Would insulating the ss liner this way be bad?

[Gark]

We have a 24' vertical run of single-wall SS liner (6" rigid round) inside a clay lined flue. The clay liner I.D. is about 6.5" X 10.5"
and the SS liner has no insulation. The top 6 - 8 feet of chimney goes through unheated attic and above the roof, and gets too much creosote. Would there be a downside to pouring vermiculite down both sides of the SS liner in the dead air space between the SS and the clay? Is this likely to hurt the SS because it stays colder where it touches clay but can heat up where contacting vermiculite?
We can stop the vermiculite from going below the block-off plate by stuffing koawool or equivalent.
Second question- Is insulating the flue like this likely to noticeably reduce the creosote (top third of the flue) given the same wood and burning habits?

 

[learnin to burn]

Insulating with the vermiculite is the way to go and will only help, it will not hurt it at all. It will help the creosote overall but you may find a light coating in the top 2 ft. instead of 6-8ft..

 

[Rougement]

This is exactly what I'm about to do, I ordered the kaowool from a seller on eBay today. The only thing I can think of that might not be code is that the liner has to be 1 inch from the flue all the way down but there are brackets you can buy to ensure you maintain clearance.

 

[oconnor]

It will work to improve the draft and reduce creosote - the total heat that remains in the liner will go up, and will improve draft in the beginning and end phases of the fire. The other piece to keep in mind is that you need clearance outside the brick chimney to combustibles (1 or 2 inches depending on external or internal chimney location). It may be worthwhile to have the clay liners removed and install the liner with insulation (more room), but until you are ready to take that step, your plan is better than leaving it with no insulation.

 

[Captain Hornet]

We lived near Pontiac Michigan in the mid 1980"s in a tri level ranch house that had a previous homeowner install. The stove was on the lowest level and was a huge TREMONT wood-coal combination. This stove used a 8 inch solid stainless pipe flue that was 30 feet high. The old owner pored childrens playground sand down between the old liner and the new pipe. He stopped about six inches from the top of the chiminy and just pored a plug of concrete into it. It was a neat installation and worked very well the entire time we lived there. I burned wood 24-7 and in Dec to mid Feb I also burnt some coal. I would clean out the pipe every spring when the burning season was over and never got more than a quart of creosote. It was a good clean install that worked well with no problems. We sold the house and moved south in the summer of 1995 and the new owner tore it all out and scrapped everything because he just couldn't be bothered with wood. I was sad because I wish I'd kept the stove.

 

[pgmr]

We have a 24' vertical run of single-wall SS liner (6" rigid round) inside a clay lined flue... We can stop the vermiculite from going below the block-off plate by stuffing koawool or equivalent.

I have used both vermiculite and perlite. The perlite is supposed to be less water absorbing, so that's what I have currently.

Definitely use some kind of flexible gasketing to prevent the loose fill from working past the lower block off plate. I tried to prevent it with some home made Thermix poured in before the loose fill, but with limited success. Need to revisit that problem some time when the stove has cooled off. We don't have a decorative surround around our stove, so the insulation can be seen occasionally on top of the stove.