Liner Insulation and Block-Off Questions

[Apiator]

I’m about to install (self-help project) a wood burning insert (Avalon Olympic or similar) into my open-hearth, 7 year-old, masonry fireplace. The current chimney top is about 25’ from ground level with a 12” square flue. The damper is approximately 6” x 34” and I’ve already removed the damper plate, but will probably need to cut a little more off the bottom of the damper to accommodate the 6” liner. After researching and reading quite a bit on this forum, I still have a few questions.

- I’ll be purchasing a S/S liner kit with the insert. The dealer from whom I’m purchasing the unit says that insulating the S/S liner is overkill. I live in north Mississippi where temps only get in the teens several days out of the year, so the winters here are mild compared to many of you. What’s y’all’s experience?? I seem to read differing opinions on this forum.

- Some folks seem to insist on a block-off plate. I assume this goes where the damper plate used to be, but will have the liner passing through it. Others have suggested putting a high temp insulation (rock wool) around the liner in the lower area, as well as up by the chimney cap. Suggestions??

- Are the block-off plate and rock wool attached somehow??

This is my first real experience with a wood stove, and I don’t want to foul it up. Many on this forum seem to have a ton of experience. Thanks for the advice.

 

[RAY_PA]

I'd at least go for the block off plate. I used a little glue to attach the rockwool to my blockoff plate. Is the chimney on an exterior wall? if so, I'd probably insulate it also.

 

[iceman]

if it is exterior yes insulate it .....
the rockwool sits on top the blockoff plate no glue is needed
check this out
https://www.hearth.com/talk/threads/11697/
what you cant see is the ceramic blanket on top the blockoof plate
if you fill any voids around the liner you should be ok ...meaning even if there is spac around your insulated liner at the bottom of the chimney fill that with rockwool as you dont want heat to go in between the liner and the actual chimney ... putting rockwool on top of the plate is good but will eventually give off some heat , however if it can get up the chimney it will stay and put more heat in your area because it will come out through bricks being heated...
if you look at my stove all of that tile above it stays very warm even after the stove is out, it takes a couple of hours to cool down ... but this is only after the stove has been going good for a while!

 

[BrotherBart]

If the chimney liner tiles are in good shape, in Mississippi I wouldn't insulate the liner for draft purposes. I would only do it as a safety item if needed because of chimney condition. It is colder here and I burn into two uninsulated liners in exterior masonry chimneys about that height and have monster draft.

As to block off plates for inserts, it is pretty much a religious thing here on the forum but millions of people burn in inserts with full liners without them and seem to do just fine. They certainly aren't a safety item with an insert with full liner and are not required by any insert installation manual or building code that I have ever seen.

 

[Apiator]

Yes...The chimney is on an exterior wall.

Bro. Bart: My liner tiles do appear to be in good shape. I don't mind insulating the liner if necessarry....just had rather keep it simple if not required. From what I gather (and I could be wrong), insulating the liner does more to protect the chimney tiles (and subsequent house) than to increase heat output in the living area.

Iceman: the link you posted shows what appears to be a custom-fit block off plate. Was that ordered specifically for your unit, or was it constructed on the spot.

Also....The Avalon Olympic which includes a blower and panels: quoted $2195.00. 25' S/S liner kit (no insulation): $400.00 This seems pretty reasonable based on my research. Anyone else??

 

[drdoct]

Blockoff plates are easy to make and yes you just stick the insulation right up there on top and then pop it into place then put a few screws to hold it. Somewhere here is a template but if you just look up and use your common sense you'll figure out where it needs to go. Use think sheet metal so that it's easy to cut with tin snips and you'll be able to make little changes on the go. Your price seems great on the liner. I have no idea on insulating because mine is an interior chimney and it works great without any. Good luck and make sure you get some good leather gloves while handling that liner.

 

[iceman]

Yes...The chimney is on an exterior wall.

Bro. Bart: My liner tiles do appear to be in good shape. I don't mind insulating the liner if necessarry....just had rather keep it simple if not required. From what I gather (and I could be wrong), insulating the liner does more to protect the chimney tiles (and subsequent house) than to increase heat output in the living area.

Iceman: the link you posted shows what appears to be a custom-fit block off plate. Was that ordered specifically for your unit, or was it constructed on the spot.

Also....The Avalon Olympic which includes a blower and panels: quoted $2195.00. 25' S/S liner kit (no insulation): $400.00 This seems pretty reasonable based on my research. Anyone else??

that was mine i measured it out and had it made in pieces to give me the wiggle room ...
if BB says you don't need a insulated liner he is prolly right..... but as mentioned before , block off plates are the thing on this site ! i would at least do the block off plate... stuff as much of the rockwool in there as you can

 

[burntime]

Brother Bart, can you hear Elk fumming? I am in Wiscosnin and although I agree with BB, the block off plate and liner insulation on an interior liner in Wisconsin was worth it. I have had it both ways and can say with confidence from experience that you will be able to choke the fire down lower and get a longer burn with it. My chimney is about 15 feet or so. Yes, I have a masonary chimney and the tiles are in great shape...for me it was just a performance thing. If you do not get as cold as in WI then its iffy. If you have a cold climate I would do it all over again to gain efficiency and burn less wood. I scrounge but if I was paying for it the decision would be really easy. Good luck!