Single-Wall Metal Vents and Chimneys: Inspection, Diagnosis, Cleaning & Repairs
SINGLE WALL METAL VENTS & CHIMNEYS - CONTENTS: Detailed Inspection & Photo Guide to single wall chimney defects. Obsolete single wall metal fireplace chimneys. Unsafe, damaged single wall metal chimney used for venting a gas appliance.
The single wall metal fireplace chimney shown at page top and shown again at below left was installed in a solid masonry fireplace in the 1960's.
It can no longer be safely used because of the new construction in the left of the photo. As you can see at below right, a building addition constructed close to the original single wall metal chimney has left it too close to the new structure. [Click to enlarge any image]
NFPA 211: single-wall pipe is not allowed for "chimneys" of one- or two-family dwellings, although may be used as connectors, i.e., between the appliance and the chimney, provided it is NOT "galvanized steel pipe" for a solid-fuel-burning appliance connector. NFPA 211:188.8.131.52
This chimney will need to be replaced with a modern insulated flue and extended in height. As long as the fireplace is not used, that corrective measure can be deferred.
The metal chimney shown at left is not a Type B gas vent and may be unsafe. Certainly it should not be in use for venting a heating appliance.
Do not mistake this single-walled vent for a Type-L vent nor for a Type-B vent even though a hasty glance may make it look like one of those.
This vent appears to be single-walled aluminum and it has what looks almost like a coffee can installed as a rain cap.
If the metal chimney we see in this photo is being used to "vent" a water heater it is probably not working and probably lacks adequate draft. The result may be carbon monoxide release in the building.
The very tall single wall metal chimney shown at left is located on a building in Manhattan and was photographed from the Lotus Club. Several stories tall you can see that the chimney is braced about every 12-feet, and is askew, loose, and rusty.
This chimey was so tall I could not photograph the entire structure in one image.
As a single walled chimney in a cold climate venting gas fired equipment, one might question its venting efficacy. In turn, condensation from poor venting might be a factor in that rusting.
Below: a single-walled metal flue extending through the wall of a barn that has been converted to a welding shop and sales facility on Highway 61 north of Duluth, Minnesota.
Single-wall metal pipes used to connect heating appliances to chimneys (metal or masonry) are discussed separately
at Single-Wall Metal Flue Vent Connectors where we provide details about single wall metal flues and their fire clearance requirements.
This article series on chimneys, chimney construction, and chimney safety provide detailed suggestions describing how to perform a thorough visual inspection of chimneys for safety and other defects. Chimney inspection methods and chimney repair methods are also discussed.
The remarkable single walled metal chimney shown at below-left was constructed using a "found" hollow aluminum electric lighting pole and is discussed by NHFireBear at CHIMNEY TYPES & MATERIALS
Dangerous Modifications to Single Wall Metal Chimneys & Flues, Passing Through the Metal Flue
Above: at this single wall metal chimney installed at a restaurant in Oxaca, Mexico, we noticed that the chimney installer and the handrail installer simply could not find an accord. Shown below in a closer look, the handrailing passes right through the chimney. Both the handrail and the chimney are unsafe.
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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.
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_Repair.php. 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 Building & Environmental Inspection, Testing, Diagnosis, & Repair
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
Carson, Dunlop & Associates Ltd., 120 Carlton Street Suite 407, Toronto ON M5A 4K2. Tel: (416) 964-9415 1-800-268-7070 Email: firstname.lastname@example.org. The firm provides professional home inspection services & home inspection education & publications. Alan Carson is a past president of ASHI, the American Society of Home Inspectors. Thanks to Alan Carson and Bob Dunlop, for permission for InspectAPedia to use text excerpts from The Home Reference Book & illustrations from The Illustrated Home. Carson Dunlop Associates' provides extensive home inspection education and report writing material.
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TECHNICAL REFERENCE GUIDE to manufacturer's model and serial number information for heating and cooling equipment, useful for determining the age of heating boilers, furnaces, water heaters is provided by Carson Dunlop, Associates, Toronto - Carson Dunlop Weldon & Associates Special Offer: Carson Dunlop Associates offers InspectAPedia readers in the U.S.A. a 5% discount on any number of copies of the Technical Reference Guide purchased as a single order. Just enter INSPECTATRG in the order payment page "Promo/Redemption" space.
The Home Reference Book - the Encyclopedia of Homes, Carson Dunlop & Associates, Toronto, Ontario, 25th Ed., 2012, is a bound volume of more than 450 illustrated pages that assist home inspectors and home owners in the inspection and detection of problems on buildings. The text is intended as a reference guide to help building owners operate and maintain their home effectively. Field inspection worksheets are included at the back of the volume.
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