High-efficiency heating with wood-burning appliances

By Marge Padgitt

With the increased prices of gas and electricty, many people have turned to alternatives for heating their homes. The new heating appliance options are varied and high-tech. Manufacturers have had over 30 years to perfect their art- new appliances are much improved over their predecessor’s- offering wood-burning stoves and fireplace inserts that are not only efficient, but use much less wood to provide the same amount of heat as their older counterparts. The re-emergence of old world masonry heater and Rumford technology offer these benefits as well. Using the renewable resource of wood makes modern wood-burning appliances very “Green” and earth-friendly.

Homeowners now have lots of choices for heating with wood.

The Rumford Fireplace– Designed by Count Rumford in the 1700’s, the shallow depth, curved throat, angled side walls, and higher opening, combined with a smaller flue provide much more heat than the standard “box style” fireplace. Compared to a standard fireplace, which produces –30% to +5% in efficiency (meaning most of the heat goes up the chimney), the +40% efficiency Rumford far surpasses its competitor. Recent testing shows that properly designed and built Rumford fireplaces, are very clean burning and produce low emissions. Don’t expect to heat the entire house, but a Rumford will definitely heat the room it is in and more.

Historic homes are perfect for utilizing the Rumford design, which looks authentic and ads ambience to the residence, but a Rumford looks great in modern homes, too.

A Rumford style fireplace

A new method of “Rumfordizing” existing fireplaces has been developed, where a box-style fireplace is transformed into a Rumford style to gain more heat. Some masons and CSIA Certified Chimney Sweeps are employing this method. Not all masons are trained properly in this method of fireplace building, so find a qualified Rumford builder at www.rumford.com, www.csia.org, or www.midwestcsc.org. 40,000 + BTU output.

 

Wood-burning Stoves- Today’s wood stoves require less wood to heat the same amount of space, and that translates into savings in the cost of wood, and in your time to prep wood and load the stove. Where loading was once required every 2 –3 hours, it is now only needed every 4-10 hours. The addition of an electric built-in blower will push the warmed air through the house, but is not necessary for the stove to work.

A wood-burning stove can be installed almost anywhere, provided there is an existing chimney that can be used, or an outside wall where a Class A chimney can be installed. Existing chimneys must be brought up to current standards with the installation of a 6” - 8” insulated stainless steel chimney liner.

Wood stoves come in a variety of styles including standard matte black or a beautiful porcelain enamel finish, and are constructed of heavy steel, cast iron, or soapstone. All stoves require a non-combustible floor and clearance to combustible walls, which is different with each manufacturer. The old 36” rule no longer applies with the newer models, so more usable space is available in the room. The EPA regulates woodburning stoves so be sure to get one that is EPA approved and do not use an older model. A professional should do the installation. 55,000—85,000 BTU output.

Hampton wood-burning insert

Wood-burning Fireplace Inserts- This appliance is inserted into an existing masonry fireplace. A correctly sized stainless steel flue liner is necessary with a connection to the wood stove. Do not install an insert with out the required steel flue liner with ceramic wool insulation—and have a professional do the installation. If used without a steel liner, the existing flue that was sized originally for your fireplace will be too large for the new appliance to draft correctly and excessive creosote will accumulate on the flue walls. Usually glazed or tar creosote is the type that occurs in this situation, and since it is highly flammable, it is the cause of many chimney fires.

A wood stove insert will produce enough heat to warm a large area (800—3,000 sq. ft.), and is extremely efficient—usually in the 73 % + range for efficiency ratings. Most inserts are EPA approved non-catalytic, which means that a catalytic combustor, which requires maintenance, is not necessary. The addition of an electric built-in blower will push the warmed air through the house, but is not necessary to provide heat. Burn well-seasoned hard woods and you’ll be happy with not only the heat your insert produces, but how little wood is used as well. The EPA regulates fireplace inserts, so be sure to get one that is EPA approved and do not use an older model. 60,000—85,000 BTU output.

Wood-burning Furnace/boiler - Capeable of producing 80,000 to 300,000 BTU’s and designed to heat an entire house or building via ducts, many woodburning furnaces may be installed alongside an existing gas furnace (provided a separate flue is available), or outside the home in a shed or protective covering. Most furnaces have electric fans and use ductwork to distribute the heat throughout the home. Wood-burning boilers use the underfloor hydronic tubing to distribute heat.

Either a Class A stainless steel chimney is required; or when using an existing masonry chimney an approved stainless steel flue liner is necessary. Do not use a tile flue liner in a masonry chimney due to danger of excessive creosote accumulation and risk of chimney fire. It is extremely important to have a professional CSIA Certified Chimney Sweep or approved manufacturer installer do the analysis of the installation area and the actual installation of the furnace and flue. This is not a do-it-yourselfer project, as there are many critical items that must be taken into consideration includingthe size of flue, location of the furnace, distance of the connecting pipe run, type of materials used, and clearances to combustibles. Find an installer at www.csia.org, or www.nficertified.org or ask the manufacturer for help in finding a qualified dealer. Do your homework when selecting a furnace or boiler as there are large differences in efficiency. The EPA currently has no restrictions on woodburning furnaces in most states (except California, Washington, Oregon, and Colorado), but has plans to do so soon. 80,000—250,000 BTU output.

Masonry Heaters– Old world technology is making a comback in the United States. Masonry heaters are a site-built or pre-cast heater core inside of a brick, stone, tile, stucco, or soapstone exterior, and built on site. The masonry mass will be at least 1,760 lbs. The heater has tight fitting doors that are closed during the burn cycle. It has an interior construction consisting of a firebox and heat exchange channels built from refractory components. A masonry heater has the ability to store a very large amount of heat, which means that you can rapidly burn a large amount of wood without overheating the house. The heat is stored in the masonry thermal mass, and then slowly radiates for the next 18 to 24 hours. Loading of wood is only required approximately once every 12 hours. The heater burns the wood quickly and all of the energy in the wood is used so there is no waste. Masonry heaters burn very clean, with little emissions, so they are environmentally friendly.

This type of heater, designed and used extensively in Europe, is now gaining popularity in the U.S. The initial cost is more than other types of heating, but due to the savings in energy bills that cost can be recuperated in as little as seven years. The heat is evenly distributed through the home without the use of ductwork or forced air. It is best to design the home around a masonry heater to get the maximum efficiency—homes that have large, open spaces with the heater in a central location are well suited for this type of heating appliance.

Added options to masonry heaters may include a pizza/bread oven, heated bench, mantle, heated hot water, and wood storage spaces. A masonry heater should be built by a qualified heater-mason contractor. Find a builder and get more information about how masonry heaters work on the Masonry Heater Association of North America website at www.mha-net.org. 80,000—250,000 BTU output.

Custom built masonry heater by Gene Padgitt

 What you need to know about wood fuel

• By burning wood for fuel, less carbon dioxide is released into the atmosphere than if the wood was left to rot on the forest floor
• Modern EPA approved woodburning fireplace inserts and freestanding stoves produce low particulates when burned properly
• While not EPA approved yet, masonry heaters are also very clean burning
• Wood fuel is less expensive than gas or electricity, and in some cases free if the homeowner has trees on his property
• Cordwood should be cut, split and stacked for at least six months prior to use and used when moisture content is below 20%
• Only burn dry cordwood – never burn treated wood since it produces toxic fumes
• All wood produces flammable creosote, which must be removed from the flue or chimney periodically to avoid chimney fires
• Have all wood-burning appliance flues checked annually and swept by a professional CSIA Certified Chimney Sweep

Resources:

National Chimney Sweep Guild: www.ncsg.org

Chimney Safety Institute of America: www.csia.org

Midwest Chimney Safety Council: www.midwestcsc.org

Masonry Heater Association of North America: www.mha-net.org

National Fireplace Institute: www.nficertified.org

Rumford Fireplaces: www.rumford.com

Hearth, Patio, and Barbecue Association: www.hpba.org

Woodheat.org