As of 2012, they have a 1-week approval process in Portland, Oregon! See below for details on applicable building codes.
If you don't live in Portland, there are still some good resources out there. A rocket mass heater
- may be exempt from EPA regulation (by weight, as a site-built masonry heater it is not a woodstove);
- may be insurable or permittable in other locations if built to the International Residential Code specs under R1002, including 'supervised or build by an experienced masonry heater builder' (ASTM standard 1602-03).
Rocket Mass Heater books and info:
Earthen building experts and links:
Building code regarding Masonry Heaters: Oregon Interpretive Ruling No. 93-47
Residential Specialty Code, Chapter 9 & 10. Cf Section 925: "Masonry stoves shall be constructed in accordance with the Building Code."
Oregon Structural Specialty Code, Chapter 10: Chimneys and Fireplaces, section R1002: Masonry Heaters (link)
Not a woodstove per DEQ: Woodstoves are under 800KG (1800 lbs) - OAR 340-262-0020
Here's the DEQ document in full:
Among other things, it says that a stove that's the main source of heat, a cookstove, or in a house whose income is below 125% of federal poverty levels, can be exempted from some (but not all) of the requirements.
The testing requirements for woodstoves (which a rocket mass heater isn't, by definition) and wood heaters (which are also supposed to be under 800 kilos, these are wood-fueled furnaces and boilers for the most part) ...
These standards are clearly designed to apply to manufacturers of retail stoves. They require testing "not to exceed 1 in 10,000 units," and in some cases as little as 1 in 100,000 units (if the manufacturer has consistently been successful in previous tests of this model).
There is no mention of site-built or masonry devices in these testing requirements.
Rocket Mass Heaters are not primarily a cookstove - there is another kind of "rocket stove" designed for cooking; the common feature is a short 'heat riser' that encourages hot burn and directs that heat to where it's wanted.
Here's the story of our quest to try this out for ourselves, which started in 2009.
We've been working with officials from the city of Portland to make it possible to get an official permit for a Rocket Mass Heater. As of summer 2012, there is a document approved through the Alternative Technology Advisory Committee (ATAC) that specifies the detailing for this 1-week approval process.
If you're wondering what is a Rocket Mass Heater in the first place, I suggest starting with this page: http://www.ernieanderica.info/rocketstoves
And for how it's going for testing and permits, I describe our experiences on my journal, here's a link to start with: http://www.journalscape.com/ecca (February 26, 2009)
The full version is also reproduced below- a highly amusing process, in retrospect.
The officials we worked with have been consistently friendly and informative. But they were at times baffled by what we were trying to do. Do not be surprised if in your area, nobody knows quite what to make of the whole thing. There are ways to smooth the path.
Relevant code sections include IRC Chapter 10 for Masonry Chimneys and Fireplaces (and especially R1002 for Masonry Heaters, here's the California version of R1002)
(Update: The finished code and drawings are now available at Portland's Building Design Services website as of summer 2012, under ATAC (Alternative Technologies Advisory Committtee). These guidelines can be used to design and apply for permits through the usual Alternative Appeals Process in Portland, and may be helpful in other locations. A big thank you to Joshua Klyber, Bernhard Masterson, Melora Golden, and all the other ReCode Portland and ATAC members who made this happen. Www.portlandonline.com/BDS/ATAC.)
We also want to get some EPA / UL testing done, to prove the claims about fuel efficiency, air quality, and heat delivery, and safety.
We are currently raising funds to pay testing fees for a prototype Rocket Mass Heater, either on-site or lab testing depending on the city's desired level of proof, and our budget. RMH's don't consume enough fuel to undergo woodstove testing, so a new testing protocol may need to be written and approved. One of our colleagues has looked into this, and there's a Washington state expert who could write and submit the necessary protocols for an indeterminate fee. The local testing lab (OMNI-Labs, near the Portland Airport) charges about $5,000 for standard woodstove testing.
If you are interested in contributing, you can make a donation via PayPal to [email protected]. Please specify whether the donation is for TESTING FEES (to be set aside for fees only) or for GENERAL RESEARCH (can be used for materials and supplies to support concurrent research projects, like refractory materials, temperature probes, travel and printing, or prototype fabrication).
So what if I want one this winter?
The biggest recommendation I would make to someone thinking about trying to get a permit for their own rocket mass heater:
If you go with "masonry heater" as the category (and there are good reasons to do so) you are likely to need a reinforced foundation. Ideally, you will want to get your design approved (under the mechanical permitting process) before building it. But this may be tricky, since the person making the decision probably won't have any idea what you're talking about.
That's why we are not too disappointed that we got the wrong permit by mistake. (We went ahead and built it as a result). At least this way, the inspectors get to actually see a working example while they try to make their decisions.
As a result of this, and the combined efforts of the citizen-led ReCode initiative and a city-approved Alternative Technologies Advisory Committee, we now have a process for permitting rocket mass heaters in Portland, OR.
Alternatives that might work for other situations:
1) Start the conversation with a tangible example. Build a prototype mock-up outdoors, and invite local officials to look at it (and sit on it, and feed it, and pet it) while they consider your permit application. They may request design or material improvements before permitting an indoor version. Many of these requests may be well-intentioned but unworkable. Try the changes on the outdoor mock-up first: some well-intentioned changes can seriously affect performance.
2) Submit designs, and use experts. Create a design, or get proven plans from someone experienced, and have an engineer or architect sign off on the drawings. Local officials are much happier approving something when a licensed professional is taking some of the liability off their hands (CYA drives policy, for sure). Likewise, some insurers will approve a masonry heater installation if you have an experienced masonry heater builder supervise or build the system. If your local experts are still not sure about it, send them to a workshop or put them in touch with us for questions. We like having engineers and architects in workshops - but we have to admit, we enjoy working with experienced masons and builders even more. Fire marshals and EPA inspectors can be fun too.
3) Build a non-permitted or exempt version. This is what most owners to date have done - and the reason why some back-to-the-landers deliberately seek out a location with minimal permitting requirements. Off-the-radar installations should still be constructed according to the best practice available, as you will be taking the responsibilities and risks upon yourself. Try to build it so as to qualify for a permit, or for an exemption, or both, in case of official inspection. Exemptions from EPA requirements may be made for antique woodstoves, wood-heat devices that are a household's only way to heat, or the only way to cook, and for devices that are over 900 KG (1870 lbs or so) and not causing any pollution complaints.
You may have better luck if you are in an area that has already accepted cob or earthen building as acceptable masonry practice, or if you have like-minded neighbors who are happy to live and let live. Some parts of Wyoming, Vermont, and other states, and some tribal reservations may not even adopt the residential codes, or may offer broad exemptions for owner-built or traditional building methods, leaving it entirely to owners' judgement what to build and how to live with the results.
Be aware that while many jurisdictions do not require permits for structures under a certain size (under 100 square feet to under 600 square feet) or for certain agricultural buildings (pole-barns, storage sheds, seasonal/camping facilities, etc), they may still require inspection once you start including utilities such as heat, electricity, or plumbing. If you get caught using an "outbuilding" for long-term residential purposes, you may be given a limited time to comply with certain requirements such as sanitary septic or inspected utilities. It's worth reading local requirements thoroughly, and having a good conversation with local officials to find out how enforcement works in practice before you admit to any particular project plans.
ASTM standard for Masonry Heaters: 1602-03
Oregon Interpretive Ruling 93-47
Residential Specialty Code Section R1002 for Masonry Heaters
and the Rocket Mass Heater code-style guidelines for Portland, Oregon: Www.portlandonline.com/BDS/ATAC.
If you are trying to get a permit, or have been able to build a permitted rocket mass heater in your region, we'd love to hear about it.
Erica and Ernie Wisner
So where does that leave our traditional, earthy, masonry fireplaces?
- Rumford fireplaces are already in code - in many parts of the US they are approved under the same EPA categories as a certified insert or woodstove, based on their much lower contribution to local smog compared to cruder square fireplaces. In Portland, you can even build a Rumford fireplace with cob (monolithic adobe) under a local code variance that was just created through Portland's Alternative Technologies Advisory process. (Rumford diagram from www.HJMasonry.com, Maryland)
- Masonry heaters have been permitted in the US for at least 15 years, and exempted from EPA regulation by weight (each is site-built of tons of masonry, and can't effectively be transported to a testing lab. But they are known to be cleaner-burning than most commercial alternatives. (They have been a proven, high-end combustion technology for home heating in Europe for several centuries, and larger versions have been approved for some commercial buildings.)
So what about Rocket Mass Heaters?
Here's the story of our attempt to build a Rocket Mass Heater, legally, under City of Portland building codes. (Journal entry at www.Journalscape.com/Ecca
(for devices which meet the definition of a woodstove): Average particulate emissions less than 4.1 g/hour, as proven by tests on not more than 1 in 10,000 of any given model of stove produced. (One in 5,000 if they were within 30% of the allowable limit on their last test.)
§ 60.532 Standards for particulate matter.
(i) At burn rates less than or equal to
2.82 kg/hr (6.2 lb/hr),
C = K1BR + K2
BR = Burn rate in kg/hr (lb/hr) K1 = 3.55 g/kg (0.00355 lb/lb)
K2 = 4.98 g/hr (0.0.011 lb/hr)
(ii) At burn rates greater than 2.82 kg/hr (6.2 lb/hr), C = 15 g/hr (0.033 lb/hr).
(2) An affected facility not equipped with a catalytic combustor shall not discharge into the atmosphere any gases which contain particulate matter in excess of a weighted average of 7.5 g/400 Environmental Protection Agency
hr (0.017 lb/hr). Particulate emissions shall not exceed 15 g/hr (0.033 lb/hr) during any test run at a burn rate less than or equal to 1.5 kg/hr (3.3 lb/hr) that is required to be used in the weighted average and particulate emissions shall not exceed 18 g/hr (0.040 lb/ hr) during any test run at a burn rate greater than 1.5 kg/hr (3.3 lb/hr) that is required to be used in the weighted average.
[53 FR 5873, Feb. 26, 1988, as amended at 60 FR 33925, June 29, 1995; 65 FR 61764, Oct. 17, 2000]
(3)(i) Except as provided in paragraph (o)(3)(iii) or (o)(5) of this section, the manufacturer or his authorized representative shall conduct an emission test on a randomly selected affected facility produced within a model line certified under § 60.533 (e) or (h), on the following schedule: If weighted aver-age certification test results were— If yearly production per model is— <2500 >2500 70% or less of std When directed by EPA, not to ex-ceed once every 10,000 stoves. Every 10,000 stoves or triennially (which-ever is more frequent). Within 30% of std Every 5,000 stoves Every 5,000 stoves or annually (whichever is more frequent). ...
Exciting - a snippet of emissions testing data from a rocket mass heater researcher in the Netherlands: Peter tests Rinchen's 8" equivalent Rocket Mass Heater
This may not be very representative of all rocket mass heaters, but it's the first emissions data I've seen.
SECTION R1002 MASONRY HEATERS
R1002.1 Definition. A masonry heater is a heating appliance constructed of concrete or solid masonry, hereinafter referred to as masonry, which is designed to absorb and store heat from a solid-fuel fire built in the firebox by routing the exhaust gases through internal heat exchange channels in which the flow path downstream of the firebox may include flow in a horizontal or downward direction before entering the chimney and which delivers heat by radiation from the masonry surface of the heater.
R1002.2 Installation. Masonry heaters shall be installed in accordance with this section and comply with one of the following:
R1002.4 Seismic reinforcing. In Seismic Design Categories D0, D1 and D2, masonry heaters shall be anchored to the masonry foundation in accordance with Section R1003.3. Seismic reinforcing shall not be required within the body of a masonry heater whose height is equal to or less than 3.5 times it's body width and where the masonry chimney serving the heater is not supported by the body of the heater. Where the masonry chimney shares a common wall with the facing of the masonry heater, the chimney portion of the structure shall be reinforced in accordance with Section R1003.
R1002.5 Masonry heater clearance. Combustible materials shall not be placed within 36 inches (914 mm) of the outside surface of a masonry heater in accordance with NFPA 211 Section 8-7 (clearances for solid-fuel-burning appliances), and the required space between the heater and combustible material shall be fully vented to permit the free flow of air around all heater surfaces.
1.1 This guide covers the design and construction of Rocket Mass Heaters, a subset of solid fuel burning masonry heaters. It provides dimensions for site constructed rocket mass heaters and clearances that have been derived by experience and found to be consistent with safe installation of those rocket mass heaters.
1.2 Values given are in English measurements, and are regarded to be standard. All dimensions are nominal unless specifically stated otherwise. All clearances listed in this guide are actual dimensions.
2.1 Combustion unit: The area where fuel is consumed and clean exhaust produced; comprising the fuel feed, burn tunnel, heat riser, barrel, and the manifold.
2.2 Combustion unit base: Area composed of the fuel feed, burn tunnel, insulation and casing.
2.3 Fuel/air feed: Area where fire is lit and fuel is added. This is the sole air intake.
2.4 Burn tunnel: Horizontal area where initial combustion occurs.
2.5 Heat riser: Internal chimney, insulated for high-temperature combustion and draft.
2.6 Barrel: Metal or masonry envelope around the heat riser that radiates heat.
2.7 Manifold: The connection between the combustion unit and the heat-exchange ducting.
2.8 Heat-exchanger: The area that absorbs heat from the heat exchange ducting and re-radiates it over an extended period of time. Comprised of the heat exchange ducting, thermal core and casing.
2.9 Heat exchange ducting: The flues that carry hot exhaust gas through the thermal mass.
2.10 Thermal core: Area directly around heat exchange ducting.
2.12 Flue exhaust: The portion of the ducting after it leaves the thermal core.
3. Significance and use:
3.1 This guide can be used by code officials, architects and other interested parties to evaluate the design and construction of rocket mass heaters. It is not restricted to a specific method of construction, nor does it provide the principles to be followed for the safe construction of rocket mass heaters.
3.2 This guide is not intended as a complete set of directions for construction of rocket mass heaters.
3.3 Construction of rocket mass heaters is complex, and in order to ensure their safety and performance, construction shall be done by or under the supervision of a skilled and experienced rocket mass heater builder.
4.1.1 6" flue rocket mass heaters can be installed for any heated space 1000 sq. ft. or less.
4.1.2 8" flue rocket mass heaters are typical and appropriate for any installation.
4.1.3 Cross sectional area shall remain consistent throughout the system except in the barrel and manifold, where it may be larger.
4.1.4 Ducting may be tapered to reduce diameter by 1" in the final third of its length to improve gas flow.
4.1.5 Total ducting length from manifold to exhaust outlet may be up to 60 feet, with 30 to 50 feet being typical. NOTE: Some configurations within this range may require special design consideration to ensure proper exhaust.
4.2 Dampers: Shall have no dampers installed that can obstruct free flow of exhaust gas. Exception: A two-way flap or valve which maintains >100% flow may be used between alternate exhaust paths.
4.3 Foundation: The combustion unit base, heat exchanger (no more than 36" in height from foundation), and bench back (no greater than 48" in height from foundation) shall be supported by a 4" concrete slab or equivalent. All other configurations shall have an engineered footing.
4.4 Combustion unit: Shall be constructed in either earthen masonry or refractory materials. If refractory materials are used, an expansion joint shall be included between combustion unit and earthen masonry.
4.4.1 Mortars, when used, shall be clay-sand, fire clay or suitable refractory mortar. Mortars may be omitted if using monolithic earthen masonry as an external seal.
4.4.2 Fuel feed:
220.127.116.11 Shall be constructed of fire brick, clay brick or equivalent refractory material rated for over 2200˚ F.
18.104.22.168 Shall have an emergency shut down lid.
22.214.171.124 Shall be the sole air intake.
4.4.3 Burn tunnel:
126.96.36.199 Shall be constructed of fire brick, clay brick or equivalent refractory material rated for over 2200˚ F.
188.8.131.52 Shall be insulated with 2" of clay-perlite insulation or equivalent underneath, above, and on all sides except the fuel feed and heat riser openings.
4.4.4 Heat riser:
184.108.40.206 Shall have a minimum height of twice the burn tunnel length.
220.127.116.11 Shall be at least three times the height of the fuel feed.
18.104.22.168 Shall be constructed of firebrick, clay brick, metal flue or equivalent refractory material rated for over 2200˚ F.
22.214.171.124 If constructed of metal flue, it shall be free from holes, wrinkles, burrs, jagged edges or other obstructions. Metal shall be high-temperature stovepipe or steel.
126.96.36.199 Shall be insulated with minimum of 2" of clay-perlite insulation or equivalent.
188.8.131.52 Shall be free from holes, wrinkles, burrs, jagged edges or other defects.
184.108.40.206 Any existing paint or surface coatings shall be removed. High-temperature coatings rated for woodstove application such as stove enamel, cast-iron seasoning oils may be used.
220.127.116.11 A cleanout shall be located near the base of the barrel that allows access to the manifold and initial ducting, or the barrel shall be configured for removal.
4.5 Heat exchanger:
4.5.1 The heat exchanger rests on 4 inches of dry stack masonry, above or including the foundation.
18.104.22.168 Shall be metal flue, ceramic flue liner, or well pointed brick. Metal flue shall be free from holes, wrinkles, burrs, jagged edges or other defects.
22.214.171.124 Shall be embedded in a continuous layer of earthen mortar for both thermal contact and gas seal.
126.96.36.199 The length of ducting encased within the heat exchanger is typically 15 to 40 feet.
188.8.131.52 Shall have a sufficient number of cleanouts such that all sections of the ducting shall be accessible.
184.108.40.206 Cleanouts shall be the same minimum size as system:
4.5.4 Thermal core shall be
220.127.116.11 Total thickness from ducting to surface
18.104.22.168 Total thickness from ducting to surface
22.214.171.124 Casing shall be compatible with thermal core, such as earthen masonry finishes over an earthen masonry core. Portland cement casings are not compatible with an earthen masonry core.
4.6 Flue exhaust:
4.6.1 Flue exhaust may be a manufactured chimney, lined masonry chimney, or horizontal exhaust.
126.96.36.199 Manufactured chimney exhausts shall be installed according to manufacturer's instructions and local building codes.
188.8.131.52 Lined masonry chimneys or horizontal exhausts shall be suitable for
4.6.2 Exterior sections of exhaust shall be located away from building air intakes and occupied areas, and protected from wind, rain, and vermin.
4.7.1 Fuel feed: A minimum clearance of 18" shall be maintained from combustible materials to fuel feed.
4.7.2 Combustion base: A minimum clearance of 4" shall be maintained from combustible materials to all surfaces.
4.7.3 Barrel: A minimum clearance of 36" shall be maintained from combustible materials to all surfaces, if installed without a heat shield. A minimum clearance of 18" shall be maintained from combustible materials to all surfaces, if installed with a heat shield including 1" air gap.
4.7.4 Heat exchanger:
184.108.40.206 Minimum distance between ducting and combustible wall shall be 6".
5.1 Inspection Points for Rocket Mass Heater Installation:
The main inspection should be performed after combustion unit, ducting, and exhaust have been installed, and while ducting is still exposed.
5.1.1 Confirm measurements:
Ratio of heat riser to burn tunnel and heat riser:
___Heat riser is about twice the length of the burn tunnel, or taller
___Heat riser is about three times the height of the feed tube, or taller
Cross sectional areas:
___Consistent cross sectional area throughout system except barrel, manifold, and possible 1" decrease in final third of flue.
5.1.2 Confirm clearances:
___EITHER ___36" from all barrel surfaces to combustibles.
___4" from combustion base to all combustibles
___Room for sufficient masonry thickness around ducting.
5.1.3 Confirm maintenance elements:
___Cleanouts provide access to manifold, ducting, and exhaust.
___Exhaust outlet is properly installed, AND
___Maintenance and operation manual is in good order, with accurate as-built drawing(s).
5.1.4 Confirm structural elements:
___Foundation appears sufficient to support final installation (4” slab or engineered footing).
___Suitable earthen and/or refractory materials are being used.
5.1.5 Inspector may request that Rocket Mass Heater be fired. If so:
___Confirm proper drafting.
5.2 Inspection Points for Completed Rocket Mass Heater
For a previously completed or engineered installation, the following may be used:
___Confirm measurements, clearances, maintenance and structural elements, as above.
5.2.2 Confirm masonry integrity:
___Masonry thickness around ducting conforms to minimum standards (3-6” or more).
___No cracks apparent in casing or visible masonry.
___Casing materials are compatible with thermal core. (No cement stucco over earthen masonry).
5.2.3 Request that Rocket Mass Heater be fired. If possible, have applicants fire their heater the day before inspection, and then again in the presence of the inspector, to simulate normal operations.
5.2.4 Confirm performance:
___Draft and seals function properly; no indoor smoke observed.
___Exterior exhaust appears clean (white or transparent)
___Surface temperatures are within tolerances (Safe to touch, except barrel and fuel feed).
5.2.5 Check any special features:
Installations may include __Heat shield(s), __Exhaust chimney, ___Bypass valve, __Gaskets/expansion joints, __Structural reinforcements, or ___Other features.
Confirm that features
___Conform to as-built drawings.
___Appear to be properly installed and functional.