once in place, and fighting to get it back down into the master bedroom closet, wasn’t worth the trouble. Instead, I built a small bench in the attic next to the Battic frame so I could push the lid up above the level of blown-in insulation, this way it could have somewhere to safely sit while dealing with any issue in the attic.

bench for attic access lid

Battic lid resting on the bench.

It’s very easy to grab the lid off the bench and bring it back down into position while slowly walking down the ladder in the master bedroom closet to make the final connection/seal.

Although the installation process was fairly straightforward and headache free for the Battic product, if I had it to do over, I think I would have the attic access point on the exterior of the structure, for example, on the gable end of the house in the backyard.

GBA – gable access to attic

Custom Gable Vents

AZdiy

Putting the access point above the air barrier would make meticulously air sealing the entry point for the attic less important, so keeping water out of the attic would be the main goal. An additional plywood buck would’ve been necessary, replicating what I did for our windows and doors (more on this later), but I think it still would’ve been the better option overall.

Putting the attic access on the exterior of the house would also mean avoiding an ugly hole somewhere in our drywalled ceiling. No matter how nicely trimmed out, these attic access points on the interior of a home never look right to me. We’ve tried to hide ours as much as possible by sticking it in our master bedroom closet, which has worked out well, but not having one at all on the interior of the house would make for a cleaner, better solution in my opinion.

If granted a do-over, I would also add a cat walk in the attic, through the roof trusses, in order to make getting to any point in the attic much easier to navigate, when necessary in the future, while also avoiding disturbing the blown-in insulation too much.

And here’s a photo of the bench in the attic, next to the opening for the Battic attic hatch, after the blown-in insulation was installed:

bench surrounded by cellulose

Bench for the Battic hatch lid.

Insulation Baffles vs. Insulation Chutes

0

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:

AccuVent label close up

And here are the installation instructions:

AccuVent install label

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, old reliable — 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 (6 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:

insulation chutes long view

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 was, 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:

sealed small piece at bottom of chute

Looking down a chute before sealing with the OSI:

close up looking down chute before sealing

Gaps visible at the edges before sealing them up with the OSI.

Same view after sealing up the gaps:

close up looking down sealed chute

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.