# Finally got around to insulating my fireplace



## mellow

Used Roxul R-15.


----------



## mellow

Before and after pictures of the fireplace


----------



## mellow

Insert back in the fireplace, and insulation about 10" up on what used to be the smoke shelf to create a soft block off plate.


----------



## mellow

I have not tried a fire yet,  still not cold enough here, but this has already cut down alot on the drafts even with a block off plate with the chimney on the exterior alot of the heat was sucked up by the bricks.   The insert touches the Roxul on the sides only,  back has about 5 inches air space and top has 10" air space.  I made sure the intakes for the secondary air on the sides are not blocked.  My insert is hooked up to a UPS for possible power outages, that will last me about 6-8 hours on full blast longer if I turn it down, so power going out overnight and it overheating will not be an issue.


----------



## jc5922

Thanks for the pics. Pretty much what I'm gonna do in my prefab unit when I do my install, minus the block off plate.


----------



## woodmiser

I would spray those batts with stove paint to lock the fibers. Just a light coating. It will keep fibers from getting all over the house.


----------



## mellow

Can't say this Roxul has fibers,  haven't noticed any like fiberglass.


----------



## woodmiser

You'll see loads of fibers laying all over... at night shine you brightest flashlight.


----------



## mellow

Thanks for the suggestion, but this material does not off gas, as soon as you put high temp paint on it you have introduced chemicals and off gassing.

I will keep an eye out to see if fibers are being sucked into the secondary air intakes,  if it is I will have to fashion some sort of filter to put over them.


----------



## kallsop

What capacity UPS are you using? I have an APC SmartUPS 1400 and wonder how long it could power the twin fans on an Osburn 2000 insert? I'd like to get at least 6 hours for an overnight burn when power is lost and the generator is turned off. After storms Irene and Alfred we lost power for 8 days combined.


----------



## mellow

Got a leftover DCM Powercom 2200VA from work.


----------



## begreen

Was the insulation approved by SBI or Flame? Flame warns about makeshift installations in the manual. That's why I ask. If uncertain, PM FyreBug, he works for SBI.


----------



## mellow

BeGreen said:
			
		

> Was the insulation approved by SBI or Flame? Flame warns about makeshift installations in the manual. That's why I ask. If uncertain, PM FyreBug, he works for SBI.



Yep,  see this thread:  https://www.hearth.com/econtent/index.php/forums/viewthread/80120/


----------



## woodmiser

mellow said:
			
		

> Thanks for the suggestion, but this material does not off gas, as soon as you put high temp paint on it you have introduced chemicals and off gassing.
> 
> I will keep an eye out to see if fibers are being sucked into the secondary air intakes,  if it is I will have to fashion some sort of filter to put over them.



The whole stove is painted with stove paint. It will only outgas for a short while.


----------



## Scott2373

That Roxul is GREAT stuff. It's what insulates my hot tub. The heater never runs unless we're in it and the cover is off! Good choice! :-D


----------



## pen

I think I'd have a metal shop (or do it yourself if you have the means) make a sheet metal surround to go in-front of that insulation and hide it / keep it in place if there is a risk of it coming down on the stove.  

Unless of course the cover is off this.  I think the last time this was mentioned, I believed the OP was wanting to actually cover the insert itself w/ the stuff.  

pen


----------



## Loco Gringo

Why insulate the brick in your fireplace? So much heat radiates back into the room from it. The block off plate is a great idea but whats the point in keeping heat between you and the outer wall? There WILL in fact be fibers/dust coming from that batting. Thats what it is, fibers, and they arent adhered. Good luck.


----------



## BKInsert

kallsop said:
			
		

> What capacity UPS are you using? I have an APC SmartUPS 1400 and wonder how long it could power the twin fans on an Osburn 2000 insert? I'd like to get at least 6 hours for an overnight burn when power is lost and the generator is turned off. After storms Irene and Alfred we lost power for 8 days combined.



You can get a deep cycle marine 12V battery and a 12VDC to 115VAC converter (like the car ones), this should last much longer than most of the standard UPS's.


That looks like an excellent idea/execution with the insulation... I will keep an eye on this thread to see what others say.  By insulating the fire box fireplace you are keeping the stove hotter, so I predict three of the following scenarios.  

1)  You would be able to run the fans on a higher speed during low burns, therefore spilling more heat into the room.
2)  By keeping the stove temp higher you can close the air intake more, therefore slowing the burn and saving on wood.
3)  I would think you would increase the efficiency of the stove as well, less heat getting lost by heating the big mass of bricks. 

Let us know what is the outcome. please.


----------



## karl

That looks like what I did to mine this year.  I have only been using for a few weeks but there is a difference. 

Once you start using it.  Let me know if you ever hear your convection jacket oil canning.

https://www.hearth.com/econtent/index.php/forums/viewthread/81380/


----------



## stejus

Loco Gringo said:
			
		

> Why insulate the brick in your fireplace? So much heat radiates back into the room from it. The block off plate is a great idea but whats the point in keeping heat between you and the outer wall? There WILL in fact be fibers/dust coming from that batting. Thats what it is, fibers, and they arent adhered. Good luck.



I think Iâ€™m with you on this one.  The fireplace â€œfirebrickâ€ could be considered an interior wall if you look at it.  Behind the firebrick is another course of mortar and brick.  So the heat absorbs into the firebrick and like you said, radiates back into the fireplace.   Most of the heat will rise and hit the blockoff.  From there, the heat will stay resident in the fireplace warming up the fireplace brick face and some will bellow out between the surround edges.


----------



## mellow

I guess you can say I have a different setup when it comes to exterior chimneys,  I had to cut out my smoke shelf due to it rusting and falling apart, so that let heat go right to the exterior bricks.  With this setup it is now fully enveloped.

As to fibers the surround is on at all times so that should block all transfer of fibers to the inside of the house,  secondary air inlets do not mix with the air circulated around the insert and go straight to the firebox, so that should be of little concern now that I think about it.

I have attached before and after pictures from my clean out door, showing the space is now fully insulated.


----------



## ScotO

I just finished up insulating my wood framed chase with the Roxul as well.....I am not drywalling it so I was going to do what woodmiser said as well......high temp paint to lock the fibers down, he is 100% right about the little fibers coming off of the insulation...while Roxul is made from a type of stone (not sure what kind of stone) and is supposedly not harmful, it can be a lung/eye/skin irritant, so it is a good idea to try to somehow encapsulate that insulation, have you though about a tin sheild or something to keep the fibers covered up?  I understand your concern about outgassing with the paint, but that would probably only be a one-time occurance....after it got warm once it shouldn't outgas again....keep us posted.....


----------



## iceman

I recently did the same to my stove... Didn't think about the fibers so I will take it out .. dont wanna clog up the stove 
And definitely don't wanna endanger my 2 year old... Thanks for the heads up


----------



## ddemmith

I did this to my old Lopi last week, what a difference.  Heat output is incredible, seems like it burns more efficient with less air as mentioned.  I used the Roxul both as a block off plate and to insulate around the insert.  I don't see how it would over fire it as it always has an air gap around the fire box with a natural draft circulating air.


----------



## mellow

Was cold enough last night to warrant firing up the insert,  it does get to operating temp faster and the fan kicks on quicker, even with a small load.   I did not do a full load in it to test an overnight burn, got started on it to late last night to get a good coal bed.  Will report back later on that.


----------



## mellow

Been able to run for a few days straight with the cold temps,  I really do not see that much difference in everyday operating, where I see the difference is in how much longer the fan stays on because the insert stays warm longer and I now have large coals in the morning after an overnight burn to get the stove going again,  before I would just have a few small coals and it would take more effort to get the fire started.

So far it was well worth the $40 for the Roxul and the time to install it.

The insert runs as normal with peaks to 550-575 top plate temp.  then back down,  the added insulation does not make the insert over fire.


----------



## BKInsert

mellow said:
			
		

> Been able to run for a few days straight with the cold temps,  I really do not see that much difference in everyday operating, where I see the difference is in how much longer the fan stays on because the insert stays warm longer and I now have large coals in the morning after an overnight burn to get the stove going again,  before I would just have a few small coals and it would take more effort to get the fire started.
> 
> So far it was well worth the $40 for the Roxul and the time to install it.
> 
> The insert runs as normal with peaks to 550-575 top plate temp.  then back down,  the added insulation does not make the insert over fire.



Thank you for the update!  Sounds like it was well worth it.  I just insulated the attic above the den where the stove is at, put 8x R30 (9") rolles for a total of 200 feet.  I only had 6" insulation before, I hope this will help with retaining the heat in the house longer.

Did you paint the insulation?


----------



## mellow

Nope,  if there are fibers that drop the surround will block them from coming into the living area.  The secondary air intakes feed the fire box so no fibers would get into the house.


----------



## Ram 1500 with an axe...

mellow said:


> Been able to run for a few days straight with the cold temps,  I really do not see that much difference in everyday operating, where I see the difference is in how much longer the fan stays on because the insert stays warm longer and I now have large coals in the morning after an overnight burn to get the stove going again,  before I would just have a few small coals and it would take more effort to get the fire started.
> 
> So far it was well worth the $40 for the Roxul and the time to install it.
> 
> The insert runs as normal with peaks to 550-575 top plate temp.  then back down,  the added insulation does not make the insert over fire.


Could the bigger coals be from using a different type of firewood? Thanks....


----------



## mellow

It was the same type wood back then, I burn a lot of Maple and Gum.  This was posted back when I had my XTD insert,  I now have a larger catalytic insert.

Needless to say the Roxul helps a lot to keep the heat in the fireplace which translates to longer burn times,  also helps to have an insert that will have meaningful heat for 12 hours per load.


----------



## resonator

Hello. So you just lined your fireplace with Roxul, it comes in contact with the insert on the sides but not the top? Any problems since you did this? Do you see any problems if the Roxul comes in contact with the top of the insert?

I've had an insert for a couple of years (Drolet 1800, bought used, some cracked bricks but works great) but like you, I'd been putting off the insulation part but there's a serious draft. I'm getting around to it now, and I happen to have Roxul soundproofing (denser than the thermal insulation but they don't report an R-value). Your post is the most relevant thing I've found. Thanks for posting those pics.


----------



## BrotherBart

A block off plate will fix the draft issue. But to answer the question, the Roxul starts getting soft around 2,400 degrees and won't burn. By the time the Roxul is trashed the insert will be a puddle of melted metal in the fireplace.

https://www.hearth.com/econtent/index.php/articles/making_a_block_off_plate/


----------



## BrotherBart

Something I have to ask. If there is a draft around that insert it means air is going up that chimney somehow. Do you have a chimney liner and is there a top plate up top that is sealed?


----------



## mellow

Drolet (sbi) is fine with using roxul up against the insert, but do me a favor and start a separate thread with your issue.


----------



## mellow

Ok sooo.. I was outside the other day and just happened to put my hand on the outside brick of my fireplace,  it was warm,  so I went out today with it being in the upper 30's and according to the IR gun my outside brick right up the middle where my insert sits was at 60 degrees.

Roxul alone is not cutting it for keeping the heat in the fireplace.

Im up in the air with pulling the Roxul and putting in Durock around the sides and back and making a block off plate out of cement board as well and then putting Roxul on top or behind that.  Durock will be lighter so If I make some metal support beams to hold it up and drill a hole for the liner just to try something different,  most of you guys are using metal.

Got a break in the weather on Saturday so might let the insert go out then pull it out (fun!) to get this done.


----------



## mellow

Updated my insulated fireplace,  went with Durock for Back and block off plate with Roxul behind and on top of that for extra insulation.  Pictures can be found here:  Got the itch again... Jotul C450 Kennebec


----------



## warm kitty

Thank you for your post. I was concerned about the insulation in direct contact with the stove. I have always burned a Consolidated Dutch West small Federal (free standing). In our new home we have an old Appalachian wood insert, which is all very new to me. Our fireplace was a steel prefab. In order to get the insert in, we had to plasma cut the damper and back out of the firebox. Of course leaving a gapping hole. I know we are losing a ton of heat up the chimney. On the first nice day, (it's 0 outside) I WILL be installing the Durock and the Roxul. I am confident this will make our stove more efficient.


----------



## mellow

Since the Durock+Roxul is doing such a good job on blocking the heat on the back and top I will be lining the sides of my fireplace with it as well this weekend.  I will be anchoring it to the steel fireplace box.


----------



## mellow

After seeing the gains from just the back piece of cement board I have gone ahead and done it properly on back,side,bottom,top.  

Just about finished:



Finished and painted with high temp black paint in case I decide to run with no surround:





Will let you guys know how it does.


----------



## warm kitty

mellow said:


> After seeing the gains from just the back piece of cement board I have gone ahead and done it properly on back,side,bottom,top.
> 
> Just about finished:
> View attachment 124034
> 
> 
> Finished and painted with high temp black paint in case I decide to run with no surround:
> 
> View attachment 124035
> 
> 
> 
> Will let you guys know how it does.


Did you go with just the Durock? I'm not seeing the Roxul. I'm keeping close tabs on your project : )


----------



## mellow

Roxul is behind the Durock on the back,  no Roxul on the sides as I do not have the room.  Also have a block off plate made from Durock on the top with Roxul on top of that.


----------



## ozibit juice

have you fired it up yet? noticeable burn time difference then before?  

it looks amazing man good work!


----------



## mellow

got the Appalachian reinstalled yesterday, checked the exact spot on the brick outside after running the insert for 12 hours and I was pleased to see that it was at 50 degrees. With the 30 degree elbow I just installed the liner is closer to the brick where I measure above the block off plate, guessing I would have seen lower temps without the elbow.

It is still to early to report on overall performance gains, but it does seem to be holding temps longer.


----------



## mellow

Loaded the insert last night at 9pm, came down this morning at 8am to the cats still purring along at 1000 degrees and the downstairs at 73, had a low of 25 overnight so I think it is safe to say the updated insulated fireplace with Roxul and cement board IS helping to keep the heat in the firebox resulting in even longer burns.

My block off plate is half inch Durock with a layer of Roxul on top of that.  The side cement boards do not have Roxul behind them, the back has Durock and Roxul behind it.  The insert does sit on top of half inch cement board now.

The addition of cement boards also helps to block out the fibers from the Roxul as a bonus.

My next upgrade will be when I redo my hearth I will get some sheets of Micore,  I will upgrade the Durock to Micore for better R value.


----------



## mellow

Just wanted to do an update with the temps in the teens and windchill in the negatives I can see a big difference between Roxul only and Roxul + Durock,   the Appalachian was a pain to get hot enough to heat the room in windy freezing temps, now it is keeping up, when I went home for lunch it was 71 degrees with the cat purring at 1500.  No other changes have been made,  just the addition of Durock.


----------



## jatoxico

mellow said:


> Just wanted to do an update with the temps in the teens and windchill in the negatives I can see a big difference between Roxul only and Roxul + Durock,   the Appalachian was a pain to get hot enough to heat the room in windy freezing temps, now it is keeping up, when I went home for lunch it was 71 degrees with the cat purring at 1500.  No other changes have been made,  just the addition of Durock.



Mellow how is the Durock holding up? Get different info on it. When installed it will prob almost touch the side of the insert in a few spots. Any issues in your estimation?

My installer is coming Monday and while he has the stove out I am going to add more Roxul in the damper and 24 ga metal block off. Want to line the box w/ Durock and hopefully, like your install I will have room for some Roxul in the back. Prob not on the sides.


----------



## mellow

Mine touches the Durock in the back, it is concrete board it will take quite a bit of abuse and heat.  I will have to be more careful with the Micore as it is more fragile.

No Roxul on the sides I don't believe is a deal breaker due to the heat going to the brick inside the house, the back is what you really want to insulate that heat loss against.  I would still suggest Durock/Micore on the sides to help reflect some of that heat back to the firebox, I do believe it has helped but I can't quantify it like I can the back.  And by quantify the back I mean stop all heat loss by measuring the bricks on the outside and seeing no temperature differences.


----------



## Nelson

Interesting idea. I have a similar set up with an exterior masonry fireplace, in which I have a small insert at the moment (looking to upgrade in the fall).

How did you go about attaching the durock/roxul to the back of the fireplace?


----------



## mellow

Nelson said:


> How did you go about attaching the durock/roxul to the back of the fireplace?



It was all tight fitting, the only place I needed to attach it to the wall was the back top,  I used some 2" metal sheet screws with washers so it didn't crack the durock.


----------



## Nelson

Cool, thanks!


----------



## theDokes

Mellow - 
How did you get the Roxul to stay in place on the top block plate?
I have my 4" pipe coming down through what is left of my old damper with Roxul stuffed into the remaining cavity - nothing on the side walls.


----------



## mellow

On the top, I made a block off plate out of my extra concrete board.  The Roxul sits on top of that as an extra insulation.


----------



## mellow

They say pictures are worth a million words so I thought I would let them do the talking.

Took these on Saturday, outdoor temp was in the lower 40's.  Insert was cruising at around 1000 on the cat and 300 on the flue.

Overview shot of my exterior chimney:




This is a picture of my baseline temp, outside temps. 41



This is a picture of right above where the insert sits, heat rises so this was the warmest spot I could find, 43
I can live with 2 degree difference. Before insulating, this spot would have been around the same temp as the picture below around 15-20 degrees warmer than surrounding spots, quite a bit of BTU's going to heat the outside brick.




Just for reference to show heat loss I have not insulated the area above where my liner goes into the terracotta.  55




Just another picture for reference, I have an insulated liner but still outputs quite a bit of heat.





Hopefully this will help people to understand the importance of insulating your fireplace if you have an exterior chimney with both Micore or concrete board AND Roxul, otherwise you are contributing to Global Warming    Just kidding


----------



## Nelson

Great pics!

I had my PE Summit Insert installed in November. Unfortunatley, due to time constraints and the installer I was using, I was unable to get Durock and Roxul on my fireplace prior to the install. However, I am planning to shut the stove down at some point this winter and get the work done. For the price of materials, it can't hurt to try. Certainly isn't going to make things worse. 

One question I had was around secondary air - any concerns that as you tighten things up in the fireplace that you might somehow be affecting the amount of air available for secondary intake? Maybe it isn't as air tight as I'm thinking it would be and, therefore, not an issue.

Either way, I'm planning to do work similar to yours (Durock on sides, Roxul and Durock in back and then Durock blockoff). 

I will try and get some temp data on my outside chimney before and I after to report back.


----------



## mellow

Nelson said:


> One question I had was around secondary air - any concerns that as you tighten things up in the fireplace that you might somehow be affecting the amount of air available for secondary intake?



Secondary air input varies from insert to insert, the Jotul 450 I had it was in the back, some is on the lower sides, my Appalachian doesn't have secondary air so it all comes from the front door. Depending on the insert I would provide an airspace for the secondary air, or even install an insulated OAK if you can. My XTD insert had secondary air on the lower right so I made sure I had airspace on that side to the front surround so air could flow cleanly.


----------



## lml999

Great write up. I recently installed Roxul and a blocking plate above my insert. I have spare Roxul and am planning on insulating behind the stove. Not sure whether I'll use durock or light sheet metal in front of the insulation. The sheet metal is so easy to use...


----------



## Clyde4

Hi Mellow,

Sorry if I missed your answer.  How did you secure the durock to the back of the fireplace without really compressing the Roxul?
I'm trying to figure out if it should attache metal studs first?
I have a hearthstone Clydesdale and a really big fireplace opening. It barely heats 1 room.
Scene:
Outside chimney
Heavy-duty SS liner, capped at the top, stuffed with Roxul around the damper only.
I'm going to install a block off plate soon. I hope that helps, though my installer says it won't help much because he capped the top of the chimney.
Chimney is 25ft+
The back wall and floor of fireplace are cold. 49 degrees (using IR gun)
The fireplace opening is 5ft wide at the front.  I'd like to insulate like you did but also put Roxul on the sides since I have the room for it


----------



## Jags

Clyde4 said:


> I hope that helps, though my installer says it won't help much because he capped the top of the chimney.



I will wager that your installer is wrong.


----------



## Schmev

Roxul is great and i never heard of it until i joined this site.  At the very least you can make a double layer block off plate with that stuff and be much better off than what some installers are doing.  

Honestly, now that i think about it i wish i could have wrapped my SS liner with it instead of the .5 inch insulated wrap it came with.


----------



## mellow

Clyde4 said:


> View attachment 151493
> 
> 
> 
> 
> 
> 
> 
> 
> 
> How did you secure the durock to the back of the fireplace without really compressing the Roxul?



I have a metal fireplace box so I drilled and tapped my holes then installed long bolts, you could do something similar using a 4" or 5" tapcon going into the brick.

Install a block off plate, you are sucking more heat up that chimney than you think.


----------



## Clyde4

Thanks for your reply. I'll do the block off plate first and then try insulation.


----------



## Clyde4

I'm waiting for the metal to come in. Going with 24ga galvanized sheet.  Tonight I had the fire going and took a few temp readings. 
The flue collar was 550.  About 30" above the insert the brick wall is 75 degrees. The rest of the room is 69-70 degrees.  The fireplace floor behind the insert not even 12" away is 60 degrees. 
I think it's safe to say I desperately need a block off plate.


----------



## Clyde4

I just installed the block off plate this weekend. I left the roxul that was stuffed in the damper, and then put 2 layers of Roxul R23 on top of the block off plate. I pinned it in place with tapcon screws, and then caulked the perimeter with hi-temp silicone. Around the liner I used the stove mortar to seal that gap.

**One thing I would highly recommend when following these block off plate instructions is to make sure you take the measurements SHORT exactly like it says.  I tried to make mine too exact and had to trim/bend/play with it etc.  the flaps will leave enough room to make up a distance, and you will have to caulk around it anyways. 

It has definitely helped. the room its in gets warm all around, and the surrounding rooms don't get cooler (like they used to). Now my problem is moving that heat to other rooms. I've been playing with a fan on the floor blowing cold air towards the fireplace. That works a little, but not great. One room however just doesn't get heat. on one side of the doorway its warm, and on the other its cold. The headers above the doorway are about 16" down from the ceiling. I imagine that's not helping. I may try the small fans in the corner of the doorway.

my burn times are longer and more complete now.  after putting 2 splits on a bed of coals and returning 2.5 hours later, I have this (see pic).  

I've been able to close the air damper to about 20% open.  I have gotten some lazy blue flames around the log on a bed of coals (not in this pic).

anyone have better luck with top of door mounted fans vs. floor fans pointed at the fireplace?


----------



## mellow

Glad to hear you are getting the benefits of insulating that fireplace.

Search the forum about fans, many threads dedicated to that already.


----------



## msjones2452

Hey there, fairly new to the site.  Were getting ready to purchase an insert, if we can make up our mind which one!  I've been following this thread and am very interested in insulating my masonry firebox.  I have an exterior wall masonry fireplace/chimney.  Definitely insulating the liner and installing a block off plate. 

Mellow, I have a question for you - actually everyone who has insulated their firebox.  Has anyone experienced any issues with their inserts?  Things like overheating of the insert/stove adaptor/liner etc. any failures of the inserts themselves.  I'm kinda gathering no one has as it hasn't been mentioned here yet but I thought I'd ask.  The insert at the top of my list is a hybrid w/a catalyst, I would think as long as I left some airspace around the insert things should be fine.  I was shooting for around 2" on the sides/back and 4" on top.  I have no idea how hot the outside walls of an insert get. Is there any concern with getting Roxul and Durock too close or tight to the stove adaptor? I would figure that would be the hottest part of the stove next to the catalyst itself.  Also, does one package of Roxul usually cover the whole project?

Thanks for any info.

Matt


----------



## mellow

I would talk to whoever makes the insert you are thinking of buying and get their blessing first.  See if they are OK with roxul touching it or if it needs clearances.  The most important part to leave an air gap is on the top, the sides do not get as hot IMHO.

1 pack of roxul will do your fireplace and a couple neighbors fireplaces.


----------



## msjones2452

mellow said:


> I would talk to whoever makes the insert you are thinking of buying and get their blessing first.  See if they are OK with roxul touching it or if it needs clearances.  The most important part to leave an air gap is on the top, the sides do not get as hot IMHO.
> 
> 1 pack of roxul will do your fireplace and a couple neighbors fireplaces.


 
Thanks for the info Mellow.  My dealer doesn't think it's a problem - at least what I've described to him with leaving an air space around the entire stove.  I'm not going to physically touch the insert at all.  Basically I'm just making my masonry firebox a little "smaller".  My biggest concern was the Roxul/Durock touching the liner w/in a few inches of where it connects to the insert.  I know the Roxul can handle the heat but I wasn't sure whether or not the actual liner would become so hot it would cause a failure. 

We finally pulled the trigger and ordered the Hampton HI400 w/a heavy wall SS flex liner.  I ordered the Roxul last night.  Everything should be here sometime next week.


----------



## Dmitry

Why do you ,guys , concerned about Roxul touching the insert? The melting point of Roxull is 2150 F. I'm actually thinking about placing Roxul  on a top of my insert to prevent heat loss to masonry and keep insert warm longer, It runs around 500 at start   and then drops to 400 F on  a top of inner box. Temp well controlled. Don't see reason not to do it . If it will start to overheat I can always remove it


----------



## Oldman47

The only issue I can see with using Roxul is that the thing it is insulating may not be designed for a situation where it cannot shed heat. If I design something and expect a 1 inch air space next to it I may make assumptions about how much cooling that inch of air will provide. If you take away that cooling is my material going to survive? That is the only down side I can see to better insulation.


----------



## Dmitry

I've looked at the  manual and it says nothing about how much air space should be around  the insert. I suppose they not going to recommend to insulate it like this because people would do crazy things , like over fire their stoves and then hold manufacturer liable .


----------



## etiger2007

In my opinion its best to get the blessing from your stoves manufacture for insulation.  I called SBI and they said go ahead and insulate the sides and back but do not do the top as it could cause an overfire situation.  If you dont get their blessing and you warp tubes or baffles good luck getting them to stand behind their warranties.


----------



## jatoxico

Personally I would not (did not) put insulation tight to my insert. Just makes sense for me to maintain a small amount of clearance. Depending upon where your inset pulls secondary air from you want to be careful not to obstruct any inlets as well.


----------



## msjones2452

Dmitry said:


> Why do you ,guys , concerned about Roxul touching the insert? The melting point of Roxull is 2150 F. I'm actually thinking about placing Roxul  on a top of my insert to prevent heat loss to masonry and keep insert warm longer, It runs around 500 at start   and then drops to 400 F on  a top of inner box. Temp well controlled. Don't see reason not to do it . If it will start to overheat I can always remove it



I'm not so worried about the Roxul.  That stuff will withstand way more heat than the average stove _should_ dish out.  I'm more worried about an "overfire" or "overheating" of the other components.  Like Oldman47 said, "may not be designed for a situation where it cannot shed heat." Also, once I get the insert in place, I will not have the ability of just removing any insulation easily.  While my firebox is fairly good size, the opening the insert must fit into is not.  I will have very little clearance on the top of the stove at the opening - not very conducive to removing insulation in short order while the stove is still hot.  I would feel a lot more comfortable maintaining some airspace around and above the insert.  However, my plan is to have Durock/Roxul approximately 4" above where the liner mates to the top of the stove.  Due to that being one of the hottest parts of the system, I was curious if there would be an issue with direct contact?  Again, not so worried about the Roxul, more concerned with overheating other components. 

I'm going to contact my salesman for more input.  Unfortunately, the manufacturer does not have any direct consumer contact information.  They rely on their dealer network.


----------



## mellow

The whole idea is to have the firebox insulated to keep the heat IN the insert.  Back is CRITICAL on an exterior chimney.  Sides are OK.  Top is CRITICAL with a Block off Plate installed.   No need to have the insulation on top of the insert if you have a proper insulated block off plate installed. 

Don't get lazy and just put Roxul on top of the insert thinking that will solve the issue.


----------



## HappyCamperMan

Sorry for jumping in on a thread that is nearly 1 year old.   However, do the answers regarding insulation change if the chimney is an internal chimney?  I have fieldstone interior chimney that runs up through the upstairs master bedroom (is sheet rocked in upstairs).   I was not home when my insert was installed so I have no idea if there is a block-off plate or insulation in my firebox.   I could take off the face and find out but have not done that.  I'm wondering if it would make any sense to pull off the face and stuff Roxul in the firebox for an internal chimney?


----------



## mellow

I would still do a block off even on an internal chimney, I just wouldn't worry as much about insulating the firebox, but I still believe that insulating the firebox helps keep the heat where it needs to be in either an exterior or interior fireplace.

At a minimum pulling the surround and stuffing the damper throat with Roxul will be better than doing nothing.


----------



## HappyCamperMan

mellow said:


> I would still do a block off even on an internal chimney, I just wouldn't worry as much about insulating the firebox, but I still believe that insulating the firebox helps keep the heat where it needs to be in either an exterior or interior fireplace.
> 
> At a minimum pulling the surround and stuffing the damper throat with Roxul will be better than doing nothing.



Thanks, Mellow...

Because I haven't pulled the surround (and wasn't around for install), I don't know if there is a block-off plate.  Do you know if it standard install procedure to put in a block-off plate or do you think it's possible that I just have a stainless flue running up my chimney with an opening around it?


----------



## mellow

I can pretty much guarantee they did not install a block off plate, it is not standard procedure even though it should be.  I am sure they cut out your damper throat enough to get the liner through and called it a day.


----------



## HappyCamperMan

Thank you, Mellow.  Sounds like a need to put this on the Honey Dew list!


----------



## Squisher

Your wife would do that for you?  You're a lucky man.


----------



## jatoxico

HappyCamperMan said:


> I haven't pulled the surround (and wasn't around for install),



If you didn't ask for a block-off or insulated liner the chances you got either are pretty slim. Typically installers will put some insulation up top between the liner and the clay tile and that's about it.

I agree with others that insulating the fire box is less critical on an interior install the reasoning being that any heat absorption by the masonry will eventually be given back to the house unlike an exterior where the heat goes out to atmosphere.

I also agree that I would pull the surround and insulate the damper area and smoke shelf w/ Roxul to keep as much heat in the house rather than sending it up the chimney and to keep the liner as hot as possible. Especially true since they may not have insulated up top as well as you might like and heat lost from there would be wasted.

With any luck you'll have room to do this with the insert in place. A metal block off would be even better and if you have the room can be installed in two pieces also w/o removing the actual insert.


----------



## Dmitry

Block off plate is important in both cases. It prevents hot air from escaping outside. The insulation of firebox very important if it is exterior chimney and not so if it's internal chimney. The stone going to absorb energy and give it away slowly hours after.   If you want quick heat output from your insert you can insulate your firebox as much as you can and use blower on full speed . If you burn on a regular basis you might be better off with blower on low and not so much roxul around. I put some in my internal firebox and it's still absorbs a lot of heat, but I've noticed that house stays warmer long after fire is gone vs other sources of heat.


----------



## Xtrl9

I asked in another thread but I'll ask here too, how would you insulate the top of your block off plate if you only had access from inside/under the fireplace?

Also is there an insulation difference of one cement board over another? I tried to read the difference and all I found out is people like certain brands differently and its great in a bathroom if you put a vapor barrier up; so nothing really about the insulating or heat radiating properties.


----------



## mellow

If you have room to pull your insert, you pull it out then install your block off plate and put the insulation on top of the block off plate before putting it up.

https://www.hearth.com/talk/wiki/make-a-damper-sealing-block-off-plate/?noRedirect=1

I have used Durock because that was what was at Lowes, as long as it is pure concrete board with no chemical fillers it will be fine.


----------



## Xtrl9

Well I don't have any insert yet so I won't have to pull it out. I'm going to fabricate the fireplace liner after I can get exact measurements for the profile of the insert I'm going to install. I want to stuff the fireplace as much as possible.


----------



## bholler

Xtrl9 said:


> Well I don't have any insert yet so I won't have to pull it out. I'm going to fabricate the fireplace liner after I can get exact measurements for the profile of the insert I'm going to install. I want to stuff the fireplace as much as possible.


You want the stove there to do that.  I have found it usually does not work out well fitting the liner and plate without the stove.


----------



## Mr. Jones

I'm at that stage right now, with extra dura rock sitting around. Was it worth it in your opinion to do all of this? Not the block off plate, as I'm doing that for sure, but behind the stove, and on the sides?


----------



## mellow

Mr. Jones said:


> Was it worth it in your opinion to do all of this?



100% worth it.  Check this post for Picture proof

Edit: Put Roxul behind the durock for the backside, it will help alot.


----------



## Roy Batty

I finally did this last week. 

Cat temp 1250 when I went out side to 31*.   Used my IR temp and got a base line on the brick of 29*.   The area where my insert would be was reading about 34*.   The chimney area above the roxul was reading about 55*.   Last year when I would check the insert area was running in the 50s.


----------



## JAJA

Great thread will the new next gen 1/2" Durock cement board by USG work for top plate and lining the fireplace


----------



## mellow

JAJA said:


> Great thread will the new next gen 1/2" Durock cement board by USG work for top plate and lining the fireplace



Check to make sure it doesn't have the styrofoam in it, if it is all concrete board and does not contain combustibles it should be good to go.


----------



## Xtrl9

Kinda funny story about this, when I insulated my fireplace and made my block off plate I cut the hole to have about 1/8th of clearance for the liner.  Due to the angle of the dangle, it was like trying to bullseye a womp rat with a t-16. I ended up breaking my block off plate in the front so now one side hangs down some from the top of the firebox.


----------



## brettdacosta

Hey guys. I'm nearly through with my installation - can't wait to have the stove back in her. I'll post pictures tomorrow, maybe.

But I wanted to ask... Why did we use the durock in the fireplace? Is it for insulation purposes (in addition to the r-15 roxul my fireplace is filled with) or more for protection of the durock? What role does it primarily play? 

I haven't really found that answer anywhere. Thanks for this thread. It really helped out.


----------



## Dmitry

brettdacosta said:


> Hey guys. I'm nearly through with my installation - can't wait to have the stove back in her. I'll post pictures tomorrow, maybe.
> 
> But I wanted to ask... Why did we use the durock in the fireplace? Is it for insulation purposes (in addition to the r-15 roxul my fireplace is filled with) or more for protection of the durock? What role does it primarily play?
> 
> I haven't really found that answer anywhere. Thanks for this thread. It really helped out.


I guess to hold Roxul in place , I didn’t use it


----------



## mellow

It holds back the fibers of the roxul but at the same time acts as an additional insulator, I got good results from using both but you are free to use one or the other in your install.


----------



## Bushels20

mellow said:


> It holds back the fibers of the roxul but at the same time acts as an additional insulator, I got good results from using both but you are free to use one or the other in your install.




I know this is an old post, but I am just about to start this same project. I am wondering, what I summation value does the Durock have? Isn’t it just like the brick? Just holds heat and passes it off somewhere? It’s not keeping the heat in is it? Or is it because it’s backed with Roxol that this concept works? I’m not questioning the idea, it’s obviously working for many of you. Just want to understand it before I go to the time and effort.


----------



## ddddddden

I believe he used the Durock just to "seal in" the Roxul.  Some folks worry about fibers from insulation material getting into their living space.


mellow said:


> It holds back the fibers of the roxul but at the same time acts as an additional insulator. . .


----------



## begreen

Bushels20 said:


> I know this is an old post, but I am just about to start this same project. I am wondering, what I summation value does the Durock have? Isn’t it just like the brick? Just holds heat and passes it off somewhere? It’s not keeping the heat in is it? Or is it because it’s backed with Roxol that this concept works? I’m not questioning the idea, it’s obviously working for many of you. Just want to understand it before I go to the time and effort.


Durock NexGen has some insulative property due to the pumice chips in it.


----------



## mellow

It is keeping the heat in, that is why I used Durock on top of the Roxul as an extra layer, plus it does help to seal off the Roxul fibers.


----------



## jimmol

Just looking at the spec sheet for Durock NexGen at https://www.usg.com/content/dam/USG...ck-next-gen-cement-board-datasheet-en-can.pdf

Avoid exposure to sustained temperatures exceeding 93°C(200°F).

Hmm, wonder how warm it is where my pipe goes up through it?


----------



## mellow

jimmol said:


> Just looking at the spec sheet for Durock NexGen at https://www.usg.com/content/dam/USG...ck-next-gen-cement-board-datasheet-en-can.pdf
> 
> Avoid exposure to sustained temperatures exceeding 93°C(200°F).
> 
> Hmm, wonder how warm it is where my pipe goes up through it?



Durock discussion


----------



## Das Jugghead

I recently started insulating my fireplace in an attempt to squeeze a little more efficiency out of my cheap Pleasant Heart wood stove.  There were pre-existing threaded holes in the angle iron for the lintel where a set of brass fireplace doors used to be.  I used the threaded holes to mount some angle iron I had in the shop to hold up the block off plate that I fabricated out of cement board.









I made a two piece cardboard template (I actually made three versions in order to get it as precise as possible.  Then I reduced the size by taking a quarter inch off the perimeter to make it easier to fit and then stuffed rock wool in all the seams.  The reason for a two piece block off plate was because I just did not want to fool with pulling the stove and reinstalling it - I will do that in the spring when I pull it for inspection/cleaning.






Before installing the block off plate I blocked off the damper throat by stuffing rock wool into it but neglected to get pictures of it.  I also precut rock wool insulation to go on top of the block off plate before installing the second half of it.  After stuffing rock wool in the seams I trimmed it off with a stupidly sharp razor blade.




To cover the seams and reduce convection through the seams I installed aluminum flashing in several layers.  I also placed rock wool along the walls of the fire place and then covered it with aluminum flashing.  The flashing serves to cover the rock wool and also helps reflect a little heat out of the fireplace.  I still need to finish the top part and integrate that into the overall set up.  It has made a difference for us in that we gained almost 5 degrees from 70 to 75 with a few runs up to 82 in the room where the stove is installed.  Mostly the burn cycles keep the room at 75.  If I had to guess I would say most of that gain is from stopping the heat from going up the chimney.  The fireplace and chimney are on an exterior wall of the house so the insulation and reflective aluminum do help isolate the heat from the heat sink.






I still need to do some fine tuning and adjustments to tidy things up.


----------



## Crawdad

jimmol said:


> Just looking at the spec sheet for Durock NexGen at https://www.usg.com/content/dam/USG...ck-next-gen-cement-board-datasheet-en-can.pdf
> 
> Avoid exposure to sustained temperatures exceeding 93°C(200°F).
> 
> Hmm, wonder how warm it is where my pipe goes up through it?


Cement Board has styrene beads within the core. Be careful.


----------



## begreen

Crawdad said:


> Cement Board has styrene beads within the core. Be careful.


Some do. It's good to check. Some like Durock use pumice granules or perlite. USG's styrene pellet board has a different name and is recommended for wet areas like showers.

Wonderboard Lite has polystyrene pellets inside.


----------



## Das Jugghead

Crawdad said:


> Cement Board has styrene beads within the core. Be careful.



Durock - I should have been more clear in that.


----------



## Das Jugghead

It does not look like much but I finally got around to fabricating and installing these deflectors at the back of the fireplace to help the convective air move out of the fireplace.  It has made an amazing difference in how much heat we have and for how long.  Right now we have been running on a bed of coals for almost two hours and it is still 72 degrees in the house.  Not bad.  In the spring I plan to fabricate a new and cleaner setup when I pull the stove for inspection and cleaning.

The real litmus test will be over the weekend when the temperatures drop to below zero.


----------



## jetsam

Hey, it's mellow's old fireplace thread.  I have linked to this thing a jillion times.


----------



## jimmol

Finished my Durock/Rolux block off. With the help of a templet I put my Rolux up around my pipe and it filled the area completely. I had purchased 1/4" Durock so it would be easier for me to put up the top and it went up fine, but I noticed it flexed more than I had hoped so I added a 1/2" piece below it. On to the insulation of the back.
As you can see from the picture, I put in insulation in the back of my fireplace as high as I could, then I put a 1/2" Durock as at back to square off the area. This piece provided part of support for my top sheet. I added more Rolux up to the top. In the front, the top piece was at a slight angle upward so it wedged just above the angle iron lip of the fireplace. Then I placed a second 1/4" Durock board to seal the Rolux in. This piece did not provide support for the top. Finally I added a 1/4 and 1/2" Durock on the right side and a 1/2" piece on the left side. These were also support for the top piece. There was not room for insulation on the side. I caulked the seams with 3M fire barrier sealant. I decided not to paint at this time as I wanted to see how the cement board handled the heat.
I will add the pictures as soon as they are approved.













1 Squaring it off



__ jimmol
__ Jan 19, 2019
__ 1



						Added insulation at the back up to where it would not fit with the Durock in in front of it...
					
















Adding the second layer of insulation



__ jimmol
__ Jan 19, 2019


















Insulation installed.



__ jimmol
__ Jan 19, 2019


















1/4" Durock over the Rolux.



__ jimmol
__ Jan 19, 2019


















Sides in place



__ jimmol
__ Jan 19, 2019



						The sides are also used to support the top. Sealed with 3M Fire Barrier Sealant.


----------



## SculptureOfSound

Very nice install jimmol. That's what I wanted to do but didn't have enough room for the Roxul and durock. I originally decided to just put in the Roxul...it was touching the sides and back of the insert. Then I learned how potentially harmful the fibers are and realized with my install the way it was they could be getting into the blower path and ripped it all out.

One thing I did do and that you may want to do that would help is to put some sheet metal (cheap galvanised would work, it won't get hot enough for zinc off gassing) over the durock. This would reflect the radiant heat back towards the insert.

I don't know how much it helps but that's what I ended up doing after taking out the insulation. It did seem to make some difference...the side brick behind the sheet metal was about 85 degrees after a few hours of burning while some exposed brick next to it was 140.


----------



## jimmol

SculptureOfSound said:


> One thing I did do and that you may want to do that would help is to put some sheet metal (cheap galvanised would work, it won't get hot enough for zinc off gassing) over the durock. This would reflect the radiant heat back towards the insert.
> 
> I don't know how much it helps but that's what I ended up doing after taking out the insulation. It did seem to make some difference...the side brick behind the sheet metal was about 85 degrees after a few hours of burning while some exposed brick next to it was 140.



I will keep that in mind. I want to see how it holds up and if the cracks seems to get worse, I will get the metal. I have a lip about an inch lower than the Durock in the front so I could put it lower and then meet the top in the back. 
I must admit, I wonder how the deflectors for the back might work. 

Thanks to all for helping make this work.


----------



## Das Jugghead

jimmol said:


> I must admit, I wonder how the deflectors for the back might work.



I am not overly familiar with your set up - is it an insert?  I have a small free-standing wood stove installed in my fireplace.  I insulated the sides and back of the fireplace with rock wool and covered all of that with aluminum flashing.  I also have a Durock block off plate in the top of the fireplace opening and more rock wool stuffed in above that and through the damper.  These things made a huge difference in the amount of usable heat output from the stove.  The last thing I did, about a week later, was add curved aluminum deflectors in the back to help the hot convective air from the back of the stove to make the transition from vertical to horizontal across the stove top and ultimately out the front of the fireplace.  The additional deflectors at the back made at least as much of an improvement as the initial insulating of the fireplace - if not more.  It is my entirely nonscientific opinion that the two improvements (insulating the fireplace and the curved aluminum deflectors at the rear) work in concert together to produce the better performance.


----------



## mellow

@jimmol nice install!  You should see a marked difference in heat output and burn times with that insulation, will especially help with that smaller firebox.


----------

