Osburn 3500 Insert Install

[Solarguy3500]

Hi Everyone, first post here. Thank you for this amazing forum and all your collective knowledge. I have already learned so much just reading through threads on here.

We moved into our house last year, which is almost 3,000 sq ft, and there was a Dutchwest stove on the hearth in front of the fireplace that the previous owners had been using. I initially thought we would use it last winter, but after doing a little investigation (pulled the top) I'm glad I didn't make a fire in it. The damper mechanism was completely broken so I would have had no way to control the fire. There were several other problems with it too including the top plate was cracked. So, we used the oil boiler and pellet stove last winter.
Here's the fireplace with the old Dutchwest on the hearth:

 

[Solarguy3500]

This year, we decided to get a new insert, and given the 3,000 sq ft living space, we wanted to get a larger insert. After some research, we decided on the Osburn 3500 with a 3.5 cu ft firebox, one of the largest I've found in an EPA 2020 certified insert.

A little info on the fireplace and chimney: Fireplace is on an exterior wall, and the masonry chimney is 26.5' from the floor of the fireplace to the top of the collar on the top plate of the existing 8" liner that's inside the 12" X 12" clay flue. The chimney has 3 flues in it. One is for the oil boiler in the basement, one for the fireplace, and the other one is currently unused.

I'm sure some will notice the vines on the sides of the chimney. They were covering the whole chimney all the way to the top, and I've removed the majority of them and will remove the rest before making my first fire in the new insert.

The Osburn arrived a couple weeks ago and I removed the Dutchwest to get ready for the install. When the existing 8" liner was installed, whoever did it was a little overzealous in cutting out the damper and breaking the firebrick in the back of the fireplace smoke shelf area, so the broken firebrick comes down pretty far on the back wall. When I make my block off plate, I'm going to bend a longer flap down about 8" on the back wall which will cover the broken firebrick below the level of the lintel. Then I plan to insulate the back and sides of the fireplace with rockwool insulation and cover it either with durock or sheet metal. I have metalworking skills, so I may go that route and paint the metal with stove paint. I will also be insulating above the block off plate with the rockwool.

 

[Solarguy3500]

Here's where I have a few questions.

As I mentioned, there is an existing 8" liner in the flue. The Osburn takes a 6" liner which I bought with the stove and my intention was to leave the 8" liner in place and run the 6" liner inside of it. I figured an extra layer of protection would be a good thing.

What I have learned from this forum however, is that without the required 2" clearance to combustibles around the exterior of the chimney (my cedar siding touches the bricks) I will need an insulated liner, and I'm not sure if an insulated 6" liner will fit inside an 8" liner. Anyone ever try this?

Even if it will fit, is it worth the hassle of trying to stuff it inside the 8" liner or should I just pull that old one out? Also, I'm wondering if I'm going to run into trouble with terminating the top of the 6" liner if there's already an 8" liner attached to a top plate on the clay tile flue. How would I secure the 6" liner at the top?

 

[Riteway]

Honestly, it sounds like it would be way easier to yank out the old liner.

 

[kennyp2339]

What I have learned from this forum however, is that without the required 2" clearance to combustibles around the exterior of the chimney (my cedar siding touches the bricks) I will need an insulated liner, and I'm not sure if an insulated 6" liner will fit inside an 8" liner. Anyone ever try this?

The actual chimney clearance would be an airspace between the framing / sheathing of the house to the back of the chimney, siding & trim are allowed to run up to the edge of the chimney.
I don't think you can terminate an anchor plate on top of an existing anchor plate without any substantial modification, which can take away the strength of the smaller anchor plate, also water leaks may become a concern with that modification.
Its best to rip out the 8" buy the blanket insulation wrap & proper termination cap and go about it that way, build it right so it lasts a long time.

 

[Solarguy3500]

Yes, the more I think about it, I tend to agree. Old liner needs to come out and the new 6" insulated liner can then be installed properly.

In the meantime, I made a cardboard template for my block off plate. Trying to decide what material to make it out of. Stainless would be ideal, but $$$. I was also thinking maybe a thicker gauge steel painted with stove paint. Maybe 20 gauge or so. Any thoughts or suggestions?

Cardboard template. Longer flap is the back. Actual metal plate will have an even longer flap. 8-10"

 

[Riteway]

Yes, the more I think about it, I tend to agree. Old liner needs to come out and the new 6" insulated liner can then be installed properly.

In the meantime, I made a cardboard template for my block off plate. Trying to decide what material to make it out of. Stainless would be ideal, but $$$. I was also thinking maybe a thicker gauge steel painted with stove paint. Maybe 20 gauge or so. Any thoughts or suggestions?

Cardboard template. Longer flap is the back. Actual metal plate will have an even longer flap. 8-10"
View attachment 268462

26 gauge steel (non-stainless) is what I used for mine. I don't think there's any benefit to going thicker than that...it would just be less flexible and harder to install. I don't think the stove paint would hurt, but I doubt it's necessary. After you still your liner top plate (with silicone sealant), there won't be any water getting down there to encourage rust.

 

[kennyp2339]

Sheet metal is fine to, perhaps a little better because you can adjust the fold over wings with a pair of pliers then drill smaller tap cons into the masonry to hold it in place. no need for all that weight.

 

[Solarguy3500]

This project has been on hold for a bit while I ordered the liner insulation kit and I'm waiting for it to arrive. I have also been thinking about building my block off plate and insulating the back and sides of the fireplace. One thing you will learn about me is that I always tend to overthink and overbuild things, and I have a feeling this project will be another example of that.

I was originally planning on using unfaced rock wool batt insulation above the block off plate and on the back and sides of the fireplace and completely covering it with sheet metal pieces to contain the dust and particles from the insulation. The plan was to make flaps so the pieces would overlap each other and either use self tapping screws to screw them together or make tabs and locks, and lock the pieces together similar to the way standing seam or flatlock roofing panels lock together.

Then I came across a thread where someone had used foil faced Roxul to insulate the fireplace back and sides. Now I'm thinking of going that route but also covering it with sheet metal for an extra reflective layer to try to get as much heat as possible back into the room. (See the pattern here of overthinking)

Just a couple days ago, I was at a local hearth/fireplace shop buying stove paint to paint my metal panels, when I noticed a product that really got the wheels turning even more. Stove boards which have a metal outer layer already, and have a non-combustible 1/2" board behind the metal which actually has an R value of 1.56. These come in several sizes and are typically used behind a freestanding stove for wall protection or in front of the hearth as floor protection. So, I got to thinking that if I could adapt these stove boards to the inside of my fireplace, I could add an additional 1.56 R value to the R value of the rock wool insulation, and have the metal layer I was going to add anyway (Now the overthinking is really kicking into high gear). Has anyone ever tried to use these for this purpose before?

https://www.hy-c.com/product/ul1618-type-2-stove-board-gray-slate-2/#1462908934129-9f89f27f-e181

Also, while the installation is on hold, I made a model of the fireplace and insert in Sketchup using the actual dimensions and measurements of the fireplace and insert so I could see how it will fit before I actually try to muscle the stove into the fireplace. Looks like the depth at the top will be a little tight especially since I'm going to be padding it out with insulation, metal, etc. so I think I'll have to take the firebrick down another course or two in the back to gain clearance.

 

[Easy Livin’ 3000]

This project has been on hold for a bit while I ordered the liner insulation kit and I'm waiting for it to arrive. I have also been thinking about building my block off plate and insulating the back and sides of the fireplace. One thing you will learn about me is that I always tend to overthink and overbuild things, and I have a feeling this project will be another example of that.

I was originally planning on using unfaced rock wool batt insulation above the block off plate and on the back and sides of the fireplace and completely covering it with sheet metal pieces to contain the dust and particles from the insulation. The plan was to make flaps so the pieces would overlap each other and either use self tapping screws to screw them together or make tabs and locks, and lock the pieces together similar to the way standing seam or flatlock roofing panels lock together.

Then I came across a thread where someone had used foil faced Roxul to insulate the fireplace back and sides. Now I'm thinking of going that route but also covering it with sheet metal for an extra reflective layer to try to get as much heat as possible back into the room. (See the pattern here of overthinking)

Just a couple days ago, I was at a local hearth/fireplace shop buying stove paint to paint my metal panels, when I noticed a product that really got the wheels turning even more. Stove boards which have a metal outer layer already, and have a non-combustible 1/2" board behind the metal which actually has an R value of 1.56. These come in several sizes and are typically used behind a freestanding stove for wall protection or in front of the hearth as floor protection. So, I got to thinking that if I could adapt these stove boards to the inside of my fireplace, I could add an additional 1.56 R value to the R value of the rock wool insulation, and have the metal layer I was going to add anyway (Now the overthinking is really kicking into high gear). Has anyone ever tried to use these for this purpose before?

https://www.hy-c.com/product/ul1618-type-2-stove-board-gray-slate-2/#1462908934129-9f89f27f-e181

Also, while the installation is on hold, I made a model of the fireplace and insert in Sketchup using the actual dimensions and measurements of the fireplace and insert so I could see how it will fit before I actually try to muscle the stove into the fireplace. Looks like the depth at the top will be a little tight especially since I'm going to be padding it out with insulation, metal, etc. so I think I'll have to take the firebrick down another course or two in the back to gain clearance.

View attachment 269160
View attachment 269161

You are right, definitely overthinking this.

I get it, I tend to overthink things myself, but, my oh my!

Use a thin gauge sheet metal for the plate, unfaced rock wool above it. The thinner the sheet metal, the easier it is to fabricate. Aluminum is probably ok, so I've heard from the experts.

Insulate the firebox behind and beside the stove if there is space. Keep the heat in the house. That foil faced stuff would work great there. I'd put the foil face on the inside, closest to the stove. And since you'll probably have surplus, use that above the plate as well.

There, now just do it.

 

[Solarguy3500]

You are right, definitely overthinking this.

There, now just do it.

Thanks, @Easy Livin’ 3000 I needed that! You snapped me out of a bad case of analysis paralysis.

I'm reminded of the old after shave commercials where the guy slaps himself in the face and says thanks, I needed that.

 

[unimog1300]

This project has been on hold for a bit while I ordered the liner insulation kit and I'm waiting for it to arrive. I have also been thinking about building my block off plate and insulating the back and sides of the fireplace. One thing you will learn about me is that I always tend to overthink and overbuild things, and I have a feeling this project will be another example of that.

I was originally planning on using unfaced rock wool batt insulation above the block off plate and on the back and sides of the fireplace and completely covering it with sheet metal pieces to contain the dust and particles from the insulation. The plan was to make flaps so the pieces would overlap each other and either use self tapping screws to screw them together or make tabs and locks, and lock the pieces together similar to the way standing seam or flatlock roofing panels lock together.

Then I came across a thread where someone had used foil faced Roxul to insulate the fireplace back and sides. Now I'm thinking of going that route but also covering it with sheet metal for an extra reflective layer to try to get as much heat as possible back into the room. (See the pattern here of overthinking)

Just a couple days ago, I was at a local hearth/fireplace shop buying stove paint to paint my metal panels, when I noticed a product that really got the wheels turning even more. Stove boards which have a metal outer layer already, and have a non-combustible 1/2" board behind the metal which actually has an R value of 1.56. These come in several sizes and are typically used behind a freestanding stove for wall protection or in front of the hearth as floor protection. So, I got to thinking that if I could adapt these stove boards to the inside of my fireplace, I could add an additional 1.56 R value to the R value of the rock wool insulation, and have the metal layer I was going to add anyway (Now the overthinking is really kicking into high gear). Has anyone ever tried to use these for this purpose before?

https://www.hy-c.com/product/ul1618-type-2-stove-board-gray-slate-2/#1462908934129-9f89f27f-e181

Also, while the installation is on hold, I made a model of the fireplace and insert in Sketchup using the actual dimensions and measurements of the fireplace and insert so I could see how it will fit before I actually try to muscle the stove into the fireplace. Looks like the depth at the top will be a little tight especially since I'm going to be padding it out with insulation, metal, etc. so I think I'll have to take the firebrick down another course or two in the back to gain clearance.

View attachment 269160
View attachment 269161

Like this? Foil faced Roxul, two layers on the back.

 

[Solarguy3500]

Like this? Foil faced Roxul, two layers on the back.

Yes! That's the stuff! In fact, I think it may have been your install thread where I saw it and got the idea from. Thanks!

Question: I assume you've had your insert installed for a while now and have been running it with this setup. How is it working for you? Is the foil face on the Roxul holding up well to the heat?

 

[unimog1300]

Yes! That's the stuff! In fact, I think it may have been your install thread where I saw it and got the idea from. Thanks!

Question: I assume you've had your insert installed for a while now and have been running it with this setup. How is it working for you? Is the foil face on the Roxul holding up well to the heat?

Yes it's been running for two winters now. In my case I can't say I noticed a huge difference. I have a 7' wide 23' tall outside masonry chimney and that's the main reason I insulated it. It's a huge heat sink. I haven't pulled the insert out since the insulation so I can't tell you how it's holding up. Can't imagine that there's anything going on with it. B HOLLER recommended to tape all the seams (joints) when I have it out next, which I will. I'll add additional layers if possible when I pull it out at some point. I used 2" thick Roxul. I bought it thru Grainger, I get a good discount there. My insert is a BK Princess 2020 compliant.

 

[Solarguy3500]

A few updates on the project from the last few days.

On Friday, I went to a local sheet metal shop and bought a 4' X 8' sheet of 22 gauge steel for $56. This should be enough for all of my metal panels I will be making. I also ordered the 2" thick foil faced Roxul for the back and sides of the fireplace. My liner insulation kit arrived too.

Over the weekend, I made templates for the metal panels I will be making. I reworked my design for my block off plate because I'm going to have to remove another course or two of firebrick on the back of the fireplace to gain the clearance for the depth of the top of the insert. My block off plate will now have a 90° bend at the back, then go down 11 7/8", then bend back about 10° and lap 8" over the firebrick on the back of the fireplace to cover the area where the top couple rows of brick are removed. I will be installing unfaced roxul batts behind that metal plate as there is some room in the far back behind the firebrick. Here's the new block off plate template: (upside down)


Once the block off plate is attached to the top and sides with Roxul above and behind it, I plan to install the foil faced Roxul on the back and sides of the fireplace. Then I will install a series of 3 metal panels over the Roxul before installing the insert to seal the fibers and dust from the Roxul so it can't get blown out into the room by the blower. This extra layer of metal should help to keep more heat in the room too. I mocked that up with cardboard too and test fit it over the weekend and it fits perfectly.


I have a friend who has a brake, so I'll cut all the metal panels out and head over to his place to bend them up.

 

[Draughts15]

Any updates? Id like to hear about the heat output and burn times!

 

[Solarguy3500]

Unfortunately, the project is on hold for a while, possibly until spring. Winter set in with a vengeance, and with the steep pitch of the roof, it's really not safe to work on the top of the chimney with snow on the roof.


The next steps in the project are going to require working at the top of the chimney. I need to remove the 8" liner that is currently in the chimney, then insulate and install the new 6" liner, so there will be a lot of climbing up and down the roof.

When I get a break in the weather, I'll definitely update this thread as my progress continues.

 

[Solarguy3500]

A quick update and a few questions on the world's slowest insert install. I had hoped to complete this project over the summer and have it ready for this winter, but that didn't happen.

First, the update:
I finally removed the rest of the vines from the sides of the chimney.


When I was pulling the biggest vines off the right side of the chimney, the flat stone fell off on the shoulder where the chimney gets wider toward the base. The roots of the vines must have gotten under that stone.


Up at the top of the chimney I started assessing the situation up there in preparation for removing the 8" liner and installing the 6" liner with insulation kit. A few things caused me concern.

The top plate for the liner for the boiler (on the left) looks like it was installed on top of another plate and it's lifting up and definitely not water tight.
The clay flue tile for the unused flue is badly deteriorated and crumbling and could become a water leak if it hasn't already.


The flue for the fireplace (center) has had the clay flue cut down flush with the chimney crown and sits at the same height as the other two flues.


The other issue is that the general condition of the crown is not good. It has cracks and channels where water has worn into it over the years.

Now the questions:
1. Should I get a stainless cap for the whole chimney with 2 holes for the boiler and fireplace (insert) flues and just cap the unused flue by not making a hole for it in the cap, or should I have a mason come and pour a new crown. I think the answer is new crown, just wanted to get some opinions.
2. I thought I read in another thread on here that if a chimney has multiple flues, they have to terminate at different heights so that smoke from the wood stove can't get easily sucked down the flue for the boiler. Is this correct, and if so, will I need to have the mason extend the flue for the insert up another foot or so?
3. Can anyone think of a compelling reason not to block up the unused flue? If it went down to the basement, I would entertain the thought of maybe getting a wood boiler or furnace at some point, but it doesn't go down that far. Ends at the first floor, so the only thing it could be used for is another wood stove in the living room right next to the fireplace where the insert will be installed. Doesn't make sense. The only other room in the house that is adjacent to the chimney is a bedroom on the second floor, and if I'm not mistaken, the code doesn't allow wood stoves in bedrooms, right?

 

[clancey]

Solarguy--you have a lot of issues with that and I hope someone comes on and gives you some good suggestions..Don't be too hard on yourself for being slow we all have been there for all kinds of different reasons---just a boosting here for you--lol old clancey

 

[begreen]

You are right on all accounts.

 

[EbS-P]

A quick update and a few questions on the world's slowest insert install. I had hoped to complete this project over the summer and have it ready for this winter, but that didn't happen.

First, the update:
I finally removed the rest of the vines from the sides of the chimney.
View attachment 285342
View attachment 285343
When I was pulling the biggest vines off the right side of the chimney, the flat stone fell off on the shoulder where the chimney gets wider toward the base. The roots of the vines must have gotten under that stone.
View attachment 285344

Up at the top of the chimney I started assessing the situation up there in preparation for removing the 8" liner and installing the 6" liner with insulation kit. A few things caused me concern.
View attachment 285345
The top plate for the liner for the boiler (on the left) looks like it was installed on top of another plate and it's lifting up and definitely not water tight.
The clay flue tile for the unused flue is badly deteriorated and crumbling and could become a water leak if it hasn't already.
View attachment 285346

The flue for the fireplace (center) has had the clay flue cut down flush with the chimney crown and sits at the same height as the other two flues.
View attachment 285349

The other issue is that the general condition of the crown is not good. It has cracks and channels where water has worn into it over the years.

Now the questions:
1. Should I get a stainless cap for the whole chimney with 2 holes for the boiler and fireplace (insert) flues and just cap the unused flue by not making a hole for it in the cap, or should I have a mason come and pour a new crown. I think the answer is new crown, just wanted to get some opinions.
2. I thought I read in another thread on here that if a chimney has multiple flues, they have to terminate at different heights so that smoke from the wood stove can't get easily sucked down the flue for the boiler. Is this correct, and if so, will I need to have the mason extend the flue for the insert up another foot or so?
3. Can anyone think of a compelling reason not to block up the unused flue? If it went down to the basement, I would entertain the thought of maybe getting a wood boiler or furnace at some point, but it doesn't go down that far. Ends at the first floor, so the only thing it could be used for is another wood stove in the living room right next to the fireplace where the insert will be installed. Doesn't make sense. The only other room in the house that is adjacent to the chimney is a bedroom on the second floor, and if I'm not mistaken, the code doesn't allow wood stoves in bedrooms, right?

New crown next summer/fall. If it hasn’t caused issues to this point what’s one more winter. Getting that scheduled now will be difficult I imagine. Taking caps off to pour crown is easy. Think ahead and don’t cut your new liner too short if the new crown is higher by an inch or 3.

As for the caps. Just seal it all with silicone. If it was my grandfather he might just silicone the whole crown.

I’d seal the unused flue with the flue balloons and follow instructions. And a silicones solid top cap for now.

Just my thoughts.

 

[Solarguy3500]

Well, after a long hiatus, the world's slowest insert install is finally back on track! Here are the updates:

A couple weeks ago the mason came and took down the crown and the top 6 courses of brick, rebuilt it with similar brick, poured a new crown and installed a stainless cap on the chimney.
Here is what the chimney looked like before:


Work in progress after the first day:


One of the hip stones had fallen off the chimney a while ago so he reinstalled that and drilled and pinned both hip stones so they won't fall off again.
After:


He also removed the old 8" liner and installed an insulated heavy wall 6" liner for the insert.

 

[Solarguy3500]

The mason also installed the insert in the fireplace and connected the liner.


I didn't bother to reinstall the door on it or put the firebrick back in it yet because I'm going to pull it out again and insulate the fireplace with Roxul and install the heat shields and block off plate I made. Once I do that, I'll do the final installation of the insert.
Heat shields:


Two piece block off plate:

 

[moresnow]

Document the firebox insulation install. If you have time.

 

[Solarguy3500]

Yes, I definitely plan on doing that. I think that is one of the most critical parts of an insert install when the fireplace is on an exterior wall because it's an opportunity to retain a huge amount of heat that would otherwise be lost through the back of the fireplace.