When it comes to the decision of whether or not to insulate a stainless steel chimney liner venting a solid fuel appliance venting wood or coal, there is really no option. It must be insulted with the proper type of insulation not only for the UL (Underwriters Laboratories) Listing, but it is usually mandated for the warranty coverage.

Masonry chimneys are built to convey flue gasses. Some standards and/or codes maintain that a chimney with a clay flue tile liner can be used to vent an appliance with a “continuous temperature of 1000 degrees F”. The problem with solid fuels is that the temperatures can reach much higher than this during a chimney fire – temperatures as high as 2000+ degrees F and even sometimes during high burn times. Combine with this with long periods of heating at higher temperatures during cold weather, and an uninsulated liner could spell a recipe for disaster.

Most masonry chimneys could not pass a UL Test because most were built right next to combustibles. A chimney on the interior of a house is supposed to have 2" of airspace clearance on all sides surrounding it and any combustible material. An exterior chimney is should have 1" clearance to combustibles on all sides.  How often do you see this? In most of the country, it's almost never. This is why it's so important to insulate a solid fuel chimney liner.

Insulation holds in heat. This helps to prevent heat transfer to surrounding combustibles. It also aids in increased draft. The most important thing that liner insulation does is give you the UL Listing as long as you are using the correct insulation for the liner brand you use.

If this doesn't convince you just consider that a chimney brick thickness is 4”. A fireplace brick thickness is usually 12” minimum. A fireplace is built to contain fire. Again, a chimney is only built to convey flue gasses.

Another benefit of insulating a solid fuel liner is increased draft, better performance and a more efficient system. Holding the heat in helps to keep the flue gasses warmer, especially because with solid fuels the heat/cold cycle is always fluctuating depending on when the appliance of fireplace is loaded. A properly sized insulated liner will get your customer the best bang for their buck.

There are two common types of insulation for chimney liners. The Ceramic Blanket type insulation and the loose fill - TherMix Insulation. To insulate with the blanket, the liner is first sprayed with 3M Spray Adhesive or another approved adhesive. Then the liner is wrapped with the appropriate ceramic blanket and then covered with a stainless steel mesh. Then the ends of the insulation/mesh are clamped to hold them together securely. Some sweeps like to use stainless steel wire to "spiral" around the liner/insulation/mesh to provide more security.

The TherMix Insulation is a dry mix that must be mixed with water to be effective. It should resemble a damp potting soil when properly mixed. This insulation is them poured around the chimney liner once it has been secured in place. 

For more information on chimney relining or to ask questions, please click here to contact our technical experts.

Here at Lindemann Chimney Supply we pride ourselves on carrying the top chimney liner brands in the industry.  We carry BestFlex, Ventinox, DuraFlex, CHIM-LITE, Flexi-Liner and Heat-Fab Pipe. Within these types of pipe we carry these types of stainless steel chimney liners: 304 stainless; 316 stainless; 316Ti (Titanium) stainless; AL-29-4C Stainless and aluminum liners.

For woodburning applications 304, 316 or 316Ti are typically used. This type of stainless steel is acceptable for woodburning applications.

For coal burning applications, 316 and 316TI are typically used. These products have additional alloys that resist the acidic nature of the coal which contains some sulfur which becomes sulfuric acid when combined with moisture.

For oil burning applications type 316, 316Ti and AL-29-4C are used. It has some sulfur and nitrates that become sulfuric and nitric acid when combined with water.

Gas burning appliances typically take 316, 316Ti, AL 29-4C and aluminum alloys. The types of stainless steel that should be used depend on the specific application and the liner and/or appliance manufacturer’s installation instructions. Typically the AL 29-4C is used for higher efficiency gas appliances. 316 and 316Ti alloys are usually used for lower efficiency appliances and water heaters.  They are also used as a chimney liner for gas logs in a fireplace. Lower efficiency appliances such as water heaters can be used with aluminum chimney liners.

We can also get liner and components manufactured in oval chimney liner, square chimney liner and rectangular chimney liners. 

For more information on chimney liners please feel free to call us at one of the following locations: Albany, NY: 877-722-7230; Atlanta, GA: 866-450-3111 or Chicago, IL: 800-722-7230. Or, click here to contact us.

If you are looking for the right type of pipe to reline a masonry chimney  - just check out our selection. We stock a variety of chimney liners from lightweight corrugated flexible chimney liners, to flexible liners with a smoothwall inside, to rigid stainless steel chimney liner pipe, to heavy flex interlock chimney liner pipe and we even carry aluminum chimney liner pipe for relining for specific types of gas appliance chimneys.

Lightweight Corrugated Flexible Chimney Liners

We have a variety of brands of lightweight corrugated flexible chimney liners. We stock BestFlex chimney liners in a .005” and .006” strip thickness. The seams of this pipe feature a 7-ply “Secure-Lock” ultra tight locking seam. We also stock DuraFlex Pro Chimney Liner that features a crimped seam. Ventinox Chimney Liner is a unique type of corrugated liner because instead of having a crimped or mechanical lock seam, the seam features a continuous weld which makes this liner leak proof. While all of the above liners are available in 316Ti, Ventinox features two types of stainless steel: Ventinox VFT in 316Ti stainless steel and Ventinox VG which is available in AL 29-4C. This material is great for relining gas flues. All of these corrugated chimney liners feature a lifetime warranty when installed according to the manufacturer’s instructions for the appropriate application.

Flexible Smoothwall Chimney Liner

A corrugated chimney liner calls for a reduction in the sizing tables for oil and gas applications. We have a hybrid liner that features a corrugated outer wall with an interlock flexible inside wall. This pipe is known as a “smoothwall” flexible chimney liner. We stock two different brands of smoothwall liner. BestFlex Smoothwall Chimney Liner is made with the latest machining technology and offers a lifetime warranty. DuraFlex SW Chimney Liner is easy to work with, utilizes Ventinox Components and features a lifetime warranty.

Heavy Flexible Chimney Liner

The best applications for a heavy flexible chimney liner is when a chimney needs to be relined for a hard-core woodburner. This type of pipe is constructed with a 4-ply interlock seam and is available in round, oval and rectangular configurations. This BestFlex Heavy Flexible Chimney Liner carries a lifetime warranty.

Oval Chimney Liners

We can ovalize a variety of lightweight corrugated chimney liner sizes right in our warehouse. We can obtain custom oval components built to your specifications. Heavy flexible chimney liners are also available in an oval configuration. These pipes also carry a lifetime warranty.

Square and Rectangle Chimney Liners

Many fireplaces are already sized so marginally that to install a chimney liner means compromising the draft. Square and rectangular chimney liners can often help to avoid the need for removing flue tiles to fit the equivalent round size. Sometimes, even after removing the tiles, the size can still be off. If you can go back in and reline the flue with the same size as the previous flue, then odds are it will draft as long as they didn't have problems previously.

Rigid Stainless Chimney Liner

Some people prefer the rigid stainless steel chimney liner. This pipe is smooth on the inside but has absolutely no flex to it. It should only be installed in a perfectly straight chimney. Sometimes this stainless steel rigid pipe is also used as a connector pipe or to pass through a code compliant thimble.

No matter what the type of liner you need for your situation, we have you covered. For more information on chimney liners please click here to contact us. Or, you can call 800-722-7230.

Here at Lindemann Chimney Supply we often get questions about the construction and types of stainless steel chimney liners. Here is a brief guide that provides information on the construction of the chimney liners that we carry.

Flexible Corrugated Crimped Chimney Liner

A corrugated crimped liner is manufactured as a corrugated material in strips. Then the seams are run through a machine that folds the raw edges over and crimps the material providing a crimped seam. As this is being done, the diameter is also dialed in and formed. We stock BestFlex and DuraFlex Pro corrugated crimped liners. This type of liner can be ovalized and/or formed in a rectangular shape.

Flexible Corrugated Welded Seam Chimney Liner

Welded seam corrugated liners are unique in this industry. As the corrugated strips are brought together in manufacturing, they are overlapped and continuously welded. This created a tight seal as well as building strength into the liner. As the corrugated strips are being fed into the machine and the strips welded the diameter is formed according to the dimensions dialed into the machine. Ventinox VFT 316 Ti is the only liner in the industry that we are aware of that features this constructions. And yes, we do carry this liner. This liner can be ovalized.

Flexible Interlock Stainless Steel Chimney Liner

An interlock chimney liner is typically manufactured in such a manner that strips are folded over creating an interlock seam. As a result, this type of liner typically has a thicker wall dimension since it is 4-ply when completely compressed. This heavier liner was one of the original types of chimney liners on the market. This liner can be made in oval, square and rectangular configurations. The brand we carry is the BestFlex Heavy-Flex liner.

Flexible Smooth Wall Corrugated Chimney Liner

This liner features a very unique construction. The inner wall is manufactured with an interlock design. This allows it to still remain flexible yet the interlock surface is relatively smooth. The exterior of this type of liner is corrugated for flexibility. As a result of the smoother interior surface, sizing restrictions that apply to gas and oil liner applications do not apply. We carry the BestFlex Smoothwall Liner.

Rigid Welded Seam Chimney Liner

One of the earliest types of chimney liners was the welded seam, rigid stainless steel chimney liner. This liner is usually manufactured with an overlap seam that is welded or a "butt seam" weld. This is where the edges are brought together, butting flush, then welded together. Rigid liners attach by one end that is a male or crimped end that slides into a flared or female end. Then pop rivets secure the joints together. HeatFab is the brand we have carried for decades.

When it comes to chimney liners there are many options available. It's very important to weigh the options against the challenges of the job and the costs. If you have any questions or would like more information on our chimney liners, click here to contact us.

BestFlex Chimney Liner Kits are available in .005" 316 Titanium-Alloy Stainless Steel. BestFlex Liner is manufactured with the latest machining technology. As a result it is has stronger corrugations and Secure-Lock Technology which effectively seals the 7-ply crimped seam with a power grip for an ultra-tight locking seam. This makes BestFlex the best choice of its kind.

It is designed to vent fireplaces and appliances that use the following fuels; wood, oil, category I gas and coal applications. Insulation is required for the UL Listing for solid-fuels. Although it's optional for gas and oil, we still suggest insulation to enhance venting performance.

We stock two kit styles. The BestFlex Tee Kit includes a 13" X 13" Top Plate with Clamping Collar, Square Lid Rain Cap, Tee With 10" Take-Off and Tee Cover. The BestFlex Insert Kit features a 13" X 13" Top Plate with Clamping Collar, Square Lid Rain Cap and Stove Adapter with Clamp.

BestFlex is UL Listed and features a Lifetime Warranty that is transferrable to new owners if the home should ever be sold.

"You may be an unlisted system if" reminds me of the "You may be a redneck" lines of the Jeff Foxworthy jokes. Let's face it. As sweeps, we come across many stainless steel chimney liner installations that would make the honorary Foxworthy "unlisted" hall of fame. We have heard and seen some pretty strange installations that were anything BUT UL Listed. In this four part article I would like to explain just how important UL Listings are. Let's start by looking at the perspective from the liner manufacturer.

What a UL Listing means to the manufacturer (part I):

A UL Listing is like a trophy of achievement to liner a manufacturer. It shows that they have put forth the effort and quality product to have their product put through the tests at UL. These tests not only include the famous temperature tests, but also torsion (bending) tests, chimney brushing tests, weighted support tests, rain tests, etc...

UL also requires that the manufacture specify all of the components that were tested and evaluated in their installation instructions down to the last pop rivet. They have to clearly spell out the method of installation and the recommended maintenance procedures including specific wording. They also have to provide and label their product with specific size and type of labels with specific wording. And as part of the listing agreement with UL, the manufacturer has to be open to surprise visits from UL where they can drop in unannounced and inspect the pipe, components, labels, instructions, etc. If the manufacturer doesn't meet the criteria then they are issued a type of warning and have a certain amount of time to correct the problem. Manufactuers take their UL Listings seriously and many won't warrant their product if it's not installed according to the listing. In fact, they will often tell say "if you don't install it according to the listing, we won't back you up if there's a problem".

To be continued...