the_felix•1mo agoMost Upvoted

Why doesn't anyone talk about creosote buildup in insulated flues?

I was reading a report from the Chimney Safety Institute of America last night. Found out that insulated stainless steel liners can hide creosote buildup way longer than clay tiles. The insulation keeps the flue gas hot, so creosote stays sticky and doesn't crust up. Means you could have 1/4 inch of third-degree glaze hiding inside and not know it. I've been sweeping these for 10 years and never caught it until a customer complained about a smell. Has anyone else seen this with insulated liners?

2 comments

2 Comments

perez.barbara1mo ago

Actually anna, that 250 degree number is way off for a modern insulated liner. Those things are designed to keep flue gases above 250 at the exit, but the liner wall itself can drop below 140 pretty quick once the fire dies down. I had a field rep from a liner manufacturer show me their testing data last year. The sticky creosote thing is real though, no argument there.

anna_hill1mo ago

Gotta chime in here because nobody's talking about the real silent killer with these things. I pulled a liner out of a house last month where the homeowner had been burning unseasoned pine for years. That gooey creosote was dripping down and pooling at the bottom like tar. The insulation was so efficient that the inside of the liner stayed above 250 degrees even when the fire was out, so the creosote never got a chance to harden and flake off. It just kept building up layer after layer until the liner was almost completely blocked. The scary part is you could run a camera up from the bottom and see nothing wrong because the stuff was still liquid and just flowed around the lens.