Stainless vs Aluminum Chimney Liner: Which One Should You Buy?

This guide explains the difference, then features four stainless flexible liner kits ranked by their listings: two Rockford Chimney Supply kits with UL1777 listing and a transferable warranty, and two Fireside Chimney Supply FireSafe kits with complete installation hardware.

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Stainless vs aluminum chimney liner: the short answer

Choose stainless steel if you burn wood, pellets or oil, or if you might ever switch fuels. Stainless liners like the four below are built for high heat and corrosive flue gases, and the Rockford kits carry a UL1777 listing in the USA and ULCS635 in Canada. Aluminum is only appropriate for gas appliances that produce cooler, cleaner exhaust. If your chimney serves a wood stove or fireplace insert, aluminum is not a candidate.

Why the gear below is all stainless

Every liner kit in this guide’s gear section is constructed of stainless steel: the Rockford kits of 316 stainless and the Fireside kits of 316 or 316L stainless. Stainless resists the moisture and acids in wood smoke that would eat through lesser metals, and the Fireside listings describe 7-ply seams and 10 corrugations forming a gas- and watertight barrier. That is the construction you want when the liner is the only thing between flue gases and a masonry chimney.

The liners, ranked

1. Rockford Chimney Supply 316 Stainless 6 Inch x 20 Feet

The top pick is the Rockford 6-inch by 20-foot kit, model 620S-AC. It is constructed of 316 stainless steel, UL1777 Listed in the USA and ULCS635 in Canada, and the Rockford Chimney Liner Warranty transfers to the next homeowner, which none of the other three listings offers. The Quick Connect System tightens with clamps, and the listing notes flexible liners install inside a masonry chimney. For a standard 6-inch wood stove or insert flue, this is the most credentialed kit here.

2. Rockford Chimney Supply 316 Stainless 8 Inch x 15 Feet

The second Rockford kit, model 815S-AC, is the 8-inch by 15-foot version with the same 316 stainless construction, the same UL1777 and ULCS635 listing, and the same transferable warranty. The larger diameter suits bigger fireplaces and stoves that call for an 8-inch flue. Everything that makes the 6-inch kit the top pick applies here, sized up.

3. Fireside Chimney Supply FireSafe 6 Inch x 20 Feet

The Fireside FireSafe 6-inch by 20-foot kit, part CB620BK, is the complete-package pick: the listing includes a 13 inch by 13 inch top plate with rain cap, a .006 inch thick stainless liner, and an appliance connector for vertical hookups. The 316 stainless liner uses 7-ply seams and 10 corrugations, and the kit is stated compatible with wood, gas, oil and pellet appliances. It weighs 23 pounds and is made in the USA. No third-party listing mark is stated, which keeps it behind the two Rockford kits.

4. Fireside Chimney Supply FireSafe 3 Inch x 20 Feet

The Fireside 3-inch by 20-foot kit is the small-diameter option, built of 316L stainless with the same 7-ply seams, 10 corrugations, top plate, rain cap and tee connector for horizontal hookups. At 15 pounds it has the lightest stated weight here. The 3-inch diameter suits small stoves and inserts; check your appliance’s required flue size before choosing, because an undersized liner chokes draft.

What aluminum liners are for

Aluminum chimney liners exist for one job: venting gas appliances. Gas exhaust is cooler and far less corrosive than wood smoke, so the lighter metal suffices. What aluminum cannot do is handle wood, pellet or oil exhaust: the heat and creosote attack it, and no aluminum liner appears in this guide’s gear section at all. If there is any chance a wood stove or fireplace will ever use the flue, stainless is the only sensible choice.

What to check before you buy

Match the diameter to the appliance

The four kits here span 3, 6 and 8 inches. The 6-inch kits suit wood stoves and inserts that call for a 6-inch flue; the 8-inch Rockford serves fireplaces and stoves that call for an 8-inch flue; the 3-inch Fireside is for small appliances. Your stove or insert manual states the required flue diameter, and the liner must match it.

Confirm the length

Three kits are 20 feet long and the 8-inch Rockford is 15 feet. Measure from the appliance flue collar to the top of the chimney before ordering, and allow for the connection at the bottom.

Look for the listing mark

The Rockford kits are UL1777 Listed in the USA and ULCS635 in Canada; the Fireside listings state code compliance but no third-party mark. A listed liner has been independently verified for the job.

Frequently Asked Questions

Can I use an aluminum liner with a wood stove?

No. Aluminum liners are for gas appliances only. Wood smoke is hotter and more corrosive than gas exhaust, and aluminum cannot withstand it. For any wood stove, fireplace or pellet appliance, use a stainless steel liner like the four kits in this guide.

Is 316 stainless better than 316L for chimney liners?

The Rockford kits use 316 stainless and the Fireside kits use 316 or 316L. The Fireside listings state compatibility with wood, gas, oil and pellet appliances; the Rockford listings describe 316 stainless liner kits for masonry chimneys that exceed chimney industry standards.

What does UL1777 mean on a chimney liner?

UL1777 is the safety listing for chimney liners in the USA, with ULCS635 the Canadian equivalent. The two Rockford kits carry both marks, meaning they have been independently verified for lining masonry chimneys. The Fireside kits state code compliance without naming a third-party listing.

Can I install a flexible liner myself?

The Rockford listings include complete do-it-yourself installation instructions with a Quick Connect clamp system, and the Fireside kits ship as complete kits with top plate, rain cap and connectors. Flexible liners install inside a masonry chimney. If you are unsure about sizing or clearances, have a chimney professional confirm the plan.

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