Introduction to the MHA

The Masonry Heater Association of North America

(MHA) was formed in 1984 to advance the technology of

masonry heating in North America and to increase the

knowledge and skills of professional heater masons. The

MHA fulfils its mandate by sponsoring laboratory

research into masonry heating technology, by working

with building and environmental regulators to ensure the

safe and appropriate use of the technology, and by

publishing information of interest to practitioners. The

MHA also maintains a professional training and certification program to recognize the competency of qualified

heater builders.

Membership in MHA is open to anyone and the

heater mason certification program has been made as

flexible as possible to encourage participation. The

certification program is intended to make it easier for

interested people to learn the skills and offer masonry

heating technology to the public; it does not function to

restrict entry to the trade.

What is a masonry heater?

An authoritative description was offered by three

respected wood combustion researchers, D.R.Jaasma,

C.H.Stern and J.W.Shelton:

“The chief distinguishing feature of these wood-burning

appliances is their ability to store heat. Combustion of a

load of fuel is intended to occur very rapidly and at high

temperatures, promoting improved combustion efficiency.

The energy released by combustion is transferred to the

large thermal mass of the appliance, and eventually

heats the living space surrounding the appliance.” (A

Preliminary Test Method for Masonry Heater Particulate

Matter and Carbon Monoxide Emissions, 1991)

A masonry heater that is designed and built according to accepted principles promoted by the MHA and its

members will burn cleanly (about 2 g/kg) and heat

effectively (about 65 per cent thermal efficiency).

Administrative office: Box 33M, Randolph, VT 05060

For more information about this document:

call (819) 647-5092

fax (819) 647-6082

email secretary@mha-net.org

visit http://www.mha-net.org

Why are masonry heaters not

EPA certified?

Masonry heaters cannot be tested according to EPA

procedures for wood stoves because:

a) the EPA test protocol requires the stove to be put on a

weight scale to determine the burn rate; this is impractical with a masonry heater which can weigh 8,000 lbs

or more,

b) EPA determined that starving a fire for air in order to

control heat output and lengthen the burn cycle is the

cause of most wood smoke; since masonry heaters do

not suppress combustion air flow, they cannot be

turned down to achieve the low burn rates required by

EPA and might exceed the maximum EPA firing rate

of 5 kg/h, depending on how the burn cycle is interpreted, and

c) they are site-built, either from prefabricated

components or standard refractory materials, and tend

to be configured specifically to match buyer

preferences and the house in which they are installed.

In developing its wood stove emissions regulation

back in 1988, the EPA was fully aware that an exemption

from testing and certification for masonry heaters would

not jeopardize the objective of reduced emissions from

woodburning systems, as this excerpt makes clear:

“The intent of the committee was to exempt from the

standards these appliances (masonry heaters) which rely

on clean-burning air-rich conditions and which have

high combustion efficiencies.” (Federal Register Feb.

1988, EPA 40 CFR Part 60)

Profile of a heater builder

Masonry heaters are sophisticated appliances that

have a long and proud history. In Europe, they were

designed and hand-built by skilled craftspersons who had

served extensive apprenticeships under the auspices of

trade associations called craft guilds. The MHA has

adapted this approach for the North American context as a

way for the industry to self-regulate and increase the skills

and knowledge of practitioners. A qualified heater mason

can custom tailor the appliance to meet the client’s specific

heating requirements as well as allow a wide range of

aesthetic expression. Heater builders choose to specialize

in this technology because it offers an environmentally

appropriate and aesthetically flexible alternative to conventional fireplaces. Heater masons are environmentally

conscious professionals who support clean air initiatives

and are not motivated to oppose, avoid or compromise

such regulations.
To be deemed to meet the EPA emissions

requirements for wood stoves, the design and

construction of a masonry heater must conform

to the following:

1. A masonry heater is a solid fuelled heating system

of predominantly masonry construction having a

mass of at least 800 kg (1760 lb) (excluding

chimney and foundation), and having an overall

average wall thickness of not more than 250 mm

(10 in.). It achieves heat storage by the routing

of exhaust gases through internal heat exchange

channels in which the flow path downstream of

the firebox includes at least one 180 degree

change in flow direction, usually downward,

before entering the chimney. The shortest

distance between the firebox exit and chimney

entrance is not less than twice the largest firebox

dimension. It is equipped with doors that are

intended to be in the closed position during the

burn cycle. Its combustion air supply system is

configured to produce a burn rate greater than

five kilograms of fuel per hour. The chimney has

a maximum flue size of 8 in. x 12 in. (200 mm x

300 mm) nominal rectangular dimensions, or 8 in.

(200 mm) round.

2. The masonry heater is constructed by a person

who holds a valid certificate of qualification

issued by the Masonry Heater Association of

North America, or the holder of such a certificate verifies in writing that the heater complies

in all respects with item 1. above.

Proposed language for the acceptance of masonry heaters in sensitive airsheds

Why responsible air quality

regulators can permit

masonry heaters

Air quality regulators recognize that the replacement of conventional wood stoves with EPA certified

models produces a clear environmental benefit. Similarly, the substitution of a conventional fireplace with a

masonry heater produces environmental benefits in two

ways; firstly by reducing smoke emissions and secondly

by displacing the consumption of other heating fuels.

While a masonry heater can be an attractive and

appealing feature of a house, its principal function is as

an efficient heating appliance. This characteristic

distinguishes the masonry heater from the strictly

decorative and wasteful conventional wood burning

fireplace. In this context, regulators should be aware that

while decorative gas fireplaces may not emit significant

particulate emissions, they waste natural gas, a fuel that

releases greenhouse gases both when it burns at the point

of use, as well as upstream during its extraction, refining

and distribution. The use of a masonry heater for heating

produces no net greenhouse gas emissions. A clear

environmental benefit.

A practical method for the

acceptance of masonry heaters

Because the emissions and efficiency performance

of a masonry heater is embodied in its structural design,

it is valid and appropriate to prescribe certain characteristics in a definition used for regulatory purposes.

Because a masonry heater is a sophisticated, site-constructed device that may be configured in a variety of

ways to meet buyer preference and the physical setting, it

is valid and appropriate to require the heater mason to

have professional accreditation.

The MHA has developed a simple means by which

air quality regulators can confidently permit the use of

masonry heaters. It consists of two parts:

1) a prescriptive definition of a masonry heater with

which an untrained person could easily distinguish

between a masonry heater and a conventional fireplace, and

2) a requirement that the unit be constructed or confirmed by a certified heater mason to increase certainty that it is indeed a heater and not a fireplace.

Below is the proposed text of a definition and

professional accreditation under which a masonry heater

may be accepted by air quality regulators.
1998 “Best Professional Judgement”

Emission Rates (EPA-600/R-98-174a) Ref. 1

Appliance type smoke g/kg

Conventional fireplace 17.3

Conventional Stove 18.5

EPA certified non-catalytic stove 6.0

EPA certified catalytic stove 6.2

Masonry heater 3.0

Actual test results of masonry heaters

Type Brand Lab smoke g/kg # of burns Ref.

Contraflow Heat-Kit1 OMNI 5.6 7 8

Contraflow Heat-Kit1 Lopez 4.5 1 3

Contraflow Heat-Kit1 VPI 2.5 15 2

Contraflow Tulikivi OMNI 5.7 7 8

Contraflow Tulikivi Lopez 3.7 21

È Pre-1991 air systems È

Í Post-1991 air systems Í

Contraflow Tempcast OMNI 3.0 7 7

Contraflow Heat-Kit2 Lopez 1.3 29 4

Grundofen Biofire OMNI 1.9 7 8

Grundofen Custom OMNI 1.4 7 8

Grundofen D.W.& S. VPI 1.0 20 2

Grundofen D.W.& S. OMNI 0.9 10 6

Swedish Mastercraft OMNI 1.9 7 5

Swedish Royal Crown OMNI 1.4 7 7

References

1. J.E.Houck and P.E.Tiegs Residential Wood Combustion Technology

Review, Volume 1. Technical Report, EPA-600/R-98-174a,

December 1998.

http://mha-net.org/docs/rwc01.PDF

2. R. Jaasma, J. W. Shelton and C. H. Stern, Final Report on Masonry

Heater Emissions Test Method Development, Wood Heating Alliance,

Washington, 1990

3. N. Senf, Recent Laboratory and Field Testing of Masonry

Heater and Masonry Fireplace Emissions, presented at the 87th

Annual Meeting of the Air and Waste Management Association,

Cincinnati, June 19-24, 1994.

http://mha-net.org/msb/html/papers-n/awma01/p-awma1.htm

4. N. Senf, Very Low Emissions Cordwood Combustion in High

Burn Rate Appliances - Early Results with Possible Implications,

presented at the 88th Annual Meeting of the Air and Waste

Management Association, San Antonio, 1995.

http://mha-net.org/msb/html/papers-n/awma02/p-awma2.PDF

5. S.G. Barnett, In-Home Evaluation of Emissions from a

Mastercraft Swedish Heater Kit Masonry Heater, prepared for

Mastercraft Masonry, Brush Prairie, (1993).

6. S.G. Barnett, In-Home Evaluation of Emissions from a Grundofen

Masonry Heater, OMNI-80119-01, prepared for Mutual Materials

Company, The Masonry Heater Association of North America, and

Dietmeyer, Ward and Stroud, Seattle, (1992).

7. R. Bighouse, S.G. Barnett, In-Home Evaluation of Emissions from a

Temp-Cast 2001 Masonry Heater, prepared for Temp-Cast 2000

Masonry Heater Manufacturing, Inc., Port Colborne, (1992).

8. S. G. Barnett, Summary Report of the In-Home Performance of Five

Commercially Available Masonry Heaters, OMNI 80132-01, prepared

for the Masonry Heater Association of North America, Reston, (1992).

Requirements for Certification

Professional Credentials Required

A candidate for MHA certification must demonstrate a working knowledge

of relevant housing and fuel burning regulations, and sufficient knowledge

of masonry work by providing proof* of successful completion of at least

ONE of the following:

(a) a bricklayer apprenticeship program

(b) certification issued by the Hearth Education Foundation (formerly

WHERF)

(c) certification issued by Wood Energy Technology Transfer Inc.

(d) or an equivalent professional credential deemed acceptable to the MHA

AND at least ONE of the following:

(a) 40 hours of work under the direct supervision of an MHA certified

heater mason

(b) successful completion of an MHA Hands-on Workshop and Test

* Proof of certification or participation, i.e. copy of certificate, diploma,

letter of successful completion. Other credentials can be judged for their

equivalency.

Field Experience

A candidate must provide evidence of a working knowledge of masonry

heater design and construction as set out in the MHA Occupational

Analysis Manual. The required evidence must consist of verifiable

documentation of THREE masonry heater construction projects

completed within the past five years. The candidate must have served as

the lead mason on at least TWO of the required projects. Required

documentation for EACH of the three projects must consist of the

following:

How masonry heaters compare with other woodburning appliance types

Note the dramatic reductions in emissions in post 1991 heaters, the result of research by MHA members.

Excerpts from the Heater Mason Training and Certification Policies and Procedures Manual

(a) ONE photograph of the heater in the process of construction and ONE

photograph of the finished unit

(b) a thorough description of the heater including firebox dimensions,

overall dimensions, wall thicknesses, main materials used, etc.

(c) the name and address of the client, and the date of construction.

Examination

(a) The candidate must achieve a passing grade on the MHA examination.

The passing grade is 70 percent.

(b) The candidate may take the examination before the other certification

requirements are met, but certification will not be granted until all

requirements are satisfied.

Maintaining MHA Certification

Annual Certification Renewal

To maintain MHA certification in good standing, a certificate holder will

pay an annual renewal fee of $50.

Continuing Education Requirement

Within each five year period after certification, the certificate holder will

successfully complete an MHA continuing education workshop and test, or

other relevant professional credential deemed equivalent by the MHA.

Failure to comply with the continuing education requirement will result in

withdrawal of certification.
the warmth and beauty of natural materials

the warmth and beauty of the natural fire

the environmentally responsible way

to burn wood at home.

a renewable energy solution

This is masonry heating . . .