I have an uninsulated liner going through 30 feet of external masonry chimney. I'm changing out my stove this year, and was considering wrapping the liner. It's $400 plus installation to wrap the liner with insulation. I'd rather not spend the money. How big a difference does it make?
Has it stayed pretty clean with your burning so far? If yes I'd leave it alone and see how it does. You can always have it done later.
If going to a cat stove, I'd say yes Stack temp run lower than no cat stoves & lower the temp, less draft. The new higher efficient stoves keep more heat inside to the house, less up the stack. Difference is it keep the flue gases hotter all the way up, you get a cleaner pipe & stronger draft.
Won't be a cat stove. Massive creosote from last year, but wood was green, and I was inexperienced, so not really a good indicator. My instinct was to leave it alone. And if still dirty with good wood, new stove, and more experience, then replace it. It's just with the stove dealer already coming, I wanted to get as much done as possible. If most people think it would make a MAJOR difference, I'd be willing to pay. Otherwise, I think I'll leave it alone.
You are going to have to define "major" difference. An insulated flue will give you a stronger draft quicker BUT with a 30' flue you probably already have a pretty good draft. An insulated flue will also extend the time between cleanings BUT with a good stove (what are you getting?) and dry wood you probably should only have to clean once a season. (I would check regularly until I was sure it was staying clean). Will $400 worth of insulation have a quick payback? Probably not but it will make a difference on stove operation. The question is will it make enough of a difference to notice. Put in a good block-off plate and make sure the top cap is well sealed and wait a year to decide on the extra insulation. KaptJaq NOTE: IMO, the insulation makes the most difference when the stove is heating up. It reduces the time until the flue is hot enough that creosote does not form and the draft gets strong. If you burn 24/7 the difference should be even less.
We let our current stove go out if no one is going to be home for a while, so lots of cold starts. So the insulation would help there. But with 30 + feet we already have good draft Getting medium size jotul castine, so would get up to secondary combustion temp a little faster. Thanks, I think I'm going to wait. I'll be stuffing rock wool at the damper area, block off plate to follow later. Question: Is it worth having them pull off the top cap and stuff some rock wool at the top, or just leave it be? .
If the draft is good then creosote build up is your main concern, to alleviate that issue just make sure you clean and inspect your chimney often. Do you clean your own chimney?
If you have already had massive creosote build up get the insulation. 30' is a long way to keep gases warm with an exterior chimney. Plus the dealer probably recommends it.
If your cap is well sealed then I would not bother it unless you have another reason to be up there. Air is a poor conductor of heat and is the main insulation. Air transfers heat by movement. As it warms near the pipe it circulates and cools near the bricks. Wrapping the liner or poured in insulation helps by making smaller pockets of air so the warm air cannot move towards the cooler surfaces and has to transfer energy to the next pocket of air and on and on.. If you have packed the bottom well and the cap is well sealed then that same mass of air is stuck in your flue. Once it warms it will keep the liner from cooling. If the cap is not sealed then warm air will escape out the top and cooler air will be sucked into the flue wherever it can, usually through the block-off plate, clean-out door, or any other crevasse it can find. This cools the flue and wastes BTUs When money is an issue I always recommend a good seal both top and bottom first. If there are still problems then poured-in can be added later when there is a little more cash around. As always with a new stove (or any changes to your install) CHECK REGULARLY until you are comfortable. KaptJaq
30' is a long way for flue gases to travel and they will cool down some, especially being an outside chimney. I think I would insulate and also install a pipe damper because at 30' it could really take off on a cold windy day.
If you can swing it I would insulate absolutely no questions asked. A warm flue is a cleaner flue without a doubt so if you can just do it and don't look back.
