Our chimney is masonry up the outside of the house and has done fine the past two seasons with the miserable exception of my first year supply of wet fuel. Second season much better and now this third season is going great regarding quality of fuel. The viewing glass stays pretty clean now but the creosote from about 8 weeks of shoulder season was nearly two 12 oz pop cans worth. I expected less with such dry wood. However, two cold starts/day doesn't help. So we disconnected the liner and slid the stove out followed by pulling down the small amount of fiberglass I had jammed in the fireplace smoke chamber area a couple years ago. Then we filled the smoke chamber area way up 30 inches with Roxul supported by a newly fabricated block off plate. The next step was to get Perlite down around the liner, from the top. I'd calculated a 4.5 bag requirement of Perlite from the stove top by estimating the inside chimney cubic area minus the liner area. We were able to get 3.5 bags in. I'm guessing the math was fairly accurate until I forgot to figure the 30 inches of Roxul in the smoke chamber. We used a makeshift funnel (traffic cone) to pour the Perlite in a 2.5 inch hole we'd drilled in the top plate. That stuff actually flowed in there like water until full. We cut a cover for the top plate after that. The 1" by 1/4" inch steel straps under the top plate is there for expansion of the liner when hot. They give the flexible caulking some room to expand/contract as the top plate tries to move up/down. So, guess we'll see if all this messing around changes anything. My chimney has always drafted just fine. I'm hoping the insulation reduces creosote buildup. I might get even better draft when the fire has reduced to the coaling states.