Roxul insulation on insert

[Egghead]

We had a Kozy Heat Z42 installed about a month ago. We are in the process of rebuilding our mantel (old one wouldn't pass combustible clearances) and I've heard the terms block- off plate and Roxul insulation thrown around. Our installer simply removed our old prefab, tore out the old chimney, and installed the new fireplace (Z42) along with Class A insulated pipe. On the fireplace end, he simply slid the new one in place in the existing hole. There is a good sized void around the fireplace with no insulation (fireplace is on an exterior wall). Since we haven't finished the surround yet, I'm still at a good point to install Roxul/blockoff plate if it's necessary. Seems I've read where using these two items can help increase burn times and allow that heat to make its way inside rather than up the chimney. I'm finding myself reloading every 3 hours or so, though when doing so I certainly have a nice bed of hot coals. The living room, where the Kozy is, certainly gets toasty and I've seen temps (with IR thermo) around the 500 degree mark. One thread I saw warned of overfiring due to the extra insulation, though I'm still not exactly sure what an overfire temp is for my unit.
My question is.....should I install these items while I'm still at a good point before finishing out and is it worth it?

 

[Bagelboy]

I would!

 

[jatoxico]

We had a Kozy Heat Z42 installed about a month ago. We are in the process of rebuilding our mantel (old one wouldn't pass combustible clearances) and I've heard the terms block- off plate and Roxul insulation thrown around. Our installer simply removed our old prefab, tore out the old chimney, and installed the new fireplace (Z42) along with Class A insulated pipe. On the fireplace end, he simply slid the new one in place in the existing hole. There is a good sized void around the fireplace with no insulation (fireplace is on an exterior wall). Since we haven't finished the surround yet, I'm still at a good point to install Roxul/blockoff plate if it's necessary. Seems I've read where using these two items can help increase burn times and allow that heat to make its way inside rather than up the chimney. I'm finding myself reloading every 3 hours or so, though when doing so I certainly have a nice bed of hot coals. The living room, where the Kozy is, certainly gets toasty and I've seen temps (with IR thermo) around the 500 degree mark. One thread I saw warned of overfiring due to the extra insulation, though I'm still not exactly sure what an overfire temp is for my unit.
My question is.....should I install these items while I'm still at a good point before finishing out and is it worth it?

Definitely worth investigating before you close it up.

Block off plates w/ Roxul insulation are pretty much advocated here when installing a stove or insert in an existing masonry chimney.

I'm not clear what you have, is it a chase or masonry? Also I am not sure about zero clearance fireplaces. If you have an unisulated chase I would think the manual will have clearances but if you want to put insulation right up to or on the fireplace I would check with the manufacturer but be careful not to obstruct the air intakes if you do.

Hopefully someone with experience installing zero clearance units can chime in.

If you need and how you construct any block off plate also depends on what your chimney is running in. The block off is meant to stop hot air radiating off a free standing stove or insert installed in a fireplace from going up and out of the house through the gap between the liner and what it runs in (e.g. clay tile in chimney). This keeps more of the heat in the house. Again without knowing if you have a chase or what and if this applies to zero clearance units I couldn't say.

It may be more a case of making sure your outside wall is insulated just like any other area of your house but bearing in mind any special clearances needed.

Can you post a pic?

 

[Egghead]

this is what it looked like once they removed our old fireplace. You can see that there is no insulation on the exterior wall portion, nor is there insulation on the sides (still exterior). The wall directly above the fireplace has insulation. The chimney is in a chase. I would think if nothing else to put insulation on the exterior wall portions- I just wasn't sure about anything above the fireplace.

 

[Egghead]

so from what I can tell, is a block off plate generally used on an insert install and not what I've got installed? Everything that I have seen has to deal with making the plate the same size as the top of the insert so that no heat can get around it. However, with my install the top of the fireplace is not as big as the actual opening. Am I looking at this correct?

 

[jatoxico]

Seems to me that you need insulate the chase on the walls and around the chimney at the base of the chase just to keep room air from going up the chase. Don't see a need for more than that. I'd use Roxul even though it may be overkill. Manual give you guidance for clearances and obstructions?

 

[rwhite]

Maybe someone else will point out the error of my ways here. If the ZC insert is rated to be that close to a combustable chase why the need for Roxul? Could you use standard unfaced batting? It would seem those 2x4s are gonna burn long before insulation would. Just asking the question here, don't go do it just based on my advice.

 

[jatoxico]

Maybe someone else will point out the error of my ways here. If the ZC insert is rated to be that close to a combustable chase why the need for Roxul? Could you use standard unfaced batting? It would seem those 2x4s are gonna burn long before insulation would. Just asking the question here, don't go do it just based on my advice.

The OP wants to block off the chase. I would use Roxul to insulate around the chimney for that. As long as you have the Roxul might as well use it on the exterior walls but it's probably not necessary and the pink stuff is OK as long as you are meeting required clearances.

 

[Egghead]

That was going to be another question....if Roxul was necessary or if regular batted insulation could be used. I could always remove the backing

 

[bholler]

I looked at the maual fo your stove and you can insulate around it but you need 72" above it to combustibles. so I would insulate the inside of the chase all the way up and not put a block off plate in theninsulate the bottom of te top plate making sure to maintain any clearances to the pipe required by that manufacturer

 

[Egghead]

Seems to me that you need insulate the chase on the walls and around the chimney at the base of the chase just to keep room air from going up the chase. Don't see a need for more than that. I'd use Roxul even though it may be overkill. Manual give you guidance for clearances and obstructions?

I think that some form of insulation would be needed, just not sure if I need to use Roxul or not. If I can get by with regular batted insulation, I can just do that since Roxul isn't readily available where I live. Also, can I get by without doing a block off plate? I'm not sure since my fireplace isn't an insert install and was a complete rip out of the old. The top of the fireplace box is square and isn't the same size (width) as the opening in my wall. All of the block off plates that I've seen are the exact same size as the top of the fireplace but these have all been inserts, I've yet to see a pic of someone putting a block off plate in an install like mine where I essentially started from scratch with my fireplace. Some have recommended insulating the chimney pipe but I can't do that- plus my pipe has insulation in it already...not quite sure what difference that would make other than keeping things super tight and not allowing any air between the pipe and chase framing. The manual says not to fill space directly above the fireplace with an material (except wood framing)....would this be to prevent overfiring?

 

[bholler]

regular insulation should be fine