“Ventless” Fireplace Products

“Ventless” Fireplace Products: Efficient Heat at What Price?

With today’s modern construction of nearly airtight homes, indoor air quality is an even larger issue than in past times. “Vent-Free” or “Ventless” gas logs, stoves and fireplaces are a very controversial subject. They aren’t 100% ventLESS or ventFREE, they basically vent into your home. Debates among scientists, the gas industry, local code officials and manufacturers are taking place all over North America. Vent-Free heaters are not new. They have been in use in Europe before WWII. Vent-Free appliances have become very popular with consumers as efficiencies run to 99%; they do not require vent pipe and involved installation; they can be installed almost anywhere (providing square footage requirements are met); and they are fairly inexpensive. The reason there are requirements for adequate square footage is to assure there is enough space to dilute the combustion by-products. All ventless appliances built after 1980 are built with an ODS (oxygen depletion sensor). This device assures that the ventless appliance will shut down if the oxygen level in the room falls to 18% or below (21% is normal). Before purchasing a vent-free appliance, there are important considerations. There are odors associated with these units. When there are other odors present in the home, such as fresh paint, cigarette smoke, household cleaners, plug-in air fresheners, oil lamps, finger nail polish, new carpet, etc., these odors and other airborne contaminants are drawn into the burner and altered by the combustion process. This creates some unusual new odors and can cause some discoloration to walls and ceiling. Another important consideration is that since water vapor is a product of combustion, this humidity is forced into the home. A vent-free heater will exhaust a significant amount of water vapor into the home. This effect can cause excessive moisture on the windows, even contributing to rotting the windowsills over time. Common results of excess moisture are wallpaper peeling, mildew, mold and furniture damage.

If you already own a vent-free appliance you should clean and inspect it regularly. Each home has its own environmental characteristics, affecting the way your appliance performs. A dirty appliance or one that is out of adjustment can cause sooting on walls, carpet and furniture. Ventless log sets are designed for the flame to come out of the burner without coming into contact with the logs. Should the logs be accidentally moved or the flame pattern be altered by a draft (such as a ceiling fan), the flame could contact the logs causing flame impingement. This situation can result in release of carbon monoxide gases. It is also another cause for major sooting problems.

Ventless products are rated 99% heat efficient. This means that 99% of the combusted fuel energy is released indoors. However, some of that energy remains trapped in water vapor until it condenses on cold surfaces such as exterior walls and windows. Manufacturer owner manuals often contain a statement requiring a nearby window be opened when the appliance is lit.

The following is an excerpt from an article in November 1998 Consumer Reports
Magazine outlining their independent testing of vent-free gas fireplaces. “…our tests confirm that these heaters contribute significantly to indoor air pollution. If you are planning to buy a gas fireplace, a vented model should be your first choice. That is especially wise if any household member has asthma or another respiratory ailment that may be exacerbated by particulate matter, or if your home is very airtight—and so will disperse the fireplace’s emissions less readily…”

A direct vent gas appliance is a better alternative. Products are available as complete fireplace units, freestanding stoves and inserts designed to fit in your existing firebox. These appliances use minimal venting, a small vent going out the side of the wall, much like a dryer vent. Direct vent heaters take their combustion air from the outside, not robbing the home of oxygen, then vent the exhaust back outside. This isolates the living area of the home from combustion wastes, maintaining your indoor air quality. Most direct vent units are in the range of 80% efficiency, many offering a lifetime warranty and realistic flame appearance. They serve as powerful heaters and/or an alternative heat source, adding value to your home.

When you really think about it, what is a fireplace? It is a contained fire within your home to provide warmth and beauty. It is often the focal point of a family gathering place. Your home is usually your biggest investment and a safe and healthy environment for you and your family. Perhaps this is not the best product to save an additional few dollars.

Preparing Your Firewood Supply

Burning wet wood is one of the top obstacles to enjoying a pleasant, efficient wood fire. The proper moisture content of your fuel wood should be about 20 percent through proper seasoning. Your wood heater cannot produce high efficiencies and low emissions without this. Burning wet wood is wasteful and problematic, not to mention a contributing factor to a dangerous chimney fire.

The following are signs of poor performance due to wet firewood:

  • Low heat
  • Short burn times
  • Smoke odor in the house
  • All smoke and little flame
  • Difficulty in starting the fire and keeping it going
  • Wood burns up too fast
  • Creosote builds up fast in the chimney, sometimes oozing all over the roof
  • Dirty glass on the modern efficient stoves
  • Blue-gray smoke from the chimney

Properly seasoning wood is not just cutting it and throwing it into a pile. You need to follow a plan. Some commercial suppliers may claim their wood is two years old, etc., but if it was just recently split or improperly piled, your heater won’t perform to its potential. This is especially true for the modern EPA stoves. Freshly cut wood is called green and contains up to 80% moisture. To dry the wood for suitable burning, you cut it to short lengths and stack it so air can freely circulate. This way the moisture evaporates from both ends of each piece. In the old days, a suitable wood shed was constructed with open slat walls and an overhanging roof to keep off the rain. The drying process usually takes 9 – 12 months.

Once your wood is properly seasoned, you need to keep it that way. Wood reabsorbs moisture like a sponge. If your seasoned wood is left in the rain, it can soak back up to its original “green state” of 80% moisture in just a matter of hours. If that happens, it needs to be re-seasoned before it can be burned.

Wood that has been properly seasoned still contains about 20-25% moisture, most of which is wood resins. These resins play an important part in the stages of wood combustion.

Stage 1: Moisture Evaporation – when wood is heated, contained moisture evaporates to form steam. In this stage, heat is absorbed, not given off.
Stage 2: Vaporization of Hydrocarbon Compounds – the chemical structure of the wood molecules begin to break down and hydrocarbons begin to vaporize. This vapor contains hydrocarbons in the form of liquid droplets (creosote) and other combustible gasses such as methane, carbon dioxide, carbon monoxide, and other combustible and non-combustible gasses. Heat is still being absorbed, not being given off.
Stage 3: Gas Vapor Ignition and Combustion – in this stage, the gasses mentioned in stage two are burned by injecting oxygen at the ceiling level of the stove, greatly reducing the emissions by about 85% and turning them into heat at the same time. In short, you’re efficiently burning your smoke!
Stage 4: Char Burning – basically the carbon in the charcoal is the only remaining combustible material. Charcoal burns with little or no flame and produces temperatures in excess of 1100° F. Stages three and four are the heat-producing stages. In the case of the older non-EPA stove, you don’t get the advantage of stage 3.

Your wood heater cannot extract heat from water. When you burn wet wood, along with all of the problems listed above, you are using up all of the energy produced by the wood to evaporate the excessive moisture in the wood.

Wood Insert Liner

What Is a Wood Insert and Why Do I Need A Liner?

A wood insert is basically a high efficient wood stove reconfigured to fit into an existing wood burning fireplace. Most wood burning fireplaces are either true masonry with brick chimneys with or without clay flue tile lining or factory built metal fireboxes with air-cooled metal chimney pipe. Both types are inefficient and drafty. Many take more heat out of the home then they add.

Fireplace inserts were first conceived in the late 1970’s. They were originally intended to simply set into the fireplace and convert the open fireplace into an efficient, solid fuel, heating appliance. However, inserts were soon associated with installation and safety problems. The principle safety issue was accumulation of creosote primarily on the interior walls of the chimney and the fireplace smoke chamber. These conditions often led to dangerous fires in the fireplace (behind the insert) and in the chimney itself. In 1984, in response to numerous chimney fires, National codes and standards (NFPA211) mandated that all inserts be installed with a stainless steel connector from the insert to the first flue liner. The following minimum conditions are also required: a) the cross section or area of the flue can be no greater than three times that of the flue collar or smoke outlet on the insert. b) inspection and cleaning must be possible c) no dilution air is allowed to enter the chimney. However, lining only to the first flue liner is very difficult to seal and cleaning is very difficult and often impossible without removing the insert and stainless steel connector. A masonry chimney is not the ideal chimney anyway for an insert installed without a flue liner. The flue gases in an efficient insert installed without a liner will cool before exiting the cap. By keeping the gases hot with a properly installed liner, they remain in the form of a gas until they have escaped from the chimney cap. The benefits of a full reline are becoming more obvious and will be even more so as you read on. The above issues apply to a masonry fireplace so what about a factory built unit that already has a stainless steel chimney? In this case, National Code (NFPA211) revolves around UL chimney listings and requires that closed combustion wood burning appliances, such as an insert, use UL103 Type HT chimney (2100 degree F tested). The chimneys used in factory built fireplaces only have to meet UL127 requirements (1700 degree F). Therefore, to be in compliance with Code, factory built fireplaces must also be relined. Furthermore, inserts typically have a 6″ flue collar as opposed to most factory built fireplaces have an 8″ or 10″ chimney. In short, to be safe, you must follow Code and use a liner when installing an insert.

Today’s Wood Stove

Today’s Wood Stove – High Efficiency & User Friendly

A wood stove means different things to different people. Some think of it as ambiance – a romantic setting with the warm glow of the flame. Some make a hobby of cutting and tending the wood with the added benefit of healthy exercise. Still others view it as function – a means of heating the majority of the home. As great technological advances have positively affected home design, construction and appliances, the same is true with the wood stove.

By 1990 negotiations between the US Environmental Protection Agency (EPA) and the hearth industry resulted in lower emission standards for wood stoves – from 40 grams per hour to less than 6 gph. For EPA approval, manufacturers were forced to build a better stove. From that evolution, today’s wood stoves burn much cleaner and produce more efficient heat from a smaller firebox size. This also results in longer burn times. To understand how these benefits occur, some explanation of wood combustion is helpful.

Wood combustion is a complex physical-chemical process during which hydrogen and carbon in the fuel are chemically combined with oxygen to form combustion products and to release heat. This takes place in the four stages of combustion.

Stage 1: Moisture Evaporation – when wood is heated, contained moisture evaporates to form steam. In this stage, heat is absorbed, not given off.
Stage 2: Vaporization of Hydrocarbon Compounds – the chemical structure of the wood molecules begin to break down and hydrocarbons begin to vaporize. This vapor contains hydrocarbons in the form of liquid droplets (creosote) and other combustible gasses such as methane, carbon dioxide, carbon monoxide, and other combustible and non-combustible gasses. Heat is still being absorbed, not being given off.
Stage 3: Gas Vapor Ignition and Combustion – in this stage, the gasses mentioned in stage two are burned by injecting oxygen at the ceiling level of the stove, greatly reducing the emissions by about 85% and turning them into heat at the same time. In short, you’re efficiently burning your smoke!
Stage 4: Char Burning – basically the carbon in the charcoal is the only remaining combustible material. Charcoal burns with little or no flame and produces temperatures in excess of 1100° F. Stages three and four are the heat-producing stages. In the case of the older non-EPA stove, you don’t get the advantage of stage 3.

There are EPA exempt stoves still being sold in discount stores and farm stores. They are exempt because they are burning at a fuel to air ratio above 35 to 1. The characteristics of these non-EPA stoves are incomplete combustion resulting in hazardous creosote buildup, excessive fuel consumption and generally shorter stove life. They are cheaper up front but costlier in the long run.

The best advanced-combustion stoves or high-tech stoves have a single lever air control for easy operation. This lever is used to control the burn rate of the wood and heat output. The stove itself has an air manifold that injects a measured amount of air into the firebox. This supports the secondary combustion, main combustion, and the air wash for a clean viewing glass. It also provides the boost air at the base of the fire for speeding up the combustion process. These quality wood stoves have another important advantage. They are simpler to operate than a non-EPA wood stove.

As important as your choice of a high-tech wood stove, is your choice of the chimney pipe and overall installation. Any airtight wood stove depends on air being pulled through it to inject oxygen, fueling the fire. This is accomplished through the proper draft of the chimney. Wood burning experts agree that the chimney is the engine that runs the stove. A properly designed chimney, using high quality components and installed by an expert is your only assurance of the proper and efficient operation of your modern EPA wood stove.

It’s the complete system and expert installation you need to evaluate. To see these stoves burning and discuss options for freestanding stoves or wood burning inserts, stop by or call your NFI certified wood burning specialist today.