Chimney Liner-Insulated or Not

ChrisP

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

5"

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

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.