Subscribe eNews Send Us Files Login

Hearth & Home May 2018

Regency Pro-Series F3500 Catalytic Wood Stove.

CAT? Non-CAT? Hybrid?

By Bill Sendelback

Manufacturers are deciding on which technology to use in order to meet NSPS Step 2.

Step 2 of the EPA’s New Source Performance Standards (NSPS), with its lower particulate emissions limits for new residential wood heaters, currently does not go into effect until May 2020. But for hearth products manufacturers, that seems like tomorrow. Most are scurrying to meet the tougher limits, and struggling to get their products ready for the marketplace. Many are still trying to determine which burn technology they should embrace in order to meet those new, tougher standards – catalytic, secondary air (questionably called “non-cat”), or hybrid technology.

Step 1 of the NSPS set particulate emissions limits at 4.5 gph for both catalytic and secondary air wood burners, and also for pellet stoves. The upcoming Step 2 will set the emissions limits at 2.0 gph for pellet stoves, and for any technology used for burning wood when those wood burners are tested burning cribwood, and 2.5 gph when tested with cordwood.

Reducing emissions from the current 4.5 gph to Step 2’s 2.0 gph may not sound like such a big deal – but it is. While a number of wood burners already meet Step 2 limits, the majority of manufacturers have yet to meet the standard with most of their product line.

“Many manufacturers still are not totally sure how they should proceed to come into compliance with the low target of 2.0 gph,” according to Jack Goldman, president and CEO of the Hearth, Patio & Barbecue Association (HPBA). “While some manufacturers think they have solved the issue of reaching the new limits, they may have certified only a fraction of their models. They are all telling us that they need more time in order to have their entire lineups certified and available to dealers.”

Secondary air technology, sometimes called “tube” technology, uses a variety of baffling to hold flue gases in the firebox longer, while secondary air tubes introduce additional combustion air to cause those flue gases to re-burn and, thus, reduce emissions. Secondary air technology generally relies on a hotter fire to do its job.

NZ3000H catalytic wood burning fireplace by Napoleon Fireplaces.

Catalytic technology uses a honeycombed ceramic or metal combustor coated with exotic metals to burn flue gases after the combustor has ignited or “lit off,” hence reducing emissions in a similar way that catalytic combustors reduce emissions in the exhaust of today’s automobiles. The combustor in wood burners feeds on dirty flue gases, so this technology thrives on lower-burning, coal-bed-type fires that produce particulates of emissions or fuel for the combustor.

Hybrid technology is a combination of secondary air and catalytic technologies. The appliance uses secondary air technology initially to reduce flue gas emissions, and then a catalytic combustor in the stove flue outlet finishes the job. For EPA certification, the NSPS considers hybrid technology as catalytic technology.

There’s no consensus among manufacturers regarding the burn technology needed to meet the 2020 Step 2 emissions limits. Some manufacturers are sticking to the tried and true technology they have been using. More are looking at all burn technologies to see what will work best for them. Some will end up using more than one technology in their product line, tailoring the technology to the needs of each model.

Super 27 non-catalytic stove by Pacific Energy.

“We’re dedicated to non-cat, or secondary air technology,” says Paul Erickson, president of Pacific Energy Fireplace Products. “We already have five fireboxes for 20 models certified to Step 2 using our secondary air technology, so why would we go to catalytic technology, especially since our dealers don’t want it.”

“We’re trying both catalytic and secondary air technologies, but we prefer secondary air,” says Wolfgang Schroeter, president of Napoleon Fireplaces. “We’re concerned that using a combustor will raise prices, and then the consumer may say, Why buy a wood stove at those prices?”

“We’re looking at both, but we, too, are concerned about adding the cost of a catalytic combustor,” says Paul Williams, vice president of Business Development for United States Stove Company. “We used cats years ago and had problems that gave cats a bad name. But catalytic technology now is much improved.”

“We’re now introducing some catalytic models certified to the 2020 standard,” says Glen Spinelli, president of Regency Fireplaces, “and we’re looking at hybrid technology to see what may be needed for the rest of our line. Yes, a combustor will add cost, so we’re looking at a thinner combustor to help contain costs.”

RSF Delta Fusion non-catalytic fireplace.

“We never liked cats,” admits Ray Bonar, vice president of ICC/RSF, “but cats have improved so much that now I don’t understand why we never used them. They allow larger fireboxes. They may add as much as $500 to the retail price, but our products already are high-end anyway.”

“We’re using both catalytic and secondary air technologies,” says Dave Kuhfahl, president of Hearthstone Quality Home Heating Products, “fitting the appropriate technology to what we need for individual models, and we’re achieving emissions rates as low as 0.6 gph.”

Ashford 30 catalytic stove by Blaze King.

“We’ve been successfully using only catalytic-burn technology since 1983,” says Alan Murphy, president of Blaze King. “Over those years, while the combustors now are much more refined and robust, we’ve learned that the stove must be designed around the combustor. Today we warranty the combustors in our stoves for 10 years.”

Murphy maintains that the reliability of both catalytic and secondary air technologies is similar. “Many forget that when secondary air models are over-fired, the baffles and air tubes can warp, deteriorate, and burn out. Frankly, there are pros and cons for both technologies.”

Travis Industries, celebrating its 40th anniversary this year, is using secondary air, catalytic, and hybrid technologies in its line of wood burners, plus forced-draft negative pressure technology in its pellet models to meet Step 2. “All these technologies are valid, and all will have a place in the future,” says Kurt Rumens, president. Catalytic and Travis’ patented Hybrid-Fyre technologies are used in the company’s largest fireboxes, resulting in its 3 cu. ft. Cape Cod stove certified to 0.45 gph.

Secondary air technology is used on Travis’ medium and small fireboxes. “It’s a function of firebox size, and it’s all market driven,” Rumens adds. “Some consumers want the cleanest burn and cleanest glass while others want a large firebox. Depending on the size of the firebox, we can use the appropriate technology.”

Lopi Rockport Hybrid-Fyre System wood stove by Travis Industries.

Of particular concern to Rumens is the affect that Step 2 may have on dealers, particularly since dealers cannot continue to sell Step 1 models after Step 2’s May 2020 effective date. “Most of our models already meet Step 2, and our goal is to have our entire line certified by May 2019, a full year before the effective date of Step 2,” says Rumens. “Dealers should have all their Step 1 models cleared out at least six months before Step 2. This sell-through will be a larger total cost to dealers than to manufacturers, and it will be a hardship for smaller dealers. So we, as an industry, must make the argument to continue to sell right now the fine clean-burn units we have.”

“We’re seeing more secondary air guys moving toward cats,” says Bob Ferguson, president of Ferguson, Andors & Company, a product development and regulatory compliance consultant, “and much of that is because secondary air technology can be less forgiving when the conditions of the burn in the firebox are not optimal, which may affect the emissions. This is especially daunting because Step 2 includes possible product emissions audits.

“Since the wood-burning test methods are known to include significant potential variability, just because of the random nature of burning wood, and there is no margin included to account for inherent testing variability in the audit test process, some manufacturers are considering adding catalytic technology to help reduce the chances of a failure of any audit.

“Secondary air guys for years have been selling against cats. Early on, there were concerns about the durability of the combustors and their additional costs. Today combustors are much improved, and the additional cost of a combustor generally is offset by the additional costs of the baffles and air tubes used in secondary air models, so the actual costs of either technology are very similar.”

“Today’s catalytic combustors still can be poisoned by chemicals, but the biggest problem for a combustor is flame impingement and excessive temperatures, greater than 1,800 degrees F,” according to Martin Morrill, vice president of Sales and Marketing for combustor manufacturer Applied Ceramics. “The design of the stove is very important to protect the combustor and take full advantage of its clean-burn abilities. Today’s combustors have an average life of from 8-12 years.”

Deciding on a burn technology is one thing. But developing that technology to work in every model is quite another challenge for each manufacturer, requiring lengthy engineering time. With the May 2020, Step 2 deadline fast approaching, most manufacturers are hoping for more time for needed engineering and testing to ensure products are ready to go to market.

The HPBA and the industry are attempting to provide that time. In March, 2018, the U.S. House of Representatives passed HR 453, extending the Step 2 effective date out to May 2023. A similar bill, S 1853, is now in the U.S. Senate and must be passed to make the 2023 effective date official. The HPBA is asking everyone in the industry to contact their senators and urge them to support S 1853.

Burn Technologies
Pros and Cons for Typical Designs




Performs best at low settings

Worst performance on high burns

Larger fireboxes

Combustor can be “poisoned” or plugged

Longer burn times

More difficult to keep glass clean

More forgiving of firebox conditions

Requires bypass damper


Combustor hates flame impingement




Cleaner glass

Smaller fireboxes

Simpler operation, no bypass damper

Performs best on medium or high burns

Hotter firebox temperatures

Shorter burn time

Less forgiving of firebox conditions





Best of both

Requires bypass damper

Cleaner glass

More complex and costly

Hotter firebox temperatures


More Stories in this Issue

May Is Barbecue Month!

It’s the start of the season. For most (some?) of us, winter has now passed, the grass is green, flowers are flowering, and an older man’s fancy lightly turns to thoughts of char-broiled burgers, or t-bone steaks, with grilled veggies, perhaps potato salad, and a cold beer.

» Continue

Leadership: The Competitive Advantage

By Mark Brock

Despite their humility and self-effacing qualities, great leaders go about their jobs with stoic determination and fierce resolve to do whatever it takes to make their companies great.

» Continue

Cooks and Their Books

By Lisa Readie Mayer

Retailers, competition pros, and other experts are releasing new books on the latest barbecue trends. You can too!

» Continue

2018 March Business Climate

In early April Hearth & Home sent a survey to 2,500 specialty retailers of hearth, patio and barbecue products, asking them to compare March 2018 sales to March 2017. The accompanying charts and selected comments are from the 186 useable returns.

» Continue

Parting Shot: Ancient Party Barn

In Postling, Kent, the architectural firm of Liddicoat & Goldhill undertook the restoration and renovation of a cluster of historic agricultural buildings into a getaway for relaxing and gathering.

» Continue