8 inch pipe and chimney installation for basement stove

[ponderosa77]

Hello group and thank you for all of the help so far.

I want to put my Fisher stove with 8 inch outlet in the basement in the largest room, which happens to be directly underneath the largest room upstairs.

The basement is somewhat unfinished, including a slab floor and wall in the immediate vicinity of the planned stove location. The basement ceiling in this room is uninsulated and the plan would be to let any stove heat rise into the upper level through the basement ceiling while also heating the basement area. Otherwise, I heat the upstairs-only with an effective gas furnace.

The gas furnace has registers in all upstairs rooms and the cold air return is upstairs. There are no registers or runs in the basement. The furnace has its own fresh air duct from outside directly into the machine room.

My stove outlet is on the rear of the stove. I would like to get an idea of pros and cons regarding different piping options, which as I see it, are as follows:

1. Elbow or T off of (T preferred for cleanup) the back of the stove and penetrate basement ceiling, pass up through the main floor in the corner of two walls, then up through the vaulted ceiling and out through the roof with appropriate clearances and triple-wall pipe; wall up/enclose pipe passing through upstairs area; total pipe length would be at least 24ft.

2. Elbow, T, or 45 off of the back of the stove, elbow or T towards the concrete wall, pass through a hole in the concrete wall, elbow or 45 to pipe bracketed to wall on outside of house.

I like option 1 for the straight run and that it looks nice and professional. However, this may add expense and complexity to the installation, including possibly requiring more pipe. It also places more of the pipe inside the home, which will probably help keep the pipe warmer, but it also places the pipe closer to combustibles. This is not an install that I would perform myself.

I like option 2 because most of the pipe is outside of the house, which seems safer. I can do the work myself and with assistance of contractors for less expense. Overall cost could be less and I have someone who can properly cut the hole. It would be nice to be able to cleanup outside as well. However, it doesn't look as nice and may not draw as well due to the horizontal runs.

I'm sure there is a lot of other insight on here regarding possibilities and they should be considered.

I also realize some would say just put a 6 inch pipe in and save for a more efficient stove. The next question to follow that would be, could you adapt from 6 inch and exhaust into an 8 inch chimney from your 6 inch modern stove? Searching around seems to indicate that is fine but going the other way from an 8 to 6 would not be fine. I've been looking at SuperVent pipe.

Pics / floor plan to follow.

Thank you.

 

[coaly]

You can increase from 6 to 8 with an older stove, but expanding flue gasses cool considerably and is not recommended. Smaller stoves with 6 inch outlets may not have enough loss to keep flue temperature high enough with the larger 8. Keep in mind 6 to 8 is almost twice the size.
Most all newer stoves are going to require 6.
Although not legal to decrease the size smaller than the stove outlet, your stove was built with an over size outlet for open door burning with screen in place. When the stove was designed, most were vented into existing fireplace flues even larger. So it will physically work fine reduced with an insulated flue. Even with an added baffle installed, at least with an indoor chimney.
Inside chimney would be Class A and clearance to combustibles would not be an issue. Follow manufacturers installation instructions. (The "pack" type double wall chimney is much smaller in diameter than triple wall)
Double wall connector pipe inside will give you higher flue temperature for the exposed outdoor insulated chimney.

The chimney pros on the site can give you more input, but the physical confines of the building may play a larger part in requiring an outdoor chimney. (and your bank account)
Are you sure you don't want an 8 just in case you find an XL ?

 

[bholler]

Installing the chimney inside will cost less in materials outside you will need a tee which is expensive and more pipe. As far as distance to combustibles just follow the instructions and you will be fine. If i was doing the install i would probably recommend 7" it will work fine with your stove now and with your height it should work fine with a new stove as well. Another thing to think about is the fact that the new largest stoves are starting to use 8" again so depending on you heating needs and budget it may make sense to just use 8" and save for one of the new large stoves.

 

[ponderosa77]

Thanks for the tips gentlemen. I was thinking all along to just match the stove outlet and had planned on 8 inches but the local fireplace guys that sell all the fancy pellet stoves and efficient wood stoves have suggested to go with 6 inch pipe. I should also consider future resale value as well, and that may dictate a 6 inch pipe. I personally don't forsee (don't want to for sure) removing the 8 inch Fisher and going with a more modern 6 inch stove, but a lot of that depends on the deal to be had. If the deal is right, then sure. I definitely want to be sure of the choice. I have already been looking around to see if any new stoves come with 8 inch outlets....

The 7 inch idea is new to me so thanks for that. I had not considered an intermediate size, and unless there is a solid reason not to do that, this idea sounds like a great compromise.

I think a straight shot up through the ceiling and then the roof would be great while in either scenario, I think at least 24 feet of pipe will be needed. I thought I saw with one of the triple wall variants that only 2 inches of clearance is required. This would be ideal because then I can run the pipe up through the basement ceiling and through the main floor while maintaining close clearance to the corner of 2 walls.

I am planning to at some point try a baffle in this Fisher Grandpa as well.

Pics will follow but 7" pipe sounds about right. I would also like to add a manual damper control with the thought that if the pipe was too large, I could use the damper a little. That should affect airflow/velocity through the pipe but probably would do nothing to prevent the cooling of expanding gasses.

So if I can go close to the wall corner in the main floor (and sheetrock it off to hide it), and use a 7" pipe (will need to do the math on volume to compare), I can go have a look at parts pricing. If I can't be so close to the wall with piping, I should plan to route out the wall instead.

How does cleanup work if there is no T and cap?

 

[ponderosa77]

Are you sure you don't want an 8 just in case you find an XL ?

That is a good idea.... I would take an XL in a heartbeat, especially if it were in as good as shape as is my father in-law's XL....

However, after moving the stove into the basement yesterday evening, I'm not sure a bigger stove will fit through the doors.... BTW, 4 of us muscled it into the house where we strapped it to a furniture dolly; two people below and 3 at the top and took it down the stairs. My stairs proved strong enough.

Now I need to settle on a pipe plan and see if I can fire it by January....

 

[ponderosa77]

Was researching wall pass through systems and saw this video on YouTube. He didn't want to have 30 degree offsets on his chimney in order to miss his soffit overhang and also wanted more than 2 inches clearance from his siding so he put the 30 offset between the wall and the tee. This offers a horizontal rise for his "longer than normal" horizontal pass through. Of course this also required custom wall standoff brackets.

I think another thing he mentioned is that it brought his cleanout tee up above grade a little higher for easier cleanout (or to prevent the tee from being below grade). The distance between grade and wall/siding in his case is very similar to mine. What is the general thinking regarding his install?

 

[ponderosa77]

Was researching wall pass through systems and saw this video on YouTube. He didn't want to have 30 degree offsets on his chimney in order to miss his soffit overhang and also wanted more than 2 inches clearance from his siding so he put the 30 offset between the wall and the tee. This offers a horizontal rise for his "longer than normal" horizontal pass through. Of course this also required custom wall standoff brackets.

I think another thing he mentioned is that it brought his cleanout tee up above grade a little higher for easier cleanout (or to prevent the tee from being below grade). The distance between grade and wall/siding in his case is very similar to mine. What is the general thinking regarding his install?

Wonder how he adapted to stove pipe on the inside of the wall. I suppose with another 30 degree chimney piece... I wonder how it drafts. Looks like a tall run to the roof...

 

[ponderosa77]

Ok, here are some installation pictures. This installation will pass from the basement, through the upstairs floor, then through the attic and out through the roof with no offsets.

First, the Selkirk Supervent pipe and chimney:


Surprisingly, it isn't beat up too badly. Taping the boxes together probably helped a lot.

Here is a look at the I-Joists, into which the support box will be installed:


The support box measures ~12 inches square so a little framing work is necessary and the framing should support the metal box on all 4 sides.


Marking the hole:


I used a drill to make a starter hole and then a sawzall tool to cut the hole:


Testing the fit of the support box. A little too tight here:


After working on the hole a little more, the box fit nicely:


I secured the box to the framing on all 4 sides using screws. Instructions allow specific nails or screws. The support box kit comes with a single chimney clamp and some little screws but I plan to use wall brackets and roof guy brackets for added chimney support. The little screws penetrate the outer stainless chimney casing but not the inner flue pipe.

After tightening the chimney clamp, the 4 small sheet metal screws are used to secure the clamp around a section of chimney while other black finishing screws can be used with the trim pieces. The support box will support a number of feet of chimney hanging below the box but most would probably prefer to see black stove pipe instead of stainless chimney pipe. Nevertheless, the amount of chimney hanging below the box may be adjusted for safety and clearances:


The chimney (with clamp installed) drops from the top down into the box. No electrical wiring should exist inside a chimney chase so I will be moving these cables:


This is 6 inch chimney coupled with a 6 inch cathedral ceiling support box measuring ~12x12x17 inches. The support box is designed to center the chimney and keep a 2 inch clearance from combustibles on all 4 sides. I have the minimum clearances but will frame the chase with wider clearances. When it comes time to build the chase, carpet will be removed and electrical will be relocated. In this picture, it is easy to see the 4 inch clearance between chimney and drywall. One or more wall brackets may be used for additional support:


It's easy to stack and twist-lock chimney sections as needed. I also have locking bands (not required but my preference) for each joint that will get installed last:


The chimney adapter transitions the chimney to stove pipe and simply twist locks into the first chimney section. When this is installed, the chimney cannot be extracted up and out of the support box, so this should be done last. Note: Plumbing is not in direct contact with the support box and can be relocated:


This type of prefab chimney is very nice. Look at the smooth inner flue:


I will be using the nicer double-wall stove pipe (for close clearances) inside as well as a clean out tee and a damper. I also have a stove top thermometer as well as a stove pipe thermometer that measures internal gas temperature. And although I don't need 6 inch clearance (due to non-combustible concrete wall and floor), the chimney will offer that clearance or more on all sides.

The two remaining challenges will be to try and fit the stove pipe, tee, damper, stove adapter, etc. to my stove and of course passing the chimney up through the attic and roof. When the rest of my Selkirk order arrives, it will contain both a firestop and an attic insulation shield. Whereas I have a cathedral ceiling and am installing near a corner, the vertical attic space may only be 12 inches or less so I may have to adapt the shield, build my own chase, etc.

Because of the cold weather, I am working on thawing the shingles and it has been recommended to use a heat gun when installing the flashing.

More pics to follow.

 

[ponderosa77]

There were a number of reasons I decided against a through-the-wall installation, including a few major ones. The core driller said he could not drill a 30 degree angle through the wall. A straight hole would place my outdoor clean out tee at or below grade and the thought of dealing with that issue was unappealing. Equally unappealing was the thought of drilling dozens of drill holes and chiseling out a rough concrete hole. Also, I didn't want a horizontal section of pipe or an expensive offset in the soffit area. Standing the pipe off the wall a couple of feet to miss the soffit overhang would make for an ugly and nonstandard installation and I didn't like the thought of cutting the rain gutter and soffit. Also, I didn't want to have to build an outdoor chase and finish it to match existing siding. Etc.

So an indoor flue installation was chosen but came with its own challenges. The 8 inch chimney would be too big for one thing. Another issue is working on the roof during cold weather. Pipe size could be an issue in more ways than one but I expect that the 6 inch pipe will be fine in my scenario because I am going to have a nice straight and tall run of indoor, insulated chimney with good height, which should draft very nicely. It will also accommodate a variety of new stoves with 6 inch outlets, such as the 30 NCH.

 

[3650]

hmmm I didnt know you can run pipe through a living space lil that... I'll be rethinking my basement installation.

 

[ponderosa77]

hmmm I didnt know you can run pipe through a living space lil that... I'll be rethinking my basement installation.

Well, there are two important points: it will be enclosed in a chase and it is class A chimney. Stove pipe can't be used like this.

I will post more pics soon. If weather permits, the roof part will get done this week.

 

[ponderosa77]

Weather is going to be sloppy this week again so I'm not sure if I can get the roof part done or not. I've assembled most of the stove pipe but am waiting for a few critical pieces to arrive, such as the damper and stove adapter. Will post some of those pics later. Here are a few more of the chimney installation.

I used a small nail to make some test holes in the ceiling drywall as well as a stud finder to make sure the chimney would work in the planned location. Those test passed so using a hand held drywall/keyhole saw, I moved on to cutting a small square test hole that I could look into. When that test passed, I cut a 12 inch round hole, taking care to use only the tip of the saw (shallow strokes). I could have just used the sawzall to make the hole but as always seems to happen, I found a surprise. The sawzall tool would have just zipped through this, which could have turned into a real problem:


This wire feeds the outlet right next to the chase, so I could simply remove this circuit but something else is tied onto it, which I haven't traced out yet. I was able to get just enough slack to just move the wire aside. Any additional slack will require the removal of a wire staple and drywall patching. This Supervent Attic Insulation Shield (AIS) is designed to fit into a 12 inch hole and after moving the wire, it fit.

However, as I suspected, using the AIS in my scenario would not be ideal because I only have something like 6-10 inches of depth in this area for the shield and the shield measures about 12 inches between the top and the square edges that are designed to nail to rafters. The other issue is there is no framing to nail the AIS to. Even if I cut a round hole in the roof and push the shield all the way through, the angle of the cathedral ceiling inside the house will present a problem:


I had to cut a ~13 inch square hole in the drywall and frame up a small square support box to place between the rafters and around the chimney hole. This provides something to attach the AIS to for support. It was very tricky to pre-build the support framework and later wiggle it somehow into the 12 inch square hole, while moving insulation aside and while working with only 6-10 inches of attic space (to avoid cutting and patching ceiling drywall). Somehow it worked.

However, after I built the support framework, I thought it would be beneficial to build an enclosed chase. I cut the OSB to match the slope of the roof and this chase prevents any attic insulation from contacting the chimney while providing the required 2 inch clearance on all sides Notice the electrical wire is no longer visible. I used screws so that I can remove these test pieces and later make more precision cuts for tighter fit if necessary:


With a fully enclosed chase of proper clearances, the AIS isn't necessary but I would like to use it anyway. When it is time to cut through the roof, the hole will be large enough to allow the AIS to push up into the chase a little further. Since there are no rafters below the AIS, the square flanges will not be needed for mounting. The AIS will be secured to the framing around the square chase. The AIS may or may not have to be trimmed to match roof slope.

Here is a preassembly test. I taped one of the stainless wall brackets and locking rings to prevent accidental injury (they are sharp). Clamps and locking rings are not fully or permanently installed because I will be separating the chimney long enough to install the required firestop shield into the support box. The brackets provide the minimum 2 inches of clearance:


Here is the firestop shield that will be installed at floor level inside the support box. It will fit around the chimney and drop into the support box. It is arriving in a delayed shipment or I would have already installed it:


The roof flashing opening is slightly larger than the chimney diameter, hence the reason for installing a storm collar above the flashing. This air gap will allow cold air into the chimney chase. I also noticed the chimney support box clamp that fits around the first chimney section inside the support box has a gap that will also allow a small amount of cold air to pass through the support box into the area near the stove. I have also ordered the supervent universal insulation, if I decide to use it:


I am looking into chase requirements for drywall, insulation, safety, etc. but planned to frame, drywall (interior and exterior), and insulate the chase around the exposed chimney. This will keep the living area warmer and safer. I will be removing all carpeting that would otherwise end up inside the chase.

I have installed the double-wall stove pipe and cleanout tee near the stove but am waiting for the damper and stove adapter. Because I ended up with some added chimney length plus chimney adapter length, my pipe was slightly too long, so the stove must sit on the slab floor for now. Later, I will remove some stove pipe length and elevate the stove.

For anyone else considering Selkirk, I am very pleased with the quality and fit of the Selkirk double wall, pre-crimped stove pipe. It has been "no hassle" pipe and allows for reduced clearances, safety, and increased performance. In fact, all of the Selkirk products so far have been of much better quality than I anticipated.

Will post pics of the stove and stovepipe area soon.

 

[ponderosa77]

Here is a look at the cleanout tee. I have a little adjustment room because of the slip joint pipe near the support box. The stove will not be this close to the wall since other components will need to be installed, such as the damper, stove adapter, etc.:


Here is a look at the (fully retracted) slip joint, the finishing band, and one of the 24 inch sections of pipe:


Here is a look at the stove and pipe:


Here is the FlueGard thermometer that will be installed on the flue pipe. The probe extends into the interior of the pipe itself, since I have double wall pipe:


Here is the Inferno stove top thermometer:

 

[begreen]

Will the wall behind the stove get a wall shield?

 

[ponderosa77]

Will the wall behind the stove get a wall shield?

It will be pulled away further from the wall but I planned on removing wall studs and having bare wall or maybe stone or brick at a later time. I did not plan to have any combustibles behind the stove due to closer clearances. That's also why I used double wall stove pipe.

I could fabricate or obtain a wall shield as well if it is recommended or required.

A local inspector let me borrow a code book checklist and I was hoping to find information about indoor chase construction but all of the information was regarding masonry chimneys. I need to find out chase wall requirements. .....

 

[begreen]

The chase is primarily to protect the pipe and to protect the room occupants from touching the pipe. It needs to honor the 2" clearances for the pipe. That's about all. I would add a vent top and bottom to recapture some of the heat coming off the pipe.

The rear clearance requirement for the stove is 36" That can be reduced down to as little as 12" with a proper wall shield.

 

[ponderosa77]

That's the one thing I don't know - how hot the chimney will get and how much radiant heat it will emit. There will be airflow inside the chase due to the gap between chimney and roof flashing. This will allow cool air to sink in when the stove is not in use. There is also the small gap around the clamp at the first chimney section in the support box and a little cool air could pass through there into the basement. I definitely do not want cold air passing from the chase into the living area. However, over insulating could overheat the chase as well.

I did find an interesting thread on the matter:
http://forums.finehomebuilding.com/...sulation/woodstove-chimney-chase-construction

I will plan to sheetrock the inside and outside of the chase but omit the wall insulation, install the firestop into the support box, install the attic insulation shield along with the Supervent JUSI insulation at the attic level, as per manufacturer recommendations, then observe the 2 inch minimum clearance in all areas.

 

[Builderml]

I installed my double wall pipe this past fall for my new furnace installation. I understand why one my want to sheetrock the inside of a chase but it is not necessary. Just to let you know, if your tight on space use metal studs for your chase framing. You can reduce your Chase size a nice amount. I am sure you know but Drywall is considered a combustible.

 

[ponderosa77]

I installed my double wall pipe this past fall for my new furnace installation. I understand why one my want to sheetrock the inside of a chase but it is not necessary. Just to let you know, if your tight on space use metal studs for your chase framing. You can reduce your Chase size a nice amount. I am sure you know but Drywall is considered a combustible.

Good idea on the metal studs. I think anything is combustible if it gets hot enough but I don't like the idea of exposed lumber. How did you build your chase?

 

[Builderml]

Good idea on the metal studs. I think anything is combustible if it gets hot enough but I don't like the idea of exposed lumber. How did you build your chase?

No exposed wood if your going to use steel studs. I have basically the same chase as you. You'll need 4 steel studs in total and one piece of steel track. Steel track is what the steel studs slide into, acts as the bottom and top plate.I attached two studs against the wall one on each side about 2 1/2" wider then the pipe for clearance. Ran a piece of track for top and bottom plate from the wall past the front of the pipe again 2 1/2" . Install a stud on each side in the front and covered with Drywall. You don't need to frame a wall across the front. Your Drywall will span from "wing wall to wing wall". Hope you understand what I am trying to say. Also when I put the top and bottom plate in I notched out for the pipe in the middle with tin snips so I can get it closer. I used 3 1/2" steel studs and only wanted 2 1/2" past the pipe so that's why I notched it. If the space won't impact you at all you can use it full width. Many different ways to frame it with steel. You could just use an L shape angle for the bottom and top plate and frame with your studs on edge " the 1 1/2" depth way". This way no need to notch anything. Hope you can make out what I am trying to say. If you need a picture drawn let me know. I'll help if I can.

 

[begreen]

Chimneys are put in wood framed chases all the time. As long as clearances are honored or exceeded it is not an issue. But no harm framing it in metal.

PS: The chimney is already at 2" from wood at the support box and at the braces.

 

[ponderosa77]

By the way, this document from Supervent is one of the best I've found at detailing and planning a basement (or 3 level) install. It's really worth a look:
https://www.menards.com/main/store/...rod_Tech_Spec/combinedBuyersGuidetechdata.pdf

Some things to notice:
1. They are only showing the support box (no firestop) where the chimney passes from the basement into the first living space.
2. They are showing a 6 inch double wall stove pipe clearance.
3. They are showing the attic insulation shield for the roof pass through area.
4. They only mention one thing about the interior chase - that the chimney must be enclosed in living areas and that the 2 inch clearance is honored.

My install:
1. I plan to use the support box together with the firestop where the chimney passes from the basement into the first living space.
2. I will be using 6 inch double wall pipe with >6 inch clearance even though the wall behind it is non combustible.
3. In addition to fully enclosed attic chase, I will be using the attic insulation shield together with the JUSI universal insulation for the roof pass through area.
4. My chase will provide more than 2 inches of clearance to the chimney.

The thing that is interesting is that Supervent wants 2 inches of clearance everywhere, yet their firestop and universal insulation is specified to be packed between the chimney and the shielding. So the insulation directly contacts the hot chimney?

My parts are arriving today. However, we will have a high of 38f with light snow/rain over 70 percent of the forecast area.

Builder, thanks for the ideas for the chase, BTW.

 

[bholler]

1. They are only showing the support box (no firestop) where the chimney passes from the basement into the first living space.

The support box is a fire stop

The thing that is interesting is that Supervent wants 2 inches of clearance everywhere, yet their firestop and universal insulation is specified to be packed between the chimney and the shielding. So the insulation directly contacts the hot chimney?

That is 2" clearance to combustibles the insulation you use needs to be non combustible so it is not an issue.

 

[ponderosa77]

Well, in consideration of the storms lining up on the west coast, that we had a high of 38 today, and that FedEx (finally) delivered the rest of my 2-week-old order, today was the day.

With some assistance from a good friend, we were on the roof a half hour after my parts were delivered and cut a 12 inch square hole in my nice roof. We first drilled 4 edge holes from inside the house to mark the edges of the square chase and then cut out a square with a skillsaw. We centered the chimney and then bracketed into position. With a storm on the way, we installed the flashing, storm collar, cap, and spark screen. It got too cold to install the guy brackets so I will have to do that later, especially since I have one more chimney section to add.

I will post pics shortly but a couple of hours later, after connecting the stove pipe to the stove and double checking everything, I did a couple of draft tests before lighting a small paper fire. Everything looks great and seems to function well. Right now I have 23ft of vertical pipe installed but I may add the remaining section for a 26ft chimney. I'll see how it drafts over a good fire first and then decide.

Later today I will install my flue and stove thermometers and try to get a nice fire going. I'll be starting out conservative and will be checking chimney temperatures, especially in the main floor area before enclosing the flue.

 

[ponderosa77]

Here are some more pictures of the stove installation. Selkirk products have been a joy to work with and the company has been great as well. The fit, finish, and quality of their products have been outstanding.

I like that they label all of their parts, including the addition of a chimney direction arrow:


Here is a look at the stove/appliance adapter. You can see the double wall construction:


Here is a look at the stove adapter installed on the stove. There is a screw hole on the pipe but I'm not sure yet how to best secure the adapter to the stove flue collar:


Here is how their reducer looks, which is a quality product as well:


Here is a look at the assembled stove pipe and how it goes together. I'm still waiting for my damper to arrive in the mail. I'm not sure but I think it will fit between the stove adapter and reducer. I have almost 36 inches of clearance from the slab/non-combustible wall as is but if the damper is installed, I will have 36 inches or more of clearance. The vertical pipe section has around 10 inches of clearance from the non-combustible wall.

I did drop some pipe sections here or there as it is a little difficult for one person to fully assemble alone, but the process has otherwise been painless. The best part has been no crimping required!:


Everything gets checked multiple times so here is a look into the flue from inside the stove:


With everything in place and an obvious draft present in the chimney, I lit a small paper fire to test the draft. Looks and behaves good so far but will build a series of larger fires this evening to test further. This fire does reveal some cracked bricks that I will need to repair or replace. I will install the flue and stove top thermometer before firing further.

I presently have 23ft of pipe/chimney and an additional section I can install when I'm able to add the roof bracket (waiting on weather again). I'm not sure if I'll be able to tell a difference between a 23ft stack and a 26ft stack but I'm pretty sure I'll add the additional section if I can properly support it. If the draft proves well enough, a later project might be to install a baffle (https://www.hearth.com/talk/threads...d-fisher-more-heat-less-smoke-under-25.74710/):


Here is a look at the chimney chase area, as yet unenclosed. Firestop and Supervent JUSI insulation are installed at support box level and the attic insulation shield and JUSI insulation are installed in the attic chase area.

The Supervent flashing is vented and the JUSI insulation instructions specify to pack the insulation between the chimney pipe and the insulation shield, and also between the chimney pipe and the firestop shield. The insulation is at least 2 inches thick by about 48 inches long out of the box and the instructions state to strip the insulation apart to make two 1 inch thick blankets, one for the attic shield and one for the firestop shield:



The support box has been vacuumed out (very important - it got quite messy). I've also installed locking bands on all of the chimney sections. Safety tape will be removed from the clamps and low voltage wiring moved out of the chase. Depending on how hot the chimney gets, I will probably elect to not insulate the 2 chase walls, especially since the attic insulation shield area is now insulated. However, I plan to drywall the inside of the chase or possibly Durock or similar.