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 and currently the PR Chair.  She is president of HearthMasters, Inc. in Kansas City, Missouri. Her husband, Gene Padgitt, is a Certified Heater Mason.

When the Wind Blows - its Cold: The indoor wind chill factor

By Doug Hargrave
Mid-Atlantic Masonry Heat

Everyone has experienced the cooling effect of a strong wind or breeze while engaging in some outdoor activity. The extent of the cooling effect is determined by the speed of the wind and the temperature of the air. For example, a warm breeze has to be significantly stronger than a cool breeze to produce a cooling effect. The cooling effect of wind can be moderated by the use of insulation and/or a wind breaker. Someone is more comfortable wearing a wind breaker in a strong breeze. In a strong winter breeze one would have to add a sweater (insulation) under the wind breaker in order to achieve the same relative comfort. When weathermen talk about outdoor temperature condition they often refer to the wind chill factor. The wind chill temperature is always lower than the air temperature. The movement of air indoors is not generally referred to as "wind", however, the effect of air movement indoors is the same as outdoors - it has a cooling effect - it does not make you warmer. Air movement is often introduced into indoor living areas in a number of different ways; a few of the prime examples are as follows: Outdoor air infiltration that causes noticeable drafts through leaky doors, windows and other openings. Forced air systems and fans that mechanically move the air Natural convection of air from a hot radiator surfaces in the primary living areas. The most uncomfortable type of indoor air movement (draft) is outdoor air infiltration that causes noticeable drafts. Just as you would wear a wind breaker for comfort in windy outdoor conditions you want the shell of your home to act as a wind breaker for indoor comfort. No amount of insulation will help if you have drafts from the outside blowing in around it. The only way to counteract the effect of this type of indoor wind chill is massive amounts of hot air which will mask the effect of the infiltration. However this is accomplished at a high energy cost and only marginal improvement in personal comfort. The first line of defense in any home heating plan is reducing the air infiltration so that drafts from the outside are not noticeable. Only after this problem is fixed should someone turn their attention to other issues in the home heating plan. In the United States the use of forced air heating systems is so pervasive that it is difficult for most people to imagine any other way of heating their home. The fact that these systems produce indoor wind chill is accepted as a necessary evil. These systems typically force heated air into a room at the outside walls (usually under the windows) and then extract return air from locations high on interior walls. This forced air ducting arrangement results in relatively strong drafts at the ceiling level while minimizing drafty conditions at floor level. In a room with standard eight foot ceilings the movement of the heated air at ceiling level mixes fairly well with the cooler air lower in the room but there is always a marked temperature difference between the warm ceiling and the cold floor. In rooms with higher ceilings (especially vaulted ceilings) the mixing results of warm air near the ceiling and cooler air near the floor is compromised by the greater separation and larger volume. In order to compensate for this, more heated air is required and more mixing of air is required. This results in more air movement and more indoor wind chill. It is not unusual for someone seated in a vaulted ceiling room during cold weather to wrap a blanket around them self as a shield from this intensified indoor wind chill. Hot radiators cause air movement through natural convection which is then felt as indoor wind chill. The best known example of this is the wood stove where surface temperatures often run between 400 - 600 °F. At these temperatures when the air in the room makes direct contact with the stoves surface it expands dramatically and quickly rises to the ceiling. Other air follows behind creating a draft at floor level in the direction of the stove. This draft is quite cool because it comes off the coolest surfaces in the room usually the least insulated window areas. The wind chill effect from the combination of hot stove surfaces combined with cold window surfaces is very noticeable. Less noticeable wind chill is felt from electric resistance or hot water radiators placed on outside walls (usually under windows). These radiator heat systems send heated air up along the cooler surfaces in the room to the ceiling level. Cooler air to replace the heated air is drawn along the floor toward the radiator but it comes from warmer areas of the room resulting in less indoor wind chill than with a wood stove or other centrally located radiators that would tend to draw air from the outside walls and windows. The question is often asked, "Wouldn't it be a good idea to use a ceiling fan to blow the hot air near the ceiling down to the floor or reverse the fan and draw the cool air up to the ceiling?" On close examination, this solution, could come right out of the pages of Alice in Wonderland. When the ceiling fan is used in the winter time to "blow" the warm air down you almost always can see the slowly turning fan blades, which means it is not really blowing the warm air down but rather just stirring it up at the ceiling level. If the fan were actually run at a high enough speed to blow the air down (or draw the air up), the wind chill factor in the room would increase substantially and your comfort would decrease. On the other hand, in the summer time, when you have hot air at the ceiling and relatively cooler air at the floor, you can turn on the ceiling fan, force the hot air down on you and the indoor wind chill will make you feel cooler and more comfortable. The fan cools in winter and it cools in summer - period.

Types of Heat Transfer

By Doug Hargrave

Mid Atlantic Masonry Heat
radianthomeheating.org

Radiant heat is transmitted from a warm object to a cooler object through infrared radiation. This is the same type of heat transfer that takes place when the rays of the sun shine on the earth. 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 warmth you feel when you sit close to another person. Another example would be the way a radiant heater warms the surfaces and objects inside a home rather than the air.

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 heat storage capacity and the transfer rate will vary with different solids. For example, the higher density of soapstone allows it to absorb and then radiate more heat per unit volume than common brick which has a lower density. The heat transfer rate within metals is much faster than the transfer rate within masonry materials.

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.

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.

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.