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Direct vent clearance distances sketch - adapted from Thermo Products & NFGC Gas Appliance Direct Vent Clearances

Distances from direct gas vent to building features

  • POST a QUESTION or COMMENT 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

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.

Page top Illustration (black and white) adapted from Thermo Products installation instructions - click to enlarge this or any other image or photo at InspectAPedia. [15]

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.

InspectAPedia tolerates no conflicts of interest. We have no relationship with advertisers, products, or services discussed at this website.

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Clearance Requirements for Direct Vented Gas Appliances

Direct vent clearances from building components & features, adapted from codes cited (C) 2017 InspectApedia.com

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.

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.

[Click to enlarge any image]

Highlights of Gas Heater Vent Clearance Distances

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).[19] The building feature's letter symbol is defined in the below table.

Table of Gas Code Clearance Distances from a Direct Vent Gas Appliance Terminal to Other Building Features
  Direct vent gas exhaust termination item clearance Distance required (U.S.) Distance required (Canada)
A Distance above grade (ground surface), balcony, deck, porch, veranda

12 inches

[note that in areas of deep snow this clearance may be inadequate and thus unsafe]

 12 inches (30 cm)
B Distance to a window or door that is operable (can be opened) 12 inches [Note 2] or 6 to 36 inches depending on BTUH

6 inches (15 cm)
for appliances =/< 10,000 Btuh (3 kw),

9 inches (23 cm)
for appliances > 10,000 Btuh (3 kw)
and =/< 50,000 Btuh (15 kw),

12 inches (30 cm)
for appliances > 50,000 Btuh (15 kw)
C Distance to a permanently closed (or non-operable) window 12 inches [Note 3] [Note 3]
D Distance to a ventilated soffit (roof eaves, overhang) above the vent terminal & within a horizontal distance of two feet from the centerline of the terminal 24 inches [Note 3] [Note 3]
E Distance to an un-vented soffit 24 inches [Note 3] [Note 3]
F Distance to outside corner of the building 24 inches [Note 3] [Note 3]
G Distance from the vent centerline to a building inside corner 3 feet [Note 3] [Note 3]
H Distance to each side of centerline extended above a [gas] meter / regulator assembly 4 feet [Note 3] [Note 3]
I Distance to a [gas] service regulator vent outlet 4 feet [Note 3] [Note 3]
J Distance to a non-mechanical air supply inlet to the building or to the combustion air inlet for any other appliance

12 inches [Note 2]

6 inches (15 cm) for appliances =/< 10,000 Btuh (3 kw),

12 inches (30 cm) for appliances > 10,000 Btuh (3 kw) and =/< 100,000 Btuh (30 kw),

36 inches (91 cm) for appliances >
100,000 Btuh (30 kw)

6 inches (15 cm) for appliances =/< 10,000 Btuh (3 kw),

9 inches (23 cm) for appliances > 10,000 Btuh (3 kw) and =/< 50,000 Btuh (15 kw),

12 inches (30 cm) for appliances > 50,000
Btuh (15 kw)
K Distance to a mechanical [systems] air supply inlet

3 feet above if within 10 feet horizontally

6 feet (1.83m)

3 feet (91 cm) above if within 10 feet (3m) horizontally
L Distance above a paved sidewalk or paved driveway on public property 7 feet [Note 4] 7 feet [Note 4]
M Distance below a balcony, deck, porch, veranda

12 inches (30 cm) [Notes 7,8]

 24 inches [Note 3]
  Distances between a gas fireplace direct vent termination cap and other building features or mechanical systems See GAS FIREPLACE VENT CLEARANCE REQUIREMENTS

...

Opinions On Additional Recommended Clearance Distances from a Direct Vent Gas Appliance Exhaust Opening to other Building Features or Equipment
Distance from a clothes dryer exhaust vent wall termination to the nearest air inlet point on a direct vent chimney 10 feet [Note 5] - CLOTHES DRYER VENT CLEARANCES & TERMINATION
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 exhaust 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]

Notes to the tables above

1. Gas Appliance Venting Code Authorities/Sources

2. For higher BTU equipment vents

the required distance can be much greater: 3 or even 4 feet to the side or below a building air opening, or 1 foot above the opening.

At DIRECT VENTS / SIDE WALL VENTS we explain the differences between the low-temperature exhaust from a high-efficiency condensing boiler and higher temperature exhaust produced by mid-range or conventional heating equipment burning gas and still higher vent temperatures and thus clearance distances that may be required for equipment burning oil or wood.

Example:

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. Gas appliance direct vent distance requirements 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. Clearance between gas vent & clothes dryer vent:

OPINION based on other clearance distances and standards discussed in the article above.

See CLOTHES DRYER VENT CLEARANCES & TERMINATION

6. Clearance distance between gas vent and air conditioner or heat pump:

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).

Also see CLEARANCE DISTANCE, HVAC

7. Direct Vent Gas Heater Terminal Clearances cited in

AMERICAN STANDARD GAS FURNACE INSTALLATION MANUAL [PDF] (2008), American Standard Heating & Air Conditioning, that in turn cites:

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. Gas Vent clearances below veranda, porch, deck, balcony:

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.

9. Gas Vent Clearance Distance to air intake and exhaust vent openings of another direct vented gas fired appliance

This is an excerpt from installation instructions for an example system, the

Aerco GF-5050 Innovation Series & ReCon WATER HEATER VENTING AND COMBUSTION AIR GUIDE [PDF] retrieved 2017/09/26, original source: http://aerco.com/sites/default/files/document/document/TAG-0043_0Q_GF-5050_INN_RECON%20Venting%20Guide_12-01-16.pdf

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:

MANUALS & PARTS GUIDES - HVAC

WATER HEATER AGE & MANUALS

Reference sources for the tables above: Gas Heater Direct Vent Clearance Distances

Direct Vent Exhaust for Heating Flues: Installation & Inspection

This topic has moved to DIRECT VENT INSTALLATION, SNAFUS & SPECS

 

Question: what is the maximum allowable length for direct vent gas heater flue & how many elbows can I use?

2017/09/11 Terry said:

I have a Goodman 60,000 BTU high efficiency Direct venting

my fresh air vent is about 3 feet below the window

my exhaust vent I want to move just right around the corner of the house approximately a total distance of about 48 inches

can I do this if not how far to the right of the window and below the window can I be with The exhaust vent thank you

This question and reply were posted originally

at DIRECT VENTS / SIDE WALL VENTS

Reply:

You will want to review GAS APPLIANCE / HEATER DIRECT VENT CLEARANCES Separate Table for Direct Vented Gas Appliances - above on this page.

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 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:

  1. the input BTUH rating of the specific heater
  2. the vent pipe diameter used
  3. the number of bends or elbows
  4. 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
1 2 3 4 5 6 7 8
40,000 2 or 2 1/2" 120 115 110 105 100 95 90 85
60,000 2 or 2 1/2" 95 90 85 80 75 70 65 60
80,000 "B" 2 or 2 1/2" 75 70 65 60 55 50 45 40
80,000 "B" 3" 200 193 186 179 172 165 158 151
80,000 "C" 2 or 2 1/2" 25 20 15 10 5 N/A
80,000 "C" 3" 200 193 186 179 172 165 158 151
100,000 2 or 2 1/2" 25 20 15 10 5 N/A
100,000 3" 200 193 186 179 172 165 158 151
120,000 2 or 2 1/2" 45 40 35 30 25 20 15 10
120,000 3" 95 90 85 80 75 70 65 60

Notes to the table above

  1. Maximum allowable limits listed on individual lengths for inlet and flue and NOT a combination.
  2. Minimum requirement for each vent pipe is five (5) feet in length and one elbow/tee.
  3. Tee used in the vent/flue termination must be included when determining the number of elbows in the piping system.
  4. 2 1/2” or 3” diameter pipe can be used in place of 2” diameter pipe.
  5. increased Clearance Configurations using (2) 45 deg. Long Sweep elbows should be considered equivalent to one 90 deg. elbow.
  6. One 90° elbow should be secured to the combustion air intake connection.

References & Sources for the table above

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.

 

Reader Q&A - also see the FAQs series linked to below

On 2022-06-30 by InspectApedia (mod) - New Yorker Model PVCG40NI-T2 clearance requirements are in manual

@Eli Boroumand,

I found that model's installation manual and have added it to our New Yorker Manuals page. The direct link to the manual is at:

New Yorker PVCG-C WATER CAST IRON GAS BOILER [PDF] (2022)

You will see in the manufacturer instructions, pages 7 and 8, the clearance requirements for the boiler as well as referral to the use of the Direct Vent Conversion Kit if pulling your combustion air directly from outside.

And in general, yes a heating appliance being properly supplied with outdoor air means that it does not need indoor air for its combustion process.

On 2022-06-30 by Eli Boroumand

@InspectApedia, Thank you! The make is a New Yorker Model number: PVCG40NI-T2

On 2022-06-29 by InspectApedia (mod)

@Eli Boroumand,

What does the installation manual for your direct vent boiler state for required clearances and space requirements? Or if you tell us the make and model, we can try to look as well.

On 2022-06-28 by Eli Boroumand

@InspectApedia-911,
Thank you! Just to clarify as long as I make enough space for clearance, I don’t have to put any additional air intake e.g louvered doors, as the direct vent boiler is pulling air from outside. Correct?

On 2022-06-28 by InspectApedia-911 (mod)

@Eli Boroumand,

You need both working space around the equipment and adequate combustion air.

Combustion air can come from outside, but you still need adequate working space.

You will see the space requirements in the installation manual for your specific boiler or furnace.

If you violate those you could be faced with having to tear out a wall simply to do repairs or maintenance on the system, or worse maintenance is not done or not done thoroughly, the system becomes unsafe.

You'll see with the clearance distance is very significant leave for different sides of the equipment. You may need three feet in front but much less on the sides and very little at the rear.

On 2022-06-27 by Eli Boroumand

I have a direct vent boiler. I’m looking to make the boiler room smaller. Is there a minimum size the room has to be or would I have to put louvered doors?

On 2022-01-24 by Inspectapedia Com Moderator - Can you install a direct vent wall furnace beneath a window?

@Larry,

Above on this page in our table titled:

Table of Gas Code Clearance Distances from a Direct Vent Gas Appliance Terminal to Other Building Features

on line "B" you'll see the recommended clearance distances between the direct vent and a window. Your vent can be "below" the window provided it's far enough below.

Please do read the article above as it answers your exact question about clearance distances required for direct wall vents, both in the text (see the clearance highlights section) and in the chart (see Letter B) shown.

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.

On 2022-01-24 by Larry

Can you install a direct vent wall furnace beneath a window?

On 2022-01-18 by Inspectapedia Com Moderator - do not modify the combustion air supply or exhaust vent outside of what the manufacturer describes

@Alan,

Apologies but I don't have a clear understanding of your direct-vent fireplace combustion air supply and combustion gas exhaust as it was designed by the manufacturer. Those design variations and details are device-specific - and may not be identical across many brands and models of direct-vent fireplaces.

So let's start with the identity of the specific brand and model of your direct vent fireplace.

Then let's look at and follow the manufacturer's instructions.

Watch out: do not modify the combustion air supply or exhaust vent outside of what the manufacturer describes.

Doing so could kill everyone in the home (a fatal carbon monoxide poisoning) or cause a house fire.

On 2022-01-16 by Alan

Can I use the outer flue for the direct vent fireplace exhaust (i.e. hot) air? And the inner flue to intake combustion air? My thinking is to have the flue help heat up the room and improve the efficiency of the fireplace.

On 2021-10-22 by inspectapedia.com.moderator

@daniel.patrickduffy,

You'll be okay if you assure that your vent cap as its components meet two sets of clearance distances:

First check against the tables given on the page above

Check and check against the clearance distance is given in the installation instructions for the specific product that you bought in for the heater that you are venting.

On 2021-10-22 by daniel.patrickduffy

I just re-vented my gas room heater through the wall, and the exterior wood siding around the pipe seems abnormally hot to the touch, so I’m worried that it was installed incorrectly.

Williams heater reventing (C) InspectApedia.com DanielPD

As you can see in the photos, it is a Williams heater, I used type “b” double wall pipe, and I have a little horizontal termination cap. I did use a thimble through the wall too (the photo of the unit is before I re-vented).

Did I do something wrong? Is it problematic for it to get this hot? Anything else to be aware of? Any feedback would be greatly appreciated! Daniel


On 2021-09-10 by mak.church (mod) - How much clearance does my heater vent need outside?

@Rj,

Gas heater vent clearances are given above on this page.

Please take a look at the section:

Clearance Requirements for Direct Vented Gas Appliances

Of course the owner's manual for your specific heater brand and model will have specific clearances that the manufacturer has determined must be respected for that very heater.

And depending on what type of trailer obstruction you're referring to, it may have its own vents and intakes to consider.

On 2021-09-09 by Rj

How much clearance does my heater vent need outside. Someone parked a trailer on front of my vent and it may be too close for proper ventilation

On 2021-09-07 by inspectapedia.com.moderator (mod) - replacing my wood furnace with a natural gas heater.

@Bill,

Because there could be chimney temperature and thus draft and thus fatal carbon monoxide poisoning worries, you should check first with the manufacturer of the specific gas heater brand and model; you may need to run a b-vent to the rooftop.

Watch out: you never convert a chimney from one fuel to another, particularly wood or oil to gas, without an expert chimney inspection, probably also a cleaning, as chimney deposits from the old fuel can form a fire or other hazard with the new fueled-devices.

On 2021-09-07 by Bill

I'm replacing my wood furnace with a natural gas heater.
When installing the 4 in. exhaust vent inside my existing 7 in. Selkirk chimney, do I have to put a double wall vent, or can I use single wall venting?

On 2021-09-01 by inspectapedia.com.moderator (mod) - fireplace through-wall exhaust vent can get hot -

@Ramiro Ruiz,

It's a fair concern that you raise as the fireplace through-wall exhaust vent can get hot - you'll probably see the word "HOT" or something like that embossed on the vent surface; that means keep people, especially children, from touching it.

Beyond that obvious hazard there are more clearance distances given above on this page.

On 2021-09-01 by Ramiro Ruiz

Hello, I just moved into a new build home. The house has a full walk-out basement so the builder installed a deck at the back of the house on the main floor, and we have a fireplace(natural gas) that the vent is at the back of the house too. The vent is about 4' feet from the deck floor. Is this legal? we will have furniture close by the vent and obviously people will be walking around socializing so I am a little concerned.

Thanks in advanced

On 2021-08-11 by inspectapedia.com.moderator (mod) - How far can I run my furnace exhaust vent pipe to clear a deck and how many pipe bends can I use?

@Patrick,

There is no one "right answer", because we need to follow the specific limitations given in the installation and operation manual for your specific direct-vent equipment: manufacturer or brand, and model number.

At the home page for this topic

DIRECT VENTS / SIDE WALL VENTS https://inspectapedia.com/chimneys/Direct_Vent_Chimneys.php

And below, I give ONE EXAMPLE - NOT AT ALL NECESSARILY RIGHT OR CORRECT FOR YOUR (un-specified) HEATER FUEL - that is excerpted from an ICP manual provided in the link I give above.

you'll find a number of installation manuals for direct vent equipment but

Watch out: remember that what you read may be incorrect and even unsafe if you're not reading the instructions for your specific venting product.


[Click to enlarge any image]

On 2021-08-11 by Patrick

How far can I run my furnace exhaust vent pipe to clear a deck and how many pipe bends can I use. Does it have to be insulated

On 2021-07-09 by (mod) - Wall Firestop may be required

@Jeff,

Possibly:

1. Your vent must follow the manufacturer's instructions including for fire clearance distances from combustibles and maximum vent length, number of bends and elbows, and outside clearance distances as well.

2. In a typical direct vent installation manual you may find text such as the following

Wall Firestop may be required by the appliance manufacturer as additional thermal protection for the wall. If the wall being penetrated is constructed of noncombustible material only, i.e. masonry block, brick, or concrete only, a hole with zero clearance to the vent pipe is permissible if allowed by the appliance manufacturer.

On 2021-07-09 by Jeff

Can a direct vented fireplace be vented through a closet through a bulkhead to an outside wall?

On 2021-07-01 by inspectapedia.com.moderator (mod) - Can I use the existing 4” liner to vent the exhaust

@Paul,

I saw this question last night and didn't know how to to answer it then, nor now. Because there is no "one size fits all correct answer"

Start with the installation instruction manual for your specific heater (whatever it is: water heater, boiler, furnace or ?) - as the BTU rates, clearances, and venting requirements vary.

Continue with the IO manual for the specific direct vent device if it's separate from the heater that it's venting.

Watch out: part of the confusion of this question is venting out through a wall rather than a roof, and also what vent material is permitted. Vent materials range from PVC piping for condensing heating equipment that runs at low temperature and vents out through a side-wall, through gas venting through a B-vent chimney to oil-fired equipment that requires an insulated flue if you're using a metal chimney.

So you can see there's no safe "right" answer to the question as phrases. Perhaps with more specifics we can narrow down the answer.

On 2021-07-01 by Paul

I am installing a direct vent gas insert with 3” intake and exhaust ports, replacing an older style gas insert which had a single 4” exhaust only. Can I use the existing 4” liner to vent the exhaust to the roof cap and connect the intake to a wall vent which would be easier to install.

On 2021-05-25 by (mod) - can the outtake vent be under an eave

@Manny,

In the gas vent clearance drawing and table above on this page see dimensions D and E for what the code suggests.

On 2021-05-25 by Manny

On a side wall vent, can the outtake vent be under an eave and if so how far up or down from the eave? Thanks

On 2021-04-16 - by (mod) -

@Madeline,

Thanks for a helpful question on venting a gas heater onto a patio.

Take a look at the table at the top of this article,

"Table of NFGC Recommended Clearance Distances from a Direct Vent Gas Appliance Terminal to Other Building Features"

at line A - Distance above grade (ground surface), balcony, deck, porch, veranda

and you'll see the typical model codes give

12" (more if there's risk of snow cover)

One would, and I would, interpret that as meaning that it's permissible to vent your gas fireplace to an outside, open patio.

The clearance from a direct vent to an overhanging roof, even a mere eaves or soffit, is given in the table above.

Watch out: there can be serious hazards if exhaust gases enter a building structure through an overhanging roof or soffit where attic or under-roof vent openings might admit exhaust gases back into the building.

Watch out: however on a patio, you want to be sure that if you're getting hot exhaust gases, that there's nothing so close to the vent that it might be damaged and of course, you wouldn't want to be sitting close to such an area either. We have seen melted plastic patio furniture, and we've seen the damage in reverse (a gas barbecue melted vinyl siding), and we've had a few readers express worry about direct vent covers clearly marked as "DANGER HOT" but installed where they might be touched by children.

On 2021-04-16 by Madeline

Can a vented fireplace be vented to an outside, open patio area? Note, the patio is open, but does have the roof overhanging part of it.

On 2021-03-09 by (mod) - gas meter vent piped away from combustion air intake for gas heater

@Matt
|
Check with your local plumbing inspector: it looks as if your vents in your photo may be a bit too close to that gas meter.

Really? Well maybe someone has already addressed this safety concern: notice that the gas regulator vent appears to have been piped away, though we can't see its destination.

If I'm right then yes, an expert also considered this an unsafe installation and addressed it by relocating the termination of the gas meter/regulator vent

I don't see any green marks.

On 2021-03-09 by Matt

Re-posting without failed image

Matt said:

I have a natural draft tank its dying so I bought a power vent tank which I will install but I have a venting question I have very limited options for where the exhaust will have to go through the wall see pic

I planned on putting it either directly right of my furnace exhaust or to the left of my gas meter Now my gas meter is vented about 12 feet down the wall so I am clear of the meter venting. I made green marks on the brick for approx location i want to run it

On 2021-02-20 - by (mod) -

@Mikeq,

Yes, Mike, but I can't safely give absolutely-correct clearance distance figures; instead you will want to check the installation manual for the specific heating products you're installing, as they differ a bit among manufacturers, heaters, vents.

On 2021-02-20 by Mikeq

Would like to know if there are terminal clearances needed for a concentric direct vent of a cat 4 furnace with a water heater b-vent terminal nearby?

On 2020-12-31 - by (mod) -

John

Thank you for the helpful question.

You're right that some Canadian direct vent clearance distances had crept into the U.S. side of the table - my typing error.

I have corrected the data in the clearance distances for direct vents and have added more details, tables, codes.

Don't hesitate to ask further questions as needed.

Your careful reading has helped me make the side wall vent distance tables accurate and so will help other readers.

On 2020-12-29 by John

Hello,
I have seen the "Table of NFGC Recommended Clearance Distances from a Direct Vent Gas Appliance Terminal to Other Building Features" in other manuals and locations and I believe the columns labeled US and Canada are switched, at least for K,L & M.

As a reference, this table and key is located in the pdf link from note 7.

Would you be able to double check this?

I ask because I am having a hard time venting my hot water heater out of my old farm house and so the only option is to route under a small deck/porch.

On 2020-12-04 by (mod)

Jim, Please find your question and my detailed reply now at the Reader Q&A section near the bottom

of TYPE B-VENT CHIMNEYS. You may need to clear or refresh your browser cache to see the updated page. We welcome your further photos, comments, questions.

On 2020-12-04 by Jim

I want to put an atmospheric vented 40 gallon gas water heater in the utility room on the main floor of a 2 story house. It will be located against an outside wall.

Double wall Type B vent pipe will run 2 feet vertical from the draft hood into a 90 degree elbow.

Then 16 inch horizontal through a wall thimble and into another 90 degree elbow.

Then 15 feet vertical up the outside of the house through the eve terminating 2 feet above the highest part of the roof within 12 feet.

My question is:

Can I leave the B vent going up the outside of the house in the open or does it have to be enclosed in a chase?
Rural Oregon location.

On 2020-12-03 - by (mod) -

Most likely yes. You will see in the installation manual for a typical direct vent gas fireplace that the vent like this quite short and run horizontally out through a wall.

There are some models that will allow vertical venting option however. So what we need to do is select a model that you like and look at the specifications and the installation manual.

On 2020-12-01 by Rick

I want to convert my wood fireplace to a direct vent gas unit running the vent pipes up my existing chimney. The chimney is 35’ tall (3 story home). Is that too tall to do this?

On 2020-11-23 - by (mod) -

Alex

I agree that you don't want to modify a gas vent - you might make it unsafe.

Where I've seen this obstruction before, the deck builder usually frames a rectangle around the vent to keep the deck framing away from the vent.

So if it's a joist that's giving you clearance trouble, you'd just cut that joist short and carry it with a header framed between the two joists on either side of the short one.

On 2020-11-23 by Alex W

Hello I been reading your site up and down. My question is about deck installation. I have direct gas vents on the back of my house. However they were installed about the height where the deck support beams would go.

Can I install the deck next to the side of it? which would be within 1 foot. Is this considered an inside corner issue, which means I need 3 feet clearance from the side of the deck?
I prefer to install on top of it, but then the vent would be within 1 foot below the deck. I also did not see a option in your guide for modifying the vent to point down.

On 2020-11-05 - by (mod) -

Joe

Thanks that's an interesting question;

In my mere opinion, as the concern is total distance from point of exit of the building to the air inlet, and as the purpose is safety, I'd measure from the closest point on the vent termination cover to the closest point on the air inlet.

The final authority is your local building inspector;

On 2020-11-05 by Joe Poland

The NFGC Recommended Clearance Distance Table for a Direct Vent Gas Appliance shows a requirement K for "Distance to a mechanical (systems) air supply inlet as 6 feet and 3 feet above if within 10 feet horizontally"

My outside air supply inlet has a hard plastic cover which only allows fresh air in thru a horizontal entry port below the main house inlet vent. This horizontal plastic entry port is 5" deep covering the main house inlet vent. Am I able to include this 5" with 31" for the total vertical separation of 3 feet to the bottom edge of the direct vent heater port?

The NFGC Recommended Clearance Distance Table from a Direct Vent Gas Appliance shows a requirement K for "Distance to a mechanical (systems) air supply inlet as: 6 feet and 3 feet above if within 10 feet horizontally."

Does this apply to an inside the house mechanical (systems) air supply exhaust inlet which is part of an Energy Recovery Ventilator System ERV ? This ERV inside the house air supply exhaust inlet draws inside air into a heat exchanger and expels the air to the outside of the house.

Fresh air is brought into the heat exchanger from an outside air inlet and passes thru the heat exchanger and is forced out vents inside the house. I would believe that the answer is that this inside the house exhaust air supply is not addressed by the above rule..

On 2020-10-27 - by (mod) -

Anthony

Thank you for the questions.

Gas heater vent clearances are given above on this page; and of course the IO manual for your specific tankless water heater brand and model will have specific clearances that the manufacturer has determined must be respected for that very heater - those may differ from what we show here.

There is no direct vent gas fired heater that I would vent up 24 feet. None of the vents discussed here run that distance.

On 2020-10-27 by Anthony

I am considering venting a tankless water heater through the sidewall from garage , what is the distance the opening needs to terminate from eaves , its on 1st story of 2 story house. Also, what is BEST practice through the roof in which I would use about 24 feet of PVC or side of house using about 3 feet of PVC ? The Location of Tankless is in the Garage

On 2020-10-12 - by (mod) - sources for clearance distance to or requirement for sealed soffits over a direct vent for a gas heating appliance

Typical gas heater direct vent clearance distances from a manufacturer's installation instructions - cited & discussed at InspectApedia.comThank you for taking the time to write about this direct vent clearance question, John.

Obviously I didn't make any of this up, though sometimes I may quote standards that are later modified. But

Bottom line: you're right that there are few model building code citations about clearance distance from gas heating appliance direct vent termination and a building soffit. That requirement is supported by some code documents, some training materials, and some manufacturers' installation instructions - thus becoming "code" by inclusion.

Below the gas vent clearance tables on this page we cite the sources of data appearing in the table.

Rows D&E in that table also refer us to note 3 that I reiterate below:

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

Continuing Discussion: John

Watch out: The safety concern here is that installers of direct vent systems on gas heating equipment should (OPINION) take care to assure that gas combustion products do not re-enter the building where in addition to condensation and moisture damage the most-serious concern is the risk of fatal carbon monoxide poisoning.

Particularly on homes whose roof overhang or eaves include a vented soffit, but even on un-vented or "closed" soffits there is a risk of combustion gases leaking into the building roof space or attic or in some constructions, an occupied top floor of the building. Code writers can't predict every possible construction configuration nor every mistake I alone have made in 50 years of construction work, inspection, and repair; so they try to write in terms of objectives.

Then, manufacturers of heating equipment are among those particularly concerned that their equipment should be installed in the safest possible manner.

For that reason code writers also typically include a provision that equipment ... "... shall be installed according to the manufacturer's instructions." I'll include an example of that language below.

So in effect even if a requirement for protection a soffit from exhaust gases appeared ONLY in manufacturers' literature, it's included in and is "code" by that requirement.

The illustration below showing a minimum of 12" clearance of gas vent to roof overhang is from ICP's gas furnace installation instructions, not-accidentally included in the employee training materials for some gas companies such as Questar (our source).

As another example (also cited in our references to the table) from CSA as incorporated by BC (British Columbia) Housing, we have at the very least a mould and moisture concern:

" If there are vented soffits above a sidewall vent, the soffit vents should be sealed for 6 feet on either side of the vent. Draw a vertical line above the vent and measure 6 feet on either side of that line. If the roof space is to be vented, ensure that there is adequate venting overall in other portions of the attic."

"When sidewall venting cannot be avoided, seal all soffit vents immediately above the vent -- even if the soffit is two floors above"

"The flue gases moving up the house can enter the attic through the soffit vents where they can condense on the framing and underside of the roof sheathing. There have been reports of moisture and mould on the underside of roof sheathing in houses with sidewall vented appliances and also on adjoining houses.

Some builders have even reported condensation and mould growth in new houses that are still under construction – where the water vapour from an adjacent home’s gas appliance is blown into the attic. Similar problems have been observed in older homes that have been retrofitted with new high efficiency gas furnaces where the venting has been put through the wall rather than keeping it through the roof."

An experienced code compliance or building inspector as well as many home inspectors emphasize that safety advice is intended to cover not just what my brother-in-law Irwin did or said was "legal" but also what people might do in a building - like convert or use the upper floor or even an attic space (such as in a cape cod home) as a bedroom.

Code requirement to install a direct vent as per manufacturer's instructions

Here's an example of the "install as per the manufacturer" citation I mentioned, from the California Code Chapter 8: Chimneys and Vents

California Building Code, 802.2.4 Direct-Vent Appliances

Listed direct-vent appliances shall be installed in accordance with the manufacturer's installation instructions and Section 802.8.2. [NFPA 54:12.3.5]

802.8.5 Vent Terminals

Vent terminals that terminate through an outside wall of a building and discharge flue gases perpendicular to the adjacent wall shall be located not less than 10 feet (3048 mm) horizontally from an operable opening in an adjacent building. Exception: This shall not apply to vent terminals that are 2 feet (610 mm) or more above or 25 feet (7620 mm) or more below operable openings. [NFPA 54:12.9.6]

802.6.2.3 Exterior Wall Termination

A gas vent extending through an exterior wall shall not terminate adjacent to the wall or below eaves or parapets, except as provided in Section 802.2.4 and Section 802.3.3. [NFPA 54:12.7.2(4)]

- retrieved 2020/10/12 original source: California Building Code, https://up.codes/viewer/california/ca-mechanical-code-2016/chapter/8/chimneys-and-vents#8

On 2020-10-12 by john keltner

Your Table "Table of NFGC Recommended Clearance Distances from a Direct Vent Gas Appliance Terminal to Other Building Features" alludes to distances that I cannot find in NFPA54 12.9. The issue at hand is distance to soffit from vent below soffit - Rows D & E on your table.

The only NFPA54 rule similar to your table is in 2021 version NFPA 54 Table 12.9.1 which states NO LIMIT to vented or unvented soffit.

Earlier versions don't specify. Where did you get your 24" distance?

Thank you for your assistance.

...

Continue reading at DIRECT VENTS / SIDE WALL VENTS or select a topic from the closely-related articles below, or see the complete ARTICLE INDEX.

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