I recently participated in a small working group that was addressing potential updates to the ASTM Standard on Masonry Heaters to include Rocket Mass Heaters in order to make it possible for them to be permitted throughout the United States, and by extension potentially Canada. Below is a letter that I delivered which explains my current position. I am publishing it here both to share that this initiative is in the works, to share my concerns about its current status, and also to see what others’ opinions are.
On behalf of our business Firespeaking, LLC and as a representative of the Masonry Heater Association’s Technical Committee, I recognize and appreciate your efforts in working to include Rocket Mass Heaters in the code with the goal of making clean-burning and efficient wood-fired heat more accessible from both an economic and legal standpoint.
While I wholeheartedly agree with the intention, I do not think that the proposed amendments to the ASTM E1602 that you are bringing forward have been made with enough consideration nor so far shown to have sufficient support by other stakeholders to merit a change to this standard at this time. As we have discussed, the existence of this standard is important to many people’s livelihoods and it is currently functioning very well to address the interests and concerns of diverse parties including masonry heater builders, designers, building officials, homeowners, and the insurance industry.
As Chip Clark of the Brick Industry Association has stated, there is an important choice to be made as to whether these efforts are directed towards including Rocket Mass Heaters in the E1602 Masonry Heater standard or whether an effort is made to create a new standard. He has also reminded us that any substantial and consequential changes to a standard referred to in the IRC/IBC codes requires review and approval at the ICC level for the updated standard to be considered vigilant.
In my understanding and to provide a summary for colleagues, there are 2 major items being proposed:
- the inclusion of rocket mass heater schematics in the list of recognized masonry heater designs, including the open down-drafting J-tube assembly as a recognized firebox for fueling heat exchangers.
- the use of metal in heat exchange assemblies including the use of a metal barrel, likely recycled, as a significant heat exchanger immediately outside of the firebox and the use of stovepipe as the inside layer of heat exchange channels.
Without going into too much detail, I don’t think that enough information has been presented to address potential concerns. While being a student of this fascinating and innovative firebox myself and having lived with one occasionally, I find it to require a level of kindling preparation and general fire-making ability and attention that I would not ascribe to the general public (at this time) in order to successfully establish and maintain draft in the heat exchanger and not cause smoke in the dwelling.
Inclusion of metal in the list of materials and heat exchange strategies is an interesting subject. It has relevance in discussion of masonry heaters as long as the overall weight of the unit is at least 1760 lbs., which is a part of the definition which easily distinguishes a unit from a woodstove. Both in the case of the barrel and the use of metal in the form of stovepipe in the heat exchange assemblies, I recommend more specific and complete definitions of the metal being used (type, specifications, gauge thickness). It has been generally accepted in the industry that stainless pipe be used to line heat exchange pathways although I don’t believe it is specifically referred to as a material. Your suggestion that 10 years be an acceptable expected lifetime for potentially corrodible materials is way below the threshold of life expectancy that a mason is usually considering and likely also under the convenience threshold of a customer investing in this type of appliance.
Quite frankly, one of my biggest concerns in the process so far is the lack of representation by stakeholders in the rocket mass heater community (eg. the voice of builders, book authors, supporting manufacturers). I would consider this a requirement to reach a standard. I have some sense that you may be speaking on others behalf which is commendable, but I recommend that you bring more people with experience to the (documented) table.
When I look at the “Codes for Rocket Mass Heaters for Portland, Oregon” document referred to, I can’t help but think that the extent of its definitions warrant a separate standard rather than extend and dilute a standard that is currently functioning.
In conclusion, I think that the inclusion of the rocket mass heater in standards which guide builders and ultimately serve the insurance industry is an interesting cultural proposition with both potential and challenges. My goal has been to share thoughts which both caution and inform the effort.
Regards,
Max Edleson
For some additional context:
- I consider Batch Box “Rocket” Mass Heaters with doors in the category of masonry heaters.
- It is the current unanimous recomendation of the MHA Technical Committee that a separate, specific ASTM standard be developed should the RMH community want to pursue this effort further.
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