High-Performance Masonry Heating

By Stephen Bushway
Deer Hill Masonry Heat

(This information is based on emission test results done with a Finnish contraflow heater design with a grate and air supply from under and in front of the grate) Whether you're a seasoned masonry heater owner or are reading this as a new owner, there are some newly discovered firing techniques you will want to employ to get the most out of your hearth. Use regular cordwood! Yes, it is not necessary to burn sticks 2" to 3" across to get the rapid, complete combustion that masonry heaters are noted for. Actually, 4" to 6" pieces such that 9 to 12 pieces will fill your firebox when cross hatched will provide better air/fuel ratio for complete, and more usable combustion. The bigger pieces allow more time for the masonry mass to soak up the fire's heat - yielding better heat transfer to your home. Place smaller wood, kindling and paper on top of this load and light from the top! The revolutionary top burn greatly reduces emissions during the dirtiest part of a firing - the first 10 minutes or so. Lighting the load from the top of the pile yields a candle-like burn, allowing the firebox to heat up as the volatile gases are being more evenly released. Take a little extra care in laying up your fire. A good "fuel load configuration" is well balanced and won't topple over prematurely. Allow a 1" airspace between pieces, placing the largest pieces first and the bottom row running "front to back" in the firebox. Don't admit air from below the grate until the fire is down to coals. Use the air slots in the door, if provided. If not, cut scrap dimensional lumber so that a piece will cover the grate and air is admitted from the front. With a top burn fire the piece will block grate air until it is burned through - well into the firing. Alternately, you can adapt your doors so that they will 3/4 inch of air between them but can not be accidentally be opened further. This modification was lab tested for emissions with excellent results. During the coal burning phase, rake the coals so they evenly cover the grate with air coming from below. It is more efficient to have one full firing than 2 fires half as large. If you've been burning small pieces kindled at the bottom in your contraflow heater, chances are there is soot in the heat exchange channels. This can effectively be cleaned from the cleanout door usin a rod and brush designed for cleaning pellet stove chimneys. This will better allow them to absorb heat from future fires. Burning cordwood has so many benefits, economy-wise. And as you're probably aware, masonry heaters provide the cleanest burning solid fuel appliances available. Now, following these simple practices you can be assured that you are providing yourself and your loved ones simple, yet state-of-the-art heat more cleanly than ever.

High-Tech Old World Technology Latest Trend in Heating

By Marge Padgitt
HearthMasters, Inc.

Sometimes old things are better than new, like old houses, historic buildings, and castles. The latest trend in home heating fits into that category. Masonry heaters have been around for hundreds of years in Europe, but are just recently catching on in the U.S. And the great thing about heaters is that they are GREEN. People needed to heat their homes in an efficient manner in olden times just as today in order to save their forests. Inefficient open fireplaces took too much of their valuable resources, so another method had to be developed. No one knows who the first mason was who came up with the idea of devising something that would retain heat for long periods of time, then radiate it into the home while using less wood, but whoever he was he was a genius.

Masonry heaters have been redesigned and altered over the years by different masons in Finland, Russia, Germany, Austria, and the United States. But heaters all have the same characteristics with complex channels to slow down and trap heat from flue gasses, and a mass of masonry to retain that heat, then radiate it to the living space over a period of up to 20 hours. By the time the products of combustion get to the exit of the flue, the smoke is white, and the particulate emissions are very low. One load of wood can usually provide heating for the average size home for 8-12 hours. Compared to even the best high-efficiency wood–burning stoves on the market today, gas and oil-fired furnaces, and certainly inefficient open fireplaces, masonry heaters can’t be beat.

Custom granite masonry heater
Courtesy of HearthMasters, Inc.

Another benefit masonry heaters offer is that they don’t require electricity, gas, or ductwork to distribute the heat. In a properly designed home with an open floor plan and the heater in the center of the home, the heat will radiate evenly throughout. Ideally, heaters are built in new home construction, but they can be added to existing homes if the layout is right. Heaters require a suitable foundation to support the massive masonry, which weighs three to six tons by the time all of the firebrick, block, cast iron doors, dampers, and exterior masonry facing is installed.

Heaters can be enhanced with heated benches to sit on, mantels, wood storage bins, and even bake ovens. Pizza and bread from a wood-fired bake oven has an incredible and unique taste that is not to be missed, and entire meals can be cooked in the oven if desired. An experienced heater mason can not only design and build the right size and type of heater for a home but make it beautiful to look at as well. An exterior finish of soapstone, tile, sandstone, or brick can make a dramatic statement. Heater masons will work with the homeowner to come up with a custom design that suits the home or use one of many masonry heater kits that are available from several manufacturers (usually incorporating soapstone) in a variety of designs.

Use of natural non-toxic materials and the renewable resource of wood make masonry heaters the perfect solution for a green home.

The trade is very specialized, with only a few heater masons scattered across the U.S. Fortunately, most of these masons will travel to do installations. Some have even traveled to Japan, China, and South America to build heaters. Often several heater masons will help each other out since these are big projects. In days of old, the heater masons kept their trade secret, even to the point of not leaving the room until the heater was completely finished so no one else could see how the interior was built. At that time, the livelihood of the masons was dependent on this secrecy. The trade is so skilled that the only way to learn is to do hands-on assistance with an experienced heater mason, and that is part of the reason the Masonry Heater Association was formed. The older masons do not want this to become a lost art, so they help train others. The Certified Heater Mason program was developed by the experienced MHA members in order to assure that the knowledge is not lost.

In the U.S. many people are not yet aware of masonry heaters, so it is a challenge for a heater mason to make a living out of just building heaters. Most heater masons also build other types of projects such as fireplaces, chimneys, outdoor bake ovens. Some are timber frame or log home builders or own brickyards. Most are very aware of the green building trend and are interested in sustainable living. Many heater masons will travel to build a heater because they love doing it and love the satisfaction they get out of building something that is very specialized.

Pricing for heaters is what most would consider being on the high end, and a long-term investment. The average cost a homeowner may expect to pay is from $15,000 to $30,000, with price depending on the complexity of the heater, material costs, and labor. The expected time to get a return on your money is approximately 10 years. The time to build a completed heater may be up to four weeks or more, depending on how many skilled craftspeople are working. Many homeowners will elect to be an assistant on the job in order to lower their costs. In some cases, if a heater mason is traveling the homeowner will put him up at their house or a local hotel. When traveling the masons usually work long hours in order to get the project done sooner.

Mark Twain discovered masonry heaters while traveling through Europe and wrote about them: "All day long and until past midnight all parts of the room will be delightfully warm and comfortable … Its surface is not hot: you can put your hand on it anywhere and not get burnt. Consider these things. One firing is enough for the day: the cost is next to nothing: the heat produced is the same all day, instead of too hot and too cold by turns… America could adopt this stove, but does America do it? No, she sticks placidly to her own fearful and wonderful inventions in the stove line. The American wood stove, of whatever breed, is a terror. It requires more attention that a baby. It has to be fed every little while, it has to be watched all the time: and for all reward you are roasted half your time and frozen the other half... and when your wood bill comes in you think you have been supporting a volcano. It is certainly strange that useful customs and devices do not spread from country to country with more facility and promptness than they do."

Find out more about masonry heaters, including technical specifications and testing results, photos of heaters, manufacturers, and a list of heater masons, contact the Masonry Heater Association of North America through www.mha-net.org. There is a chat list set up for anyone interested in masonry heaters at http://groups.yahoo.com/group/MasonryHeaters.

Marge Padgitt is a past board member for the MHA.  She is president of HearthMasters, Inc. in Kansas City, Missouri. Her husband, Gene Padgitt, is a Certified Heater Mason.

PRICIPLES OF RADIANT HOME HEATING

By Doug Hargrave
http://www.radianthomeheating.org 

 

Graphic courtesy of Valor

Understanding the differences between conduction, radiation and convection heat transfer is relatively easy. Understanding how they relate to each other in a radiant home heating situation is much more complex. To some degree conduction, radiation and convection exist in all types of home heating systems; however the proportions of each can be quite different from system to system. This difference in proportions will affect the comfort within the home and the efficiency (cost) for heating the home.

TYPES OF HEAT TRANSFER
Radiant heat is transmitted from a warm object to a cooler object through infrared radiation. The distance between objects, their surface area and their temperature difference affect the rate of the radiant heat exchange. A good example of radiant heat transfer is the way in which the sun warms the surface of planets in the solar system. Another example would be the way a radiant heater warms the surfaces inside a home.

When the distance between two solid objects of differing temperatures goes to zero and they come into direct contact, the heat exchange between them is then called conduction. Conduction between solid objects results in a faster rate of heat exchange than that of radiation. A good example of this difference is the amount of heat one would feel holding their hand just above a hot stove (radiation) versus actually touching the stove (conduction).

Heat transfer within solid objects is accomplished through conduction. The amount of heat applied to the surface of the object, the amount of mass (weight) the object has and the density of the mass (weight per unit volume) affect the rate of conduction within the solid object. For example, the higher density of soapstone allows it to absorb and radiate more heat per unit volume than common brick of a lower density.

Heat transfer within gases is quite different from heat transfer within solids. Gases have relatively little mass (weight) and very little density (weight per unit volume) when compared to solids. Unlike solids gases can dramatically expand or contract their density. Their density expands when they are heated and contracts when they are cooled. Warm gases that are expanded are lighter than cool gases that are contracted. The difference in weight causes warmer gases to rise and cool gases to fall creating movement within the body of gas. This movement is called convection. The speed of the convection (movement) is largely determined by the how much and how quickly heat is introduced into the body of gas. For example, a 600 degree wood stove causes much more convection (air movement) than a 200 degree masonry heater in the same living area.

RELATIONSHIPS BETWEEN TYPES OF HEAT TRANSFER

Home heating systems employ some type of heated surface which is used to transfer heat into the home. The heated surface may take different forms and be in different locations.

For example:

• Forced Air Furnace - located outside the primary living area with a heat exchanger that heats air which is then circulated via ducts to rooms in the primary living area. The air enters the primary living area from the duct work under pressure and is forced to return to the furnace through another set of ducts.
• Hot Water Baseboard Furnace – located outside the primary living area with a heat exchanger that heats water which is then circulated via pipes to rooms in the primary living area. In the primary living area the heated water runs through a baseboard heat exchanger warming room air which then circulates by natural convection.
• Electric Baseboard Heat – located in the primary living area with a heat exchanger that heats air which then circulates by natural convection.
• Hot Water Radiator Furnace - located outside the primary living area with a heat exchanger that heats water which is then circulated via pipes to rooms in the primary living area. In the primary living area the heated water runs through a radiator. The radiator must have enough mass to store the heat from the incoming water. The heat in the radiator dissipates into the room through a combination of natural radiation and convection. The proportion of radiation versus convection is dependant on the size, design and location of the radiator in the room.
• Hot Water Radiant Floor Furnace - located outside the primary living area with a heat exchanger that heats water which is then circulated via pipes to rooms in the primary living area. In the living area the heated water runs through a network of pipes imbedded in the floor giving up its heat to the mass of the floor. The floor gives up its heat to the room largely through natural radiation and some conduction to the objects in direct contact with the floor. Convection from the floor is minimal in comparison to heat transfer by radiation and conduction.
• Electric Radiant Floor Elements – located in the primary living area with heating elements embedded in the mass of the floor. The floor gives up its heat to the room largely through natural radiation and some conduction to the objects in direct contact with the floor. Convection from the floor is minimal in comparison to heat transfer by radiation and conduction.
• Wood Stove – located in the primary living area a heat exchanger (firebox) heating relatively little thermal mass. The heat dissipates into the room mostly through natural convection and some through radiation. The proportion of radiation versus convection is dependant largely on the temperature which the stove is operated.
• Masonry Heater – located in the primary living area with a heat exchanger (firebox) that heats its substantial thermal mass. The heat stored in the thermal mass dissipates into the room mostly through natural radiation and some through convection. The proportion of radiation versus convection is dependant on the size, design and location of the masonry heater in the room.

In the descriptions of home heating systems enumerated above I have given some general indication as to the proportions of the various heat transfer types for each system. I would now like to group these systems in some general proportional categories.

• Convection - Forced Air Furnace, Hot Water Baseboard and Electric Baseboard heat predominately by convection.
• Convection/Radiation – Wood Stoves heat predominately by convection with radiation accounting for a smaller amount.
• Radiation – Hot Water Radiant Floors and Electric Radiant Floor Elements heat predominately by radiation with a small amount by convection and very little by convection.
• Radiation/Convection – Hot Water Radiators and Masonry Heaters heat predominately by radiation with convection accounting for a smaller amount.

 Tulikivi brand Gemini Fireplace

The common element that is present in category 3 and 4 heat systems and is missing in those of category 1 and 2 is the presence of significant thermal mass for heat storage. The thermal mass present in large radiators, floors and masonry heaters significantly lowers the temperature of the heated surface area that transfers heat into the home. When these surface area temperatures stay in the 75 to 150 °F range heat transfer by radiation will predominate. Between 150 to 300 °F range heat transfer by radiation and convection will even out. Above 300 °F heat transfer by convection will predominate.

Masonry Heaters Good Value for Home Heating

By Marge Padgitt
HearthMasters, Inc

Masonry Heaters are arguably a the best value when considering heating alternatives.  They are old world technology at its best, having been in use for over 500 years in Europe, and a carefully guarded secret until now. Masonry heaters are designed with a site-built or pre-cast heater core inside of a brick, stone, tile, stucco, or soapstone exterior, and built on site by a heater mason.

Components of a masonry heater: The masonry mass of a heater will be at least 1,760 pounds whic needs to be supported correctly.  The heater has tight fitting cast iron or steel doors with ceramic glass that are closed during the burn cycle. Heaters have an interior construction consisting of a firebox and heat exchange channels built from refractory components. A masonry or Class A stainless steel chimney is also required.  Specialty manufacturers in the U.S. and Europe supply these components.

Soapstone heater kit
Courtesy of HearthMasters, Inc.

How Masonry Heaters Work: The heat is stored in the thermal mass, then slowly radiates out for the next 18 to 24 hours. This produces a quiet, comfortable, radiant heat. Many arthritis and fibromyalgia patients prefer radiant heat, because it penetrates deeply.  This is an added benefit of using a masonry heater.
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 virtually no waste. The heater burns very clean, and practically no emissions are produced, so masonry heaters are definitely environmentally friendly and "GREEN." The EPA is currently looking at masonry heater guidelines, and heaters are listed in the International Residential Code.
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, fans, 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 and tall ceilings are well suited for this type of heating appliance.
Home builders should investigate masonry heaters as an alternative heating method in order to address concerns about environmental inpact and green building. Masonry heaters are built with natural non-toxic components (firebrick, brick, stone, etc.).  They can be used for primary heating or supplemental heating purposes.   

Custom-built granite heater with bake oven and
heated bench.  Courtesy of HearthMasters. inc.

Feature Options:

• Pizza/bread/bake oven on the kitchen side
• Heated bench to sit on
• Mantles
• Wood storage spaces
• Fireplace on one side
• Cook top
  

A masonry heater should be built by a qualified heater-mason contractor.  Codes must be followed, and heaters are on the high end of difficulty for masons. Find a Certified Heater Mason, see photos of heaters, find component supplier and heater kits, and find out more about how masonry heaters work on the Masonry Heater Association of North America website at www.mha-net.org.