There has been a lot of work in the 'permitting' space over the past 5 years.
The answer does depend a lot on your local building officials - local politics is made up of local people responding to personal motives and past
experience.
That said,
There are three main concerns for building offices regarding rocket mass heaters:
1) EPA requirements: Not regulated. (Masonry heaters in general and most rocket mass heaters would be considered an exempt, site-built device, not currently regulated by EPA. Getting the EPA official letter of exemption takes about $4-5,000 in lab fees; we may be able to do an independent lab test and get an actual 'certificate of exemption' for our favorite model combustion unit within the next year or so). Unlike most manufactured appliances, there is no certification program for site-built masonry heaters, and unless you use a core kit there will be no EPA or UL stickers to reassure your inspectors.
2) Weight loads and structural support: Rocket mass heaters typically weigh a few tons, but that weight is distributed horizontally so the actual dead loads are something like 120-150 lbs/sf for most designs. Taller versions may be up to 450 lbs/sf. If you build on a 4" garage slab-on-grade, or a similar ground-level footing (compacted gravel has been used in many off-grid versions), the mass can't fall on anyone and structural considerations are pretty minimal. If building on top of a suspended floor, over a basement or occupied floor of the house, or in a manufactured home, structural issues may be much more considerable and require an engineer to continue with the permitting process.
3) Clearances to combustibles: If building in a
cob or masonry home with non-combustible walls, there are very few concerns about combustibles. If building in conventional buildings (stud-framed), we typically follow clearances for a non-certified woodstove around the barrel, ASTM masonry heater standards around the combustion unit and firebox, and the heat-exchange bench itself (when built properly) is a zero-clearance structure that can have cushions or fabric in direct contact.
Here are 4 approaches to permitting that have worked:
1) Stay under the requirements and under the radar.
If you don't have a mortgage, you are not required to carry home insurance, and you don't care about re-selling your property, you can stay off-grid and build non-permitted structures. This is the approach favored by Cob Cottage Company (they don't even own the
land the school is on, but have a lifetime lease from a local property owner who is passionate about ecological living); they routinely teach 'Get Off the Treadmill' workshops and also advocate building very small buildings (under 200 square feet) that generally fall under the permitting threshold and can be legally built without permits.
This is likely the cheapest, most
sustainable approach, and also a good practice exercise for those who are serious about alternative lifestyles. I have seen many full-scale, permitted homes with one or more small cob cottages ("sheds" for official purposes) in the back where the owners or guests stay when the whim takes them. Some owners even rent out the main house after fitting out their comfortable shed. Areas like Vermont, parts of Wyoming, and many rural counties may not have any residential building code requirements to speak of, and you can legally build whatever you choose, at your own discretion.
Of course, people who are interested in this approach are probably not even watching this
thread. It does pay to research your local building codes thoroughly, so that you can meet the letter of the local law / address their top-priority concerns (or at least convince an inspector that your structures do so). Knowing the law allows you to choose wisely and weigh the risks of any blatant violations.
2) Exemptions: Research local building requirements, and ask experienced local builders, to discover any useful exemptions.
- In many areas, non-certified 'woodstoves' can be exempt from burn bans or the EPA certification system if they are your only way to heat, only way to cook, or an antique. (This may not address insurance concerns, however). While most rocket mass heaters wouldn't qualify as a woodstove based on weight, they do tend to impress inspectors favorably based on surface temperatures and clean exhaust. If you do get a surprise inspection, and the inspector likes what he sees, it can make a big difference if these exemptions apply.
- Masonry heaters are exempted by weight under current EPA regulations (as is any solid-fueled appliance over 900 KG - about 1800 lbs). They may fall under a separate structural / mechanical permitting process to check the weight loads and clearances to combustibles. But if the building office doesn't have a permitting process for masonry heaters, you could make the argument that a permit is not required, follow the ASTM standard, and see how it flies.
- In some areas, there is a subtle distinction between permittable and non-permitted structures. In our area, for example, a 'pole building' or barn does not require a permit but a 'shop' or 'garage' does (to the best of my understanding, the distinction has to do with power and utility hookups, and whether there are poured cement slabs, foundations, or just post-and pier.). So a small difference in building design can make a big difference in permitting costs and requirements.
Know these local distinctions before you build.
- Cabins or seasonal housing (yurts for example) may not fall under the same requirements as permanent housing. Again, research local code, build to the best standard wherever possible, but use any applicable distinctions to reduce permitting requirements or spread them out over time.
- Likewise, some areas have really weird local restrictions - Reno, NV does not allow more than one wood-burning device per property / per acre for larger properties; if they see two chimneys you could be in trouble. Missoula, MT has a 'stagnation zone' where wood-burning devices are banned but older ones may be 'grandfathered in.'
Local research is essential. The above examples may not apply to your area.
3) Direct Inquiry to Insurance Agent: In several cases, owners just asked the insurance agent about building an exempt, site-built masonry heater. One of our clients did this; the insurance agent did a little research and then said "People improve their cabins themselves all the time; if you have someone who knows what they're doing on site to supervise the
project it
should be fine." (This substantially agrees with the ASTM standard, which specifies clearances to combustibles and that an experienced masonry heater builder either install or supervise the project.)
In this case, we did an on-site design consultation, advised about weight support and clearances, and the client did the bulk of the work himself and is very happy with the results. (He is one of the only people who's done a box-style 'portable' design, filled with 3/4"-minus gravel; he uses it on weekends only, but reports it has been doing great. Can't compare fuel efficiency with the full-mass versions because of the different usage pattern.)
I believe there have been several other 'insurance-approved' installations: in Georgia, in Vermont, and within up-to-code earthen buildings in California.
Many insurers simply require that all devices installed in a home be 'up-to-code,' and will refer you to the local building office if there's any question about what the local codes require.
4) Local Building Office: Before 'making the final decision,' some of our clients approach the local building office. The big question seems to be 'Have you permitted any masonry heaters in this area? What are the requirements, and what does it cost? If appropriate, you can discuss your research into hybrid masonry heaters (AKA rocket mass heaters), and that you are considering something more efficient and safer than a woodstove, but hoping to find a similarly friendly permitting process for about the same cost ($150-300 for most localities' woodstove installation permit).
The local building office may know whether an exemption or an appeals process would be workable. If they have never even heard of masonry heaters, and don't know how to permit an EPA-exempt site-built device that is neither a woodstove nor a fireplace, then you have a choice whether to engage and try to establish a local precedent for permitting them (a process that may take years and $$) or whether to walk away without revealing your address and say, "I'll keep thinking about it."
The
city of Portland, OR now has a 1-week approval process using a code-like set of parameters we helped develop; other areas may apply their usual process for approving a masonry heater or any large appliance.
We have more details of how that happened on our website at:
http://www.ernieanderica.info/rocketmassheaterpermitting
We also have a selection of building-official-friendly documents that summarize what a
rocket mass heater is, how it relates to existing codes and ASTM standards for masonry heaters in general, and some local findings and sample code from the Portland, OR permitting process. We also have an Owner-Operator Manual (with lots of fill-in-the-blank sections for the as-built drawings and site-specific details). We currently email a free copy to people on request, but I think I'll put them up on our online store for a token amount. (Our online sales site doesn't allow free downloads, but we can do something like $0.50 or $1.)
I'll post the link at our shop once I get them up:
http://www.ErnieAndErica.info/shop
Yours,
Erica W
4
...). I was showing my husband the video, and the first thing he said was: "It will never pass".
