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Metal B-Vent clearance codes & specifications:
Clearance distances for a B-vent to combustible materials in floors, walls, ceilings, attics, roofs.
This article series describes B-vent metal chimneys used for gas-fired appliances. We discuss fire safety, fire clearances, and other gas appliance venting details for b-vent chimneys.
We also provide a MASTER INDEX to this topic, or you can try the page top or bottom SEARCH BOX as a quick way to find information you need.
Ceiling, Wall & Wall Clearances for B-Vent "flue pipes"
Type B Chimney Fire Clearance Details
Sketch of a Type "B" vent provided courtesy of Carson Dunlop Associates [at REVIEWERS], a Toronto home inspection, education & report-writing firm. [Click to enlarge any image]
Type B-vents are double-walled metal chimneys/flues and can be used only with listed, draft-hood equipped gas appliances.
A Type B vent is intended for relatively low-heat applications.
B-vents are not permitted for use with incinerators and are not intended for use with appliances burning anything other than LP or natural gas.
Interior Installations of Gas Vent Connectors in all Buildings
Where the chimney extends through any zone of a building (outside that in which the heating appliance connected to it is located), it shall be provided with an enclosure having a fire resistance rating equal to or greater than that of the floor, ceiling, wall or roof assemblies through which it passes. (Selkirk 2015)
Vertical (Floor, Ceiling and Roof) Penetrations
All vertical penetrations where the vent passes through a combustible floor, ceiling or roof, require a Fire Stop (p/n 5x18CI) or Roof Jack be installed.
See Table 1 for proper framing dimension and refer to the Fire Stop or Roof Jack Section for proper installation. Non-combustible Floor, Ceiling & Roof Penetrations do not require a Fire
Stop or Roof Jack. (Selkirk 2015)
Horizontal (Wall) Penetrations
Horizontal systems passing through a combustible wall require the use of a Wall Penetration, for relative temperatures with clearances. See Table 1 for proper framing dimensions and refer to Wall Penetration section for installation instructions.
Non-combustible wall penetrations do not require a Wall Penetration. - (HeatFab 2015)
1) If a ceiling or wall has a fire resistance rating and is penetrated by a Models G, PS, or IPS Grease Duct, then the duct shall be enclosed with a continuous enclosure
extending from the penetration, through any concealed spaces, to or through the roof so as to maintain the integrity of the fire separations required by the applicable building
NOTE: If penetrated by Z3 or Z4 no additional enclosure is required however the appropriate Through Penetration Firestop (TPF) must be used. See Through
2) If a ceiling or wall does not have a fire resistance rating and is penetrated by a Model G, PS or IPS Grease Duct installed at the correct minimum clearance for unenclosed duct, then no enclosure is required.
3) Where the Model G, PS and IPS ducting extends through any story of a commercial building above that in which the connected appliances are located, it must be enclosed in the upper stories with walls having a fire resistance rating of not less than one hour for buildings of two or three stories in height.
If the commercial building is four stories or more in height, the enclosure wall shall have a fire resistance rating of not less than two hours. (Selkirk 2015)
Question: For a propane furnace flue pipe how much clearance is needed through ceiling area?
Brenda Grant said:
For a flue pipe from a propane furnace how much clearance is needed as it goes through ceiling area?
Can one put in metal mesh to prevent insects or critters from coming down from the attic?
Reply: use a ceiling shield, wall shield, collar, support that is Listed, Approved as a fire block and for fire safety
Where a metal chimney passes through building floors, ceilings, walls,
Most-common gas vent
If you are using a B-vent (typically a double-walled air-insulated vent for gas appliances, typically you'll see a fire clearance stamped right into the metal of the chimney, stating 1-inch MINIMUM clearance to combustibles - as you'll see in this photo
[Click to enlarge any image] You'll see that the manufacturer, Amerivent has stamped this Type B gas vent as requiring 1" clearance to combustibles.
If you cannot meet the 1-inch B-vent clearance you may be able to use a zero-clearance chimney material. More information: CLASS A CHIMNEYS, MetalBestos™
Possible gas vent
If you are using a "zero-clearance" insulated chimney such as CLASS A CHIMNEYS, MetalBestos™ the product label might it for zero clearance - or rated for in-contact with combustibles.
However a review of contemporary insulated chimneys such as the SuperVent and SuperPro by Selkirk frequrenly require a 2" fire clearance around most penetrations through building walls, floors, ceilings, roofs, unless the wall or floor is made of noncombustible material (like concrete).
Unlikely: single wall propane gas appliance vent
As you've read above, a B-vent is the proper venting connection between a conventional LP gas or natural gas heating appliance and the outdoors.
Occasionally we find an older installation of a gas fired heater that uses a single-wall metal flue between the appliance and a masonry chimney: this might be acceptable depending on local codes and restrictions where you live, if proper fire clearance distances are kept.
The proper term for this connector is a "flue vent connector" but plenty of normal people use the word "flue" or the phrase "stack pipe" loosely for any sort of chimney or chimney connector.
Watch out: a single wall metal flue vent is not safe if it passes through combustible floors, walls, ceilings, roofs.
How to Cover the Open Fire-Clearance Gap at B-vent Passage through Walls or Ceilings
Watch out: You do NOT and should NOT use a home-made insect screen to cover the fire clearance opening.
Rather you should buy a UL-Listed (approved for fire safety) Type B Gas Vent collar and firestop such as the MetalBest 104460 Galvanized RV 4" Type B gas vent collar and firstop or such as the MetalBest RV-GC shown in the photo below. The products you use for this application, if you're in North America, should be Tested and Listed to
UL1738 & ULC S636.
and widely available from your heating and plumbing supplier, building supply stores, and even online at Walmart.
Watch out: even using light-weight B-vent chimney sections, the total weight of the chimney extending up through the roof will require support at one or more locations, typically using a ceiling support, attic support, or roof support system provided by the manufacturer. Additional fire blocking and shields are required at each of those passages.
Watch out: Keep in mind that a building permit and inspection is usually required for installing a heating appliance and its vent or chimney - something that you might think you won't enjoy but something should ask-for, since the inspection will improve the safety of your home.
For Venting Residential, Commercial & Industrial Appliances Category I, II, III & IV Appliances, HeatFab, 5030 Corporate Exchange Blvd., Grand Rapids MI 49512 USA, Tel: 800-772-0739, Website: www.heatfab.com retrieved 2017/07/22, original source: http://heatfab.com/~/media/pigcins07302015.pdf
Commercial/Industrial Venting Products Sales Office Selkirk Corporation 5030 Corporate Exchange Blvd SE Grand Rapids, MI 49512 USA Tel: 800.848.2149 Selkirk Canada Corporation
375 Green Road Stoney Creek, ON L8E4A5 Tel: 888.735.5475 Website: www.selkirkcommercial.com retrieved 2017/07/22, original source: http://selkirkcommercial.com/~/media/selkirk/reference-documents/ common/file/installation/pressure-stacks/ model-psipspressure-stack/installation-instructionsmaintenanceguide.pdf
Excerpt: An Attic Insulation Shield must be installed where a chimney passes from a lower living space into an upper living space or into an attic space. It is designed to keep insulation materials from coming into contact with the chimney and will protect up to a 10" (250 mm) thickness of insulation.
Where height restrictions will not permit the use of the Attic Insulation Shield, an enclosure from the attic joist to the roof joist will be sufficient. All chimney enclosures must maintain the required minimum air space clearance of 2" (50mm) to the chimney.
When enclosing the chimney below the roof line, a Rafter Radiation Shield (RRS) must be installed at the roof level ...
UL 103 Type HT
Continue reading at TYPE B-VENT ROOFTOP CLEARANCE or select a topic from closely-related articles below, or see our complete INDEX to RELATED ARTICLES below.
Mark Cramer Inspection Services Mark Cramer, Tampa Florida, Mr. Cramer is a past president of ASHI, the American Society of Home Inspectors and is a Florida home inspector and home inspection educator. Mr. Cramer serves on the ASHI Home Inspection Standards. Contact Mark Cramer at: 727-595-4211 mark@BestTampaInspector.com
John Cranor is an ASHI member and a home inspector (The House Whisperer) is located in Glen Allen, VA 23060. He is also a contributor to InspectApedia.com in several technical areas such as plumbing and appliances (dryer vents). Contact Mr. Cranor at 804-747-7747 or by Email: email@example.com
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 firstname.lastname@example.org
Roger Hankeyis 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 #211-3.1 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.
"Chimneys and Vents", 789 CMR 68.00 Massachusetts Building Code, web search 10/15/2010, original source:
780 CMR: STATE BOARD OF BUILDING REGULATIONS AND STANDARDS
THE MASSACHUSETTS STATE BUILDING CODE - quoting: 6801.11 Multiple-Appliance Venting Systems.
Two or more listed and labeled fossil fuel-fired
appliances shall not be connected to a common
natural draft venting system unless permitted per
applicable requirements of 248 CMR or 527 CMR.
For solid fuel-burning appliances, see 780 CMR
Chimneys and Vents, Chapter 18, M1801,model building code - [on file as Code_Chim_Res_C_18.pdf] - widely used by U.S. & Canadian Municipalities,
"Model DFS L-Vent / Type B Gas Vent Installation Instructions", Selkirk Corporation, 5030 Corporate Exchange Blvd., Grand Rapids MI 49512, Tel: 800-433-6341 & Selkirk Canada Corporation, PO Box 526, Depot 1, Hamilton ON L8L 7X6, 888-735-5475, web search 10/15/2010, original source: www.mass.gov/Eeops/docs/dps/780%20CMR/780068.pdf
"Type L Temperature Venting Systems [on file as L_Vent_Metal_Fab.pdf] - ", Installation and Maintenance Instructions, Metal-Fab Inc., PO Box 1138, Sichita KS 67201, 316-943-2351, Email: email@example.com website: www.mtl-fabinc.com
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 - 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.
The Illustrated Home illustrates construction details and building components, a reference for owners & inspectors. Special Offer: For a 5% discount on any number of copies of the Illustrated Home purchased as a single order Enter INSPECTAILL in the order payment page "Promo/Redemption" space.
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.
Special Offer: For a 10% discount on any number of copies of the Home Reference Book purchased as a single order. Enter INSPECTAHRB in the order payment page "Promo/Redemption" space. InspectAPedia.com editor Daniel Friedman is a contributing author.
Special Offer: Carson Dunlop Associates offers InspectAPedia readers in the U.S.A. a 5% discount on these courses: Enter INSPECTAHITP in the order payment page "Promo/Redemption" space. InspectAPedia.com editor Daniel Friedman is a contributing author.
The Horizon Software System manages business operations,scheduling, & inspection report writing using Carson Dunlop's knowledge base & color images. The Horizon system runs on always-available cloud-based software for office computers, laptops, tablets, iPad, Android, & other smartphones