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Chimney Liner-Insulated or Not

ChrisP Member Posts: 6
Hi all,

Having a Buderus 115 3 Section boiler being installed in a couple weeks to replace an old and getting ready to leak Burnham RS-110 from 1988.

The Buderus will vent into a 38ft external Masonry chimney that was also built in 1988 and uses traditional flue tiles. We will have a 5" diameter stainless liner installed two days after the boiler is installed.

The Chimney Sweep who will install the liner added that I may want to also insulate the liner for an additional amount of money. He mentioned that some boilers require it and others don't.

If I don't do it now, he will recheck in the spring for any issues like condensation and then we would of course have to insulate for a bit more money as it would be a poured liner instead of the wrap.

Any experience around this area and if insulation must be used? Like to save a few bucks if I could. Never had draft issues before on the older boiler which I guess is another reason for insulating.

Thanks in advance.


  • ChasMan
    ChasMan Member Posts: 462

    How did they decide that 5" was the correct size?

    It should be 4" But I know the boiler has a 5" connector in the back. I would contact Buderus and make sure 5" is what you need. I know nothing of the effect of insulation on the liner. It is suposed to keep the liner warm between firings. A warm liner would increase the draft. With a 5" liner and 38 feet of it plus the flue connection I bet when it gets hot it will suck your boiler up onto the roof.
  • Jack
    Jack Member Posts: 1,047
    Do it once,

    do it right. Definitely insulate the liner. This is especially so on an exterior chimney. If it is a straight shot I'd suggest looking at MG Dura-vents Duraliner. I represented Dura-liner a few decades ago when this product was introduced. I am working with it today on my new home where I found a full length liner in the old chimney. I have to add to it. I had forgotten what a neat system that was. IF you can get an approval from the manuf and AHJ to go down to 4" you can line with pellet vent. It is L-vent, double wall and an excellent liner system...again, with approval. At 38" I'll bet the 4" would whistle right along. Check Appendix E in NFPA 31. I cannot find my copy right now.
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