Unlined Wood Stove Insert (Slammer)
Many homes that were originally built with an open face masonry (made of brick) fireplace have had a heavy duty wood burning stove insert installed. Installing a wood stove insert is a very popular option for folks looking to warm their home with wood heat rather than expensive electricity or gas. Heat from a wood stove is a deep, penetrating heat that saturates walls, floors, furnishings, and other objects in order to create a lasting warmth, often lingering hours after the fire is extinguished.
During the oil crisis in the 70’s, folks were desperate to find a heating alternative to fossil fuels. The wood stove industry exploded overnight, and just about everybody who had a welding shop was suddenly in the business of building and selling wood stoves. Unfortunately, this type of growth in the hearth industry quickly led to some serious growing pains.
Being a fledgling industry, wood stove manufacturers were working with a very limited knowledge about wood stove performance and safety. A common method for installing a wood stove insert was to simply slide it into the fireplace and light it up! In order to keep smoke from billowing into the room, the stove had an attached metal “surround panel” with some sort of gasketing material (usually household fiberglass) attached to the backside. This type of installation was called an “Unlined Wood Stove Insert” or in abbreviated industry language, a “slammer”.
The name “Unlined Wood Stove Insert” indicates that the wood stove insert has been installed into your fireplace without it’s own insulated stainless steel tubular liner connecting it to the very top of the chimney. “Slammer” is a slang term to indicate that someone just “slammed” or slid it into the fireplace without connecting any liner to it.
So what’s wrong with having an unlined wood stove insert installed in your fireplace? Unfortunately, sad experience has taught the wood stove industry that this type of installation is undesirable and potentially unsafe for several reasons:
1. Increased risk of a chimney fire: Installing an unlined wood stove insert into your fireplace will often cause excessive creosote to build up, and therefore increase your risk of having a chimney fire. Excessive creosote buildup will occur due to:
a) Longer Residence Time: Burning wood with a normal open face fireplace allows massive quantities of air to be sucked from the room into the fireplace (to feed the fire), and is then drawn up the chimney quickly. Installing a wood stove into the fireplace is like sticking a big cork in the bottom end of the straw (your chimney) and only allowing miniscule amounts of air to be sucked in. This decrease in air velocity means the smoke (creosote) takes longer to travel up the chimney, and therefore has more time to condense to the inner walls of your chimney’s flue.
b) Excessive Cooling of flue gases: What happens when you take a can of cold soda out of your refrigerator and set it down on your table? Usually, the moisture in the air is somehow magically attracted to the cold surface of the can, and beads of moisture quickly condense on its surface. Just like water vapor in the air, creosote (wood smoke) is also attracted to cold surfaces, and will readily stick to (condense) onto any cold surface it contacts. During the winter, the brickwork of your masonry chimney is often exposed to the cold winter environment. With an unlined wood stove insert acting as a cork and slowing the velocity of the smoke as it rises up and out of the chimney, the smoke has more time to cool down while within your chimney and condense to the inner walls of your chimney’s flue, thus creating excessive creosote buildup.
c) Increased Turbulence: With an unlined wood stove installed in your fireplace, turbulence also plays a significant role in causing excessive creosote buildup. Rather than being forcefully drawn directly up and out of the chimney flue as is the case when burning with an open face fireplace, an unlined wood stove causes smoke to be swirled around as it blindly seeks to find its way past twists and turns up and out of the chimney. As we chimney sweeps like to say; “There’s no such thing as Smart Smoke”. Smoke must be given as direct and straight a path as possible in order to get it up and out of the chimney with minimal friction and turbulence.
To really rub salt in the wound, unlined wood stoves inserts often cause “3rd Stage” or “Glazed Creosote” to form. Because this type of creosote contains large quantities of potential energy (BTU’s), it is exceptionally dangerous should it catch fire. In addition, glazed creosote it is also very difficult and expensive to have removed.
2. Poor draft: Unlined wood stoves are notorious for being difficult to get a fire started due to poor draft. The colder the day (and therefore the colder the chimney), the more difficult it is to get the flue warmed up and a good draft established. Poor drafting wood stoves often lead to smoke spillage into your home and lots of frustration!
3. Higher maintenance costs: In order to clean an unlined wood stove insert properly, the wood stove must be removed from the firebox, and then completely re-installed during each cleaning. Moving a 300lb – 500lb wood stove around is hard on the back, more time consuming, and therefore more expensive to the customer.
If your wood stove insert was installed as a “slammer”, we highly recommend you have A to Z install a fully insulated stainless steel liner that connects directly to your wood stove and travels the entire height of your chimney to the very top. If your wood stove insert is one of those dreaded “slammers”, A to Z will recommend you have it relined properly. By relining your wood stove insert with stainless steel liner you’ll be able to avoid the headaches and hazards listed above!
The new stainless steel liner will be properly sized to match your wood stove’s venting requirements and will not only help keep you and your family safer (by keeping creosote buildup to a minimum), but also dramatically improve draft and significantly reduce your maintenance costs as it’s swept each year!
A to Z has been lining wood stove slammers for over a decade and has the expertise and experience required to not only do the job right, but also ensure your experience is enjoyable and easy.
Contact us today and we’ll be happy to get you started on the road to having worry-free fires!
Does your fireplace have the proper hearth and floor protection? The pros at A to Z know all the code requirements and can make the necessary repairs to keep you and your family safe.
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Thank you for the good job you did cleaning my dryer vent! The dryer dries much faster now with far less wasted energy! I also now am able to relax knowing I don’t have such a fire hazard anymore.
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