Fireplace insert: Insulate the exterior, or not?

[pdqdl]

OK! I have just about determined that I need 6" x 17' to 20' of chimney liner. Now for the tough choice. The kits will come with an attachment plate at the top, designed to suspend the liners, so this simplifies that question. So far as I can tell from the descriptions, there isn't much difference in the various attachments, and I won't even need the "T".

Selkirk brand kit from Menards, but 4-6 days later arrival at $356.00. The Selkirk has an extra 5' of liner in the kit, but is made of 304 Stainless steel, as best I can tell.
https://www.menards.com/main/heatin.../1768134/p-1444453715488-c-6895.htm?exp=false

Rockford brand from Home Depot, but it is only 20' long. Made out of 316 Stainless, however. At $538.00, I don't know if the "smooth wall" feature and the better grade of steel is significant enough to spend an additional $182.00.
https://www.homedepot.com/p/Chim-Ca...s-Steel-Chimney-Liner-Kit-SW620SSKF/204673930
(The same exact kit is available at Lowes for $568.00, but it seems to be privately branded)

(or $518.00 at Amazon, with lower tax rate!)​

Worthy of mentioning: the Home Depot, Lowes, Amazon, and Walmart kits all feature the same picture on the product, but Lowes and Walmart refer to their chimney as "Double ply", I suspect this is just a marketing trick, but don't know for sure.

If anyone has a brand preference or other recommendation, please let me know.

 

[gggGary]

On minor changes can make the difference:

This stove replaced a wood burner with a rusted out heat exchanger when I moved here.

It was where the furnace had been, about 3' out from the 6" square tile chimney flue opening, connected with 6" single wall smoke pipe.
Was an SOB to run, hard to light, fire would die, it would smoke up the house.
When I moved it tight to the chimney, using about 2' of double wall connector pipe/elbow. That fixed it, never a problem since.
It was previously in the living room,

and ran like a champ there on about 6' of triple wall from the ceiling straight up to a cap.

One trick I learned; if you can a get a fresh air vent at or near the basement floor then pipe it up to near the ceiling, it won't create cold drafts.

 

[pdqdl]

One trick I learned if you can a get a fresh air vent at or near the basement floor then pipe it up to near the ceiling and it won't create cold drafts.

Sorry, I'm not quite getting the picture on how that would help.

EDIT: It sounds kind of like an outside air connection, but attached high above the stove?

 

[pdqdl]

And... I've thought of another question.

I started this project thinking I would insulate everything as much as possible to improve the draft of the stove, but I am beginning to think that will be unnecessary and prove to be a waste of money. I figure that I haven't had any creosote for the last 22 years, so keeping the flue warm to prevent condensation shouldn't be an issue. To that extent then, all the heat in the flue will be somewhat trapped by a well insulated cap and the barrier I intend to put where the damper should be. That will be a significant savings.

Same story for insulating the outside of the fireplace insert. If I trap any escaping heat at the top of the hearth area with a good seal, the former fireplace will warm up pretty quickly off the exposed flex pipe, and this should make an adequately warm backside to the insert that it too will be more efficient.

@gggGary, you mentioned previously that I shouldn't insulate the flue. Have I seen the light at last, or do you have other comments?

 

[dboyd351]

View attachment 1222026

The doggies sure do love a fire, don't they?

 

[gggGary]

And... I've thought of another question.

I started this project thinking I would insulate everything as much as possible to improve the draft of the stove, but I am beginning to think that will be unnecessary and prove to be a waste of money. I figure that I haven't had any creosote for the last 22 years, so keeping the flue warm to prevent condensation shouldn't be an issue. To that extent then, all the heat in the flue will be somewhat trapped by a well insulated cap and the barrier I intend to put where the damper should be. That will be a significant savings.

Same story for insulating the outside of the fireplace insert. If I trap any escaping heat at the top of the hearth area with a good seal, the former fireplace will warm up pretty quickly off the exposed flex pipe, and this should make an adequately warm backside to the insert that it too will be more efficient.

@gggGary, you mentioned previously that I shouldn't insulate the flue. Have I seen the light at last, or do you have other comments?

To be honest I had to jog my wood heating info /lore brain cells, it's been a while since I had to do much to my systems. Your plan sounds good/great. But I might insulate the back (and side?) walls of the fireplace, no sense trying to heat masonry that's exposed to the outside. You can see I have a piece of fireproof insulation behind my basement stove, for the same reason, heating a concrete wall doesn't add much benefit. I don't run that basement stove all the time just when I'm down in my shop working or when it's super cold, for plumbing protection and to warm the floors a bit.
On the vent pipe; Let's say somewhere in the basement punch a 4" hole in the wall, then on the inside add a 4"elbow and pipe pointed up to 6'. the warm inside air acts like a stopper that keeps cold air from moving up and constantly flowing out at floor level.
I figured this out when a required 12"square boiler room outside air opening would freeze fuel oil at floor level in sub zero temps, I added a 12" elbow with an open pipe that went 6' up the wall. That stopped air flow unless the boiler was running pulling it in past the resistance of buoyant warm air inside the pipe. IE a thermal trap.
On not insulating a flue; chimney fires are always a possibility, insulation can let the pipe overheat and melt or collapse, free air around it will circulate and keep it below red hot much longer than if it's insulated. Free air within the chimney will still allow the pipe to quickly get and stay warm enough to aid draft.
hope that helps.

Just for fun, my current living room stove.

The air channels and vents in the masonry induce enough airflow that I have no need for a circulating fan.
The orange is a steel wood box with an outside loading door and top door.

Heated this house with 100% wood except for long trips away for 20 years now.

 

[pdqdl]

The air pressure balancer pipe makes perfect sense, but cannot work at my house. All my interior walls are below ground, and probably run at about 50°- 60° year round. A bit cool in the summer, and damned cool in the winter. There is only a sheet of paneling covering the 45" tall foundation wall.

You asked for pics:
The fireplace, hearth landing, and mantel




Good thing you suggested the sawzall. I couldn't get to all the parts with either the grinder or the sawzall. I did get it done, though. It took me longer to get that little stub of pipe out of the stove than it took me to cut the whole flue pipe off.

Here are the two pipe sections I couldn't pull out from the top of the chimney. Notice how little creosote was in them. Nothing sticking to the sides of the chimney, either. Not bad for 22 years of burning, eh?
.....

Now it's damned chilly in the basement. I plugged it up with the cover plate until some parts show up.

 

[pdqdl]

...The orange is a steel wood box with an outside loading door and top door.
View attachment 1222107 View attachment 1222108 View attachment 1222109
Heated this house with 100% wood except for long trips away for 20 years now.

I like that idea. Not too practical for my house, however. I've thought about knocking out a section of the basement wall and building an extra room underneath the deck to store stuff in, and maybe give in a back yard exit. The City would never find out, and we could use the space. Unfortunately, I've never gotten that ambitious.

 

[JRM]

To insulate the back of your box why not just tack weld short bolts to the exterior. Wrap in kaewool and fix with fender washers/nuts. You could always cut off excess length once the blankets are installed if clearance is an issue.

 

[pdqdl]

That was exactly what I was thinking, too. I just haven't yet decided to do it.

I've been wondering why none of the insert manufacturers seem to do that. Insulating against the cold behind the stove makes sense to me, and I don't know why it isn't done. They even publish efficiency statistics for these wood burners, so I'd think there would be motivation to insulate the exterior to control the heat delivery better.

There has got to be a reason it isn't done by all of the manufacturers, but I haven't worked it out yet.