# Type B gas furnace vent roof termination clearance



## HN2018 (Dec 10, 2018)

Hi,

Is there a code specifying clearance distance for a gas furnace vent to a roof louver exhaust vent?

I am re-roofing and have a gas furnace vent terminating within 1 feet to the side of a roof louver exhaust vent.  I have searched but not sure if there is a code about how far to terminate a furnace vent from an exhaust vent.  There are no vertical walls or windows nearby.  This is a one story single family home (duplex) and roof pitch is 4/12.

I am wondering if it is this close to an exhaust vent that wind can blow gas vent into the exhaust vent.

Thank you for your help.


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## my250r11 (Dec 11, 2018)

If They are both exhaust there is not an issue.


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## classicT (Dec 11, 2018)

No minimum separation is required per code as both are exhaust. I would make sure to have some separation for heat dissipation. The exhaust gasses can be fairly hot, enough to melt plastic within a foot or two.


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## HN2018 (Dec 11, 2018)

Thank you for your replies.

I also emailed the city inspector the same question and their answer is : three feet according to the 2016 California Mechanical code.

I searched the web and found section 802.6 for gas venting but that does not saying anything about my situation.

There is a section on kitchen venting, section 510.9.1 part 3 quoted below:

*510.9.1 Rooftop Terminations*

    3. A vertical separation of 3 feet (914 mm) below an exhaust outlet for air intakes within 10 feet (3048 mm) of the exhaust            outlet.

I would rather move the gas vent now before I shingle over it but I am not sure I have three feet to move it.  I can move it above the louver exhaust vent about one foot and it will be about two feet under the ridge.

Any suggestions or comments.

Thank you.


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## classicT (Dec 11, 2018)

Cali uses its own code, to which I am not familiar with. Seems odd to require separation if both are exhaust, but never know in California. Give it a day or two and one of the California guys will answer.


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## HN2018 (Dec 11, 2018)

I emailed back the city inspector to clarify.  I also left them a voice message and an inspector called me back.  He seems to think there is a code clearance but he said that if I can easily move it, go ahead and move it.  This inspector was probably not the same one that emailed me.

In any case, I moved the furnace vent three feet away between the ridge and the roof louver.

Thanks all for your replies.


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## ICE (Dec 11, 2018)

I suspect that the "roof louvered exhaust vent" is an attic vent.  Is that correct?


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## HN2018 (Dec 11, 2018)

Yes, it is an attic vent.


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## ICE (Dec 11, 2018)

An attic vent is not an opening into the building.


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## mtlogcabin (Dec 12, 2018)

Some older homes the combustion air is taken from the attic and ducted low into the room containing the furnace. In  this instance there could be a possibility of pulling CO into the building. Contractor should verify where the combustion air is coming from
see 2012 IMC
FIGURE 304.6.1(1)
ALL AIR FROM OUTDOORS—INLET AIR FROM VENTILATED
CRAWL SPACE AND OUTLET AIR TO VENTILATED ATTIC
(see Section 304.6.1)


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## HN2018 (Dec 12, 2018)

Thank you everyone for your answers.

I moved the furnace vent to above the attic vent opening about three feet away.  Now I can continue with my re-roofing.


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## ICE (Dec 13, 2018)

mtlogcabin said:


> Some older homes the combustion air is taken from the attic and ducted low into the room containing the furnace. In  this instance there could be a possibility of pulling CO into the building. Contractor should verify where the combustion air is coming from
> see 2012 IMC
> FIGURE 304.6.1(1)
> ALL AIR FROM OUTDOORS—INLET AIR FROM VENTILATED
> ...


You definitely have a point.  I have been down the road of moving a flue vent away from away from an attic vent.and I was overruled by our mechanical section.  I think I will try it again with what you have provided.  Thanks.


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