Chimney Liner Insulator?

[Bigun]

We are about to install a wood burning insert into a fireplace in a 1973 built house. The chimney is about ~24' tall with a 11"x11" ID/13"x13" OD terracotta opening at the top, planning on using a 8" diameter liner. The chimney *IS NOT* in the middle of the house, but rather sticks a bit out of the wall of the house (6" or so). I've been looking at liners and faced with the option to purchase one with or without insulator (about a $400 difference). I've been mulling the decision in my head of whether or not the liner would be worth the money, especially since I plan on cleaning the liner annually to knock out any creosote build-up.

*AND* if it's decided I need the liner.... any recommended sites to purchase an insulated liner from?

 

[pen]

What stove is this going to be attached to? If the stove has an 8 inch stove collar, then you'll of course want the 8 inch liner you described. Most modern stoves use a 6 inch stove collar, which then would be the liner size you should go with.

If using the 8 inch pipe, make sure you look at the dimensions / call ask about the outside diameter of the pre-insulated pipe that it will fit down OK. I think most should so long as your tiles are pretty straight, but there might not be as much extra room as you think. With a 6 inch liner, you'd have no trouble at all.

Make certain you scrub the heck out of the terracotta before the liner goes it.

Also, consider building a blockoff plate, or at least packing the area around the liner in the top of the firebox where the flue itself starts, with roxul insulation.

pen

 

[Bigun]

I'm attaching it to a Forrester wood insert. It has a rectangular exhaust port (13.75" x 3.375") that needs to be adapted to whatever size I wish. I did the math and the area of the rectangle shaped exhaust worked out to 46.4" square and the 8" sleeve area worked out to ~50.24" square. If I went with a 6" sleeve, the area of vent would be ~28.26" square. A 7" would be ~38.47" square. An 8" sleeve is the only one to have a close enough area to compensate the area of the original exhaust port without going under.

Now, if it can't fit, then I'll do what I have to do and go with a smaller one. The one thing I haven't done is get a strong flashlight and shine it down the chimney to check for straight brickwork/obstructions.

As far as the cleanliness of the terracotta chimney, I had an inspector come out and inspect the chimney and clean it to burn wood in the fireplace (I was originally going to burn wood without an insert). But after I have burned two fires in the fireplace with little to no heat being put into the house, I stopped burning, closed the damper, and began to look options that would get heat out of my wood. I think the terracotta is clean enough, I looked at it after I had burned the fires and only saw a thin white layer of ash.

Which kinda brings me back to the original question: With insulator, I'm looking at adding 0.5" in diameter to the sleeve.... so assuming if I can't fit an 8" with 1/4" insulator, am I better off going with 8" with no insulator, or a 7" with insulator? Or just going with a standard size exhaust and stick a 6" with insulator?

 

[Excavator]

As stated if insulation not used make sure you build block off plate at top of fire box.
I installed insulated 8 inch liner and built a block off plate for best of both worlds.
I had to use sawzall and cut out the damper frame in the center and chip out few fire brick to allow room to drop the 8 inch straight down and then connect to stove with T and clean out cap at very bottom.

 

[Bigun]

Ok, I'll go insulated. That said, would it be safe to go down to a 6" liner if I need to?

 

[Excavator]

My Vermont Castings recommends 8 inch unless keeping doors closed. Then 6 inch is fine
Most stoves need 6 inch so you should at least do some research on your stove requirements but I am thinking you will be fine with 6
I used Chimneylinerdepot.com http://www.chimneylinerdepot.com/store/chimneylinerkit.php

 

[Bigun]

My Vermont Castings recommends 8 inch unless keeping doors closed. Then 6 inch is fine
Most stoves need 6 inch so you should at least do some research on your stove requirements but I am thinking you will be fine with 6

It was made in 84', can't find anything on it. But I'll put in 6" just in case I replace it with something else in the future.

 

[Bigun]

Ouch... a liner kit with 1/2" insulation (6" x 25', includes a cleaning kit), the adapter to go from rectangle port to round 6", and a container of furnace cement, a little over $900 (shipping and all)! Is that about right?

 

[Excavator]

Ouch... a liner kit with 1/2" insulation (6" x 25', includes a cleaning kit), the adapter to go from rectangle port to round 6", and a container of furnace cement, a little over $900! Is that about right?

Thats about right, I paid more for the 8 inch and it hurt the wallet BUT it sure was the best money I could have spent after having piece of mind and much much better burning and heating results. My house might have burnt down by now if I did not do this. Plus the liner stays cleaner and is easy to keep clean