Friday, September 25, 2020

EPA and states vigorously defend wood stove audit testing

States share more variability test data and raise serious problems with certification process 

Updated on Oct. 20 - The EPA responded to HPBA’s lawsuit, saying that it is recycling old arguments and using a flawed analysis, and that its lawsuit should be dismissed. Eleven states and one air agency also filed a brief in agreement that provided compelling new data about testing variability and asserted that recent stove certifications are full of errors and deficiencies.
The states’ brief may be influential as it provided recent test data in an arena where very little publicly available data exists. Beyond showing that many stoves can provide repeatable emission data, states say that the ASTM 3053 cord wood method, “an industry-developed test … produces more variability than Method 28R,” the standard EPA crib wood method. The brief also cited recent testing that shows “manufacturers could generate more reliable ASTM 3053 test results by conducting certification tests in a manner that was more representative of consumers’ ordinary use of the stoves.”

We provide a brief analysis and then provide excerpts of key parts of legal briefs by the three parties: EPA, states and HPBA and also the NESCAM memo with variability test data. The briefs are long and parts are technical, but we encourage stakeholders to read these excerpts as they provide important details and context on federal wood heater regulation and the final stages of the much anticipated HPBA lawsuit.

The strong response from the EPA shows that while enforcement has not been a high priority recently, it is heavily invested in maintaining its ability to conduct audits, even though it may have only done so once or twice since the first NSPS in 1988. The 1988 and 2015 NSPS give the EPA the right to retest a stove after it has been certified, known as an audit. However, none of the three briefs ventures to discuss what circumstances could or should give rise to an audit, or whether they would be completely random.  More routine audits every 2 - 5 years for the higher volume stove models could be an option.

HPBA is the one litigant in a larger case that has gradually dissipated to one narrow issue: audit testing.  The EPA appears to be on solid ground and is backed by many states and non-profit interveners.  The data relied on by HPBA is now very old and no manufacturer is offering newer data showing high testing variability.  

The variability of emissions testing with pellet stoves or boilers had barely been mentioned in the past. For the first time, data was submitted about pellet stove variability by NESCAUM and cited in the states' brief.  AGH believes data like this is important to build greater confidence in and support for pellet technology as a core part of residential renewable heat policy. 

These briefs also come on the eve of the EPA sell-through announcement. Stuart Parker, a reporter for Inside EPA filed a story that noted “many of these same states are also threatening EPA with a lawsuit if it as expected finalizes its sell-through of wood stoves not compliant with step 2 emissions standards. The eleven states closely coordinated their response and highlighted the more notable restrictions that they have enacted to “to mitigate the risks of wood-burning devices.”

Next in the litigation process will be the September 28 filing of briefs by the non-profit intervenors, who include the American Lung Association, Clean Air Council, and Environment and Human Health, Inc.  Then, HPBA will have a chance to respond to the EPA and states by October 9, when they can rebut, if they so choose, the validity of the new testing data submitted by NESCAUM. Only after that will the DC Circuit Court schedule oral arguments which will almost certainly be virtual.  Finally, the three person panel of judges from the DC Circuit could either be more liberal or conservative and may give some indication of what arguments they may be favorable disposed to rule on.  The full briefing schedule can be found here.

AGH is an independent non-profit that has worked with all stakeholders to advance cleaner and more efficient wood and pellet heaters that can help reduce fossil fuel use and compliment solar panels, heat pumps and other renewable technologies. AGH sided with industry in supporting a limited sell-through of Step 1 heaters and has sponsored a series of technology competitions to demonstrate innovative solutions to reducing emissions in real world settings. AGH supports the audit provisions in the 2015 NSPS to provide important safeguards to determine potential flaws and lapses in certification testing and better understand emissions from different stove designs in real world settings.

To download the full briefs, click here for PDFs of the EPA brief, the States' brief, the HPBA brief, the Intervenors' Brief and the NESCAUM memo. The excerpts below have only been altered by removing citations, footnotes and subheadings.

1. Excerpts of EPA brief

Simi Bhat, Senior Trial Attorney, DOJ
Residential wood heaters generate small particles of pollution that can cause difficulty breathing, heart problems, and even premature death. These emissions are so pervasive that EPA estimates that residential wood heaters account for nearly twenty-five percent of cancer risks from toxic air pollution and fifteen percent of noncancer respiratory risks.

After conducting its own analysis on variability and considering other data on newer heaters, EPA concluded that variability was not as high as HPBA supposed, but still present.

HPBA now recycles the same argument about variability, but applies it only to the compliance audit process. Oddly, HPBA ignores its own success—the final standards reflect variability. EPA did not need to adjust the audit provisions because EPA adjusted the standards themselves, both by allowing a margin for variability in the emissions limits and by improving precision in testing.

While HPBA may be concerned that EPA may not administer the audit provisions fairly, this concern is unripe. EPA has not yet conducted an audit under the 2015 Rule. A hypothetical failed audit test by unknown margins with unknown context does not lend itself to judicial review at this time. If EPA revokes certification, that decision can be challenged. This petition should be dismissed.

Residential wood heaters collectively emit hundreds of thousands of tons of particulate matter throughout the country every year. At times and places of high use, wood heaters can contribute over fifty percent of daily particulate matter pollution. Because residential wood heaters are located in residential areas and emit pollution at low heights, even a small amount of pollution from these devices can cause disproportionately high exposure. This exposure is not fleeting because residential wood heaters are often used around the clock.

The manufacturer Woodstock Soapstone submitted comments comparing HPBA’s data to Woodstock Soapstone’s more recent data for three room heaters. Woodstock Soapstone attributed the difference between the variability it observed in test results of its heaters and the variability HPBA described to the “deep[] flaw[s]” in HPBA’s dataset.

Puget Sound concluded that HPBA “disregarded basic questions of data quality and representativeness.” For example, HPBA relied on results from the highest emitting wood heaters, which can have large differences in test results, instead of analyzing the entire dataset. But the variability of the “worst performing” device does not represent the variability across the board. Puget Sound further observed that HPBA’s data reflected “different sampling methods, locations, testing protocols, testing locations, span many years, and do not include data from a balanced or representative cross spectrum of the stoves and independent variables.” Even if HPBA’s dataset were representative and reliable, which Puget Sound did not believe, the real variability was far less than HPBA calculated. Puget Sound discovered that HPBA simply used the wrong statistical measurement to express variability as ± 4.5 to 9 gram/hour. The correct value for the (problematic) dataset of old heaters would be approximately ± 1.5-2 gram/hour.

EPA contracted with the Brookhaven National Laboratory to investigate, among other things, the repeatability of results from hydronic heater tests. Brookhaven tested the heaters by burning wood at three different rates, as specified in the test method for hydronic heaters. At the highest burn rate, results for three replicate tests were within 15% of each other. At the two other burn rates tested, the results were within 3% and 10% of each other. EPA concluded from this study that the “repeatability of cord wood test method” for hydronic heaters can be “very good.” 79 Fed. Reg. at 37,261. Before seeing the results of the Brookhaven study, HPBA had postulated that precision in hydronic heater testing would likely be similar in precision to other wood heater testing

The final 2020 standards are less stringent than initially proposed because EPA incorporated a margin of variability in the standards. EPA concluded that if “precision” in testing “is no better than 1.0 [gram/hour],” the final emissions limit of 2.0 [gram/hour]” for room heaters tested with crib wood would adequately reflect the emissions reductions achieved by stoves that tested at 1.0 gram/hour

The differences between the 1988 and 2015 audit provisions are slight. In the 1988 Rule, EPA required that the audit test be performed at the same laboratory that performed the certification test, until EPA could determine overall test method precision. Test method precision can be broken into two components. There is variability in test results when the same device is tested in the same laboratory multiple times (intralaboratory precision), and there is variability in test results when the same device is tested in different laboratories (interlaboratory precision). Under the 1988 Rule, once EPA determined test method precision, EPA would allow an additional margin equal to only interlaboratory precision when determining whether a device failed the audit test.

EPA did not need to make special allowance for variability in the audit provisions because EPA had already accounted for variability when setting the standards. Even the outdated analysis championed by HPBA does not support the need for any further buffer in the audit provisions.

Manufacturers will have a further opportunity to submit evidence on variability should any of their devices fail an audit test. EPA will consider any relevant evidence manufacturers present during an audit hearing, including evidence on variability. No other mechanism is necessary to address variability in audits.

EPA left the audit process in the 2015 Rule largely unchanged from the original 1988 Rule. Variability has never before been an issue in the implementation of the audit provisions, and HPBA offers no good reason to think it will now.

If EPA revokes certification following a failed audit test, a manufacturer can challenge that decision at that time. HPBA’s challenge to the possibility that EPA might revoke certification based on an unknown test result in the face of unknown rebuttal evidence in a future audit is unripe.

HPBA does not once mention in its brief that the audit process includes the opportunity for manufacturers to present additional evidence. Given that variability is already incorporated into the standards, as discussed above, and that EPA will consider any relevant evidence presented in an audit hearing, EPA did not need to make yet another allowance for variability in the audit provisions.

The only circumstance in which consequences are automatically triggered without a hearing is if a wood heater fails the audit test by 50% or more of the standards. If a device fails so egregiously, then EPA will suspend the certification after giving the manufacturer 72 hours’ notice of the suspension. This suspension may be withdrawn by EPA, and the manufacturer will still have the same opportunity to present any relevant evidence at a subsequent hearing to avoid final revocation.

The 50% exceedance trigger for suspension allows for even greater variability than HPBA itself calculated based on its old and flawed dataset.

2. Excerpts of States brief

Nicholas Buttino, Assistant Attorney General for NY


The amici States have a compelling interest in protecting their citizens from the emissions of wood-burning devices, which produce multiple pollutants that cause serious health effects. To advance this compelling interest, the amici States have enacted their own measures to mitigate the risks of wood-burning devices, and have participated in efforts to reduce wood-burning device pollutants at the federal level.

The state studies described in this brief confirm that there is no merit to petitioner Hearth, Patio & Barbecue Association’s objections to the audit-testing provisions in the 2015 Rule. As the States’ analyses demonstrate, the audit-testing provisions are necessary to ensure compliance with the Rule’s emissions standards. Petitioner’s testing variability concerns are overblown: those concerns are based on flawed statistical analysis and avoidable testing choices made by the manufacturers themselves. Accordingly, the States urge this Court to uphold the Rule in full, and reject the petitioner’s challenge.

Emerging research shows that long term exposure to PM2.5 increases the mortality rate from COVID-19, including in minority and low-income communities.

The health effects of wood-burning devices are acute in the amici States. The amici States have hundreds of thousands, if not millions, of residents who rely on wood-burning devices for heating. New York alone contains nearly 150,000 homes that use wood as a primary heating source and 500,000 homes that use wood for supplemental heat. In Vermont, 22% of homes use wood as a primary heating source, and 35% of households burn wood for at least some heating.

The amici States agree with EPA that petitioner’s challenges to the Rule are meritless, for the reasons stated in EPA’s brief. The States file this brief to inform the Court of the States’ own research, which underscores that the audit-testing provisions challenged by petitioner are necessary to ensure compliance with emissions standards, and that petitioner exaggerates testing variability as an impediment to reliable auditing.

The Alaska Department of Environmental Conservation has conducted a systematic review of wood-burning devices that have been certified to be compliant with EPA standards. The Department found that 59% of the certifications had inaccurate certification data, and 64% had certifications based on non- representative testing methods—i.e., methods that were not consistent with ordinary consumer use. What is more, three certifications lacked certification test reports altogether. These results suggest serious problems in the certification process. And those problems in the certification process in turn demonstrate why EPA must have a way to check on manufacturers—and hold them accountable—through audits.

The Curkeet study suffers from three main defects. First, the Curkeet study incorrectly applied statistics applicable to a normal distribution to data that was not normally distributed. Second, the Curkeet study improperly divided its dataset and drew conclusions from data that were not representative of the dataset as a whole, allowing particularly extreme values to be highlighted and taken out of context. Finally, the Curkeet study conflated absolute difference in values with a confidence interval, leading to a dramatic overestimate of uncertainty. Based on these problems with the Curkeet study, EPA reasonably discounted Curkeet’s conclusions.

NESCAUM’s analysis shows that testing variability may be minimized if manufacturers use a reliable certification test and scrupulously follow that test method. In issuing the Rule, EPA required labs to follow a certification method designated Method 28R, but allowed for approval of alternative test methods. At the request of manufacturers, EPA approved ASTM 3053, an industry-developed test, as an alternative test method. But using ASTM 3053 produces more variability than Method 28R because ASTM 3053 contains fewer specific instructions. To illustrate, where Method 28R states that manufacturers should use fuel logs that are no less than 5/6 the length of the firebox, ASTM 3053 contains no such limitations.

A NESCAUM study shows the testing variability that may result from ASTM 3053. NESCAUM tested six wood stoves, including five that used ASTM 3053 for their certifications and one that used Method 28R. NESCAUM replicated the results of the stove certified using Method 28R—in other words, there was no substantial testing variability using that method. However, two of the five stoves using ASTM 3053 had high variability between the certification test results and NESCAUM’s results. NESCAUM determined that these stoves used non-typical fueling approaches, such as by burning short logs or logs stacked in unusual ways, which likely explained the variation in test results.

NESCAUM noted that manufacturers could generate more reliable ASTM 3053 test results by conducting certification tests in a manner that was more representative of consumers’ ordinary use of the stoves. For example, the manufacturer of one of the stoves in NESCAUM’s study used the ASTM 3053 test for certification, but with a representative testing technique (by loading the stove as a consumer would). NESCAUM found that that stove emitted almost exactly the amount in NESCAUM’s test that the stove was certified to emit.

3. Excerpts of HPBA Brief

David Chung, Counsel to HPBA

In the 2015 Rule, EPA set very low particulate matter (“PM”) emission standards for wood-fired residential heaters. Not only did EPA require manufacturers to achieve compliance with those low standards during the certification testing process, EPA also promulgated audit testing requirements that allow the Agency to require a manufacturer to retest an EPA-certified appliance either at the same laboratory that conducted the initial certification testing or at another laboratory unilaterally selected by EPA. These requirements are problematic because EPA did not account for the long and well established facts that: (i) the results of repeatedly testing an appliance at a single laboratory often vary significantly (intralaboratory variability); and (ii) there is even greater variability among the results of testing the same appliance at different laboratories (interlaboratory variability). This is generally referred to as “test method imprecision” or “testing imprecision,” but is sometimes also referred to as “test method uncertainty” or “test method variability.”

EPA tried to address test method imprecision in its prior (1988) new source performance standards (“NSPS”) for wood stoves in two ways: promulgating higher emission limits that assumed and accounted for a certain level of intralaboratory variability; and conditionally restricting where and how audit testing could occur, at least until EPA studied and better understood interlaboratory variability. Together, these safeguards helped divide the risk of test method imprecision between EPA and manufacturers, the overwhelming majority of which were—and still are—small businesses. This risk sharing was sensible in light of the inherently variable nature of wood burning and the many potential sources of variability given the complexity of wood heater test methods and the fact that testing can span nearly a full week.

EPA inexplicably proposed to make no such accommodations to account for variability in developing the 2015 Rule. HPBA thus commented at length about testing imprecision, urging the Agency not to require audit testing at all given the demonstrated magnitude of both intralaboratory and interlaboratory imprecision. HPBA also reminded EPA of the need to account for test method imprecision when setting emission standards if the Agency insisted on finalizing audit testing requirements. EPA’s proposal placed manufacturers in the unfair position of not only having to meet very low PM emission limits but having to achieve results that leave a large enough margin below the applicable limits to account for testing imprecision in the event their appliances are audited.

Faced with significant objections to its proposal to effectively ignore testing imprecision, EPA improperly dodged those objections by offering conclusory or illogical responses or (worse) ignoring them altogether. And EPA entirely failed to explain why, in the 2015 Rule, it abandoned the more sensible approach to audit testing and addressing test method imprecision it had codified in the 1988 Rule.

4. Excerpts of the NESCAUM memo

Lisa Rector, Policy & Program Director, NESCAUM

TO: NESCAUM Board of Directors

FROM: Barbara Morin and Lisa Rector, NESCAUM

RE: Reproducibility of Test Results in Step 2 Stoves

DATE: September 4, 2020

Development of new test methods for residential wood heating appliances has been part of Northeast States for Coordinated Air Use Management’s (NESCAUM’s) research agenda for the last eight years. As part of that initiative, NESCAUM purchased and tested several Step-2 certified appliances at contracted research laboratories during the past two years. The primary intent of that research effort was to determine how testing procedures affect emission performance measurements. To establish a foundation for this research, baseline particulate matter (PM) emission performance testing was conducted on the study devices using current certification test procedures. Note that the research lab did not attempt to replicate certification results, nor did it follow the detailed instructions manufacturers provide to the labs, which are sometimes identified in test reports.

The results of the NESCAUM baseline tests are also useful for informing discussions regarding the compliance audit specifications in US EPA’s 2015 New Source Performance Standards (NSPS) for Residential Wood Heaters.

Step-2 Pellet Stoves

The NESCAUM study evaluated three Step-2 certified wood pellet stoves with differing heat outputs and pellet delivery systems, identified here as Stoves 11, 13, and 14. The study tests were conducted according to the ASTM 2779 method, which is the Federal Reference Method (FRM) used to certify the compliance of pellet stoves with NSPS emission standards.

The emission results (ERs) measured in all of the pellet stove study runs were lower than 3.0 g/h, the audit test level that would trigger the initiation of revocation procedures. All of the softwood runs were also lower than the 2.0 g/h NSPS emissions limit for Step-2 stoves.

The results indicate that compliance audits are a reasonable requirement for assuring compliance with emission standards for pellet appliances. While ERs were substantially higher in runs with hardwood pellets than with softwood pellets, replicate runs with the same fuel produced reproducible results.

ASTM 2779 does not include specifications about the physical parameters of the pellet fuel used for testing. Because the composition of the pellets has a marked effect on the ERs, it is crucial that test reports include an elemental analysis of the pellets used in the test to enable a fair comparison with audit results. EPA should also consider requiring the use of pellets that are representative of the range of wood pellet types in typical consumer use, including hardwood pellets, in certification tests for these appliances.

Step-2 Cordwood Stoves

The NESCAUM research included the assessment of six Step-2 stoves. One of those stoves was certified using the EPA Method 28R (M28R) crib wood test, and the other five stoves using the ASTM 3053 cordwood method.

The ERs measured using the IDC alternative protocol for Stove 7, 12, 15, and 17 would not trigger the actions required when audit testing shows results greater than 150 percent of the standard. As in the baseline testing, however, the IDC ERs for both Stove 9 and 16 were substantially above the certification values and would trigger revocation proceedings. The considerably elevated emissions measured in those stoves, using both the baseline and alternative testing protocols, is evidence that the poor performance is attributable to poor combustion design rather than test method variability and precision issues.

Although the variability in the Stove 16 test runs was within acceptable parameters, the ERs in all runs in that stove were consistently elevated, suggesting that certification values for this appliance are not representative of in-use performance. Stove 9’s run variability was an outlier in the study, and its highly variable performance across testing methods supports the need for replicate testing and compliance audits.

Conclusions on Cordwood Stoves

The results of the baseline and alternative testing of cordwood stoves provide evidence that compliance audits are reasonable and necessary for assuring that those appliances conform with emission standards. Baseline and alternative test protocols measured ERs for four stoves was consistently below levels that would trigger revocation actions. The study identified two stoves with substantially elevated and, in one, highly variable emissions that would trigger further compliance activity. Analysis of additional data from the study indicated that elevated or variable emission levels did not result from test method precision or variability issues but instead were an indicator of elevated emissions performance. Problems with the certification testing procedures and operation of those two stoves would likely have been detected by compliance audits.


Taken together, the results of NESCAUM’s analysis indicate that the compliance audit requirement is reasonable and would be an effective tool for compliance assurance if fully implemented. The study was able to reproduce certification test results in both pellet and cordwood stoves according to the audit criteria specified in the NSPS, when those certification tests were conducted appropriately. Furthermore, the analysis demonstrated that an audit would likely identify substantial issues associated with unrepresentative operating and fueling procedures and with appliances that have highly variable performance.

The compliance audit requirement in the NSPS rule provides a mechanism for avoiding the inappropriate certification of high-emitting stoves. NESCAUM’s research indicates that replicate testing, such as is used in compliance audits, provides critical compliance assurance procedures necessary to maintain the integrity of the regulatory program. The data also suggest that the emissions measured in audits of well-designed appliances that have been certified using appropriate testing procedures will be acceptable within the tolerances specified in the current 2015 NSPS for Residential Wood Heaters. 

5. Excerpts from Intervenors' Brief

Respondent-Intervenors American Lung Association, Clean Air Council, and Environment and Human

Timothy Ballo of Earthjustice, counsel
for Intervenors

Health, Inc. (collectively “Intervenors”) embrace, but do not repeat, EPA’s argument that the rule under review reasonably accommodates testing variability, through both the emission standard levels EPA selected and the compliance audit process it prescribed. 

Petitioner Hearth, Patio, and Barbecue Association (“HPBA”) seeks to eliminate EPA’s ability to enforce the updated emission standards. HPBA does not contend the emission standards are themselves unlawful, nor does it attack the test methods EPA has adopted and through which HPBA’s members certify that their products comply with the standards. Instead, HPBA asserts that there is too much variability in test results for EPA to rely on audit testing to find that a wood heating device does not comply with the standards. In sum, HPBA’s position is that although the test method is accurate enough to identify products that HPBA’s members can sell, it is not accurate enough to identify products that they must stop selling. 

If this Court is persuaded that EPA has failed to explain aspects of its decision to adopt the audit testing regulations included in that rule or to respond to comments opposing that decision, vacatur is not the appropriate remedy. This Court should instead remand the matter to EPA for additional explanation. 

It is clear that EPA could take lawful action on remand to retain the compliance audit provisions HPBA has challenged. The more recent studies of variability discussed in EPA’s Brief show there is sufficient evidence to support a determination to retain the existing regulations. 

Supporting Amici have detailed the widespread problems with manufacturers’ certifications of compliance with EPA’s wood heating device standards and how manufacturers have implemented EPA’s test procedures in ways that yield favorable outcomes. Nor are Amici alone in recognizing that manufacturers have made choices when conducting certification tests that achieve compliance at the risk of generating unrepresentative values. For example, the lead author of the study HPBA relies on to claim EPA’s audit testing provisions are unreasonable has suggested the ratings achieved for certification purposes “are biased toward low values,” in part because labs select favorable start-up procedures and “may have imposed significantly tighter controls of fuel selection and arrangement than required by [EPA].”

6. Excerpts of HPBA's Corrected Reply Brief (filed on Oct. 15)

Amanda Shafer Berman, an
attorney for HPBA
The U.S. Environmental Protection Agency’s (“EPA”) brief is an exercise in post hoc rationalization. The Agency failed to provide a reasoned basis for its audit  testing requirements in the 2015Rule, which barely mentions—much less adequately explains—major changes in those requirements from the 1988 Rule. 

Nor did EPA analyze the key issue of interlaboratory variability, e.g.,by making findings on the magnitude of such variability, in promulgating the 2015 Rule.

EPA nonetheless asks this Court to uphold its decision to allow wood-fired heaters to be audit tested at any federal or private laboratory of EPA’s choosing— without making any allowance for interlaboratory variability—based on a combination of conclusory statements and its belated assessment of record data. These are not acceptable bases to uphold agency action. But even if this Court entertained EPA’s post hoc justifications, the information EPA now highlights does not support its decision, and this Court therefore should vacate (not merely remand) the challenged audit testing provisions given the seriousness of the errors and the lack of disruptive consequences that would result from vacatur. 

Having failed to support the 2015 Rule’s audit requirements on the merits, EPA attempts to avoid review on ripeness grounds. EPA argues that it intends to audit manufacturers rarely, so judicial review should await some future enforcement action. But the Clean Air Act (“CAA”) commands that pre- enforcement, facial challenges to EPA rules be brought within sixty (60) days of promulgation. And this Court has repeatedly held that legal issues such as whether the 2015 Rule’s audit provisions are reasonable and supported; whether EPA responded to comments; and whether EPA explained why it abandoned the 1988 Rule’s approach to auditing should—and indeed must—be adjudicated now.


Friday, September 18, 2020

AGH urges DOE's bioenergy office to expand focus of funding

The Bioenergy Technologies Office of the U.S. Department of Energy recently asked for input on promoting the development and testing of low-emission, high-efficiency wood heaters. The deadline to reply is 5:00 PM on Monday, September 21, 2020 and the Alliance for Green Heat (AGH) continues to urge stakeholders to provide feedback to the DOE.
Diagram of stove field testing unit.

We also urge stakeholders to reinforce points made by AGH in your submission to the DOE. Please feel free to copy any of the points we make below, put them in your own words and/or develop them further. If you feel any of our points are off-base and should be changed or expanded, please email John Ackerly at For more background, click here.

Dear DOE,

Thank you for requesting input through this Request for Information (RFI). We are especially thankful that BETO has embraced this relatively small effort to distribute $5 million to support developing and testing new wood heaters. We are also mindful that the effort required to run a $5 million grant program may be similar to the effort required to run a $50 million program.

The wood heating manufacturing community has not had this kind of support from a government agency in the past several decades. However, it came at a time when the manufacturing community was in the final stage of testing to meet the stricter 2020 EPA emission standards. Much of the community does not have experience applying for federal grants, which can be challenging for smaller firms.

R&D labs could apply to test stoves after certification to help assess effectiveness of designs on emission performance.

We are encouraged that some of the questions posed in this RFI may indicate BETO is open to expanding the focus of future grant cycles. Questions on the performance of stoves already installed in homes and field testing are important as they embrace the life cycle of heaters. Congressional language has urged BETO to “support development and testing of new domestic manufactured low-emission, high efficiency residential wood heaters.” Testing of new heaters can also occur once they are installed in the field. Testing can include various iterations of round robin testing before or after certification. And, the development of new heaters can include the development of component parts, software applications, and other essential stages in the development process, not just the final act of assembling a finished stove for certification.In short, we fully support BETO to follow the Congressional language and not add additional restrictions or preconceptions about the traditional stove certification process.

We think that the barriers to developing and testing new stoves are not the only barriers stove manufacturers face. Thus, we are unsure if the list of technical questions you ask will solicit robust feedback on many key issues pertaining to the development of heaters. The engineering expertise and solutions to these questions can be built up. Many academics, non-profits and jurisdictions are eager to engage in more field testing of new stoves, and to do additional types of testing before deployment. 


Norbert Senf, AGH's board chair, introducing the SBI team at the 4th Stove Design Challenge. SBI later won one of the DOE grants with their US partner.

We understand from discussions with industry that few of the larger mainstream stove manufacturers have applied for grants in the last two grant cycles. Yet, there are urgent funding needs in the broader wood heating sector to help the development and testing of genuinely cleaner and more efficient wood heaters.

Renewable energy technology development often happens quickly when there is significant government subsidies and expanding consumer demand. The DOE’s programs supporting solar PV, paired with Congressional support for significant tax breaks, is a good example.

BETO’s program can help on the technical side of this equation by promoting the development and testing of heaters that meet the requirements of modern renewable energy incentive programs. These programs often need to better understand field performance characteristics of the technology in question.

Round robin testing at US stove labs are badly needed to assess testing variability.

Unlike some European counties, U.S. federal and state agencies have barely ventured into the realm of aggressively promoting the cleanest heaters, which first requires the development and testing of classes of heaters that are appropriate for greater deployment. State policy frameworks are beginning to shift from decarbonizing electricity solely to also include decarbonizing heat, and it is likely that the federal government will do so as well in coming years. BETO can play a vital role in preparing for this by focusing on technical issues related to heater development and testing.

We are providing answers to those questions where we have the most expertise and where we think BETO can be most influential.

Technological Barriers

1. What are the critical technical hurdles for improving performance of stoves for new installations (e.g. combustion chamber design, combustion air management, controls, mixing, sensors, etc.)?

A. We applaud BETO’s focus on supporting efforts to develop automated heater controls, as these are one of the most effective ways to improve performance over the lifetime of the heater.

2. What are the critical technical hurdles for improving performance of stoves already installed in homes (e.g. combustion chamber design, combustion air management, controls, mixing, sensors, etc.)?

A. Some technical solutions, such as adding an ESP, exist; however, these quickly can become more expensive than a stove replacement. The most cost-effective changes relate to the fuel used, and significant change in this area may require new local and state firewood regulation. For BETO’s mandate to support not just the development of heaters but also testing, there is much work to be done on testing new heaters that have just been installed in homes to better understand how performance can be improved.

3. What practical and new techniques are used to significantly reduce transient emissions (startup, shutdown, load changes)?

A. Automation of stoves is one of the most promising ways to improve transient emissions. Changes in test methods are also vital, and test methods depend on developing data about transient emissions and making that data transparent to the public.

4. What practical and new techniques are used to measure transient emissions that could be implemented in laboratory or field testing?

A. There is an increasing variety of technologies to measure not just transient emissions, but all emissions, both in the lab and in the field. The problem is that there is little funding or mandates for them.

5. How can new exhaust emission control technologies be developed and practically deployed?

6. How could integrated hybrid systems, in which biomass heaters are combined with other technologies such as heat pumps, solar, and high efficiency gas and liquid-fired appliances, be a route to reduced emissions? What are the technology barriers to this approach?

A. Many of these systems exist as prototypes or are on the market, especially in Europe. There are few technology barriers to this approach. When policies mandate increasing residential renewable heating, hybrid systems will emerge to make use of the strengths of different technologies and the seasonal costs and availability of electricity, solar, biomass and stored energy. BETO could play an important role by focusing future FOAs on hybrid systems and making R&D funding available for the integration of wood heaters with heat pumps. Funding could be routed through heat pump companies, wood heater companies or even software companies to achieve this. Integrating solar thermal with biomass thermal also holds tremendous potential.

Annual emission testing using handheld devices like the Testo 380 is vital to understand impacts of wear and tear on emissions.

7. How could field measurement methods be improved to ensure that biomass-appliances do not create local air quality issues in long-term use?

A. Testing new heaters in real world settings is vital before and after the certification process. Manufacturers need equipment to enhance their beta testing in homes during the winter(s) before they finalize and certify products. Academics and non-profits can use existing or newly developed equipment to test emissions of newly certified heaters once they are installed in homes. In terms of ambient air quality, a variety of sensors, including the Purple Air sensor network, exist or could be developed to help understand impacts of stove groupings. States that have enforcement capacity and use opacity criteria in the field, such as Washington State, have experience with identifying and understanding why certain stoves may be particularly problematic. Sensors or sensor networks could also calculate the benefits of deploying the cleanest heaters, instead of perpetually trying to monitor, enforce and manage emissions of traditional certified wood stoves that can burn unseasoned wood at low air settings at any time.

8. What stove features commonly encourage end-users to purchase new or replace a wood heater? Or, what stove features are commonly attractive to the end-user?

A. Price is a top consideration. Clean glass is another. Aesthetics are always a driving factor. The actual or perceived ease of use can be very important. Heating capacity, log size and burn time are key for many consumers. There are also different considerations for wood versus pellet stove customers, and for those looking for a primary versus a periodic or secondary heater. Fuel management is also a big issue, with some operators switching to pellets to avoid the enormous work of wood stoves, and others giving up pellet stoves because they can’t lift 40-pound bags. For pellet stoves, durability, reliability and access to professional service should be higher priorities than they are currently. BETO could play a very productive role in developing durable pellet stoves that use interchangeable, easily sourced replacement parts, for example.9. What advantages or disadvantages would continuous field performance data provide for advancing stove designs?

A. This sort of data is extremely valuable, and funding programs to collect it would help develop and test new wood heaters. This data is also helpful in developing new test protocols, which in turn would lead to changes in stove design. Depending on the metrics produced and how they are communicated, data could help consumers operate stoves better. It could also help stove R&D departments, especially if the data came from the stove manufacturer's own stoves. If this data is only available in summary form via a regulatory agency, it would have diminished applications. There is tremendous potential and a wide range of opportunities to gather certain types of field performance for different stakeholders: users, neighbors, retailers, manufacturers, air quality agencies, academics, etc. Continuous field performance data is currently collected by solar PV installers, internet providers and auto makers, for example, for a wide variety of purposes. One of the most obvious is to help with remote trouble shooting, which in turn leads to the R&D of software and hardware that avoids those issues.

Tools and Capabilities

1. How are trial-and-error test methods used to improved stove performance and advance stove design (i.e. development by implementation of incremental change and testing)?

2. Is access to performance testing facilities a barrier to development?

A. Most mid-sized and larger manufacturers have their own in-house labs for testing. Increasingly, the definition of a testing facility or testing lab is broadening, as more affordable and handheld equipment comes on the market, enabling anyone to enhance their in-house testing capacity. The third-party labs used for certification have the capacity to handle testing but the time and cost involved is a barrier. If the time and cost involved were less, companies may engage in more R&D and update their stove designs more often. Currently, when a stove model gets certified, it can remain unchanged on the market for 10 or 20 years, or until required by the EPA to test again to meet a new NSPS.

3. What in-house test methods are relied upon to validate and facilitate wood heater development?

4. How much could rapid performance measurement methods shorten R&D test cycles?

5. What specific test methods would be of interest to your enterprise?

A. A variety of test methods and practices are of great interest to AGH, starting with cord wood testing using test methods involving multiple labs, or being used on new stoves after installation in the field.

Stove testing is often considered as exciting as watching paint dry. Here, AGH researcher Gabriel McConnel assists in DOE's Brookhaven lab in advance of a Stove Design Challenge.

6. How are modeling and simulation tools being applied to improve wood heater designs?

7. How could modeling and simulation tools be improved to meet your needs?

8. What are the fundamental modeling gaps to enable broader use of modeling and simulation such as Computational Fluid Dynamics (CFD) to improve wood heater design?  

9. How are current measurement methods meeting your needs for evaluating performance and emissions from wood heaters? What could be done better?

A. Current methods usually do not evaluate heater performance apart from the narrow conditions under which they were tested. There is much potential in affordable measurement methods. The more complex part is whether manufacturers will have the motivation to use them.

10. What performance/emissions measurements are most challenging to obtain? What makes obtaining these measurements challenging?

11. What are three primary challenges your enterprise faces for advancing stove designs?

A. 1. Funding. AGH could engage in extensive activities to advance stove development and testing with more funding.

2. Lack of a more robust community of academics, non-profits, agencies and private sector companies involved in innovative stove designs and testing.

3. Lack of policy frameworks that focus on decarbonizing residential heating and a lack of incentives for the very cleanest and most efficient heaters.


John Ackerly,


Alliance for Green Heat