Definition, photos, sketches of of Class-A chimneys, Metalbestos chimneys
Definition, photos, sketches of
Type B-Vents, Type L Vents
Definition, photos, sketches of Triple Wall Metal or Super Chimneys, 629 chimneys & 650-C Chimneys
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This article defines the types of manufactured metal chimneys. We explain the difference between Class-A Chimneys, Metalbestos chimneys, Type B Vents, Type L Vents, Triple Wall metal chimneys, and Super Chimneys, 629 Chimneys, and 650-C Chimneys. Each of these chimney types has specific intended uses, fire clearances, and installation requirements.
Readers of this article should also see Chimney Types & Materials.
We give definitions of these terms just below, but beware: different people will use these words with different meanings.
Define Chimney: a chimney is a passage through which smoke and combustion gases pass out of a building.
A chimney may be made of masonry such as brick, stone, or concrete block. Depending on its age and local custom, the walls of a chimney may be thin - a single brick in thickness or thicker (safer) made of several bricks or made of masonry block or stone.
A chimney may also be lined with clay flue tile liners, asbestos-cement transite pipe, cement, metal, or flexible stainless steel.
A chimney may also be constructed of metal, such as a double-walled Metalbestos™ insulated chimney.
A masonry chimney (lined with transite pipe) and a metal chimney are shown here in Carson Dunlop's sketch.
Define Flue: a flue is in most cases a synonym for chimney.
Define Vent: A metal chimney which is "thin walled" - either a single wall of metal or a thin double wall in some areas is called a "vent".
A double-walled metal flue used for venting gas fired appliances in the U.S. and Canada is a Type-B vent. In some areas a single-walled vent might be used for gas-fired equipment such as a water heater.
A single-walled metal vent or a Type-B vent would be unsafe if used to vent a woodstove or oil-fired equipment.
A metal vent is shown here in Carson Dunlop's sketch.
Define Flue Vent Connector: a flue vent connector is a metal pipe used to connect a heating appliance such as a heating boiler or water heater to its chimney or vent. Flue pipe and stack pipe are usually synonyms for flue vent connector. Generally a flue-vent connector is single-walled steel and must be routed with proper clearance from combustible materials. See Flue Vent Connectors - Boilers, Furnaces for details about single wall metal flues and their fire clearance requirements.
Types of Metal Chimneys and Metal Vents
Definition of Manufactured Chimneys
Manufactured chimneys of multiple metal walls or plastic have less weight than masonry chimneys and can be supported from the structure since they can
deflect as the building moves with no problem. Readers should also see our more broad list of chimney types at Chimney Types & Materials.
Some segmented cementitious
manufactured chimneys can be supported with a steel bracket bolted to
reinforced joists to carry the weight.
Often manufactured chimneys are enclosed in a wood-framed and sided structure for cosmetic reasons.
List of Manufactured Metal Chimney Types
Here are the principal types of manufactured metal chimneys. We discuss each of these in the articles below.
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Additional technical contributors & reference sources for this article are listed below.
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Thanks to Luke Barnes for suggesting that we add text regarding the hazards of shared chimney flues. USMA - Sept. 2008.
Arlene Puentes, an ASHI member and a licensed home inspector in Kingston, NY, and has served on ASHI national committees as well as HVASHI Chapter President. Ms. Puentes can be contacted at ap@octoberhome.com
Roger Hankey is principal of Hankey and Brown home inspectors, Eden Prairie, MN, technical review by Roger Hankey, prior chairman, Standards Committee, American Society of Home Inspectors - ASHI. 952 829-0044 - hankeyandbrown.com
NFPA 211 - Standards for Chimneys & Fireplaces, NFPA 211: Standard for Chimneys, Fireplaces, Vents, and Solid Fuel-Burning Appliances, 2006 Edition (older editions and standards are found at the same bookstore)
NFPA #211-3.1 1988 -
Specific to chimneys, fireplaces, vents and solid fuel burning appliances.
NFPA # 54-7.1 1992 -
Specific to venting of equipment with fan-assisted combustion systems.
GAMA -
Gas Appliance Manufacturers' Association has prepared venting tables for
Category I draft hood equipped central furnaces as well as fan-assisted
combustion system central furnaces.
National Fuel Gas Code, an American National Standard, 4th ed. 1988 (newer edition is available) Secretariats, American Gas Association (AGA), 1515 Wilson Blvd., Arlington VA22209, and National Fire Protection Association (NFPA), Batterymarch Park, Quincy MA 02269. ANSI Z223.1-1988 - NFPA 54-1988. WARNING: be sure to check clearances and other safety guidelines in the latest edition of these standards.
Fire Inspector Guidebook, A Correlation of Fire Safety Requirements Contained in the 1987 BOCA National Codes, (newer edition available), Building Officials and Code Administrators International, Inc. (BOCA), Country Club HIlls, IL 60478 312-799-2300 4th ed. Note: this document is reissued every four years. Be sure to obtain the latest edition.
Uniform Mechanical Code - UMC 1991, Sec 913 (a.) Masonry Chimneys,
refers to Chapters 23, 29, and 37 of the Building Code.
New York 1984 Uniform Fire
Prevention and Building Code, Article 10, Heating, Ventilating, and Air Conditioning Requirements
New York 1979 Uniform Fire Prevention & Building Code, The "requirement" for 8" of solid masonry OR for use of a
flue liner was listed in the One and Two Family Dwelling Code for New
York, in 1979, in Chapter 9, Chimneys and Fireplaces, New York 1979
Building and Fire Prevention Code:
"Top Ten Chimney (and related) Problems Encountered by One Chimney Sweep," Hudson Valley ASHI education seminar, 3 January 2000, contributed by Bob Hansen, ASHI
"Rooftop View Turns to Darkness," Martine Costello, Josh Kovner, New Haven Register, 12 May 1992 p. 11: Catherine Murphy was sunning on a building roof when a chimney collapsed; she fell into and was trapped inside the chimney until rescued by emergency workers.
"Chimneys and Vents," Mark J. Reinmiller, P.E., ASHI Technical Journal, Vol. 1 No. 2 July 1991 p. 34-38.
"Chimney Inspection Procedures & Codes," Donald V. Cohen was to be published in the first volume of the 1994 ASHI Technical Journal by D. Friedman, then editor/publisher of that publication. The production of the ASHI Technical Journal and future editions was cancelled by ASHI President Patrick Porzio. Some of the content of Mr. Cohen's original submission has been included in this more complete chimney inspection article: InspectAPedia.com/chimneys/Chimney_Inspection.htm. Copies of earlier editions of the ASHI Technical Journal are available from ASHI, the American Society of Home Inspectors.
Natural Gas Weekly Update: http://tonto.eia.doe.gov/oog/info/ngw/ngupdate.asp Official Energy Statistics from the U.S. Government
US Energy Administration: Electrical Energy Costs http://www.eia.doe.gov/fuelelectric.html
Books & Articles on Chimney Inspection, Testing, Diagnosis, & Repair
Ceramic Roofware, Hans Van Lemmen, Shire Library, 2008, ISBN-13: 978-0747805694 - Brick chimneys, chimney-pots and roof and ridge tiles have been a feature of the roofs of a wide range of buildings since the late Middle Ages. In the first instance this ceramic roofware was functional - to make the roof weatherproof and to provide an outlet for smoke - but it could also be very decorative.
The practical and ornamental aspects of ceramic roofware can still be seen throughout Britain, particularly on buildings of the Victorian and Edwardian periods. Not only do these often have ornate chimneys and roof tiles but they may also feature ornamental sculptures or highly decorative gable ends. This book charts the history of ceramic roofware from the Middle Ages to the present day, highlighting both practical and decorative applications, and giving information about manufacturers and on the styles and techniques of production and decoration.
Hans van Lemmen is an established author on the history of tiles and has lectured on the subject in Britain and elsewhere. He is founder member and presently publications editor of the British Tiles and Architectural Ceramics Society. Available at the InspectAPedia Bookstore.
Chimney & Stack Inspection Guidelines, American Society of Civil Engineers, 2003 - These guidelines address the inspection of chimneys and stacks. Each guideline assists owners in determining what level of inspection is appropriate to a particular chimney and provides common criteria so that all parties involved have a clear understanding of the scope of the inspection and the end product required. Each chimney or stack is a unique structure, subject to both aggressive operating and natural environments, and degradation over time. Such degradation may be managed via a prudent inspection program followed by maintenance work on any equipment or structure determined to be in need of attention. Sample inspection report specifications, sample field inspection data forms, and an example of a developed plan of a concrete chimney are included in the guidelines. This book provides a valuable guidance tool for chimney and stack inspections and also offers a set of references for these particular inspections.
NFPA 211 - Standards for Chimneys & Fireplaces, NFPA 211: Standard for Chimneys, Fireplaces, Vents, and Solid Fuel-Burning Appliances, 2006 Edition (older editions and standards are found at the same bookstore)
More Information on Building Diagnostic Inspections and Repairs
NFPA 211 - 3-1.10 - Relining guide for chimneys
NFPA 211 - 3-2 - Construction of Masonry Chimneys
NFPA 211 - 3-3 - Termination Height for chimneys
NFPA 211 - 3-4 - Clearance from Combustible Material
NFPA 54 - 7-1 - Venting of Equipment into chimneys
Brick Institute of America - Flashing Chimneys
Brick Institute of America - Proper Chimney Crowns
Brick Institute of America - Moisture Resistance of Brick
American Gas Association - New Vent Sizing Tables
Chimney Safety Institute of America - Chimney Fires: Causes, Effects, Evaluation
National Chimney Sweep Guild - Yellow Pages of Suppliers
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