Practical Fireplace Heating

Wood stoves and furnaces supplanted fireplaces centuries ago, but with the right design fireplace heating is still practical.

| October/November 1994

  • 146 fireplace heating - cover2
    Modern designs make fireplace heating a practical option.
  • 146 fireplace heating - rumford fireplace
    The Rumford fireplace on the right was a more efficient design for radiating heat than the conventional fireplace on the left.
  • 146 fireplace heating - small fireplace
    A small, decorative unit.
  • 146 fireplace heating - franklin fireplace 2
    Profile view of air flow in the Franklin fireplace design.
  • 146 fireplace heating - franklin fireplace 1
    The fireplace design Ben Franklin developed in the 1740s was intended to prevent smoke from filling a room.
  • 146 fireplace heating - kacheloven fireplace
    A kacheloven's performance relies on both air channels and thermal mass

  • 146 fireplace heating - cover2
  • 146 fireplace heating - rumford fireplace
  • 146 fireplace heating - small fireplace
  • 146 fireplace heating - franklin fireplace 2
  • 146 fireplace heating - franklin fireplace 1
  • 146 fireplace heating - kacheloven fireplace

Remember back in 1970-something when one of the Nixon daughters led a TV tour of the White House in steamy Washington, D.C., and innocently reported that "Daddy likes to turn up the air conditioning and have a fire in the fireplace"? Gasoline prices had just been oil-embargoed through the roof, taking home heating and cooling costs right along with them. For those of us who didn't have taxpayers to foot the bill, that off-the-cuff admission was particularly galling and further alienated the rebellious, draft age, newly environmentally sensitive 'Nam era American youth that I was at the time.

That's an almost forgotten and largely forgiven era. Richard is history. (Along with your squandered youth and mine — right, dear reader?) Besides, he was no different than the vast majority of Americans who considered the living room fireplace more a source of entertainment than anything else. The invention of wood-burning stoves in the late 1700s initiated the eclipse of fireplace heating as a practical alternative for ordinary citizens. Open fires, the source of warmth and cooked meals for mankind since the dawn of time, was relegated to Boy Scout camp-outs. And the traditional fireplace/flue complex lost its utilitarian value and became a component of design and decor, a fixture in house architecture, an excuse for a mantle and a mirror or painting; it was no longer the home's central source of light, motion, and warmth.

Today, a typical fireplace has a low, deep firebox and large throat (the opening between firebox and flue) and is designed primarily to evacuate smoke, even when the fire is newly started. At a full, roaring blaze it radiates only 10% of the heat energy contained in its fuel out into the room — just enough to give the effect of a cozy, toe-warming fire and take the chill (natural or artificial) off a room. The rest of a fire log's rich concentration of sun-energy is lost up the flue. Along with the smoke goes (fossil fuel heated) room air that must be continually replaced by cold outside air, reducing the heating effectiveness of the fireplace and creating chilly drafts.

Fire in an Open Box 

Very early American fireplaces, based on an English model unchanged since the Dark Ages, were primitive and inefficient — little but a hood with a pair of side jambs and a smoke hole located somewhere along the top. The flue damper wasn't invented till Ben Franklin dreamed it up in the mid-1700s. To keep warm air in and keep cold air from streaming down the flue and into the room, a cold fireplace was closed off with a not-very-effective stove board. Many colonial fireplaces consumed 10 or more cords of wood a winter. Householders stayed as warm as they could by bundling up, sitting on benches inside the huge walk-in kitchen fireplace (the "inglenooke" in Chaucerean Middle English), or huddling in front of a small parlor fireplace, benefiting only from the little heat that managed to radiate through the up-roaring draft that was being pulled in from behind them. People roasted in front and froze in back unless they wrapped in blankets or sat in high-backed settees.

1700 to Present 

It wasn't easy to experiment with heating appliance design in the early days. Each fireplace was a permanent installation requiring tons of masonry and a house. An experimental fireplace/flue combination that didn't work had to be torn down and rebuilt... So, change was slow.

Early fireplace builders followed one rule: a small fireplace should be taller than wide, a large one wider than tall. So in colonial homes, you'll find big old walk-in cooking fireplaces filling most of the wall of a kitchen and smaller, high-backed heating fireplaces in other rooms. Fireplaces on second stories were smaller than those down below and used smaller vents into common flues, so as not to overpower first-floor fires that had farther to draw to exit the chimney. Still, each home owner or mason was his own expert; firebox dimensions and flues often followed inefficient, snaking paths through house walls. Fireplace-to-flue-openings and flues themselves were universally larger than efficiency would suggest. With smoke-detaining, rough walls, they had to host one or more chimney sweeps — small boys, for the most part, who were sent climbing up the whole length of the flue plying their brushes.

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