How glass-ceramic helped realize Ben Franklin’s wood stove ideal

By Karen Elder, SCHOTT North America, Inc.

Benjamin Franklin famously invented bifocals and discovered electricity, but less known is his hand in the creation of the modern wood stove. In a time before gas and electric heat, Franklin sought a better stove, one that allowed homeowners to see and feel heat without inhaling harmful smoke. His desire drove him to develop the Franklin stove, a metal-lined fireplace featuring an open front that heated rooms more efficiently and reduced smoke exhaust. Franklin’s principles remain a benchmark for wood stoves today.

The advent of glass-ceramic and closed stove systems have realized Franklin's ideals in a way he never could have imagined. Fireplaces and stoves sealed using heat-resistant glass-ceramic offer an unobstructed view of the fire, more evenly radiate heat throughout a room, and stop all smoke and particulates from entering the house while trimming emissions, making them better for the environment too. Here's how glass-ceramic has helped to revolutionized stoves and fireplaces.

Ben Franklin came from the Anglo tradition that prioritized seeing the fire and resisted the more efficient Germanic traditions which sealed the firebox.  It could be argued that he set back the movement for high efficiency heating by popularizing a stove with an open front, even though closed stoves had already proved the efficiency and smoke reduction benefits of a closed firebox.  The technology battle between those that favored open fireboxes, including Franklin, and those that favored closed fireboxes went on for over a century and is explored in detail in a wonderful book by Professor Brewer, Priscilla called From Fireplace to Cookstove.

Improved air quality

Older methods of heating, such as open fireplaces and inefficient wood stoves, are notorious for their emissions, both indoors and out, and Franklin was well aware of the problem, adding a complex siphon system to his stove that drew smoke up the chimney and out of the house.

Glass-ceramic has taken the drive for healthier indoor spaces to a new level. Sealed with heat-resistant glass-ceramic, modern wood stoves and fireplaces make it impossible for smoke or particles to enter the home. These fireplaces funnel smoke and other particles up the chimney, leaving homeowners the comfort of an indoor fireplace without subjecting their families to smoke and particles.

And because modern stoves burn hotter and cleaner, few emissions reach the atmosphere. Modern wood stoves are often 50 percent more efficient than traditional stoves, and they can reduce particle emissions by 70 percent, impacting indoor and outdoor air quality.

Visibility

Both Ben Franklin and modern fireplace designers would agree: Few sights are more mystifying than a fire. In contrast to wood stoves that seal off the fire behind cast iron or steel doors, the original Franklin stove featured an open-front design to offer a prime view of the flames. Modern fireplaces sealed with glass-ceramic inherited this attribute and offer unobstructed visibility through transparent glass fronts -- sometimes from multiple angles. Manufacturers can produce glass in a variety of different shapes, sizes, and designs -- including 270-degree curved glass -- that allow homeowners to enjoy the fire from anywhere in the room.

Stronger safety

While the Franklin stove boasted an aesthetically appealing open-front design, the open flames posed potential fire threats for homeowners. Modern fireplaces enclosed with glass-ceramic solve this problem. Heat-resistant ROBAX glass-ceramic panes, for example, can withstand heat spikes and temperatures up to 1400 degrees Fahrenheit, containing flames and preventing sparks and ashes from spilling out and igniting while allowing the aesthetic view of the fire that Franklin envisioned. 

More efficient heating

Franklin’s stove contained a system of baffles and inverted siphons to repurpose escaping fumes as an efficient source of heat. Energy efficiency has new meaning in modern stoves and fireplaces. Closed fireplaces sealed with glass-ceramic burn fuel more efficiently and radiate heat more evenly than traditional fireplaces. Glass-ceramic allows fires to burn hotter, and radiate heat more evenly throughout the room.

The higher temperatures also save fuel. By burning hotter, glass-ceramic-enclosed fireplaces fully consume the wood, and produce a slower burn. Fireplaces sealed with ROBAX glass-ceramic can burn up to 43 percent less wood and can produce up to 26 percent more heat per kilogram of fuel than a standard open, wood-burning fireplace under the same conditions.

The ideas behind the glass-ceramic-enclosed fireplace are centuries old, but modern technology has transformed ideas into outcomes. New woodstoves and fireplaces sealed with glass-ceramic provide aesthetic appeal, better air quality, improved safety, and greater heating efficiency, making them the optimal choice over traditional open, wood-burning fireplaces. If Ben Franklin were alive today, he’d be sure to upgrade.

On America’s 250th birthday, a look at Ben Franklin and wood stoves in 1776

In 1776 in North America the open hearth remained the everyday default for cooking and much domestic heat, but significant innovations were already present and spreading unevenly—concentrated in port towns, shipyards, and wherever foundries, skilled metalworkers, or immigrant masonry traditions existed.

The idea of “closed” or “airtight” wood or cook stoves were far from reality for most Americans, even though they were beginning to emerge and take hold in Europe. Part of the challenge was economic: it was cheaper to build a stone hearth and chimney that to buy a steel stove. But part of the challenge was cultural and emotional: many people believed the open flame was healthier than flames in a closed box.

The man in the middle of these debates was none other than Ben Franklin, one of the core founding fathers of America, who was also an inventor, tinkerer and publisher. To have such a renowned founding father so intimately connected with the lowly wood stove has been a complex legacy. The Alliance for Green Heat has often commented on this complex legacy because those complexities live on today: millions of Americans want an open flame in their living room, just as Ben Franklin did, despite the negative health impact. 

As we celebrate America’s 250th anniversary, we should remember that Ben Franklin’s role was far

Franklin's original design.

greater than most of us appreciate. He was the only founding father to sign four of the key documents that enabled us to be the independent country we are today. The declaration of independence in 1776 was just the beginning. We still had to win the war, and Franklin was the architect of our relationship with France, a decisive ally. He was a signatory of the Treaty of the Alliance with France in 1778, the Treaty of Paris in 1783, and finally, the US Constitution in 1787. Not to mention that during this entire period, he kept tinkering on wood stove designs when living here, in London and in Paris. Of all his tinkering, the wood stove was the one he stuck with all of his life, as it was such an important technology.Franklin’s reputation as an inventor of the wood stove is larger than what he actually invented. Nothing that he invented sold well, and nothing really survived other than what was adapted by others. He never even invented a “stove.” He tried to invent a more efficient fireplace but it was a commercial failure because it had a downdraft that didn’t work, filling the room with smoke. The most famous inventor who took the Franklin and adapted the design was David Rittenhouse, who got rid of the downdraft and added folding doors. But because of Franklin’s name and popularity, and because he purposely did not patent the device, the Rittenhouse stove lived on as the Franklin stove and still lives on today.

As we celebrate the 250th anniversary of our country, its worth remembering that energy supplies have always been vital for America and it began with wood. In the 1770s wood was the primary domestic fuel in towns and cities. Just like today, prices and availability varied seasonally (higher in winter) and by proximity to woodlands and navigable transport. Urban centers like Philadelphia, Boston, and New York relied on timber brought in by wagon or boat, so haulage/boat freight often added more to the retail price than the raw timber did.

The Revolutionary War also disrupted the firewood trade, provoked requisitions and impressment of

Today, this is the Franklin stove
model, with folding doors and no 
downdraft.

supplies by both armies. Boston’s port closure (1774) and wartime blockades created acute local shortages and relief drives for firewood.

But it was a period of change away from a renewable carbon based fuel and towards non-renewable carbon fuels. By the 1880s–1890s coal (anthracite and bituminous), manufactured gas, and later coke and electricity were displacing cordwood in many cities.

Rapid urban industrialization and expansion of railroads made coal cheaper and more convenient for heating, cooking, and industry. Cities shifted from cordwood toward anthracite/bituminous coal and manufactured gas for lighting/heating; rural households and small towns often remained wood-dependent longer and some still do.

Railroads also helped the firewood trade, enlarging supply regions and smoothing seasonal shortfalls. Where rail access was good, wood prices tended to fall or stabilize; where railroads were absent or local woodlands were depleted, prices rose.

More efficient, closed stoves reduced per-household wood consumption and coal- and gas-burning appliances further cut demand for cordwood in urban homes. The reliance on firewood in the 1700s, and heavy demand through most of the 1800s created devastating deforestation, and our forests didn’t begin to recover until he late 1800s–early 1900s. Full recovery was uneven by region and continued through the mid‑ to late‑20th century.

If we hadn't discovered coal, our forests
would have been cut down far more than 
they were.

Ben Franklin sought to reduce the amount of wood we needed to heat our homes by participating in a process that continues today: how to design cleaner and more efficient stoves that consistently work in the hands of homeowners. Two hundred years later, another prominent figure – President Jimmy Carter – carried forward that legacy by installing modern, efficient wood stoves in the White House, and urging Americans to use them to save energy.

West Penn Power Sustainable Energy Fund Helps Support the Wood Stove Decathlon

The Alliance for Green Heat and the West Penn Power Sustainable Energy Fund (WPPSEF) are working together on the Wood Stove Decathlon to help make affordable wood stoves cleaner and more efficient. Wood heat is a vital source of renewable energy for homes across the state of Pennsylvania and throughout the mid-Atlantic region but technology advances are needed.

The Wood Stove Decathlon, modeled after the Solar Decathlon, is a technology competition to see which team can best design and build affordable solutions to making wood stoves less prone to operator error.  Even today’s EPA certified stoves perform poorly when loaded with unseasoned wood and not given enough air, which results in excessive air pollution.

The Wood Stove Decathlon was partially inspired by the legacy of Ben Franklin, who in 1744 launched what has become known as the “Franklin stove” – considered by many to be the forerunner of American-designed efficient stoves.  In 1826, the Franklin Institute sponsored a contest with a $100 purse for the best cookstove design of the year, during a time when the price of wood was skyrocketing due to deforestation.  There have not been any other stove competitions until now, when the motivation for a technology challenge has more to do with the necessity of reducing fossil fuel use and improving air quality.

 At the Decathlon, there will be a series of educational panels on innovation in wood heat technology.  Joel Morrison, Director of WPPSEF will be speaking on a panel Tuesday morning, Nov. 19.  Mr. Morrison said, “WPPSEF is delighted to support the Wood Stove Decathlon which will drive innovation and lead to cleaner, more efficient stove designs.”

Between 2000 and 2010, wood heat grew 65% in Pennsylvania, nearly double the national average and nearly three times faster than any other heating fuel.  As of 2012, 145,000 or 2.9% of Pennsylvania residents heated primarily with wood or pellets and more than half a million use it for secondary heating.

The Wood Stove Decathlon is being held on the National Mall in Washington, DC from Nov. 15 – 19.  Partners include WPPSEF, Popular Mechanics, USDA, DOE’s Brookhaven National Lab and state agencies in New York, Washington, Oregon and the District of Columbia. For more info: http://www.forgreenheat.org/stovedesign.html.

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The Alliance for Green Heat, the organizer of the Wood Stove Decathlon, is a non-profit organization promoting cleaner and more efficient wood heating. Visit http://www.forgreenheat.org for more information.

The West Penn Power Sustainable Energy Fund invests in the deployment of clean energy technologies throughout the West Penn Power service region. Investments are made to promote: the use of renewable and clean energy, energy conservation and energy efficiency, and the attraction, establishment and retention of sustainable energy businesses. Visit www.wppsef.org for more information.  

Downdraft Wood Stoves: Consumers Beware

The simplicity of the non-catalytic stove makes it the most popular type of stove in North America by far.  With most non-cats, the consumer only needs to worry about a single lever to regulate the amount of air in the firebox.  But some consumers unwittingly buy a very unique kind of non-cat, a  downdraft stove, and often regret it.  

June 2021 update: The number of new downdraft models are dwindling but they still appear on the second hard market.  We are not aware of any on the market now.  Please let us know if you know of one. AGH has applied for DOE funding to design and build a new type of fan-assisted downdrafted stove that would overcome the issues of older, manual designs.)

There used to be a handful of downdraft stoves on the market but were gradually been pushed aside by non-cat stoves with air tubes that reburn smoke as it exits the firebox.  The downdraft stove works with a second lever that engages a by-pass damper which forces the smoke down into a chamber where heat can reburn it before it goes back up the chimney. 

Almost all stoves on the market today do not try to get smoke to go down, but rather try to reburn it on its journey upward with secondary air introduced through holes in tubes or in upper wall of stove – or with a catalyst. Hybrids use both tubes to inject for secondary air and a catalyst.  (Click here for more on cat, non-cat and hybrid stoves.)

Downdraft stoves tend to be finicky, need to be very hot to work properly and are more prone to leaking smoke into the house.  Most consumers should not consider them unless they know what they are getting into and are prepared to be much more engaged with their stove.  The same can be said about catalytic stoves.  Consumers should understand that they need to know how to use the second lever that engages the by-pass damper and occasionally check the catalyst, and replace it when it needs replacing.

Stove change out programs, that switch out old stoves with new, EPA certified models may want to exclude downdraft stoves from eligible replacements as they may be the hardest class of stove to run consistently without visible smoke. 

The downdraft stove became popular in the 1980s when Vermont Castings used it to extract more heat from a stove and to help pass the emission testing required by the state of Oregon, and later by the EPA.  The by-pass damper helped slow down the fire, create turbulence, and extract more heat from the hot gases before they went up the stack. The Resolute Acclaim, one of the most popular wood stoves of the last century, was a downdraft stove.  It clocked in at 3.4 grams per hour and continued selling through the 2000s, but has since been taken out of production.

The Harman TL300 is a downdrafter but now discontinued and Vermont Castings may have discontinued theirs.  The Lopi Leyden and the Avalon Arbor (same stove) went off the market in 2012. There may be better designs of downdraft stoves that are easier to operate in other countries.

The original Frankin stove
was a downdraft with no
front door and often
made for a smoky house.

Downdraft stoves have existed for centuries in various designs. The original stove invented by Ben Franklin also had a downdraft incorporated into the design, and it is one of the reasons that the stove was so finicky and disfavored by the majority of consumers. Franklin himself admitted that the stove was difficult to operate and took lots of attention and wasn’t something that “could be left to the servants.”  Later iterations of the Franklin stove added a door and most got rid of the downdraft.

Consumer feedback

Hearth.com is a premier chat room for wood stove experts and rookies alike. It contains a lot of good feedback on downdraft stoves:

- “The creosote smell when closing the bypass is not an uncommon issue with the downdrafting stoves. I've seen Harman stove owners complain with it as well. I will sometimes get it. Sometimes not. It's not noxious, just a faint odor that I can do without. CO monitor pays it no mind.”

- “I wish a group of downdrafters could get their heads together on this one and figure out what is going on. It's a common problem to different stoves. Maybe that box full of smoke is letting some escape at the joints.”

- “I've smelled it when the draft was strong, but typically it comes when the flue has begun to cool down a little. Loading lid was a prime suspect, but I regasketed it and sat a cast iron pot on there.”

- “Downdraft stoves are notoriously fussy and demanding of a strong draft.”

- “The Leyden has undergone a few changes of the years. There are some ports that need thorough cleaning "Monthly" as well and they are not easy to reach. Make sure these ports are cleaned regularly. Your manual shows how to do this correctly.”

- “These stoves have to be seriously hot to work.”

- “I sometimes get a bit of smoke when loading. Mostly because I'm too lazy to do it right. Again, operate the stove as designed and if it doesn't work, get a look at the flue, check for ash buildup, etc.. ... your flue design is gonna be a tough one.”

- “I don't want to melt your stove down, but my hunch is that you're not getting it hot enough on a 3-4" coal bed.”

- “Is the wood very well seasoned? That is very important with this stove as is a good draft.”

- “I would try running your stove top temperature a little higher (650-700) before you go to secondary burn, typically you get some drop in stovetop temperature when you close the damper.”

- “The Lopi Leyden is a very problematic stove. You don't want it, believe me!”

- “I also suggest to take off the Vermont Castings Resolute and Lopi Leyden. Both use a different mechanism to achieve a clean burn than the other non-catalytic stoves. Both stoves usually have a steeper learning curve, can be prone to costly repairs and are better suited for full-time burners which does not seem to be your intention.”

- “As others have mentioned, the Oakwood (and other downdrafts like Lopi Leyden and certain Vermont Castings models) can be a bit fussy about dry wood and good draft, requires a bit more babysitting and longer learning curve, and is not well suited to slower/lower burns in months like November and April.”

- “You want a stove with tubes in the top or a catalyst. Avoid stoves that draw smoke down into the back of the stove. For example: Vermont Castings, some Harman's and Lopi Leyden.”

Behind the Scenes Look at the Wood Stove Decathlon

The lead-up to most big events is full of planning, fundraising and trying to foresee the unexpected.  The cost for running the Wood Stove Decathlon alone is daunting: this event would cost north of $250,000 in hard expenses – not including salaries of staff – but the generosity of so many in and outside of the wood stove industry is bringing the hard costs down to about $100,000.  We will publish the complete budget, but we also wanted to describe what’s going on behind the scenes with the teams, testing, exhibits, VIPs and panels.

The DOE organizers of the Solar Decathlon warned us that the first time attempting to stage a competition like this is by far the hardest.  After all, as far as we know, the Decathlon is the first such wood stove competition since the time of Benjamin Franklin.  We don’t know yet if there will be a second Wood Stove Decathlon.  That depends in part on you and the feedback we get afterwards. (You will get a survey.)

Testing: At the core of the Wood Stove Decathlon is the testing of 13 very different wood stoves.  These stoves have been selected, from a pool of nearly 50 designs, as finalists of the Next Generation Wood Stove Design Challenge, a year-long, international competition.  The results of the testing will be publicly posted each day in the tent and on our website. 

One of the biggest strengths of the Decathlon has been the judges who have donated hundreds of hours of time to ensure that the rules and testing is accurate and fair. Testing is being done primarily by Tom Butcher and Rebecca Trojanowski from DOE Brookhaven National Lab (for more about the testing process, click here.)  The real challenge at the Decathlon will be testing so many stoves multiple times in a period of 5 days.  We cannot afford to miss a single day due to faulty equipment so we are going to have back-ups for key instruments.

Fair and accurate testing of the stoves’ particulate emissions is by far the most complex challenge of the Decathlon.  And, it would be the most expensive aspect of the Challenge if we had to pay market rates for it.  Fortunately, we do not.  The Judges will be using recently released equipment on loan from Wohler and Testo mobile particulate analyzers – developed by competing German companies – to test the stoves to exacting German standards.  Through a grant from NYSERDA, the Alliance for Green Heat is covering $25,000 in expenses by DOE Brookhaven National Lab to test and calibrate the particulate analyzers.  

Set up: For the organizers, the Decathlon will begin on Monday the 10^th when the tent is set up on the National Mall.  The tent, generator, lighting, etc. is the biggest single expenditure at $36,000.  We are using Tents LLC for the majority of our logistical needs as they are a very experienced company who’ve often worked with the National Park Service and are very familiar with the extensive rules and regulations that come with hosting an event in the shadow of the Washington monument.  On Tuesday, the teams and their stoves will begin to arrive.  By Wednesday, all the stoves will have arrived.  The challenge here is installing 13 stoves in only 2 days, and ensuring that we have all the right equipment.  Even one trip to the hardware store will slow us down considerably.  The installation process would have been very expensive but for the generosity of ICC Chimney who is overseeing installation and donating all the chimney pipe.  Chimney Safety Institute of America trained chimney sweeps are generously donating the skilled labor to do the installations.  And, Hearth Classics is donating the hearth pads, a vital piece of every safe stove install.  Lastly, two cords of seasoned wood, donated by Chris Holmgren at Seneca Creek Joinery, will be delivered and stacked in a firewood room prior to testing.  

Fueling:  After much debate, the judges decided to use cord wood to test the stoves to best simulate their performance by consumers and to test using a cordwood testing protocol, which is currently not used by the EPA.  Ben Myren, who has run one of the EPA accredited wood stove test labs for decades is in charge of fueling and prepared a draft fueling protocol for the judges.  Ben is generously donating all of his time to be part of this unique and educational event.  The fueling protocol will undergo further testing at Brookhaven National Lab prior to the Decathlon.

Exhibit Area: There are about 15 exhibit spaces for companies and organizations to showcase innovative products, ideas and services.  This is not a trade show, and while exhibit space is being purchased, no sales, solicitations or any other commercial activity is allowed to take place at the event (per National Park Service Rules and Regulations).  You will see some very exciting new equipment, projects and components!

The Speaker Area: We are hosting 25 panel discussions on a wide range of issues related to innovative stove design, cutting edge policy discussions and education for homeowners.  The panels will be an hour in length, and begin around 10am and conclude around 4pm running from Saturday through Tuesday.  Speakers include partners, exhibitors, judges, teams and experts who will participate in panel discussions about topics such as the sustainability of biomass, the future of wood stove technology and innovation in stove design.  Weekend panels tend to be more general and designed for homeowners and consumers.  Panels on Monday and Tuesday are more specialized, and designed for a policy, industry and professional audience.

VIPs: We are extending invitations to Secretary level officials, some of whom have indicated an interest. One member of Congress has already accepted to speak at the Awards Ceremony and many more are considering it, and we are still getting our invitations out.  We are also reaching out to about a dozen Ambassadors from countries where wood heating is very popular. Please invite your member of Congress to attend.  You can get a sample letter and tips to contact your representatives here.

Education, Door Prizes, etc.: The entire Decathlon is about education, and we are fortunate to have Popular Mechanics as one of the founding partners of the Design Challenge.  They are hosting People’s Choice Award where you can vote for what you think is the most innovative design.  There will also be door prizes, quizzes to test your wood heat IQ, and hopefully even an appearance by Smokey the Bear, thanks to our partners at the US Forest Service.