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" Classic brick-and-mortar fireplaces aren&amp;#039;t exactly hot these days, according to Joe LaVecchia of New Jersey&amp;#039;s Abbey Hart Brick &amp;amp;amp; Stone. &amp;quot;We used to sell a million firebricks a year in the 1970s,&amp;quot; he says. &amp;quot;Now it&amp;#039;s more like eighty or a hundred thousand.&amp;quot; It&amp;#039;s not that the hearth&amp;#039;s allure has been extinguished\u2014it&amp;#039;s a cost issue. Between the prerequisite concrete foundation and a mason to do the job, a traditional fireplace can cost $10,000 to $15,000 to install. Then there&amp;#039;s efficiency. Typical fireplaces draw and vent interior air that a homeowner pays to heat with a furnace. The image of dollar signs streaming out of a chimney comes to mind.  The most common alternative today is the fuel-efficient, direct-vent gas fireplace. Carpenters can install the prefab firebox, which costs a fraction of a traditional fireplace. Still, nothing duplicates a crackling hearth. The old flame\u2014fascinating and elemental\u2014dies hard. CHIMNEYS: THE INSIDE STORY  1. FLUE Smoke rises through ceramic flue liners in about 95 percent of brick chimneys, Tyler McClave of flue-maker Superior Clay says. Round models span 3 to 36 inches in diameter; rectangular flues get as big as 24 x 24. But a 12 x 12 square is typical, and two flues often run side by side in a single chimney. 2. SMOKE SHELF Wood smoke rises from the firebox and collects along the smoke shelf, a horizontal termination that prevents smoke from traveling downward from the chimney and into the house. Located about 8 inches above the top of the firebox, the shelf? has a concave surface that collects rainwater and debris. 3. DAMPER The metal door atop the firebox closes when the fireplace is dormant to seal the drafty chimney from the home interior. It&amp;#039;s not a perfect seal, McClave says, because a refrigerator-style rubber gasket can&amp;#039;t last in intense heat. Common-sense note: Never light a fire with the damper closed. 4. FIREBRICK Also known as refractory brick, firebrick has an inherent ability to expand and contract with rapid heating and cooling. Face brick, which clads chimneys, cracks and fails when used to line a firebox.   &amp;amp;gt; BTU Breakdown &amp;amp;gt;&amp;amp;gt;&amp;amp;gt;   EFFICIENCY AIDS  Nearly 80 percent of the heat a fireplace generates goes up the chimney rather than radiating into a room. Cut down waste with blowers, which move heat from the firebox out to the room, and tap into the chimney&amp;#039;s radiant-heat potential with a grate that stacks logs up against the bricks. When the fire dies, close a set of glass doors, which help seal cool, drafty flues. DIRECT-VENT GAS FIREPLACE  PROS Concentric pipes draw in outdoor air and expel exhaust gas. Natural gas or liquid propane fuels flames in a sealed chamber. Ceramic-fiber logs glow without burning. The box reaches full heat in only 15 minutes. CONS Lacks the fun of the bellows, a poker and a smoky aroma. Tempered-glass-face temperatures approach 500 F, a burn risk, especially for children. The manufacturer Lennox now offers free protective screens.  $$$ About $1700 a unit; $3500 installed ASK A CHIMNEY SWEEP Why Is My Fire So Smoky? Step one is to open the damper, Chimney Sweep Inc. president Tom Oyen says. The other common problem is insufficient updraft\u2014try opening closed doors (or windows) in a room with a smoky fireplace. When Do I Need A Sweep? Have the chimney swept annually, or as every two cords of wood are burned, Oyen says. Burn seasoned wood to slow creosote buildup. What&amp;#039;s Seasoned Wood? Ideal wood has 20 to 25 percent moisture content. &amp;quot;It should burn end to end, like a cigar,&amp;quot; Oyen says. How Do You Sweep It? &amp;quot;Brushes and a shop vac. We carry 14 sizes of 22-gauge wire brushes,&amp;quot; Oyen says. &amp;quot;We seal the firebox and work from the top down. The tines fit snugly to pop the creosote loose. The soot settles, and we vacuum the fireplace with a 0.5-micron filter.&amp;quot; BTU BREAKDOWN    Black Locust ($235/Cord)  Fast-growing and heat-dense with 27.9 million Btu per cord, black locust is an excellent firewood with one caveat: It&amp;#039;s very tough to split.    Cherry ($300/Cord)  With a nice fragrance, few sparks and low resistance to splitting, cherry has only one big drawback: low energy density, just 20.4 million Btu per cord.     Rock Maple ($250/Cord)  A nice hardwood popular on the East Coast, maple is easy to split and makes excellent, long-lasting coals. It averages about 25 million Btu per cord.     Ash ($250/Cord)  Ash has low smoke, a mild fragrance and 24.2 million Btu of heat per cord. It&amp;#039;s usually part of a New England woodpile.    White Oak ($290/Cord)  Red or white oak\u2014with low smoke, minimal sparks and 29.1 million Btu per cord\u2014is fine firewood available throughout the U.S. "^^<http://www.w3.org/2001/XMLSchema#string>
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