What the standard does
UL 1777 covers chimney liners meant to be installed under NFPA 211 and building codes. A liner that is listed comes with a defined system: the tube, its top and bottom connections, and any insulation the listing requires. Swapping parts can step outside the listing.
Why insulation matters
A cold liner in a big masonry stack loses draft and collects creosote. Insulation keeps the flue warm, and in a chimney that lacks full clearance it may be part of what makes the system acceptable. A sweep can tell you what yours needs.
Sizing the liner
Match the liner to the stove outlet. A 6 inch stove takes a 6 inch liner, and an insert uses the size stated in its manual. Oversizing is a common mistake, and undersizing can breach the stove listing.
How listings use it
Many low-cost kits print an alloy and a wall thickness but name no standard. Our reviews say so. A liner sold by the foot for this kind of job is a part of the chimney, so check the listing before you compare prices.
Questions that keep arriving by post
Does a stainless liner have to be insulated?
Often, yes, and the answer comes from the liner’s listing and the state of the chimney. An inspection tells you. Insulating also keeps the gases warmer, which helps draft and limits creosote.
Which alloy should a wood stove liner be?
Sellers offer 304, 316, 316Ti and 321. Check what the liner’s listing covers for wood. Alloy tells you about corrosion and heat resistance, and it is not a substitute for the listing.
Last reviewed November 1, 2026