Gas Appliance Direct Vent Clearances Distances from direct gas vent to building features
GAS APPLIANCE DIRECT VENT CLEARANCES - CONTENTS: clearance distances required between a direct vent side wall terminal & building components, mechanical systems, windows, soffits, openings, decks, walks, etc.
POST a QUESTION or READ FAQs about the installation or diagnosis of sidewall vent or direct vent chimney or flue exhaust systems for heating appliances: oil, gas, other fuels firing heating appliances & fireplaces
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Direct vent exhaust clearance distances for gas fueled appliances:
Table & illustrations of the required space between a direct or side-wall vent for a gas fired heating appliance and building windows, doors, corners, gas meter, air intakes, sidewalks, balconies & decks and other building features.
This article series describes side wall vent systems for conventional & mid-range-efficiency heating boilers, furnaces & water heaters. We include for comparison, low temperature side wall vent systems used by high efficiency or condensing boilers, furnaces & water heaters.
Clearance Requirements for Direct Vented Gas Appliances
Exhaust Vent Termination Clearance Requirements
In a table below we provide a complete list of required clearance distances between the air intake or combustion gas exhaust vents for direct vented heating appliances.
[Click to enlarge any image]
Some highlights include:
The exhaust vent terminal shall be located at least 3-feet above any forced air inlet located within 10-feet.
See [the figure at page top] for a depiction [courtesy of Thermo Pride] of the minimum required clearances between vent terminations and building features according to the National Fuel Gas Code (NFGC).
The vent terminal shall be at least 12-inches below, 12-inches horizontally from, or 12-inches above, any door, window, or gravity air inlet into a building. The bottom of the vent terminal shall be located at least 12-inches above grade.
The exhaust vent terminal shall not be located:
over public walkways or over an area where wetting of surfaces by condensate, or water vapor, could create a nuisance or hazard,
near soffit vents, crawl space vents, or other areas where condensate or water vapor could create a nuisance, hazard, or cause property damage, and
where wetting of components by condensate, or water vapor, could be detrimental to the operation of pressure regulators, relief valves, or any other equipment.
The vent terminal shall be installed a minimum of 14-inches from any obstruction and 3-feet from an inside corner of an L-shaped structure (see table below).
Page top Illustration adapted from Thermo Products installation instructions - click to enlarge this or any other image or photo at InspectAPedia. 
Colour illustration of direct vent sidewall terminal clearance distances adapted from American Standard Furnace installation instructions that in turn cites ANSI Z223.1/NFPA 54 National Fuel Gas Code for US installations and cites CSA B149.1 Natural Gas and Propane Installation Code for Canadian direct vent gas vent installations.
Table of NFGC Recommended Clearance Distances from a Direct Vent Gas Appliance Terminal to Other Building Features
Direct vent gas exhaust termination item clearance
Distance to an air conditioner or heat pump compressor/condenser unit to the nearest point of a direct vent gas heater exhaust
24 inches to 6 feet [Note 6]
Distance to air intake and exahust vent openings of another direct vented gas fired appliance
At least 3 feet (0.9 m) above any forced air inlet located within 10 feet (3.1 m). [Note 9]
CSA B149.1, Natural Gas and Propane Installation Code
National Fuel Gas Code, ANSI Z223.1 / NFPA 54 
Gas Fired High Efficiency Furnace Down Flow & Direct Vent (Sealed Combustion) Thermo Pride Model CMA1-50N & CMA2-75N Installation and Service Manual"  [cites & recounts illustrations & clearances from the U.S. National Fuel Gas Code
Note 7 below
2. For non-direct vent applications such as the side-wall vent appliance shown earlier on this page, the required distance is much greater: 4 feet to the side or below the opening, or 1 foot above the opening.
Typical clearance from an operable window to a direct vented gas appliance vent outlet:
6 inches (15 cm) for appliances up to 10,000 Btu/hr (3 kW), 12 inches (30 cm) for appliances between 10,000 Btu/hr (3 kW) and 100,000 Btu/hr (30 kW), 36 inches (91 cm) for appliances above 100,000 Btu/hr (30 kW)
3. This distance requirement may vary in order to be in accordance with local building codes, the gas supplier, and the equipment manufacturer's own product installation specification
Clearance must be in accordance with local installation codes and the requirements of the gas supplier
3.a. for a gas fireplace exhaust termination cap, 3 feet (91cm) within a height of 15 feet (4.5m) above the meter / regulator assembly
3.b. for a gas fireplace exhaust termination cap, 3 feet (91cm) above - if within 10 feet (3m) horizontally
4. In direct vent applications, this clearance distance must be in compliance with local building codes, the requirements of the fuel gas supplier for the heating appliance in use, and the appliance manufacturer's instructions. For non-direct-vent applications (that is, side wall venting only), the required clearance is 7 feet.
A vent shall not terminate directly above a sidewalk or paved driveway that is located between two single family dwelling and serves both dwellings.
5. This is the author's OPINION based on other clearance distances and standards discussed in the article above.
6. This is the author's OPINION considering that heat from the gas exhaust vent blowing onto an A/C compressor unit condensing coil could impact the coil's ability to condense refrigerant back to liquid form, affecting the condenser unit's efficiency and life. I'm considering the situation in which the hot gas exhaust blows onto the air intake side of a condensing coil.
(Most modern condenser units draw cooling air in from the unit sides and push it out the unit's top).
In accordance with the current CSA B149.1 Natural Gas and Propane Installation Code.
In accordance with the current ANSI Z223.1/NFPA 54 National Fuel Gas Code.
8. Permitted only if veranda, porch, deck, or balcony is fully open on a minimum of two sides beneath the floor.
Watch out: there could be other more dangerous conditions: if the air intake vacuum created by the A/C compressor / condenser unit actually draws air or gases out from the nearby direct vent gas heater or from a passive-vented (atmospheric vented) gas fireplace appliance, that increased draft may impact the safe operation of the gas burner, risking dangerous or even fatal carbon monoxide hazards.
Separately, if a different compressor unit design caused the unit's exhaust to blow into the gas heater exhaust vent, that could prevent safe venting of exhaust gases. Where either these conditions are possible I'd increase the clearance distance to 10 feet or 3 meters.
Watch out: check with the manufacturer of your heating equipment to determine their recommended clearances between direct vent openings when you are installing multiple direct-vent appliances at the same building.
For help finding the manufacturer of your gas fired equipment see these two links offering both equipment installation and operating manuals and age decoding help:
B-VENT SIZING, Hart-Cooley [PDF], sizing guide for Type B Gas Vents for Category 1 Appliances, All Fuel Chimney for oil-fired appliances and open-face fireplaces, Hart & Cooley, 5030 Corporate Exchange Blvd. SE Grand Rapids, MI 49512 USA, Tel: (800) 433-6341 Website: hartandcooley.com retrieved 2017/09/26,
This Measure Guideline covers installation of high efficiency gas furnaces. Topics include: when to install a high efficiency gas furnace as a retrofit measure; how to identify and address risks; and the steps to be used in the selection and installation process.
The guideline is written for Building America practitioners and HVAC contractors and installers. It includes a compilation of information provided by manufacturers, researchers, and the U.S. Department of Energy (DOE), as well as recent research results from the Partnership for Advanced Residential Retrofit (PARR)
Building America team.
Content that can be shared with homeowners is written in a way that can be understood by that audience.
Dura-Vent Direct Vent Pro IO MANUAL [PDF], Venting System For Direct Vent Gas Stoves and Fireplaces, Simpson Dura-Vent, Inc. PO Box 1510 Vacaville CA 95696-1510 USA Customer Service Support 800-835-4429 wwww.duravent.com retrieved 2017/09/26,
Where you will find a table of all of the required minimum clearance distances from the vent outlet (or a vent intake) and other building features like windows and doors.
In GENERAL and excerpting from Goodman's GMVC96 Installation and Operation Manual,
The vent termination of a direct vent application must terminate at least 12 inches from any opening through which flue gases may enter a building (door, window, or gravity air inlet).
AND the Installation & Operation Manual for your Goodman heater because there are individual heater model-dependent safety and functional restrictions on how you can extend and route the vent piping between the heater and the exit point: there are constraints on the diameter and length of piping and also on the number and type of bends or elbows that can be used. If you violate these the system may not vent properly and it could be unsafe.
In the Goodman heater manual I use as an example (Watch out: you didn't give your heater model so this our excerpt may not be correct nor safe for you), and using a 60,000 BTUH Goodman MVC96/CVC96 Direct Vent (2 - Pipe) system, the maximum allowable length FOR THAT BTUh example depends on
the input BTUH rating of the specific heater
the vent pipe diameter used
the number of bends or elbows
specific installation instructions from the manufacturer for your heater brand and model
Assuming use of a 2" or 2 1/2" diameter vent pipe, with
1 elbow the maximum length can be 95 ft. ,
2 elbows, 90 ft.,
and so on, dropping another 5 ft. in length for each elbow up to a maximum of 8 elbows and 60 ft.
The company warns:
Adhere to these instructions to ensure safe and proper furnace
performance. The length, diameter, and number of elbows of the
vent/flue pipe and combustion air pipe (when applicable) affects
the performance of the furnace and must be carefully sized. All
piping must be installed in accordance with local codes and these
instructions. - Goodman MVC96/CVC96 Direct Vent manual cited below
You can find the Goodman furnace manual I cite at our list of HVAC manuals provided at GOODMAN HVAC MANUALS and there you will find contact information for the company so that you can be sure you have the correct instructions and the installation and operation manual for your specific heater.
Watch out: the Goodman furnace direct vent length table given below is adapted from that manual and it might not be correct for your heater and model. Check with your manufacturer or your supplier.
Example Table of Maximum Direct Vent Gas Furnace Vent Lengths
Goodman *MVC96/*CVC96 Direct Vent (2 - Pipe) and Non-Direct Vent (1- Pipe) 6
Maximum Allowable Length of Vent/Flue Pipe& Combustion Air Pipe (ft) 1, 2
Heater Input BTU Rating
Vent Pipe Diameter4 Inches
Number of Elbows in Total Vent Run3, 5
2 or 2 1/2"
2 or 2 1/2"
2 or 2 1/2"
2 or 2 1/2"
2 or 2 1/2"
2 or 2 1/2"
Maximum allowable limits listed on individual lengths for inlet and flue and NOT a combination.
Minimum requirement for each vent pipe is five (5) feet in length and one elbow/tee.
Tee used in the vent/flue termination must be included when determining the number of elbows in the piping system.
2 1/2” or 3” diameter pipe can be used in place of 2” diameter pipe.
increased Clearance Configurations using (2) 45 deg. Long Sweep elbows should be considered equivalent to one 90 deg. elbow.
One 90° elbow should be secured to the combustion air intake connection.
Source: GOODMAN TWO STAGE GAS FURNACE CV96 & MVC96 [PDF] Installation & Operating Manual, (Type FSP CATEGORY IV Direct
or Non Direct Vent Air Furnace), retrieved 2017/09/11, original source: https :// www.questargas.com/ ForEmployees/ qgcOperationsTraining/Furnaces/ Goodman_GMVC96_Installation.pdf
Watch out: the installation and operation manual used as an example here includes additional vent and vent termination requirements that must be respected for safety and for proper functioning of the heating equipment.
Use the "Click to Show or Hide FAQs" link just above to see recently-posted questions, comments, replies, try the search box just below, or if you prefer, post a question or comment in the Comments box below and we will respond promptly.
 "Instructions for Installing FIELD Type AF Barometric Draft Controls," Form No. 31 DC 30666, Field Corporation, Mendota, IL 61342, web search 04/02/2011, original source: http://www.fieldcontrols.com/pdfs/04592700.pdf, Field Controls, Kingston, North Carolina 28501, Tel: 919-522-3031
 Tjernlund Draft Controls, A Series (single action for oil, solid fuel, and fan-assisted gas burners) and B Series (double action for gas heating appliances), web search 04/02/1011, original source: http://www.tjernlund.com/Tjernlund_8500490.pdf , Tjernlund Products, Inc., 1601 Ninth Street, White Bear Lake MN 55110-6794, Tel: 651-426-2993 or 800-255-4208 website: www.tjernlund.com Email: firstname.lastname@example.org
 "Gas Side Wall Power Venters", Tjernlund Corporation, 1601 9th Street
White Bear Lake, MN 55110-6794 Tel: 800-255-4208, Website: tjernlund.com/gassidewall.htm, Quoting: Side Wall Vent Systems save time and money and are excellent for electric to gas/oil, renovations, new construction or for replacing deteriorated chimneys. Side wall venting saves costly materials and labor on two, three or more story runs. It also increases living space by cutting out interior chases. Proven safety interlocks assure proper exhaust, a feature conventional chimneys do not offer in today's homes and buildings.
 "Oil Side Wall Vent Systems", Tjernlund Corporation, 1601 9th Street
White Bear Lake, MN 55110-6794 Tel: 800-255-4208, provides SS2 SideShot Wall Vent System. Website: .tjernlund.com/oilsidewall.htm Quoting: The SideShot® models SS1 and SS2 SideWall Vent Systems include the UC1 Universal Control ... [ and are ] designed for oil fired heating equipment or a deluxe gas vent system. Factory wired safety and operating controls allow simple interlock with any burner. ... SS2 features a self-cleaning stainless steel, backward inclined impeller and sealed ball bearing motor for virtually maintenance free installations.
Tjernlund Corporation also provides a Sidewall Venting sizing tool for oil fired heating equipment (www.tjernlund.com/Sizing/Oil.htm) and a separate tool for gas fired heating equipment (www.tjernlund.com/Sizing/gas.htm).
 Bradford White Sidewall Power Venter Kit, Field Controls, Tel: 252-522-3031, Website: www.fieldcontrols.com
 National Fuel Gas Code (Z223.1) $16.00 and National Fuel Gas Code Handbook (Z223.2) $47.00 American Gas Association (A.G.A.), 1515 Wilson Boulevard, Arlington, VA 22209 also available from National Fire Protection Association, Batterymarch Park, Quincy, MA 02269. Fundamentals of Gas Appliance Venting and Ventilation, 1985, American Gas Association Laboratories, Engineering Services Department. American Gas Association, 1515 Wilson Boulevard, Arlington, VA 22209. Catalog #XHO585. Reprinted 1989.
 "Tankless water heater side wall vent termination", Rheem Corporation, Website: http://www.rheem.com/products/tankless_water_heaters/
 "Gold™ CGs Gas-Fired Water Boilers Venting Supplement: sidewall direct exhaust, vertical direct exhaust, sidewall direct vent, vertical direct vent models
 "Be Alert, Keep Sidewall Vents Clear", Vermont Gas Corporation, P.O. Box 467, Burlington VT 05402 Delivery: 85 Swift St, South Burlington VT 05403. Phone: 802.863.4511.
Email: CustomerService@VermontGas.com, web search 4/1/2012, original source: vermontgas.com/winter/vents.html
 "Power Venting, SWG/CV Power Venter, ComboVent Power Venter, Field Controls, FIELD CONTROLS, LLC
2630 Airport Road
Kinston, NC 28504
 "Gas Fired High Efficiency Furnace Down Flow & Direct Vent (Sealed Combustion) Thermo Pride Model CMA1-50N & CMA2-75N Installation and Service Manual", Thermo Pride, Thermo Products LLC, PO Box 217, North Judson, IN 46366, Tel: 574-896-2133, retrieved 12/30/2012, original source: www.thermopride.com/pdf/mg-508.pdf, copy on file as Thermo_Pride_CMA1-50N_CMA2-75N_Installation_mg-508.pdf
Carson, Dunlop & Associates Ltd., 120 Carlton Street Suite 407, Toronto ON M5A 4K2. Tel: (416) 964-9415 1-800-268-7070 Email: email@example.com. 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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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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