Monday, December 5, 2011

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.

Wednesday, October 5, 2011

New Masonry Heater Education Program Available

By Richard Smith
Executive Director
Masonry Heater Association of North America
The Masonry Heater Association of North America has developed a new education program known as HMED (Heater Masons Education & Development) program. This program will:
  • Provide an education program that starts with basic information and skills training.
  • Provide a standard curriculum that will be delivered in facilities throughout North America.
  • Provide opportunities to earn continued education credits for various certification programs.
  • Promote safe building practices for everyone interested in building masonry heaters.
  • Establish a training system that is specific to North America.
MHA’s education program provides an excellent opportunity to someone to learn the basic
theory and construction of a masonry heater.
Classes are currently scheduled for:
September 17 – 20, 2011 in Perth, Ontario, Canada, level one, modules 1 &2
November 04 – 07, 2011 in Shaftesbury, Massachusetts, level one, modules 1 &2
Other locations to be announced. Costs vary according to location.
What are Masonry Heaters?
A masonry heater is a special type of fireplace made of stone, brick, stucco or tile which will  heat your home safely and comfortably.  Masonry heaters burn wood, which is North America's  cheapest and most abundant bio-fuel.  We currently use less than 10 percent of available  deadfall timber from our forests.  Masonry heaters burn efficiently and with very low emissions, which make them extremely “green”. 
Masonry heaters work on the principal of thermal storage due to the considerable thermal mass of the materials used in their construction (most of them are heavy, often weighing tons).   The best masonry heaters soak up most of the heat from the wood blaze within the firebox through a cleverly designed system of channels or chambers which "harvest" heat from the  hot  gases as they pass by.  This energy migrates through the masonry slowly until it reaches  the surface where it illuminates" the room with invisible rays of heat known as infrared radiation.  This way heat from a fire in the morning can still be warming a home in the evening.
For more information contact the MHA office:
 
Masonry Heater Association of North America
          Richard Smith, Executive Director
          2180 S. Flying Q Lane
          Tucson, AZ. 85713
           (520) 883-0191
          execdir@mha-net.org (email)
          www.mha-net.org (website)

MHA 2011 Contest Winners

By Marge Padgitt
HearthMasters, Inc.
Seven winners took trophies home at the fourth annual Masonry Heater Association contest at Wildacres Retreat in North Carolina April 9, 2011. The contestants were required to design and build their own project alone or with assistance from others in their company. Entrants submitted their best work to be judged by a panel of experts who scored each entry on a point system based on skill in craftsmanship, aesthetics, creative use of materials, and overall design. The judges did not know who the entrants were. Judging was particularly difficult, because all of the entries were completed by skilled craftsmen and all of the work was exceptional. Larger photos of the projects are available at www.mha-net.org.

The Winners are: 

Bell Heater by Jim Frisch

Masonry Heater Category:

First place- Jim Frisch of Western Masonry, Inc. in Spokane, Washington. Modification of existing fireplace and floor framing, installed a custom corner bell heater with heated hearth bench. The shell is finished with Eagle Mountain and Chief Cliff Ledgestone and a Bluestone mantel and hearth.

 

Second place-Dave Wilcox of Wilcox Masonry in Wapakoneta, Ohio.  
Third place- Sean Johnston and Juha Ahokas of Warmstone Fireplaces and Designs in Livingston, Montana. (photo coming soon)
Custom-designed bake oven by Jessica Steinhauser
Bake Oven Category:
First place
- Jessica Steinhauser of Stonehouse Pottery in Guelfph, Ontario, Canada.  This striking red tile indoor cook oven or “tischherd” was designed and built using eight shades of red for the kachel tiles, inspired by the famous French brand of Le Creuset cookware.  The corners are beveled and stainless steel doors and trim were used to finish the look in a modern style home.   


Second Place- Dan Givens of Stone Castle Masonry in Esther, Alaska. (photo coming soon)

Third Place- Marty Pearson of Stone Comfort in Cumberland, Rhode Island. (photo coming soon)


Masonry Category:
First place—Jeffrey Owens of JTO Masonry Construction, Inc. in Allen Park, Michigan.  This spiral staircase is a reproduction of a 12th century castle stairway. That is fully hidden with functional bookcases.  The stairs provide  access from the master bedroom to a fitness room on the basement. The owners wanted something unique so I cam up with this Gothic design with a candle niche at both entries.  For authenticity, the staircase was to rotate clockwise in order to put right-handed attackers at a disadvantage trying to wield their swords as they walked up the right side.

The Jerry Frisch Award

The winner of the Jerry Frisch Award this year was Doug Hargrave of Mid-Atlantic Masonry Heat in Troy, Virgina. The award is named for one of the MHA founders, Jerry Frisch, who has gone above and beyond in helping the Masonry Heater Association of America and its members, and who has willingly shared information about building masonry heaters and bake ovens. Each year the MHA award committee and current president selects someone who shares Jerry’s commitment to the industry.  Previous winners were Jerry Frisch, Tom Trout and Norbert Senf. Doug Hargrave has been instrumental in his role as Treasurer, getting the MHA on track with finances, and completing professional reports and systems for the organization.

The Masonry Heater Association of North America hosts an annual meeting and workshop in Wildacres, North Carolina and several workshops in different locations through out the United States where masons can learn how to build masonry heaters and bake ovens. The Certified Heater Mason program, also sponsored by the MHA, is available to MHA members. A new educational program has been released this year, which is designed to introduce masons to how masonry heaters work and how they are constructed.

Wood-burning masonry heaters are site-built high-efficiency appliances that utilize thermal mass and interior channels to contain heat, then release it slowly throughout the day. Masonry heaters, also known as Kachelofens, Ceramic stoves, Finnish Heaters (pystuuni), Russian Stoves, Swedish Heaters (kakelugn or “contra-flow”) have been used for at least 500 years in Europe, and made their way to to North America in the 1970's. There are now heater builders across the U.S. and Canada.

For more information contact Richard Smith, Executive Director of the Masonry Heater Association of North America at 520-883-0191 or execdir@mha-net.org.

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.