So, I've been doing a lot of reading on running a liner on an existing chimney for putting an epa compliant insert in my fireplace. From what I understand, it only needs to be stainless, and the flex pipe style seems prevalent. The top caps will center and seal out rain from the chimney, and the SS liner. I'd make an insulated sheet metal block off for the damper area to keep heat in the house. But here's where I'm lacking info on the net. Do I need to insulate the entil flex pipe liner with either a blanket type around the liner, or fill the chimney with the loose type chimney insulation? I think either full insulation would get costly. I'm not certain which insert I'll get, but with either a 13" x13" or is it 14 x14? Clay lined chimney, it would take a lot of the loose type insulation. Isn't the air between the masonry / clay liner and a sealed top and bottom of chimney a good enough insulator? Or would that in insulated section cool off and have more chance for creosote build up? It's probably a 18 -20' tall chimney total.
Is it an internal chimney or on an external wall? If it is on an external wall I would insulate the liner from top to bottom and put a good block-off plate at the bottom. I also stuff some mineral wool near the top below the top plate. External flues get cold. First off this sometime causes difficulty in getting the draft started when you light the stove. Also if the pipe is exposed to cold air it will condense the vapors in the smoke and cause creosote. The wrap insulation usually works well. The loose fill is better but more expensive. It also causes problems if you have to work in the flue. Open the block-off plate and where do you think the loose fill is going to go? If you have an internal chimney then insulation is better but you could get away with a good block-off plate and stuffing some mineral wool down a couple of feet from the top. This will prevent any airflow through the area around the liner. Stagnant air is a pretty good insulation. The masonry chimney is warmed by the house surrounding it and never gets that cold. As long as it is well sealed top and bottom you should not have any problems. YMMV. I'm sure others will pipe in with their thoughts. More information on your plans will help the answers... KaptJaq
Thanks for the detailed response! It's an external wall chimney. So, I'm thinking roxul or other type insulation above a sheet metal block off plate for the Damper plate I will take out, then the wrap type insulation on the liner, then top liner block off and a cap.
You just brought something up that I didn't think of. I installed an insert last year and could not fit the blanket type insulation around the flex liner. So far I haven't seen any adverse effect from no insulation but may try the loose type in the future. What I didn't think of that you mentioned was the block of plate to cover the space where the damper was removed from. What will you use to fasten the plate ? screws or high heat silicone or both ? I wonder how much heat I lost from that opening being open still. Thanks for the idea and good luck with your new insert. Jim
KaptJaq had a great response to this question, I agree with it. My suggestion would be the blanket vs the fill, if you ever needed to service the SS flue or had a problem with holding in the fill it would come out. The flue can operate inside the clay flue with a top and bottom plate but it would not be as efficient as an insulated flue. It's a no brainer in order to keep creosote at bay.
I'll use screws, bolts, hi temp silicone, or anything to keep that block off plate in place. I have not really taken a good look at what I'm working with to be able to answer exactly how I'll mount it. Yeah, I saw a few guys mention that the installs by "professionals" didn't do this step, so the homeowner removed the insert and put an insulsted block off plate in. He said he noticed a big change for the better one he did this. Who knows of the best place to buy the insulation blanket?
I usually use Rockford... http://www.rockfordchimneysupply.com/ Liner kits: http://www.rockfordchimneysupply.com/flexible-liner-kits.php Insulation kits: http://www.rockfordchimneysupply.com/insulation_kits.php KaptJaq
