Rumford fireplaces are tall and shallow to reflect more heat, and they have streamlined throats to eliminate turbulence and carry away the smoke with little loss of heated room air
Back in England, Rumford applied his knowledge of heat to the improvement of fireplaces. He made them smaller and shallower with widely angled covings so they would radiate better. And he streamlined the throat, or in his words “rounded off the breast” so as to “remove those local hindrances which forcibly prevent the smoke from following its natural tendency to go up the chimney…”
The objective is to reflect or re-radiate as much heat out of the face of the fireplace as possible. It doesn’t hurt to whitewash the firebox or to insulate behind the firebrick. It does hurt to cover the opening with glass doors, which cut about 80% of the infrared radiation. Tall, wide shallow fireplaces [the Rumford design] tend to smoke. The other half of Rumford’s genius is his intuitive understanding of fluid dynamics – way ahead of his time. By rounding the breast to “remove those local hindrances which forcibly prevent the smoke from following its natural tendency to go up the chimney…” he essentially created a venturi, a nozzle, like an inverted carburetor, that shot the smoke and air up through the throat into the receiving smoke chamber.
Because the true Rumford design is based on the science of airflow, it does not smoke. If you have a Rumford-like fireplace that does tend to smoke, something is wrong: either it’s a pseudo-Rumford with a bad throat design, or the throat’s obstructed or has been damaged. True Rumford fireplaces simply do not smoke—that’s why they were so popular.
The fire in a Rumford fireplace is laid with a large horizontal log at the back and smaller logs placed vertically, leaning over it. View a Rumford Fireplace (PDF)»
The main thing that distinguishes a masonry heater is the ability to store a large amount of heat. This means that you can rapidly burn a large charge of wood without overheating your house. The heat is stored in the masonry thermal mass, and then slowly radiates into your house for the next 18 to 24 hours.
If you burn wood fairly rapidly, it is a clean fuel. If you try to burn it too slowly, the fire will change from flaming to smoldering combustion. The burning process is incomplete and produces tars. Atmospheric pollution increases dramatically. This is important if you are planning an energy-efficient house. The average energy demand of your house will be quite low. For most of the time, it may require only 1 to 2 kW of heat. For most conventional woodstoves, this is below their “critical burn rate”, or the point where they start to smolder.
Masonry heaters fill the bill perfectly. If you need even a very small amount of heat, such as between seasons when you simply want to take off the chill, you simply burn a smaller fuel charge–yet you still burn it quickly. The large surface is never too hot to touch. You have a premium radiant heating system with a comfort level that simply cannot be equaled by convection or forced air systems.
- A mass of at least 800 kg. (1760 lbs.).
- Tight fitting doors that are closed during the burn cycle.
- An overall average wall thickness not exceeding 250 mm (10 in.).
- Under normal operating conditions, the external surface of the masonry heater, except immediately surrounding the fuel loading door (s), does not exceed 110 C. (230 F.).
- The gas path through the internal heat exchange channels downstream of the firebox includes at least one 180 degree change in flow direction, usually downward, before entering the chimney.
- The length of the shortest single path from the firebox exit to the chimney entrance is at least twice the largest firebox dimension.
Soapstone is quarried like granite and marble. It is a steatite stone and its primary components are magnesite, dolomite, chlorite, and talc. It can range in age from 300 to 400 million years old depending on which part of the planet it is drawn from. As talc in soapstone is soft to the touch, it gives the smooth feeling of rubbing a piece of dry soap. Thus the name was derived – “Soap” stone. No. You can’t wash with it.
For thousands of years, soapstone has been used throughout the world for tools, carafes, vases, goblets, sculptures, fireplaces, etc. In early American history, soapstone was used primarily for building blocks, sculpting and urns. As villages and towns began building home structures, a popular choice for the do-it-all sink was soapstone. It could be easily cut to shape with non stone cutting tools. Four styles of common sinks from the 1800’s and early 1900’s were the Philadelphia, Chicago-Wright, Boston-Williams and the good old New England Double Bowl (our most popular). In early New England, Soapstone uses ranged from fireplace hearths to countertops, sinks, and oven fireplace stoves. In different parts of the world, soapstone is still used as a daily staple for mixing bowls, cook-tops, cookware, and oven baking decks. Currently in the USA and in different parts of the world, soapstone is used for the largest variety of items ever yet – including balusters, stair treads, window sills and island tops. It’s fast becoming a very popular choice by designers and architects and it’s one of a kind texture and look make soapstone one of the most aesthetically pleasing stones to be used for the job.
True Soapstone is inert. Alkalis and acids won’t affect it as they will a granite, marble, or slate. For over one hundred years, soapstone sinks and tiles have been used in science class rooms and labs along with work tables and counter tops. Its longevity to long term – high traffic use is amazing!
Because of its truly remarkable and natural heat retention characteristics, soapstone is widely used for masonry heater fireplaces, wood stoves, fireplace liners and pizza ovens. Soapstone heaters and fireplaces heat very quickly from burning coal, pellets or wood, the soapstone will then slowly radiate heat very evenly for hours on end. Even after the fire has long gone out!
Q: Since soapstone is soft to the touch, does this mean it’s absorbant?
A: Though soapstone is soft to the touch it is far from absorbent. If the surface picks up a stain or discolors, this is literally – just on the surface – and can be scrubbed or sanded off. Slates, marbles, most granites, limestones and travertines are absorbent. Soapstone is not.
The Benefits of a Wood-Burning Insert
A wood-burning insert slides into your existing masonry or metal fireplace and burns real logs.
Your installer snakes a stainless steel liner down your chimney and fits a decorative flange made of black cast iron or steel or colored porcelain around the insert, hiding its steel sides and filling the gap between the box and your hearth.
A front door with ceramic glass radiates heat into the room. You open the door to stack the wood, then shut it, on most models, while your fire is burning. Most wood-burning inserts also create convection heat with a fan located underneath the firebox.
Wood-burning inserts can heat anywhere from 1,000 to 3,000 sq. ft., depending on their size. Inserts are small enough to fit into most traditional masonry fireplaces.
An insert designed to heat 1,500 square feet will burn for three to five hours before you need to reload; for 1,500 to 3,000 sq. ft., you usually have an eight- to 10-hour burn window.
Wood burning inserts can be installed in almost any situation whether it be new construction, remodel, or replacing an existing insert. New framing can be installed to accommodate for the size of your new insert. This goes for almost any type of insert (gas,wood,pellet).
The Benefits of a Pellet Insert
This prefabricated convection heater slides into your existing fireplace — prefab or masonry. Instead of loading logs, you pour in pellets — rabbit-food-sized bits of compressed, recycled wood waste and other renewable substances.
Just like the wood insert, a pellet insert is a sealed combustion box with a partially glass front door, and is surrounded by a decorative flange. It vents through your existing masonry chimney. To operate the system, buy a bag of pellets, pour it in, press a button, and have fire. On some, you just set the thermostat and let the stove do the rest.
Unlike a wood-burning insert, pellet stoves need electricity — to start the fire, operate the blowers, run the auger feeding the pellets to the burn pot, and run the computer board monitoring the system.
Pellet stoves can heat 1,000 to 2,500 sq. ft., depending on their heat-generating capacity and the size of the fuel hopper.
Among the cleanest-burning home heating appliances, it uses waste products to create energy. Some stoves can burn alternative fuels such as dried cherry pits, which you can buy in 40-pound bags from hardware and home stores.
The Benefits of a Gas Fireplace Insert
Today’s gas inserts are heat-producing dynamos that use propane or natural gas to power a steady flame dancing on fake logs, decorative modern glass chips, or stones behind a sealed glass face.
Gas inserts can be used in masonry or prefab fireplaces; they can be vented through the existing chimney (or a wall for a free-standing unit).
Gas is the easiest insert to use and requires very little maintenance beyond the annual check. Flip a switch; have fire. Its best application is for zone heating—turning up the gas in the room you’re in and lowering the thermostat in the rest of your house.
Green Factor: 58% to 85% efficiency rating, says HPBA; very little pollution, smoke, ash, or creosote. Zoned heating allows you to reduce overall fuel consumption.
(Information gathered from houselogic)
A Wood Burning Insert Below
When choosing a wood stove, consider the size of the space you’ll be heating. Wood stoves come in different sizes, and can be sized to heat a single room or an entire home.
- Small stoves are suitable for heating a family room or a seasonal cottage. In larger homes with older central furnaces, you can use a small stove for “zone heating” a specific area of your home (family or living room). This can reduce fuel consumption, conserve energy and save you money while maintaining comfort.
- Medium stoves are suitable for heating small houses, medium-sized energy-efficient houses, and cottages used in winter.
- Large stoves are suitable for larger, open plan houses or older, leakier houses in colder climate zones
The two general approaches to meeting the EPA smoke emission limits are non-catalytic and catalytic combustion. Both approaches have proved effective, but there are performance differences. Although most of the stoves on the market are non-catalytic, some of the more popular high-end stoves use catalytic combustion. Because they are slightly more complicated to operate, catalytic stoves are suited to people who like technology and are prepared to maintain the stove properly so it continues to operate at peak performance.
Non-catalytic stoves do not use a catalyst, but have three internal characteristics that create a good environment for complete combustion. These are firebox insulation, a large baffle to produce a longer, hotter gas flow path, and pre-heated combustion air introduced through small holes above the fuel in the firebox. The baffle and some other internal parts of a non-catalytic stove will need replacement from time to time as they deteriorate with the high heat of efficient combustion.
In catalytic combustion, the smoky exhaust is passed through a coated ceramic honeycomb inside the stove where the smoke gases and particles ignite and burn. Catalytic stoves are capable of producing a long, even heat output.
All catalytic stoves have a lever-operated catalyst bypass damper which is opened for starting and reloading. The catalytic honeycomb degrades over time and must be replaced, but its durability is largely in the hands of the stove user. The catalyst can last more than six seasons if the stove is used properly; but if the stove is over-fired, inappropriate fuel (like garbage and treated wood) is burned, and if regular cleaning and maintenance are not done, the catalyst may break down in as little as 2 years. (EPA note: Garbage should never be burned in a wood stove or fireplace.)
A Few Safety Tips
- Keep flammable objects away from your stove, especially clothing, drapes, furniture, newspaper, and kindling.
- Never put ashes in a cardboard box. Ashes should only be placed in a metal ash bucket. Once you have cleaned the ashes from your stove, the best thing to do with the ashes is to spread them above the snow that covers your vegetable garden. (Wood ashes contain potassium, a plant nutrient; ashes also help neutralize acidic soil. Never put wood ashes near blueberries, since blueberries prefer acidic soil.) If you can’t spread ashes in your garden immediately, place the ash bucket outdoors, away from the house, on a patch of bare ground, on a concrete slab, or in the snow — never on a wooden porch.
- Don’t turn on your range hood fan while your wood stove is operating unless you’re sure that the exhaust fan won’t make your stove backdraft.
- Before you go to bed, shut down the air intake dampers on your wood stove to a low setting.