Call This Origin of the Species, Part II

The scene is a remote office in Ellicott City, Md., the office of Robert Thullman. It is a spacious room, long enough for Thullman's large desk at one end and the appartus of an engineering laboratory at the other. At this latter end awaits the object of Thullman's inventive mind.

Walk this way.

Sitting, waiting, brooding, is Thullman's machine. From it tiny twisting wires angle like threads of life toward devices that monitor its progress. My Heaven, at any minute we will hear the crash of thunder and the crack of lightning and this thing will be alive.

Thullman regards his work and says, cuttingly, "Most stoves have been built, rather than designed."

After more than 20 years in the pre-fabricated fireplace business, engineer Robert Thullman, president of Thullman Eastern Company, is turning his attentions to wood stoves. His current experimental stove has enough gear hooked up to it to burn in quadrophonic sound.

Thullman, whose ingenuity helped lead the way to making fireplaces that actually heat, and who earned several patents in the process, hopes to turn the same magic on the charming technological dinosaurs known as wood stoves. He is in the vanguard of technologists whose search for maximum efficiency is taking solar energy (of which wood stoves, too, are a part) out of the yards of backwoods ecologists and into the living rooms of increasingly energy conscious Middle Americans.

In energy jargon, these new developments are known as the "systems approach."

Look, for instance, at changes in pre-fabricated fireplaces. When Tullman first started making them in 1954, they were, perhaps, 10 percent efficient, efficiency being the measure of how well the fireplace used the chemical energy in wood logs to heat the air in the house. In the last 25 years, Thullman has tripled, or even quadrupled, that figure.

This he and other engineers have achieved by several methods. Adding glass to fireplace fronts keeps combustion from sucking up warm inside air and spitting it out the chimney. Fans draw colder air into the fireplace, warm it and circulate it. Heat exchangers trap some of the energy that might otherwise by lost up the flue. Ducts draw on outside air, rather than continually re-heating already warm inside air. Room-to-room ducts distribute heated air through walls to other parts of the house.

Although fireplaces remain inferior to wood stoves in efficiency, techonologically they are light years ahead. It only remains for wood stoves to catch up.

What changes have been made are taking the public by storm. In the past two or three years, more manufacturers are marketing stove models that fit into standard masonry fireplaces. These airtight circulation stoves, appealing to many, dealers say, because they do not take up space in the middle of the living room, are called "inserts."

Timberline in Winchester, Va., for instance, began manufacturing its insert two years ago. The unit fits into any standard fireplace (36 inches wide and 29 inches high) and seals off the fireplace opening with a metal plate and insulation.

Timberline's Winchester plant, serving the middle Eastern Seaboard states, is already 3,000 units behind on orders from its dealers this year, said company sales manager Donald Linder. When production of the insert began, the plant was on a single shift. In an attempt to keep pace with demand, management has since started a second and a third shift. Linder says he receives 15-20 calls a week from persons seeking to open a dealership.

"It's almost a headache at this point," he says.

Inserts are constructed as a stove within a stove: the firebox is contained by an outer shell. On the Kemwood, made by Kemmerer Manufacturing in Richmond, Va., the firebox is surrounded by insulation to force heat through the front and prevent it from leaking out the sides. The Timberline stove uses natural convection to draw cooler room air in through the bottom, circulate it within the space between the two boxes and exhaust it back into the room through an opening near the top of the stove.

Inserts are priced similarly to their free-standing cousins, in the $600 range. Some have fans, or optional blowers, to aid in circulating air warmed by the fire chamber.

Besides the inserts, you will find many stove dealers stocked with a vast array of models to fit many budgets. Prices range from $100 to $1,000 including radiating, circulating, pot-bellied, squat, fat, tall, lean, windowed, big doors and little doors from manufacturers here and abroad. But if the stove you want costs $500, be prepared to spend again that much for installation and chimney parts. The average chimney costs $225 for a one-story house, $400 for two stories. Installation will cost about $195 or $245 and enclosing exposed pipes $100- $125.

And this is only a hint of what is to come in wood burners.

Wood stoves, for all their charm, are seldom more than 40-50 percent efficient. Experts believe more improvements will make better use of wood energy that now escapes up the flue.

"Why not make a stove that could be more responsive, safer and more efficient?" Thullman asks.

One problem with wood stoves is that most of their heat is released through radiation rather than convection (as with a forced-air furnace). This can result in a fire hazard when the stoves are installed improperly, too near combustibles in the house.

Thullman is experimenting with a fan that blows against the underside of a free-standing stove. The fan circulates the heated air while simulataneously reducing the temperature of the stove, something akin to drawing heat off an air-cooled engine.

Inside the stove, Thullman has installed a pipe that speeds up firing with forced air.

That is only the beginning. Increasingly, says Timothy Maxwell, mechanical engineer at Auburn University's wood burning laboratory, technology is moving toward wood burning furnaces -- the so-called "systems approach."

Engineers are looking at ways to better store energy released by wood stoves and to improve methods of circulating it through the house. Improving wood stove efficiency includes making more use of outside air, tapping duct systems to move heated air from room to room, and combining stoves with water storage tanks, similar to those now used with solar heating panels.

While these developments are being hammered out on the drawing boards, stove fanciers should look for improvements in stove labeling. Auburn University, the testing arm of the industry's trade group, Fireplace Institute, has been working on an energy efficiency label for stoves. The proposed label would be similar to those that already appear on air conditioners to show efficiency ratios.

Within the next year or so, after professionals in the field have concluded their review of the proposed efficiency testing standard, customers should begin to see manufacturers advertising precise indications of how well their stoves work.

The institute label would show how many pounds of wood the stove burns per hour, how many BTUS the stove can be expected to release each hour, the percent of efficiency at which it operates and how many cubic feet of room air the stove will use each minute in the process.

Maxwell said the Fireplace Institute plans eventually to submit its test to the American Society of Heating and Refrigeration Engineers (ASHRE), the professional engineering group behind most heating appliance test standards used in this country.